Good question.
I see two possible answers, and will expose my ignorance by saying I've no idea which dominates:
1)? High currents and high voltages can both be present, but perhaps not at exactly the same place and time.
2)? We have some energy going in from the transmitter, some energy being radiated out,?
and a whole lot of energy stored in that high Q resonant circuit.
Jerry
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On Mon, Dec 23, 2019 at 08:12 AM, Bill Cromwell wrote:
Hi,
I haven't been reading this entire thread so I may have missed some statements.
A daily driver is the car (or truck) we drive to work every day. And to grocery store. As opposed to a precious collectible vehicle that we wouldn't risk in highway traffic. Or the Rolls Royce we only take to church on Sunday.
I have noticed that (30,000 Volts at 30 Amps) thing before. That is 900,000 Watts. From whence comes 900,000 (that is nine hundred thousand) Watts from a source of five or ten or even fifteen hundred Watts? It ain't happening in *this* universe. If we tickle the feedline with even a five watt transmitter it is possible for some antenna systems to develop very high voltages at some points. The current will be reduced proportionally. Reactances in the system can (will) transform voltage (and simultaneously current). As in any transformer when one increases in magnitude the other decreases. Without any losses the power will remain the same. The caveat - there is always some loss in *this* universe.
I have a couple of "mag-loops" here and broadcast receiver air variable caps do the tuning duties up to about ten watts. A tiny bit of dust got into one and at around 8 watts there was a tiny spark. When the dust burned away the spark/arc stopped. Probably my 100 Watt transmitter would require something more robust. But this is a *QRP* forum. Those same small air variables work well in L-network antenna matching circuits at 100 watts (my personal maximum available power level) into random, end-fed wires.
Happy Holidays to all people of all faiths everywhere and..
73,
Bill KU8H
|
This shows 600 kv per centimeter:??
The Nov 1996 QST article cites the 1994 ARRL Handbook as stating teflon is good for 1 to 2 kv per mil (thousandth of an inch).
600 kv/cm * 2.54cm/inch / 1000mil/inch? =? 1.524 kv/mil
So I think everybody agrees.
Jerry
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On Mon, Dec 23, 2019 at 10:59 AM, Kurt Loken wrote:
Hello Jerry,
?
The most conservative dialectic strength I¡¯ve seen for virgin Teflon is around 20KV/mm. ?My 0.1mm Teflon dialectic will be just fine for a qrp loop. ?The upper end I¡¯ve seen on the spec for virgin telling is 70KV/mm...which even means it has a shot at 100w for my 10 foot loop...that would be good fun to try...heh heh. ?;)
?
Kurt-ae6uj
|
Hello Jerry,
The most conservative dialectic strength I¡¯ve seen for virgin Teflon is around 20KV/mm. ?My 0.1mm Teflon dialectic will be just fine for a qrp loop. ?The upper end I¡¯ve seen on the spec for virgin telling is 70KV/mm...which even means it has a shot at 100w for my 10 foot loop...that would be good fun to try...heh heh. ?;)
Kurt-ae6uj
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On Dec 23, 2019, at 12:15 PM, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
?Kurt, Yes, more than 2x the calculated skin effect depth would be best. But have a big roll of foil bought for EMI use that is only 1 mil thick, and would probably use that. A skin effect depth of 0.6mil means that all but 37% of the 14mhz energy is in that top 0.6mil. So if we are aggressively conserving copper, a 1 mil thickness of copper at 14mhz is? making good use of all the copper (both sides), though effective resistance at 14mhz is somewhat higher than it would be if it were 2 mil.? If I care, I can go twice as wide with my cheap 1mil foil. A loop built of 1 mil foil would be impossibly floppy, hence the plan to stick it to the laminate strip. The question remains if the laminate strip will have some sort of adverse effect. Amazing what you can do on 50mW with slow digital modes. Can't imagine a few mils of teflon deteriorating at that kind of power level. I find extremely low power messaging over long distances without dependence on any infrastructure to be compelling, and potentially very useful.? Even if it takes several minutes to say "We are all OK". Having it fully portable makes it even better. That will most likely continue to be an EFHW for me, but mag loops are very cool. Picture looks fine, by the way. I'm curious what you arrive at, especially for the capacitor. Jerry, KE7ER? On Mon, Dec 23, 2019 at 09:00 AM, Kurt Loken wrote:
Jerry...You will want to make sure you do 2x the skin depth if you use a strip...the rf will be on both sides if it is a single strip like mine.? The lower the freq the thicker you have to go.? I will never go under 80M for anything I personally do.? 35um is the skin depth at 3.5Mhz.? So 2x is 70um is around 3 mils...but probably best to not cut it to the edge.? I went with 10 mils...20 mils is easier to work with as it holds it shape better if you desire less support structures.? 10 mils is pretty floppy, but I have plans for a deployment system that I think 10 mils will work before for...so that is my choice.
?
The teflon I am using is virgin stuff (best not to not have additives you don't know in it) and the thickness is 0.1 mm....I have thicker teflon around the outside of the ends also (not in use as a dialectic), but that is an experiment in seeing if that makes the drift less.??
?
|
Kurt,
Yes, more than 2x the calculated skin effect depth would be best.
But have a big roll of foil bought for EMI use that is only 1 mil thick, and would probably use that.
A skin effect depth of 0.6mil means that all but 37% of the 14mhz energy is in that top 0.6mil.
So if we are aggressively conserving copper, a 1 mil thickness of copper at 14mhz is?
making good use of all the copper (both sides), though effective resistance at 14mhz is somewhat higher
than it would be if it were 2 mil.? If I care, I can go twice as wide with my cheap 1mil foil.
A loop built of 1 mil foil would be impossibly floppy, hence the plan to stick it to the laminate strip.
The question remains if the laminate strip will have some sort of adverse effect.
Amazing what you can do on 50mW with slow digital modes.
Can't imagine a few mils of teflon deteriorating at that kind of power level.
I find extremely low power messaging over long distances without dependence on any infrastructure
to be compelling, and potentially very useful.? Even if it takes several minutes to say "We are all OK".
Having it fully portable makes it even better.
That will most likely continue to be an EFHW for me, but mag loops are very cool.
Picture looks fine, by the way.
I'm curious what you arrive at, especially for the capacitor.
Jerry, KE7ER?
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On Mon, Dec 23, 2019 at 09:00 AM, Kurt Loken wrote:
Jerry...You will want to make sure you do 2x the skin depth if you use a strip...the rf will be on both sides if it is a single strip like mine.? The lower the freq the thicker you have to go.? I will never go under 80M for anything I personally do.? 35um is the skin depth at 3.5Mhz.? So 2x is 70um is around 3 mils...but probably best to not cut it to the edge.? I went with 10 mils...20 mils is easier to work with as it holds it shape better if you desire less support structures.? 10 mils is pretty floppy, but I have plans for a deployment system that I think 10 mils will work before for...so that is my choice.
?
The teflon I am using is virgin stuff (best not to not have additives you don't know in it) and the thickness is 0.1 mm....I have thicker teflon around the outside of the ends also (not in use as a dialectic), but that is an experiment in seeing if that makes the drift less.??
?
|
Rob, I assume that it is copyrighted. However, I don't believe that any of the lessons ended up referencing it, so you are probably fine without it. It is a great resource and well worth the purchase. It was included as a pdf with my copy of Experimental Methods in RF Design that I bought from arrl last year.
Mike M. Ku4qo?
Poking around
Prerequisites???
??
IS "Solid State Design for the radio amateur"?
the book that came as 28mb PDF with EMRFD?
Is that PDF? copyright material that is not
allowed to be shared?
==============================================
Ok folks, here are the prerequisites for the
elmer project. This list
was compiled with the help of the "elmers" so we can get a head
start on
the theory. Please read this carefully if you plan on
participating in
the class.
1) All posts regarding the elmer project must have a subject
that starts
with elmer101:
2) Students must have access to the ARRL Handbook, 1995 or later
(1998
preferred).
This can be obtained directly from the arrl or other
(discounted)
sources ( i.e. , local and mail order Ham
radio
dealers)
The following references are extremely helpful but not required.
a) Solid State Design for the radio amateur
??????? arrl has this book.
b) Databook for homebrewers and QRPers by NA5N
??????? Paul Harden has agreed to provide this book at a
substantial discount
for the people in the class. I will post the info shortly.
=======================================================
Steve,
It's been over 20 years, but the original info is still on my
qsl web page . You are welcome to print and
use the info as you wish, just not for profit.
On 12/23/2019 07:27 AM, Michael
Maiorana wrote:
Again, there's nothing special about the NorCal
version of these docs. The originals are on my qsl web page.
This is the site that was used during the original class back in
1997. All the authors (me included) gave permission for anyone
to use the material there. There's lots to learn there,
especially with some of the great analysis that Glen Leinweber
did. Enjoy!
Mike M. Ku4qo
On Sun, Dec 22, 2019, 11:38 PM
Mark - N7EKU < n7eku@...> wrote:
Sorry guys,
I posted the copies here without permission so I need to
remove them.? Please google online yourself if you want to
read them.
73,
Mark.
|
Poking around
Prerequisites???
??
IS "Solid State Design for the radio amateur"?
the book that came as 28mb PDF with EMRFD?
Is that PDF? copyright material that is not
allowed to be shared?
==============================================
Ok folks, here are the prerequisites for the
elmer project. This list
was compiled with the help of the "elmers" so we can get a head
start on
the theory. Please read this carefully if you plan on
participating in
the class.
1) All posts regarding the elmer project must have a subject
that starts
with elmer101:
2) Students must have access to the ARRL Handbook, 1995 or later
(1998
preferred).
This can be obtained directly from the arrl or other
(discounted)
sources ( i.e. , local and mail order Ham
radio
dealers)
The following references are extremely helpful but not required.
a) Solid State Design for the radio amateur
??????? arrl has this book.
b) Databook for homebrewers and QRPers by NA5N
??????? Paul Harden has agreed to provide this book at a
substantial discount
for the people in the class. I will post the info shortly.
=======================================================
Steve,
It's been over 20 years, but the original info is still on my
qsl web page . You are welcome to print and
use the info as you wish, just not for profit.
On 12/23/2019 07:27 AM, Michael
Maiorana wrote:
toggle quoted message
Show quoted text
Again, there's nothing special about the NorCal
version of these docs. The originals are on my qsl web page.
This is the site that was used during the original class back in
1997. All the authors (me included) gave permission for anyone
to use the material there. There's lots to learn there,
especially with some of the great analysis that Glen Leinweber
did. Enjoy!
Mike M. Ku4qo
On Sun, Dec 22, 2019, 11:38 PM
Mark - N7EKU < n7eku@...> wrote:
Sorry guys,
I posted the copies here without permission so I need to
remove them.? Please google online yourself if you want to
read them.
73,
Mark.
|
Jerry...You will want to make sure you do 2x the skin depth if you use a strip...the rf will be on both sides if it is a single strip like mine.? The lower the freq the thicker you have to go.? I will never go under 80M for anything I personally do.? 35um is the skin depth at 3.5Mhz.? So 2x is 70um is around 3 mils...but probably best to not cut it to the edge.? I went with 10 mils...20 mils is easier to work with as it holds it shape better if you desire less support structures.? 10 mils is pretty floppy, but I have plans for a deployment system that I think 10 mils will work before for...so that is my choice.
The teflon I am using is virgin stuff (best not to not have additives you don't know in it) and the thickness is 0.1 mm....I have thicker teflon around the outside of the ends also (not in use as a dialectic), but that is an experiment in seeing if that makes the drift less.??
FYI all...
I turned down my power to 50mW on my WSPR transmitter this morning for fun...running it for a bit this morning.? ...not from my basement though ;)
If I do want to use WSPR to test for 5W qrp, is 50mW really the right power?? The size of the WSPR signal is 6Hz.? CW "bandwidth" appears to be another one of those topics that folks like to debate.? I have a red pitaya I use for listening and for CW skimming.? The spectrum of a CW signal in HDSDR really seems to show CW signals being conservatively ~100hz.? That would mean that you need a factor of 16.6 to adjust your WSPR power.? So my 50mW signal would be less than a watt wouldn't it for CW even after this adjustment?? Wouldn't 200mW (the previous map I showed) be more like 3.3 W?? ?Is my math wrong?
Kurt-ae6uj
On Mon, Dec 23, 2019 at 10:13 AM Jerry Gaffke via Groups.Io <jgaffke= [email protected]> wrote: From web calculators, even with 5w into a mag loop there will be on the order of 1kv across the cap.
And it goes up from there with the square root of the power.
An air dielectric repairs itself, so if power is increased higher than it should be, you can back off when you see the arcing.
As mentioned in post? ?/g/qrptech/message/534? teflon is destroyed once some max voltage is reached.
And the discussion pointed to there suggests that air spaces between the teflon and the plates can cause trouble as well.
Moisture from the air won't help, a major issue if you are mounting it up on the roof.
The article on the trombone cap of Nov 1996 QST states that teflon has a breakdown voltage of over 1kv per mil.
Their 1/16" of teflon is perhaps 20x times as thick as needed for moderate power of perhaps 20 watts.
At what point is it so thick that it is robust enough to be a "daily driver"?
Hard to imagine that 20x is not good enough to overcome issues with air spaces and humidity.
I can see where a butterfly cap is better than most other manufactured air variables.
Especially if the plates of each section are welded or brazed, not simply pressed together,
Most caps simply can't deal with with several dozen amps of RF, and efficiency falls quickly?
if there is even a fraction of an ohm there.
But something like two PCB plates bolted together with a bit of an air gap, an adjustment screw
spreading the far end a bit further by warping the plates, should work?as well as a butterfly cap.?
Have large PCB clearance areas around all the screws, and use nylon screws.
A skin effect calculator on the web shows that at 14mhz, most of the current is flowing in
the first 0.0006" of copper.? So one or two mill thick copper foil should be sufficient for the loop,
and quite possibly better than most coax that many use on mag loops (especially if used?
with coax connectors).? As mentioned earlier, solder is 10x the resistivity of copper, and while
soldering large areas of two copper surfaces together gives a very low DC resistance,
skin effect will need to be considered here as well.
All sorts of stuff to learn.
If I get serious about building one, I will indeed look for some mag loop forum to haunt.
These are issues we don't normally encounter.
Jerry, KE7ER?
On Sun, Dec 22, 2019 at 09:08 PM, Kirk Kleinschmidt wrote:
What does Lee say about Teflon? He says that vacuum and butterfly caps are better. :)? Good enough for me.
?
|
From web calculators, even with 5w into a mag loop there will be on the order of 1kv across the cap. And it goes up from there with the square root of the power. An air dielectric repairs itself, so if power is increased higher than it should be, you can back off when you see the arcing. As mentioned in post? ? /g/qrptech/message/534? teflon is destroyed once some max voltage is reached. And the discussion pointed to there suggests that air spaces between the teflon and the plates can cause trouble as well. Moisture from the air won't help, a major issue if you are mounting it up on the roof. The article on the trombone cap of Nov 1996 QST states that teflon has a breakdown voltage of over 1kv per mil. Their 1/16" of teflon is perhaps 20x times as thick as needed for moderate power of perhaps 20 watts. At what point is it so thick that it is robust enough to be a "daily driver"? Hard to imagine that 20x is not good enough to overcome issues with air spaces and humidity. I can see where a butterfly cap is better than most other manufactured air variables. Especially if the plates of each section are welded or brazed, not simply pressed together, Most caps simply can't deal with with several dozen amps of RF, and efficiency falls quickly? if there is even a fraction of an ohm there. But something like two PCB plates bolted together with a bit of an air gap, an adjustment screw spreading the far end a bit further by warping the plates, should work?as well as a butterfly cap.? Have large PCB clearance areas around all the screws, and use nylon screws. A skin effect calculator on the web shows that at 14mhz, most of the current is flowing in the first 0.0006" of copper.? So one or two mill thick copper foil should be sufficient for the loop, and quite possibly better than most coax that many use on mag loops (especially if used? with coax connectors).? As mentioned earlier, solder is 10x the resistivity of copper, and while soldering large areas of two copper surfaces together gives a very low DC resistance, skin effect will need to be considered here as well. All sorts of stuff to learn. If I get serious about building one, I will indeed look for some mag loop forum to haunt. These are issues we don't normally encounter. Jerry, KE7ER?
On Sun, Dec 22, 2019 at 09:08 PM, Kirk Kleinschmidt wrote:
What does Lee say about Teflon? He says that vacuum and butterfly caps are better. :)? Good enough for me.
?
|
Hi,
I haven't been reading this entire thread so I may have missed some statements.
A daily driver is the car (or truck) we drive to work every day. And to grocery store. As opposed to a precious collectible vehicle that we wouldn't risk in highway traffic. Or the Rolls Royce we only take to church on Sunday.
I have noticed that (30,000 Volts at 30 Amps) thing before. That is 900,000 Watts. From whence comes 900,000 (that is nine hundred thousand) Watts from a source of five or ten or even fifteen hundred Watts? It ain't happening in *this* universe. If we tickle the feedline with even a five watt transmitter it is possible for some antenna systems to develop very high voltages at some points. The current will be reduced proportionally. Reactances in the system can (will) transform voltage (and simultaneously current). As in any transformer when one increases in magnitude the other decreases. Without any losses the power will remain the same. The caveat - there is always some loss in *this* universe.
I have a couple of "mag-loops" here and broadcast receiver air variable caps do the tuning duties up to about ten watts. A tiny bit of dust got into one and at around 8 watts there was a tiny spark. When the dust burned away the spark/arc stopped. Probably my 100 Watt transmitter would require something more robust. But this is a *QRP* forum. Those same small air variables work well in L-network antenna matching circuits at 100 watts (my personal maximum available power level) into random, end-fed wires.
Happy Holidays to all people of all faiths everywhere and..
73,
Bill KU8H
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On 12/23/19 12:08 AM, Kirk Kleinschmidt via Groups.Io wrote: Sorry, Kurt,
A "daily driver" is an antenna that stays in service for long periods of time and is used daily (as opposed to something whipped together for one reason or another). It's a motor vehicle reference. I guess I'm getting old!
The Teflon data I'm remembering is/was in the mag loop archives when everything was hosted on Yahoo Groups (may now be at groups,io?). I don't have access right now, as I'm traveling, but perhaps someone else is on both lists who might?
Because of the unusual electric and magnetic properties encountered by mag loop materials (30,000 V at 30 amps, anyone?), almost nothing other than vacuum and air variables with no physical contacts (butterfly caps) emerges as stable and non-lossy.
These and many additional materials have been tested over the past 50 years, not just by hams, but by the military and commercial companies developing the mag loops are related stuff.
Leigh, VK5KLT, who has been intimately involved in military and commercial mag loop design (and the underlying science) for the past 50 years, is an accessible and approachable authority on all details of materials, feeding and construction. He's a regular on the Mag Loop list, and his papers are available on the web. He emails, too.
What does Lee say about Teflon? He says that vacuum and butterfly caps are better. :)? Good enough for me.
I have worked up various trombone/Teflon approaches over the years, but after I studied a lot more I set them aside.
In short, it works, but it's not ideal.
Also, if I'm remembering the photo correctly, you may have had some wires running up one side of the mag loop from bottom to top? Consider centering these on the main axis of the loop, as maintaining loop balance can also be critical (hence the practice of splitting the loop down the center when running wires, installing motors and caps, etc). With massive circulating currents on the loop, objects that are closer to one side of the loop than the other can mess things up. The same goes for items in the environment (wires, trees dog houses, cars, air conditioners, etc).
Regards,
--Kirk, NT0Z
My book, "Stealth Amateur Radio," is now available from www.stealthamateur.com and on the Amazon Kindle (soon)
On Sunday, December 22, 2019, 10:36:30 PM CST, Kurt Loken <kurt.loken@...> wrote:
What do you mean by ¡°daily drivers?¡± ?Can you also share some data that Teflon is lossy at rf?
Thanks for the help.
Kurt
On Dec 22, 2019, at 9:26 PM, Kirk Kleinschmidt via Groups.Io <sohosources@...> wrote:
?
Historically, Teflon hasn't been suitable for "daily drivers" over time, whether trombones or otherwise. It's fine for proof of concept, but it's far from ideal and it's lossy at RF. Not when used in "regular" antennas, but in magnetic loops, which are a whole nother breed.
What's been proven ideal? Vacuum and butterfly. That's pretty much it.
If you just want to crank out a "foxhole" loop, why not simply solder a short length or RG-8 coax (not foam dielectric, but the hard stuff) to the loop ends and cut the cable until the SWR analyzer says it's resonating on your chosen frequency? True, resonance moves around a bit with heat and humidity, but for single-frequency work it has been successfully used. And at 20 meters and up you'll have a few kHz of resonance to play around in.
I'm not trying to stifle innovation, but as an experienced mag loop builder and user (30 years now), I know that all of the things you're noodling around with have been tried before. The mag loop groups have treasure troves that detail what works and what doesn't. And of course, Youtube is filled with "revolutionary" loops that "work" after a fashion but absolutely don't work anywhere near as well as they could.
It takes about the same amount of farting around to make a mag loop that "works" as it does to use proven methods that are known to "work well" or define the state of the art.
Vacuum and Butterfly. Sounds like a country song! Or a mantra.
BTW, if you want an awesome autotuner designed for mag loops, complete with global temperature compensation, CAT and SWR inputs, and lots of other goodies, check out Loftur's masterpiece at:
To automatically tune a Magnetic Loop Antenna - Loftur E. J¨®nasson - TF3LJ / VE2LJX <>
To automatically tune a Magnetic Loop Antenna - Loftur E. J¨®nasson
- TF3...
<>
Best of luck,
--Kirk, NT0Z
My book, "Stealth Amateur Radio," is now available from www.stealthamateur.com and on the Amazon Kindle (soon)
On Sunday, December 22, 2019, 5:54:16 PM CST, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:
Yes, if bandwidth is maybe 10khz, mechanical stability will be a real concern.
My laminate thing, like a lot of mag loops I see, could be a bit floppy.
But perhaps an advantage, distort the circular shape to tune it?
Another thought about tuning, similar to a book cap, but uses FR4 board warping as a hinge:
Have two PCB's perhaps 2" x 12" of one sided copper, 3 inches of copper removed from one end of each.
The copper foil ends solder to each of the two PCB's at the ends that still have copper.
Place one board over the other with teflon in between with copper facing copper, the 3" of removed copper on opposite ends.
Two screws through one end hold them together firmly, the teflon well compressed here.
The other end has some sort of screw with spring arrangement to adjust the distance between the two boards there
If this is part of my foil on laminate antenna, could separate the two boards by removing those screws
when coiling the antenna up tight for transport.
nanoVNA here, but not yet dangerous with it.? Touch part of touch screen not working.
Need to spend a full day just figuring out the menu, or get NanoVNA-Saver going.
Also an AQRP VIA.
Agree on needing something more than a DVM.
Jerry
On Sun, Dec 22, 2019 at 02:42 PM, Kurt Loken wrote:
The stability issue is real and controlling overlap with a motor
is a challenge of engineering in and of itself. For myself I
consider it a challenge and part of the fun.
Also...I have really come to believe that I don¡¯t know how anyone
builds a magloop or experiments with them without a proper antenna
analyzer. I would be lost without mine. Not sure if you have one,
but they make experimenting easier.
--
bark less - wag more
|
I am not a "critic" of your efforts Kurt - I applaud them.? Further, let me help you.? Please see this link:? /g/qrptech/files/N0WL%20files/The%20St.%20Louis%20Slide%20Whistle%20%20QQ.pdf? It is an article that I wrote for QQ several years ago about my experiments with mag loop capacitors. An "ideal" capacitor for a mag loop is NOT a vacuum.? You need one with a high dielectric coefficient and also high breakdown voltage.? A vacuum has neither.? Quality Teflon is very good, but Mylar is even better than Teflon.? I use Duralar brand because its breakdown voltage (off the top of my head) is about 10x a vacuum and it's dielectric constant is about 3.5x a vacuum.? That allows you to create a capacitor that is a fraction of the size of a air or vacuum capacitor.? If you read the material handling sheet for Duralar you will see that it is very temperature stable. Two comments about practical application: 1.? You can never achieve rated dielectric constant in a practical capacitor using Duralar, but you still do pretty good.? There is always some air between the capacitor plates and the Duralar that will derate the dielectric constant.? However, that air does NOT impact the breakdown voltage. 2.? Be wary of air gaps on the side of the capacitor!? Make sure the diaelectric goes way over the edge of your copper plates or you will get arcing around the edges. Finally, I don't find the comment that you can't use solder helpful.? It isn't correct.? If you understand that solder is a poor resistor and that resistance is the enemy of loop antennas, then you will be able to design a practical solution.? If you *must* use solder, then use lots of it!? And remember that where you usually put the solder joints in a mag loop is were you typically have low current. Keep up the good work! jon N0WL ps If we all used dipoles, no one would have discover the Yagi...
|
You should cherish your critics because they make you better. ?Sorry if I got hot under the collar, Kirk. ?Thanks for the link to the controller...good stuff.
Shirley...great point...I mainly care about 5W CW qrp. ?I will change the WSPR power.
Incidentally...found a great article on WSPR use:
Cheers,
Kurt-ae6uj
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On Dec 23, 2019, at 7:04 AM, w8diz <w8diz@...> wrote: ?
I wish to 100 percent endorse the below email !!!
Merry Christmas
-Diz, W8DIZ
On 12/23/19 2:20 AM, mike.carden wrote:
On Mon, Dec 23, 2019 at 4:00 PM Kurt Loken < kurt.loken@...>
wrote:
There are many, many ways to make an antenna that's worse
than a dipole, and all of those that are better than a
dipole are at least an order of magnitude more difficult to
make.
MC
VK1MC
|
I wish to 100 percent endorse the below email !!!
Merry Christmas
-Diz, W8DIZ
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On 12/23/19 2:20 AM, mike.carden wrote:
On Mon, Dec 23, 2019 at 4:00 PM Kurt Loken < kurt.loken@...>
wrote:
There are many, many ways to make an antenna that's worse
than a dipole, and all of those that are better than a
dipole are at least an order of magnitude more difficult to
make.
MC
VK1MC
|
Kurt,
lQQks gQQd
Thanks for sharing
I dabbled a bit with homebrew STL and always considered WSPR one of the best tools for both signal strength and directivity reports.?
For example..
Rotate STL 90 degrees between every TWO transmissions.
...the following cutNpast? from my (N3AAZ) blog at WSPRNET.ORG:
""Queen Anne's County ARC? (K3QAC) show N tell 2018/03/06:
My homebrew mag loop sets QAC/ARC 40m WSPR record!
K3QAC to DP0GVN (wow good ears at South Pole)
FM19xb to IB59uh
13,399 klicks times (0.63) = 8,441.4 miles
At two Watts? = 4,220.7 miles per Watt""
xxxyyyzzz
Please, I would like to see more detail of your capacitor.
Where is the best location for the capacitor top or bottom of loop?
72 73 74 P^3
John
N3AAZ
|
Buy wire...hang a dipole.
A great deal of hard earned wisdom resides in those words. There are many, many ways to make an antenna that's worse than a dipole, and all of those that are better than a dipole are at least an order of magnitude more difficult to make.
--? MC VK1MC
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Again, there's nothing special about the NorCal version of these docs. The originals are on my qsl web page. This is the site that was used during the original class back in 1997. All the authors (me included) gave permission for anyone to use the material there. There's lots to learn there, especially with some of the great analysis that Glen Leinweber did. Enjoy!
Mike M. Ku4qo
On Sun, Dec 22, 2019, 11:38 PM Mark - N7EKU < n7eku@...> wrote: Sorry guys,
I posted the copies here without permission so I need to remove them.? Please google online yourself if you want to read them.
73,
Mark.
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Nah, don't give up. I'm quite curious as to what you come up with. Experimentation is the best part of this hobby. Don't confuse advice from experience with a personal attack.
Sometimes stuff works, other times it doesn't. I spent hours trying to get the simple little lm386 Regen receiver to work with zero success. I played with it until I got bored, then shelved it. Keep playing and please do show us what you come up with.
Mike M. Ku4qo
That controller you link to is similar to what I have in mind...but an iPhone would be the interface to the user.
...but when I have someone with 30 years of knowledges telling me to give up...I¡¯m at a loss of what to do. ? Am I wasting my time with the idea of building anything in my own?? Can¡¯t I just buy a commercial loop and save a lot of trouble.? I think so. ?
Buy wire...hang a dipole.
On Dec 22, 2019, at 10:36 PM, Kurt Loken via Groups.Io <kurt.loken= [email protected]> wrote: ? What do you mean by ¡°daily drivers?¡± ?Can you also share some data that Teflon is lossy at rf?
Thanks for the help.
Kurt? On Dec 22, 2019, at 9:26 PM, Kirk Kleinschmidt via Groups.Io <sohosources=[email protected]> wrote:
? Historically, Teflon hasn't been suitable for "daily drivers" over time, whether trombones or otherwise. It's fine for proof of concept, but it's far from ideal and it's lossy at RF. Not when used in "regular" antennas, but in magnetic loops, which are a whole nother breed.
What's been proven ideal? Vacuum and butterfly. That's pretty much it.
If you just want to crank out a "foxhole" loop, why not simply solder a short length or RG-8 coax (not foam dielectric, but the hard stuff) to the loop ends and cut the cable until the SWR analyzer says it's resonating on your chosen frequency? True, resonance moves around a bit with heat and humidity, but for single-frequency work it has been successfully used. And at 20 meters and up you'll have a few kHz of resonance to play around in.
I'm not trying to stifle innovation, but as an experienced mag loop builder and user (30 years now), I know that all of the things you're noodling around with have been tried before. The mag loop groups have treasure troves that detail what works and what doesn't. And of course, Youtube is filled with "revolutionary" loops that "work" after a fashion but absolutely don't work anywhere near as well as they could.
It takes about the same amount of farting around to make a mag loop that "works" as it does to use proven methods that are known to "work well" or define the state of the art.
Vacuum and Butterfly. Sounds like a country song! Or a mantra.
BTW, if you want an awesome autotuner designed for mag loops, complete with global temperature compensation, CAT and SWR inputs, and lots of other goodies, check out Loftur's masterpiece at:
Best of luck,
--Kirk, NT0Z
My book, "Stealth Amateur Radio," is now available from
and on the Amazon Kindle (soon)
On Sunday, December 22, 2019, 5:54:16 PM CST, Jerry Gaffke via Groups.Io <jgaffke= [email protected]> wrote:
Yes, if bandwidth is maybe 10khz, mechanical stability will be a real concern. My laminate thing, like a lot of mag loops I see, could be a bit floppy. But perhaps an advantage, distort the circular shape to tune it? Another thought about tuning, similar to a book cap, but uses FR4 board warping as a hinge: Have two PCB's perhaps 2" x 12" of one sided copper, 3 inches of copper removed from one end of each. The copper foil ends solder to each of the two PCB's at the ends that still have copper. Place one board over the other with teflon in between with copper facing copper, the 3" of removed copper on opposite ends. Two screws through one end hold them together firmly, the teflon well compressed here. The other end has some sort of screw with spring arrangement to adjust the distance between the two boards there If this is part of my foil on laminate antenna, could separate the two boards by removing those screws when coiling the antenna up tight for transport. nanoVNA here, but not yet dangerous with it.? Touch part of touch screen not working. Need to spend a full day just figuring out the menu, or get NanoVNA-Saver going. Also an AQRP VIA. Agree on needing something more than a DVM. Jerry On Sun, Dec 22, 2019 at 02:42 PM, Kurt Loken wrote:
The stability issue is real and controlling overlap with a motor is a challenge of engineering in and of itself. For myself I consider it a challenge and part of the fun.
Also...I have really come to believe that I don¡¯t know how anyone builds a magloop or experiments with them without a proper antenna analyzer. I would be lost without mine. Not sure if you have one, but they make experimenting easier.
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You're doing your own thing. Understood. Enjoy.
--Kirk, NT0Z
My book, "Stealth Amateur Radio," is now available from
www.stealthamateur.com and on the Amazon Kindle (soon)
On Monday, December 23, 2019, 2:42:47 AM CST, Shirley Dulcey KE1L <mark@...> wrote:
You can use WSPR for antenna testing for other modes. Just cut your output power to compensate for its power efficiency. Use at least 20dB less power than you would for CW, so if you're trying to see where you could get with a 5W CW signal, use 50mW instead. For SSB testing, drop your power even lower.
Well hell...you are telling me I could have done all this work in my basement and not the kitchen table?? Wow.? My wife will be happy to hear that. ? They really have a racket going to claim WSPR is good for antenna testing.? Do you have a chapter in your book on that?? You need to get the word out that is a worthless testing tool.
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You can use WSPR for antenna testing for other modes. Just cut your output power to compensate for its power efficiency. Use at least 20dB less power than you would for CW, so if you're trying to see where you could get with a 5W CW signal, use 50mW instead. For SSB testing, drop your power even lower.
Well hell...you are telling me I could have done all this work in my basement and not the kitchen table?? Wow.? My wife will be happy to hear that. ? They really have a racket going to claim WSPR is good for antenna testing.? Do you have a chapter in your book on that?? You need to get the word out that is a worthless testing tool.
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Well hell...you are telling me I could have done all this work in my basement and not the kitchen table? ?Wow. ?My wife will be happy to hear that. ? They really have a racket going to claim WSPR is good for antenna testing. ?Do you have a chapter in your book on that? ?You need to get the word out that is a worthless testing tool.
I am not designing my loop for 80 and 160. ?
I don¡¯t know what you ¡°get¡± or what your game is, but you make a lot of assumptions. ?it is amusing you show me a link to a controller that has an option for tracking its tuning to SWR and then you give me a story about how instability is insurmountable. ? Got it.
toggle quoted message
Show quoted text
On Dec 23, 2019, at 1:37 AM, Kirk Kleinschmidt via Groups.Io <sohosources@...> wrote:
? I get it. I'm not trying to stifle experimentation. I simply want to steer you toward the best resources.
Self-resonant mag loops made from strap (where the insulated ends overlap to provide the C to the loop's L), work best at VHF, where the high Q of the antenna still provides enough low-SWR bandwidth around the resonance point to minimize the effects of insulation-induced instabilities (temperature and humidity effects, too).
At 160 and 80 meters, however, when bandwidths are 3-5 kHz, more stable materials are beneficial or necessary.
Using WSPR to reference/define antenna performance is somewhat moot unless all you want to do is WSPR, at which point making a useful antenna becomes 40-dB "easier" than if you're trying to make an antenna that will be used for more conversational or more conventional modes. I congratulate you, but working DX via WSPR with any mag loop, even indoors or in the basement, is the norm and not the exception. If you run the numbers regarding propagation path loss, antenna gain, and the sensitivity of the WSPR demodulation process, you'll see that those distances are expected and on track. To make those QSOs via SSB, CW, or even PSK-31 takes a better-performing antenna/mag loop or more RF power, but it is still doable, even indoors. Many mag loop users, myself included, have made ocean-hopping SSB QSOs with mag loops sitting on the kitchen table while running QRP (5-10 W PEP) Again, scaling the numbers for power and the efficiency of the WSPR decoder, the events are approximately equivalent.
I don't know how to remove posted pix. Maybe it's not even possible.
Regardless, I'm just having a conversation here, so don't let me get in your way. I think what you're doing is fantastic. I have been doing my best to steer you toward the best methods and materials, but personal experimentation always earns my respect. Other readers, perhaps lacking your skills and determination, may want to know about what experts and experimenters have already discovered about how to make top-performing mag loops and mag loop autotuners. I have provided those links and references as part of our conversation.
Regards,
--Kirk, NT0Z ? Rochester, MN
My book, "Stealth Amateur Radio," is now available from
www.stealthamateur.com and on the Amazon Kindle (soon)
On Monday, December 23, 2019, 12:05:52 AM CST, Kurt Loken <kurt.loken@...> wrote:
Hello Kirk,
I think you might not be seeing what you think you are seeing.? I really made a big mistake posting here.? I wish I could delete my picture.? If anyone reading this knows how to delete photos from the group here, I would appreciate?help at making it so.? You get working on something and you want to share...but I'm not ready to share this stuff yet. ?
That "wire" on the side isn't a wire at all...it isn't what you think it is.? It will have zero effect on the loop...I guarantee it.? It is teflon and plastic not metal. ? There is NO METAL above the feed point other than those temporary push to fit connectors in the 3D printed cap.?
There are many choices that go into a design and one of them is cost.? Yes, a vacuum variable cannot be beat...though all the soldering of connections and all the peripherals (motors, shafts, etc.) that people seem to think are okay to put around them might lead to a debate on that subject.? There are some horrible designs on the internet...most of them have vac variables.? I am trying to make a low cost self tuning magloop with solid performance.? I think I can do that (including the electronics) for the cost of a single vac variable cap.? I would think this would interest someone who writes about stealth antennas.?
Teflon is not lossy in rf.? What material beats it?? Polystyrene?? Not much else. ?
The loop I'm making I also intend to use indoors, it is not meant to be used permanently mounted outside. ?
This map I show below were confirmed receipts yesterday of my 0.2W transmission from the loop in the picture sitting where the picture was taken...on my kitchen table.? I have reached hawaii and europe from that table using 0.2 watts on other days. ? No whip antenna would do that...feel free to try and let us know how it works out.
<Screen Shot 2019-12-21 at 1.36.55 PM.png>
Kurt-ae6uj ???
On Sun, Dec 22, 2019 at 11:08 PM Kirk Kleinschmidt via Groups.Io <sohosources= [email protected]> wrote: Sorry, Kurt,
A "daily driver" is an antenna that stays in service for long periods of time and is used daily (as opposed to something whipped together for one reason or another). It's a motor vehicle reference. I guess I'm getting old!
The Teflon data I'm remembering is/was in the mag loop archives when everything was hosted on Yahoo Groups (may now be at groups,io?). I don't have access right now, as I'm traveling, but perhaps someone else is on both lists who might?
Because of the unusual electric and magnetic properties encountered by mag loop materials (30,000 V at 30 amps, anyone?), almost nothing other than vacuum and air variables with no physical contacts (butterfly caps) emerges as stable and non-lossy.
These and many additional materials have been tested over the past 50 years, not just by hams, but by the military and commercial companies developing the mag loops are related stuff.
Leigh, VK5KLT, who has been intimately involved in military and commercial mag loop design (and the underlying science) for the past 50 years, is an accessible and approachable authority on all details of materials, feeding and construction. He's a regular on the Mag Loop list, and his papers are available on the web. He emails, too.
What does Lee say about Teflon? He says that vacuum and butterfly caps are better. :)? Good enough for me.
I have worked up various trombone/Teflon approaches over the years, but after I studied a lot more I set them aside.
In short, it works, but it's not ideal.
Also, if I'm remembering the photo correctly, you may have had some wires running up one side of the mag loop from bottom to top? Consider centering these on the main axis of the loop, as maintaining loop balance can also be critical (hence the practice of splitting the loop down the center when running wires, installing motors and caps, etc). With massive circulating currents on the loop, objects that are closer to one side of the loop than the other can mess things up. The same goes for items in the environment (wires, trees dog houses, cars, air conditioners, etc).
Regards,
--Kirk, NT0Z
My book, "Stealth Amateur Radio," is now available from
and on the Amazon Kindle (soon)
On Sunday, December 22, 2019, 10:36:30 PM CST, Kurt Loken < kurt.loken@...> wrote:
What do you mean by ¡°daily drivers?¡± ?Can you also share some data that Teflon is lossy at rf?
Thanks for the help.
Kurt? On Dec 22, 2019, at 9:26 PM, Kirk Kleinschmidt via Groups.Io <sohosources=[email protected]> wrote:
? Historically, Teflon hasn't been suitable for "daily drivers" over time, whether trombones or otherwise. It's fine for proof of concept, but it's far from ideal and it's lossy at RF. Not when used in "regular" antennas, but in magnetic loops, which are a whole nother breed.
What's been proven ideal? Vacuum and butterfly. That's pretty much it.
If you just want to crank out a "foxhole" loop, why not simply solder a short length or RG-8 coax (not foam dielectric, but the hard stuff) to the loop ends and cut the cable until the SWR analyzer says it's resonating on your chosen frequency? True, resonance moves around a bit with heat and humidity, but for single-frequency work it has been successfully used. And at 20 meters and up you'll have a few kHz of resonance to play around in.
I'm not trying to stifle innovation, but as an experienced mag loop builder and user (30 years now), I know that all of the things you're noodling around with have been tried before. The mag loop groups have treasure troves that detail what works and what doesn't. And of course, Youtube is filled with "revolutionary" loops that "work" after a fashion but absolutely don't work anywhere near as well as they could.
It takes about the same amount of farting around to make a mag loop that "works" as it does to use proven methods that are known to "work well" or define the state of the art.
Vacuum and Butterfly. Sounds like a country song! Or a mantra.
BTW, if you want an awesome autotuner designed for mag loops, complete with global temperature compensation, CAT and SWR inputs, and lots of other goodies, check out Loftur's masterpiece at:
Best of luck,
--Kirk, NT0Z
My book, "Stealth Amateur Radio," is now available from
and on the Amazon Kindle (soon)
On Sunday, December 22, 2019, 5:54:16 PM CST, Jerry Gaffke via Groups.Io <jgaffke= [email protected]> wrote:
Yes, if bandwidth is maybe 10khz, mechanical stability will be a real concern. My laminate thing, like a lot of mag loops I see, could be a bit floppy. But perhaps an advantage, distort the circular shape to tune it? Another thought about tuning, similar to a book cap, but uses FR4 board warping as a hinge: Have two PCB's perhaps 2" x 12" of one sided copper, 3 inches of copper removed from one end of each. The copper foil ends solder to each of the two PCB's at the ends that still have copper. Place one board over the other with teflon in between with copper facing copper, the 3" of removed copper on opposite ends. Two screws through one end hold them together firmly, the teflon well compressed here. The other end has some sort of screw with spring arrangement to adjust the distance between the two boards there If this is part of my foil on laminate antenna, could separate the two boards by removing those screws when coiling the antenna up tight for transport. nanoVNA here, but not yet dangerous with it.? Touch part of touch screen not working. Need to spend a full day just figuring out the menu, or get NanoVNA-Saver going. Also an AQRP VIA. Agree on needing something more than a DVM. Jerry On Sun, Dec 22, 2019 at 02:42 PM, Kurt Loken wrote:
The stability issue is real and controlling overlap with a motor is a challenge of engineering in and of itself. For myself I consider it a challenge and part of the fun.
Also...I have really come to believe that I don¡¯t know how anyone builds a magloop or experiments with them without a proper antenna analyzer. I would be lost without mine. Not sure if you have one, but they make experimenting easier.
<Screen Shot 2019-12-21 at 1.36.55 PM.png>
|
I get it. I'm not trying to stifle experimentation. I simply want to steer you toward the best resources.
Self-resonant mag loops made from strap (where the insulated ends overlap to provide the C to the loop's L), work best at VHF, where the high Q of the antenna still provides enough low-SWR bandwidth around the resonance point to minimize the effects of insulation-induced instabilities (temperature and humidity effects, too).
At 160 and 80 meters, however, when bandwidths are 3-5 kHz, more stable materials are beneficial or necessary.
Using WSPR to reference/define antenna performance is somewhat moot unless all you want to do is WSPR, at which point making a useful antenna becomes 40-dB "easier" than if you're trying to make an antenna that will be used for more conversational or more conventional modes. I congratulate you, but working DX via WSPR with any mag loop, even indoors or in the basement, is the norm and not the exception. If you run the numbers regarding propagation path loss, antenna gain, and the sensitivity of the WSPR demodulation process, you'll see that those distances are expected and on track. To make those QSOs via SSB, CW, or even PSK-31 takes a better-performing antenna/mag loop or more RF power, but it is still doable, even indoors. Many mag loop users, myself included, have made ocean-hopping SSB QSOs with mag loops sitting on the kitchen table while running QRP (5-10 W PEP) Again, scaling the numbers for power and the efficiency of the WSPR decoder, the events are approximately equivalent.
I don't know how to remove posted pix. Maybe it's not even possible.
Regardless, I'm just having a conversation here, so don't let me get in your way. I think what you're doing is fantastic. I have been doing my best to steer you toward the best methods and materials, but personal experimentation always earns my respect. Other readers, perhaps lacking your skills and determination, may want to know about what experts and experimenters have already discovered about how to make top-performing mag loops and mag loop autotuners. I have provided those links and references as part of our conversation.
Regards,
--Kirk, NT0Z ? Rochester, MN
My book, "Stealth Amateur Radio," is now available from
www.stealthamateur.com and on the Amazon Kindle (soon)
On Monday, December 23, 2019, 12:05:52 AM CST, Kurt Loken <kurt.loken@...> wrote:
Hello Kirk,
I think you might not be seeing what you think you are seeing.? I really made a big mistake posting here.? I wish I could delete my picture.? If anyone reading this knows how to delete photos from the group here, I would appreciate?help at making it so.? You get working on something and you want to share...but I'm not ready to share this stuff yet. ?
That "wire" on the side isn't a wire at all...it isn't what you think it is.? It will have zero effect on the loop...I guarantee it.? It is teflon and plastic not metal. ? There is NO METAL above the feed point other than those temporary push to fit connectors in the 3D printed cap.?
There are many choices that go into a design and one of them is cost.? Yes, a vacuum variable cannot be beat...though all the soldering of connections and all the peripherals (motors, shafts, etc.) that people seem to think are okay to put around them might lead to a debate on that subject.? There are some horrible designs on the internet...most of them have vac variables.? I am trying to make a low cost self tuning magloop with solid performance.? I think I can do that (including the electronics) for the cost of a single vac variable cap.? I would think this would interest someone who writes about stealth antennas.?
Teflon is not lossy in rf.? What material beats it?? Polystyrene?? Not much else. ?
The loop I'm making I also intend to use indoors, it is not meant to be used permanently mounted outside. ?
This map I show below were confirmed receipts yesterday of my 0.2W transmission from the loop in the picture sitting where the picture was taken...on my kitchen table.? I have reached hawaii and europe from that table using 0.2 watts on other days. ? No whip antenna would do that...feel free to try and let us know how it works out.
Kurt-ae6uj ???
On Sun, Dec 22, 2019 at 11:08 PM Kirk Kleinschmidt via Groups.Io <sohosources= [email protected]> wrote: Sorry, Kurt,
A "daily driver" is an antenna that stays in service for long periods of time and is used daily (as opposed to something whipped together for one reason or another). It's a motor vehicle reference. I guess I'm getting old!
The Teflon data I'm remembering is/was in the mag loop archives when everything was hosted on Yahoo Groups (may now be at groups,io?). I don't have access right now, as I'm traveling, but perhaps someone else is on both lists who might?
Because of the unusual electric and magnetic properties encountered by mag loop materials (30,000 V at 30 amps, anyone?), almost nothing other than vacuum and air variables with no physical contacts (butterfly caps) emerges as stable and non-lossy.
These and many additional materials have been tested over the past 50 years, not just by hams, but by the military and commercial companies developing the mag loops are related stuff.
Leigh, VK5KLT, who has been intimately involved in military and commercial mag loop design (and the underlying science) for the past 50 years, is an accessible and approachable authority on all details of materials, feeding and construction. He's a regular on the Mag Loop list, and his papers are available on the web. He emails, too.
What does Lee say about Teflon? He says that vacuum and butterfly caps are better. :)? Good enough for me.
I have worked up various trombone/Teflon approaches over the years, but after I studied a lot more I set them aside.
In short, it works, but it's not ideal.
Also, if I'm remembering the photo correctly, you may have had some wires running up one side of the mag loop from bottom to top? Consider centering these on the main axis of the loop, as maintaining loop balance can also be critical (hence the practice of splitting the loop down the center when running wires, installing motors and caps, etc). With massive circulating currents on the loop, objects that are closer to one side of the loop than the other can mess things up. The same goes for items in the environment (wires, trees dog houses, cars, air conditioners, etc).
Regards,
--Kirk, NT0Z
My book, "Stealth Amateur Radio," is now available from
and on the Amazon Kindle (soon)
On Sunday, December 22, 2019, 10:36:30 PM CST, Kurt Loken < kurt.loken@...> wrote:
What do you mean by ¡°daily drivers?¡± ?Can you also share some data that Teflon is lossy at rf?
Thanks for the help.
Kurt? On Dec 22, 2019, at 9:26 PM, Kirk Kleinschmidt via Groups.Io <sohosources=[email protected]> wrote:
? Historically, Teflon hasn't been suitable for "daily drivers" over time, whether trombones or otherwise. It's fine for proof of concept, but it's far from ideal and it's lossy at RF. Not when used in "regular" antennas, but in magnetic loops, which are a whole nother breed.
What's been proven ideal? Vacuum and butterfly. That's pretty much it.
If you just want to crank out a "foxhole" loop, why not simply solder a short length or RG-8 coax (not foam dielectric, but the hard stuff) to the loop ends and cut the cable until the SWR analyzer says it's resonating on your chosen frequency? True, resonance moves around a bit with heat and humidity, but for single-frequency work it has been successfully used. And at 20 meters and up you'll have a few kHz of resonance to play around in.
I'm not trying to stifle innovation, but as an experienced mag loop builder and user (30 years now), I know that all of the things you're noodling around with have been tried before. The mag loop groups have treasure troves that detail what works and what doesn't. And of course, Youtube is filled with "revolutionary" loops that "work" after a fashion but absolutely don't work anywhere near as well as they could.
It takes about the same amount of farting around to make a mag loop that "works" as it does to use proven methods that are known to "work well" or define the state of the art.
Vacuum and Butterfly. Sounds like a country song! Or a mantra.
BTW, if you want an awesome autotuner designed for mag loops, complete with global temperature compensation, CAT and SWR inputs, and lots of other goodies, check out Loftur's masterpiece at:
Best of luck,
--Kirk, NT0Z
My book, "Stealth Amateur Radio," is now available from
and on the Amazon Kindle (soon)
On Sunday, December 22, 2019, 5:54:16 PM CST, Jerry Gaffke via Groups.Io <jgaffke= [email protected]> wrote:
Yes, if bandwidth is maybe 10khz, mechanical stability will be a real concern. My laminate thing, like a lot of mag loops I see, could be a bit floppy. But perhaps an advantage, distort the circular shape to tune it? Another thought about tuning, similar to a book cap, but uses FR4 board warping as a hinge: Have two PCB's perhaps 2" x 12" of one sided copper, 3 inches of copper removed from one end of each. The copper foil ends solder to each of the two PCB's at the ends that still have copper. Place one board over the other with teflon in between with copper facing copper, the 3" of removed copper on opposite ends. Two screws through one end hold them together firmly, the teflon well compressed here. The other end has some sort of screw with spring arrangement to adjust the distance between the two boards there If this is part of my foil on laminate antenna, could separate the two boards by removing those screws when coiling the antenna up tight for transport. nanoVNA here, but not yet dangerous with it.? Touch part of touch screen not working. Need to spend a full day just figuring out the menu, or get NanoVNA-Saver going. Also an AQRP VIA. Agree on needing something more than a DVM. Jerry On Sun, Dec 22, 2019 at 02:42 PM, Kurt Loken wrote:
The stability issue is real and controlling overlap with a motor is a challenge of engineering in and of itself. For myself I consider it a challenge and part of the fun.
Also...I have really come to believe that I don¡¯t know how anyone builds a magloop or experiments with them without a proper antenna analyzer. I would be lost without mine. Not sure if you have one, but they make experimenting easier.
|
Kirk Kleinschmidt, NT0Z
Shirley Dulcey KE1L