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OT:Tube Regenerative Receiver 12SN7/12V6

 

Awhile ago, when the regenrx yahoo group was active, I built several different iterations of regenerative receiver on the same small chassis.? It started as a twinplex, then changed to a 6SJ7 detector / 6SN7 dual audio amp, then the version it is now.? The problem is I can't remember or find the article it came from.? It uses a both sections of a 12SN7 as a regen detector/Audio preamp and the 12V6 as an audio amplifier.?? It has an audio output transformer but no interstage choke.? The original used 6 volt filaments but I used 12 so could power from the shack 13.8 PS.

Anyway, after pulling the radio off of the shelf, was listening for awhile.? It tunes about 7-10 Mhz and receives AM, Sideband, and CW pretty well.? Appreciate if someone can remind me of where got the article to build this one.? Or, point me to a group with folks building tube regenerative receivers.

Curt KB5JO
Re: Magloop prototype

 

Not that I have this all clear in my head.

Even if 90 degrees out of phase, the instantaneous power when current is at -45 degrees and voltage at +45 degrees
is half of your 54.6 kVA.? But 180 degrees later the same level of instantaneous power is moving in the opposite direction.
So there really is a huge amount of power circulating between the inductor and the capacitor.
Do I have that right?

Imagine sending CW with no key shaping, the transmitter goes from 0 watts to 100 watts in a microsecond or less.
How long does it take the mag loop currents to build up to that 54.6 kVA?
And then I assume the mag loop keeps radiating after key up for about the same amount of time.

I may have to kick off LTSpice and see how this really works.
My understanding of resonance more than a little shaky,

Jerry


On Tue, Dec 24, 2019 at 10:29 AM, Jerry Gaffke wrote:
Which is to say that the current and voltage are not both high at the same time.
They are out of phase.
Hide quoted text

?


On Tue, Dec 24, 2019 at 09:16 AM, Nick Kennedy wrote:
Remember that when you multiply the current times the voltage across the capacitor, you are calculating reactive power, not watts.?
?
Re: Magloop prototype

 

Which is to say that the current and voltage are not both high at the same time.
They are out of phase.


On Tue, Dec 24, 2019 at 09:16 AM, Nick Kennedy wrote:
Remember that when you multiply the current times the voltage across the capacitor, you are calculating reactive power, not watts.?
?
Re: Magloop prototype

 

Remember that when you multiply the current times the voltage across the capacitor, you are calculating reactive power, not watts.?

In an example from , take a 10¡¯ circumference loop 0.5¡± in diameter at 14 MHz and 100 W. The loop current is 18.6 A and voltage across the capacitor is 2,967 volts, both RMS. So the reactive power is their product which is 54.6 kVAR (kilo-volts reactive).

In this example, the loss resistance and radiation resistance are about equal at 0.075 and 0.074 ohms for 50% efficiency.

The real power would be I^2 times R or 18.4^2 times 0.149 ohms giving ... 50 W.? Oops, that should be 100 W so something¡¯s off in my thinking or in this calculator.

I do believe it will come out. But Mrs. Santa Claus is calling. To be continued.

73-

Nick, WA5BDU

On Tue, Dec 24, 2019 at 12:45 AM Jerry Gaffke via Groups.Io <jgaffke=[email protected]> wrote:
Got to be the "same place and time" thing.
No way a system that small can contain anything like a megawatt of power.


On Mon, Dec 23, 2019 at 12:17 PM, Jerry Gaffke wrote:
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


On Mon, Dec 23, 2019 at 08:12 AM, Bill Cromwell wrote:

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?
Re: Magloop prototype

 

Got to be the "same place and time" thing.
No way a system that small can contain anything like a megawatt of power.


On Mon, Dec 23, 2019 at 12:17 PM, Jerry Gaffke wrote:
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


On Mon, Dec 23, 2019 at 08:12 AM, Bill Cromwell wrote:

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?
Re: 2n2xx Transceiver R.I.P.

 

I originally wanted to build a?surface-mount version of the 2n2/40,? but after playing around with a surface mount layout using toroids in the mixers, I wasn't getting the size reduction?I was looking for. So I ordered some of the cheaper ADE-1-24 surface mount mixers for a second surface mount version that I may do later, but moved forward with a through-hole version.

This is only the receiver section of the 2n2/40+ schematic and pcb (sans VFO and LO which will be done digitally). I followed the updated iteration of the design (thanks Jerry) that has the Norton amplifier and FET mute circuit. I did not include the audio amplifier. I did the layout on a 100mm x 100mm board and I still have room left, so maybe I'll add the audio amp, or maybe just drop the board size to 100mm x 80mm. I was able to route all the signals on the top layer. The bottom is a complete ground copper pour.? For fun, I included pads for both through-hole Schottky diodes and those tiny surface-mount dual Schottky packages for the mixers. Those should be matched quite well being on the same substrate. I still have a ton of work to do on annotating the silkscreen, plus verifying the board to the schematic.

I ordered a couple of the Nokia 5110 LCD modules for the display. These are extremely low power and should do nicely for a VFO display. I'd like to keep the VFO and micro-controller power under 25mA. I should be able to run the Atmega at 1MHz to keep the power low, plus dump the USB and LEDs.?

Any feedback is appreciated.
Mike M.? KU4QO
Re: Magloop prototype

 

Impressive!
That loop is definitely doing the right thing!

Jerry


On Mon, Dec 23, 2019 at 12:57 PM, Kurt Loken wrote:
My last map I'll post.? This is what I got today at 50mW transmit. ? If I have all my math right...this is equivalent?to about 1 watt CW. ?20 Watts SSB.? I would really like someone to correct me if I'm not using this WSPR stuff right. ?
Re: Magloop prototype

Kurt Loken
 

My last map I'll post.? This is what I got today at 50mW transmit. ? If I have all my math right...this is equivalent?to about 1 watt CW. ?20 Watts SSB.? I would really like someone to correct me if I'm not using this WSPR stuff right. ?


73,

Kurt-ae6uj

On Mon, Dec 23, 2019 at 2:17 PM Jerry Gaffke via Groups.Io <jgaffke=[email protected]> wrote:
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



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
Re: Magloop prototype

 

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



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
Re: Magloop prototype

 

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



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
Re: Magloop prototype

Kurt Loken
 

¿ªÔÆÌåÓý

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



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.??
?
Re: Magloop prototype

 

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.??
?
Re: Elmer 101 SSDftra

 

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?

On Mon, Dec 23, 2019, 12:13 PM Rob via Groups.Io <roomberg=[email protected]> wrote:

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.

Re: Elmer 101 SSDftra

Rob
 

¿ªÔÆÌåÓý

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.

Re: Magloop prototype

Kurt Loken
 

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.
?
Re: Magloop prototype

 

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.
?
Re: Magloop prototype

 

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

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
Re: Magloop prototype

 

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...
Re: Magloop prototype

Kurt Loken
 

¿ªÔÆÌåÓý

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


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
Re: Magloop prototype

 

¿ªÔÆÌåÓý

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
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