Re: loop material question
John, there is nothing wrong with flat material....except dimensional stability and wind loading.? Even for TX, people have used aluminum flashing to build loops (look up "midnight loop").? It's appealing because no special roller dies or welding/soldering are needed.? Maybe there is a small increase in AC resistance (relative to the same width rolled into a tube) due to proximity effects, but this would probably be small even for a TX loop and completely insignificant for RX as others have pointed out.? If you really want to use sheet stock and can form it into a "U" cross-section, or something similar, for mechanical stability, you'd probably be happier with the overall result.
?
Dan - K3GMQ
?
|
Re: loop material question
So the loop would resemble something like . The antenna in the picture is horizontally mounted but can be mounted vertically as well. There are manuals on the web as the Isoloop has not been manufactured in decades. Tubing gives a bit more structural regidity but there is no reason why a flat strip of the proper type of metal cannot work as long as properly supported.
73, kevin kc6pob
On Monday, January 13, 2025 at 05:24:08 PM PST, Superlite via groups.io <superlite17@...> wrote:
It would be left flat. Not tubular. So it would be a circle of 6” wide copper sheet I have a lot of scrap laying around. Mainly my question is does the element need to be round. ?My loop would be more like a tunnel I suppose. Instead of using tubular material I’m going to use flat metal. Wondering how wide would be too wide. I’m pretty much unlimited in the diameter I could make it. Was thinking about staying at 1m-1.5m diameter.?
|
Re: loop material question
It would be left flat. Not tubular. So it would be a circle of 6” wide copper sheet I have a lot of scrap laying around. Mainly my question is does the element need to be round. ?My loop would be more like a tunnel I suppose. Instead of using tubular material I’m going to use flat metal. Wondering how wide would be too wide. I’m pretty much unlimited in the diameter I could make it. Was thinking about staying at 1m-1.5m diameter.?
|
Re: loop material question
Just wondering if using a sheet of material and rolling your own tube would really be any cheaper or provide any significant benefit over just using readily available copper water tubing available at big box stores for like 20 dollars? Or aluminum fuel tubing? (Not sure of the cost)
?
Tom
?
|
Re: loop material question
wow, thanks for all of the replies.?
yes. I could use 16 or 20oz copper sheet or .032 aluminum.?
I see many people modify existing loops to use copper pipe. Is it necessary to use a round material? Does the cross section of the loop material matter on a rx only loop??
|
Re: loop material question
A circle encloses the
largest area for a given length of material, so the largest
received signal. Loops made of wire are generally square for the
simplest support structure. Loops made of tubing can be
self-supporting and are often squares or octagons using 90 or 45
degree elbows to avoid having to bend tubing.? With a metal
shop, you are pretty much unlimited.
On 1/13/2025 4:47 AM, Simon via
groups.io wrote:
toggle quoted message
Show quoted text
Hi
Welcome.
We need much more info on what you intend to make before advice can be reliably given.
Ie.. active pre amped no tune loop antenna,( ie lz1aq type,) high q tuned? Dia of loop, frequencies of interest etc etc.
However, in general there is no such thing as too big a tube diameter.( dia of tube not loop.) Its usually limited by what you have/ can get/ bend/ not worth the effort due to no real world gains, etc.
A name to call you?
Regards Simon g0zen
|
Re: loop material question
It is generally accepted that copper and aluminum are very good conductors of RF currents...
Maybe Dave missed that message & assumed the OP was referring to sheet steel or tin. Regardless, for a Rx antenna, it is of little consequence.
|
Re: loop material question
I'll contribute with my additional question (ouch):
?
When the thing is a small NON-resonant magnetic loop, for RX-only... is the loop material thickness meaningful?
?
73, Jukka
|
Re: loop material question
?
?Hi Dave
John said rx only.
Dave , at time of my reply where I said bigger the better no frequency was specified..ie if was for vlf then all good etc. obvs if for hf then there is a limit along with dia of loop. Thats why I asked for more info.
Regards Simon
|
Re: loop material question
Not to the point of conductor diameter, but one of my reservations using sheet metal.? Considering a mag loop must support large RF currents, I'd be a bit hesitant to use sheet metal.? It is not a particularly good DC conductor which indicates it is not a good conductor of RF currents.? Since skin depth depends on resistance of a material at frequency, a bad conductor is bound to introduce more I^2 x R losses.? Since the mag loop configuration is roughly 15 to 20 dB below a full sized dipole at the same frequency and identical physical surrounds, I'd be cautious of introducing any more loss.
Just my take on your proposal.
Dave - W?LEV
Thanks by the way. Forgot to add that in my reply ??♂??
John is my name.?
|
Re: loop material question
Thanks by the way. Forgot to add that in my reply ??♂??
John is my name.?
|
Re: loop material question
currently using an mla30+, I am incapable of not tinkering.?
pre amped, probably will use LZA1Q but wouldn’t mind something stateside.?
?
Possibly tuned with dual gang capacitor.?
?
really my question is can I use sheet metal instead of tubing? I have a sheet metal shop and access to copper and or aluminum sheet and coil. If we are looking for the lowest inductance would for eg a 1m diameter loop made from 6” wide copper be acceptable??
|
Re: loop material question
On Mon, Jan 13, 2025 at 12:47 PM, Simon wrote:
However, in general there is no such thing as too big a tube diameter.
Hi, Simon
A thicker tube diameter causes a higher loop capacitance and therefore has an impact on the self-resonance frequency of the loop.
?
regards, Fred
|
Re: loop material question
Hi
Welcome.
We need much more info on what you intend to make before advice can be reliably given.
Ie.. active pre amped no tune loop antenna,( ie lz1aq type,) high q tuned? Dia of loop, frequencies of interest etc etc.
However, in general there is no such thing as too big a tube diameter.( dia of tube not loop.) Its usually limited by what you have/ can get/ bend/ not worth the effort due to no real world gains, etc.
A name to call you?
Regards Simon g0zen
|
Hello,
lots of great info here. I am new to the group IO format, just created an account. I have been paging through the topics and tags but I cannot seem to find anything that deals directly with the shape of the loop material. I have been debating building an upgraded receive only loop. I see most loops are made of round material, either tubing, wire, coax etc.. i am wondering if using sheet metal cut to a certain width then passed though a 3 pin roller to achieve the correct diameter would be OK? The 3 pin can also take up to 3/8" solid or hollow round stock. How wide would be too wide??
?
Thanks a lot
?
|
Re: Items that may be of interest to some
Le samedi 11 janvier 2025 à 11h06, Everett N4CY a écrit :
Happy New Year 2025 Everett
Thank you for your new document and for all your information and advice disclosed on this group
Best regards
Bernard
?
|
Items that may be of interest to some
I have attached a link the has information on some of the items that I have designed that may be of interest to the group that will enhance your listening experience on the bands.
?
Everett N4CY?
?
?
https://www.icloud.com/iclouddrive/05098Uoz4s1Mo19gRTsehNv7g#Offerings_of_N4CY
|
Re: AlexTune: max brightness != lowest SWR?
There could be many explanations for this, but I'll offer a few of the more likely ones.
?
It may simply be that your loop is not a 50 ohm match, and when tuned for "maximum smoke", the actual input impedance is something other than 50 ohms.
?
The Alextune is basically a simple RF "sniffer", and the nearby E-Field energises a LED, which glows more brightly as the RF field strength increases.
?
I think the W2LI magnetic loop antenna is a slightly different design to the Alex loop, in that it uses two capacitors in what is often called a "Navy Match" and it doesn't use a separate feed loop.
?
As a result, the RF field around the tuning box may not be entirely produced by radiation from the loop itself, and some of it may be from the internal wiring. Therefore, the localised E-Field, where the Alextune is attached, may not correspond to maximum radiation in the far field. I note that some versions of the W2LI magnetic loop also have an extra external balun box, which also suggests that here may be some unwanted feeder radiation too, which is not uncommon with many commercial loops. This will also distort the local E-Field around the antenna.
?
If you are feeding the loop via a length of coax. The SWR you observe at the radio end, may not be the same as the SWR at the interface between the coax and the loop. If you tune the loop for best match at the radio end, it may well be something different at the loop, but as long as the radio is happy with the match, the SWR protection shouldn't kick in, and the radio should be producing it's maximum output power. However, modern transmitters don't have a 50 ohm output impedance, but they are designed to deliver as much power as possible to a 50 ohm load, as long as the output voltage and current don't exceed the rated limits of the PA devices. As a result, they can sometimes be "fooled" into producing more output into something that is not an exact 50 ohm resistive load, but one has some reactance present.
?
I hope this helps.
?
Martin
|
Re: A link with will show items that might be of interest
Glads,
Thanks, now I will have to figure this out.?
On Saturday, January 11, 2025, 11:32 AM, Gedas via groups.io <w8bya@...> wrote:
you need to grant
access to everyone
Gedas, W8BYA EN70JT
Light travels faster than sound.....
This is why some people appear bright until you hear them speak.
On 1/11/2025 11:59 AM, Everett N4CY via
groups.io wrote:
I have attached a link the has
information on some of the items that I have designed that
may be of interest to the group that will enhance your
listening experience on the bands.
?
Everett N4CY
?
|
Re: A link with will show items that might be of interest
you need to grant
access to everyone
Gedas, W8BYA EN70JT
Light travels faster than sound.....
This is why some people appear bright until you hear them speak.
On 1/11/2025 11:59 AM, Everett N4CY via
groups.io wrote:
toggle quoted message
Show quoted text
I have attached a link the has
information on some of the items that I have designed that
may be of interest to the group that will enhance your
listening experience on the bands.
?
Everett N4CY
?
|
Superlite
Robin Midgett
Everett N4CY