What are the typical wire gauges used for winding RF coils ?

[lordvader88]

I want to order solid copper wire for making various RF coils. And I only have 24AWG and something a bit thinner from a CRT TV yoke. I have lots of 12AWG too, so far tonight I have't gotten that working in a Colpits oscillator I made.

What are the most common sizes I should order for making typical RF stuff, AM radio and up to VHF/UHF ?

[cdev]

Frankly, you sound like you've got it covered. For some applications you might want to use enameled wire so you can wrap it closely. And for VHF and UHF especially, coils will be much smaller.

Since you mentioned AM radio lets assume you are talking about MW and HF receive applications. See the links below.

For a receiver wire size can be small but different kinds of wire effect the capacitance between turns and so will impact the self resonant frequency. Also wire size impacts the "Q" factor.

For some kinds of applications, high Q is very desirable. Basically Q is sort of the inverse of lost energy.

The more conductive the metal is the better but the crucial region is the skin of the wire. So, the highest Q will be attained if the wire is silver plated. The wider the wire and also the wider the diameter of the coil the more inductance and Q, but because of the skin effect, tubing works as well (better by weight) than solid wire. Also, copper tape in a helical winding works really well.


There is also wire "litz wire" that uses multiple independent conductors, it has very good characteristics for RF coils at MW and low HF. It's kind of a woven wire.

Also - there are web pages where different kinds of wire (and insulated wire) are compared. Some kinds of insulation are really undesirable. 

I have some (old) insulated solid wire that is not very good as RF inductors, its clearly because of the insulation because when I remove it it works fine.

Here, this is very very good:

http://www.g3ynh.info/zdocs/comps/part_1.html

http://www.g3ynh.info/zdocs/comps/part_2.html

Also very very good

http://hamwaves.com/coils/en/



http://www.g3ynh.info/zdocs/comps/index.html

[lordvader88]

what wire gauges do people keep on hand for this ?

[cdev]

Solid wire is what I have always used for HF experiments, filters, preselectors. Solid copper wire. But as I said, silver plated wire would be better. There is some product you can use to cheaply plate copper wire, I've always meant to get some.  Because of the skin effect, it doesnt need to be solid silver. Silver plating wire works just as well. Tubing such as refrigeration tubing, might be better.

See Jeri Ellsworth's magnetic loop video (part 1) on YouTube for an example of a practical use of this knowledge (wide wire can develop higher Q).

Also, tape, copper tape, for example, can work really well in inductors. Its both wide and has a low inter turn capacitance for its surface area. (but what is the optimal winding angle and distance?)


See the links I added above.

what wire gauges do people keep on hand for this ?

[ahbushnell]

Solid wire is what I have always used for HF experiments, filters, preselectors. Solid copper wire. But as I said, silver plated wire would be better. There is some product you can use to cheaply plate copper wire, I've always meant to get some.  Because of the skin effect, it doesnt need to be solid silver. Silver plating wire works just as well. Tubing such as refrigeration tubing, might be better.

See Jeri Ellsworth's magnetic loop video (part 1) on YouTube for an example of a practical use of this knowledge (wide wire can develop higher Q).

Also, tape, copper tape, for example, can work really well in inductors. Its both wide and has a low inter turn capacitance for its surface area. (but what is the optimal winding angle and distance?)


See the links I added above.

what wire gauges do people keep on hand for this ?

Try Litz wire. 

[David Hess]

For free standing RF coils, I usually end up with a minimum wire size determined by the need for mechanical strength.

[cdev]

"Doh" the simple answer to silver plating things is *damn* silver plating them!

Why didn't I think of that! God, I can be awfully dumb sometimes.

I am actually completely set up for it, could dial in a voltage and current, even a low one with my bench supply.

My mom used to do artwork and one of the things she did in her art involved an electroplating process.. she actually got the idea from the nine or ten year old me.

But I haven't done it in years. And Ive never done it with silver. But it would definitely be the thing to do to get high-Q coils.

I know silver is expensive, so if I did it, I would want to both get the right kind and not waste any of it in the solution.

I will have to look into this.

People should check out this URL
http://hamwaves.com/coils/en/

This web page details how to make really gorgeous RF coils - ones which would likely cost an arm and a leg if you bought them today.

[lordvader88]

What is a typical gauge wire inside a like PCB mount RF can like a 455kHz IF trans, it's like fine hair size. Do people try winding them at home, and do they work ? I have a few of those 5 pin cans w/ferrite cores, that are blanks (I can wind them myself into whatever)

[SeanB]

Those normally use 36 or 48SWG wire, some of them use Litz wire for the lower skin loss, but that is getting kind of hard to find these days.

[ahbushnell]

Those normally use 36 or 48SWG wire, some of them use Litz wire for the lower skin loss, but that is getting kind of hard to find these days.

Litz wire is still sold.  It's used in power electronics. 

https://www.newenglandwire.com/en/products/litz-wire-and-formed-cables

[SeanB]

Power yes, but try getting it in the thin gauges these formers will fit, there the individual wires are often 60SWG, about as thick as a fine hair.

[ahbushnell]

http://www.hanssummers.com/ift.html

There are links to home made IF transformers here that might be helpful.