[Elecraft] magnetic loop antennas

[Walter Underwood]

Some people use 1/4 inch flexible copper tubing, the kind you use to hook up the icemaker on a refrigerator. You can hammer the ends flat, drill a hole, and connect them. It is about $1/foot and reasonably self-supporting. 

This appnote at MFJ has some good information on DIY loops:

http://www.mfjenterprises.com/antennatalk6.php

wunder
K6WRU

On May 20, 2013, at 7:31 PM, Ron D'Eau Claire wrote:

> As an alternative to copper pipe, you might consider copper foil. RF flows
> along the surface of the conductor so it matters little how thick it is. You
> might take something like PVC tubing, form it into the required loop, and
> cover it with copper foil. Just be sure you use a single piece so you don't
> have to "splice" it anywhere around the loop that would require the RF
> currents to cross the splice. You might get away with a soldered seam
> running all the way around the loop but I suspect the solder wouldn't do
> anything. Just be sure the copper overlaps along the edge. Use tape or
> ty-wraps to secure the copper. 
> 
> Next to the ohmic losses in the loop itself, the majority of losses in loops
> is in the junctions connecting the loop to the capacitor and in the
> capacitor itself if it has a sliding contact to the rotor.
> 
> 73, Ron AC7AC
> 
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Vic K2VCO
> Sent: Monday, May 20, 2013 7:07 PM
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] magnetic loop antennas
> 
> I googled 'flexible conduit' and what I see looks like BX cable -- made out
> of a single flat piece of metal wrapped in a spiral shape. If this is what
> you are talking about, it would be AWFUL for this purpose -- it would have a
> very high RF resistance and so be very inefficient. There are very high
> currents in the loop and you have to keep the resistance at RF as low as
> possible -- that's why large-diameter copper tubing is good.
> 
> Do you have a link to a picture of the stuff you are looking at?
> 
> On 5/20/2013 6:43 PM, Bill Blomgren wrote:
>> I saw the great writeup on the magnetic loop antenna and the inventive 
>> High Voltage capacitor for tuning the thing. I'm looking at one of 
>> them strictly because I'm stuck in an apartment.
>> 
>> The fact it should be good for 100 watts is perfect for what I'm looking
> at buying.
>> 
>> I'm just wondering about the copper pipe used for the outer loop... I 
>> spotted some very reasonably priced flexible conduit that could be 
>> used for the "loop" proper.  Do what is necessary to bond the 
>> capacitor into the rig, and it would appear to be a reasonable 
>> alternative to the rather pricy copper pipe. (They want your first born
> here for that, and the thieves are busy collecting anything that isn't
> nailed down.
>> 
>> Thoughts on that for its larger diameter, which should help with the 
>> coupling to the rest of the world...
> 
> --
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco/
>