magnetic loop antennas
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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... ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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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/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Bill Blomgren
Loop can work well in an apartment.
Good to know what is in/behind walls if possible. Voltages and field strengths can be very high so care is in order. Resistance in loop increases losses. With respect to copper versus less expansive materials. You get what you pay for. 73 es GL KL7JT On May 20, 2013, at 9:43 PM, "Bill Blomgren" <[hidden email]> 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... > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Bill Blomgren
Hello,
I built one that works great for 40 & 30m: http://radiopreppers.com/index.php/topic,180.0.html Gil. -- PGP Key: http://keskydee.com/gil.asc On May 20, 2013, at 9:43 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. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Vic Rosenthal
You can use thick coax with PL-159/SO-239 connectors…
This way your loop is packable. Gil. -- PGP Key: http://keskydee.com/gil.asc On May 20, 2013, at 11:05 PM, Walter Underwood wrote: > Some people use 1/4 inch flexible copper tubing ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: magnetic loop antennas
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In reply to this post by Vic Rosenthal
You can just use heliax. Works perfect.
Dr. William J. Schmidt - K9HZ / J68HZ/ 8P6HK/ ZF2HZ Owner - Operator Big Signal Ranch Staunton, Illinois email: [hidden email] -----Original Message----- From: [hidden email] [mailto:[hidden email]] On Behalf Of Vic K2VCO Sent: Monday, May 20, 2013 9:07 PM To: [hidden email] 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/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Bill Blomgren
Hi
I live in an apartment (temporary) and built a 36" diameter magnetic loop with a vacuum variable capacitor bought off eBay, tuned by a motor drive. It is optimized for 20 and 17 meters, but works well on all bands from 40 to 10 meters (this really depends on the capacitance range) It tunes to a low SWR on my KX3 and works very well outside, clear of the building. But on the apartment balcony the performance is poor, as it is too close to rebar in the concrete framing and the steel mesh in the stucco walls Roger NZ6RQ / ZL2BHW -----Original Message----- From: Bill Blomgren [mailto:[hidden email]] Sent: Monday, May 20, 2013 6:43 PM To: [hidden email] Subject: [Elecraft] magnetic loop antennas 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... ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Bill Blomgren
An alternative is to use a length of 1/2-inch Heliax using only the
outer shield. This stuff it pretty easy to find at hamfests and much cheaper than the copper in it. I plan to make a 6-foot loop with some (someday). I have an old U100 rotator that could rotate it on a ten foot pole. 73, Ed - KL7UW ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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