Thanks for your replies, I'll find some suitable pipe and post back with progress/pics/results. :)
It was pointed out to me that my test loop is actually a full wave loop on 10m, so its not in magnetic loop territory yet. There's a capacitor on its way so hopefully will be able to get it into magnetic loop mode and see how well the noise is suppressed.
ab1ga .. thanks for the pointers in the right direction
Last edited by mw0uzo; 03-31-2011 at 04:28 PM.
I've started using self-adhesive copper tape on fibreglass rods to keep the weight and cost down. Some of the rods were salvaged from a burnt-down frame tent that someone abandoned. 8mm and 10mm rods or tubes are useful because you can still use soldered plumbing fittings to join them.
The tape was widely sold for slug deterrent but it's cheaper to buy from the internet.
Yeah I've seen the copper tape trick, did you post a thread about it a while ago?
I nabbed some manky but thick coax the other day for making a better loop. I'm going to make it smaller this time for portable use, with a faraday loop.
For the high voltage capacitor for the larger version, I've got some glass and copped clad board that I'm going to turn into a variable capacitor. Two pieces of copper clad at 20cmx20cm will be around 1000pF, with one plate mounted on a screw thread for adjustment.
I built a mag loop using copper tubing, but for receiving only. I used a capacitor from an old Hammarlund s-38 and a small stepper motor to adjust it remotely. Worked OK, never got around to build one to xmit.
Is there a page that has a magnetic loop calculator?
Here's one, a collection of generally good stuff, but some of the codes were written by someone who is now an SK, so probably not kept current with current versions of OS/Browser, etc:Originally Posted by KG4CGC
http://www.smeter.net/antennas/single-turn-loop.php
Thanks. I used to check out that site a lot.
Fed up trying to find decent capacitors, I dismantled my manual ATU. I changed the loop material to a 4.7m circumference of RG-213 coax and got rid of the gamma match and used an unshielded Faraday loop. Two of the variable capacitors in parallel got it resonant on 80m. I can now hear stations clearly when before they were completely swamped in noise and inaudible. There is still quite a lot of noise however, approx S7.
Further improvement expected to improve RX S/N further is use of a shielded Faraday loop. Not tested on TX yet - a further version made from large diameter copper tube is likely necessary as well as a custom made butterfly capacitor and motor drive for convenient use and 100w of handling power.
It really is quite surprising, the S/N improvement over a wire dipole. Its not the holy grail, but it is significantly improved. (YAY!)
Excellent! Could you possibly include some pictures? Visuals help. :)
Yeah - I'll take some photos today.
Noise is so strong here that the small unshielded faraday loop of 96cm circ. removed from the main loop picks up s2 to s3 of noise! :o
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