Help !!!
I am having problems getting my SGC-237 auto-coupler to tune a horizontal loop on the lower bands. The wire loop is installed around the UPVC gutter of the house. I know this aerial will be a real compromise, but I was led to belive it would at least tune OK on all the HF bands.

My SGC-237 is installed as follows:
My radio (FT847) has about 25m of RG213 coax before it gets to the SGC-237, the coupler is mounted outside under the eves of the roof. For an aerial I have installed a loop consisting of about 38m (125ft) of 2.5mm diameter insulated wire that is zip-tied to the UPVC rain gutter and this runs around the circumference of my house.
If I remove the 12v supply to the coupler but keep it in-line, when I use an SWR analyser the loop is resonant at 19.965MHz with an SWR of 1.1:1, the at 20.260MHz the SWR creeps up to 3:1 and at 19.680MHz I also see an SWR of 3:1. (Does this sound right? where more or less should a loop of 38m be resonant?).

With the tuner powered up as normal it tunes very fast and as expected from 30m (10MHZ) all the way to 6m (50MHz) with no issues at all. However I really want to use the coupler with the same loop on 40, 80 and 160m as well. But on these lower frequencies the coupler just sits there tuning and tuning with no success.

Due to planning problems in my area, I have no choice but to use a stealth type hidden aerial and from what I have read, the SGC-237 should tune from 160m to 6m using a similar loop installed around the UPVC gutter.

Looking forward to any help or ideas for other "All Band" steath aerials etc.

73 de Colin G1IVG

Colin,

Theoretically a 125ft loop should be resonant just below 8MHz. Your "less than ideal" environment will shift that frequency a lot, but not up to 20MHz - that sounds very odd.

I would expect the tuner to cope with the loop on 40m, but 80m or 160m is probably expecting too much.

Have you tried looking for resonance at lower frequencies with your analyser? 20MHz sounds much too high to be the fundamental.

73,
Steve G3TXQ

I've tuned similar loops with my SG-231 with no issues.
It does provide a match at 160m, but of course no spectacular performance.

Email SGC support, they are usually quite helpful.

ive got the sgc-230 its tuned everything ive tried loops,verticals and end feds sometimes u have to trim a few inches to get it tune on all hf bands though.
if that does not work the sgc could be faulty as they should tune nearly anything within in reason.
ive even tried it mobile and it tunes my 9 ft tank whip on all bands from 160-10m wont work well on the lower bands but it does tune up no problem.

Sorry for the delay in my reply. Many thanks for the reply's Steve, Garry and Kevin......

It looks like when the 12v is removed from the coupler it shorts the aerial connection to the ground in the coupler, therefore when I used my MFJ-249 with the 12v removed I got the crazy 19.9MHz reading.

In the end I had a good read on one of the Yahoo Groups and decided to have a good luck inside the coupler. The RF sensing diodes are prone to blow if you tend to run high power during the tune process. It was suggested that I should replace all of the SMD diodes D1 through to D9 in the SGC-237 and I did this earlier this week and the loop now obtains a low SWR from 6m down to 80m with quick tuneup and no problems. I still can't get it to tune on 160m but I'm not too bothered about loosing just one band. I may have a go at adding a large coil in the loop over the summer to see if that helps.

I'm going to run it on 5w on WSPR on Saturday on 10MHz and see who can hear me.

Once again thanks for those who helped me with this.

PS... Kevin the 10m SSB radio I bought from you is working very well, I'm using it for transverting onto 2m SSB. I repaired one of the push buttons on the front panel and also replaced the display backlight.

Regards
Colin G1IVG

glad u was happy with it mate i had it off a friend but never really got around to using it much on 10m.

good luck on 10mhz mate...