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Author Topic: Delta loop and SG-237  (Read 5103 times)
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« on: April 28, 2002, 01:38:18 PM »

In the recent issue of QST they have an artical on the Delta loop antenna connected to an SG-237 tuner. I was quite interested in trying one out until I read the comments on the SG-237. They were such things as it won't work over 100 watts SSB or 50 watts CW and unless you have a very good grounding on it, it will be quite erratic also it is not waterproof. They have already stated that the MCU chip should be replaced by a newer version. Now that sure lets the wind out of your sails. If anyone has any possitive reports on this setup, please reply as  I am thinking about trying one but I need encouragement on this subject. Bill
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AC5E
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« Reply #1 on: April 28, 2002, 06:43:46 PM »

I have never tried the SG-237 but several of my friends have had decent results with the more robust SGC tuners. I don't see why one of them would not be perfectly acceptable for any modern tranciever. Barefoot, of course.

73  Pete Allen  AC5E
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W0FM
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« Reply #2 on: April 29, 2002, 10:07:59 AM »

Hi Bill,

I have used the SGC-230 coupler for many years.  It is weather resistant and water tight and I would have to assume that the '237 is made to the same standards.  I have used the SGC-230 with long wires and loops with good success and never had a problem electrically with the unit.  Like most "auto tuners" (SGC likes the term "coupler") the 100 watt power limitation is typical.  A good ground is important.  SGC has been very good about support and upgrades.  I think you would like the '237.

73 de Terry, WØFM
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K3AN
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« Reply #3 on: April 29, 2002, 04:53:33 PM »

I agree with W0FM that a good ground is important when using a SGC autotuner. Therefore I am very surprised that the SGC and delta loop configuration shown in the May QST article works.  The ground lug on the tuner is connected to one leg of the delta loop, so the entire tuner "floats" above RF ground. Apparently the tuner can find and hold a match, without constantly hunting for a low SWR, even in this ungrounded configuration.

I guess it just shows that when it comes to antenna experimentation, you don't know what will work until you try it.

Has anyone ever experimented with adding ferrite or iron powder cores over the coax and power feed, at the tuner, to improve an SGC's stability?
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W0FM
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« Reply #4 on: April 29, 2002, 07:10:15 PM »

That's a good point.  I don't believe that Steve Ford had his SG-237 grounded in his May 2002 QST Delta Loop article, because, as you state, the loop makes a complete circuit back to the ground lug on the coupler.  A loop looks like a short circuit, but presents a (relatively) matched load to the transmitter.

The grounding I recommended was with reference to long wires, whips or verticals used with auto couplers like the SG-237.  They need to work against ground. I'm pretty sure the loop just "floats" like just mentioned.

Terry, WØFM
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KQ6EA
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« Reply #5 on: April 29, 2002, 08:51:48 PM »

I've used my SGC 230 in a variety of loop configurations with good to excellent results. I've used it with 180' of wire in a rectangular loop, 135' in a square loop, and 135' in an upside down triangular loop, fed at a center, bottom vertex. The best working one one was the triangle, but the others worked well, too. I've never used an additional ground, except with vertical wires, or random wires, and have never had any stability problems. While Steve's loop follows the conventional wisdom and configuration, my upside down version worked extremely well, and was easier to implement in my location.
Jim KQ6EA
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