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Author Topic: Suddenly SWR  (Read 2048 times)
AA1ZH
Member

Posts: 8




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« on: September 13, 2005, 12:00:24 PM »


I have an Icom 706IIG that I'm running mobile, with a High Sierra Sidekick.  Suddenly, my SWR is high (off the chart), on all HF bands.

What I don't understand is that if it were a grounding issue, why was it tuning before?  I've taken a close look at connections and cables, but nothing's jumping out at me.

If anyone has some specific suggestions on what to check, or what it could be, I'd appreciate it.

FWIW, I noticed there's similar (but not identical) issues posted here:

http://www.eham.net/forums/MobileHam/7327

Thanks.
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AH6TA
Member

Posts: 4




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« Reply #1 on: December 14, 2010, 02:53:22 PM »

I'm having the same issue, and also can't see anything out of whack. Still searching for a solution.

I have a Yaesu FT-857D and the Sidekick with the HS tuner. It worked just fine for about six months, then all of a sudden would not tune properly (ie., give the appropriate metering on the display) on any band of HF. The VHF/UHF was fine.

I get an SWR warning almost all the time, no matter what the tuning. What seems to help is to unplug the ACC input to the radio from the controller switch, and simply adjust the antenna coil to get the strongest RX signal on a given frequency.  The SWR warning goes away. My signal is not coming out well...folks on Kauai Island hear me, and on Oahu, but Big Island (which should be a cakewalk for 100 watts on 40 meters...and used to be) is a challenge.

At one point I even sent the radio into Yaesu for repair...and they said there was nothing wrong with it and sent it back ($150 down the tubes). It has done the same thing with a HS tri-mag mount, a standard ball mount, and now with a brand new 5" screw-in mag mount.  Of course, Jim at HS insists there can't be anything wrong with the antenna.

I've been a ham for 40 years, and thought I had a pretty good handle on things...but this has me bazonkered ;-)
« Last Edit: December 14, 2010, 03:16:18 PM by Elaine Albertson » Logged
W5DQ
Member

Posts: 1209


WWW

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« Reply #2 on: December 15, 2010, 03:38:24 PM »

AA1ZH,

Did you get a resolution to your problem?

Suggestion would be for folks who post problem queries to follow up on them so the 'listeners' can see what works and doesn't work to fix them.

Thanks

Gene W5DQ
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Gene W5DQ
Ridgecrest, CA - DM15dp
www.radioroom.org
W9MMS
Member

Posts: 118




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« Reply #3 on: December 15, 2010, 05:17:42 PM »

It could be Common Mode Current.
www.k0bg.com
Pay attention to his article on
1) Common Mode Current
2) Antenna Matching
3) Antenna Controllers

73 de Milverton.
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WB6BYU
Member

Posts: 12974




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« Reply #4 on: December 15, 2010, 05:31:24 PM »

Quote from: AH6TA
...What seems to help is to unplug the ACC input to the radio from the controller switch, and simply adjust the antenna coil to get the strongest RX signal on a given frequency.  The SWR warning goes away...


So the automatic controller can't tune the antenna to resonance, but it can be done manually and
the antenna can give a low SWR?  Have you confirmed that by putting an SWR meter in the line and
checking the reading?  You should be able to tune it manually for minimum SWR or maximum power
output.  If so that would seem to indicate that the problem is in the controller, not the antenna.
You might have blown a diode in the phase detector or some such problem.


Quote
My signal is not coming out well...folks on Kauai Island hear me, and on Oahu, but Big Island (which should be a cakewalk for 100 watts on 40 meters...and used to be) is a challenge.

Is this with the antenna tuned manually for good SWR?  It might be due to propagation - 40m hasn't
been its normal self for short to medium range coverage for the last few years.  You can go here:

http://www.ips.gov.au/HF_Systems/7/1

and run a "Local Area Mobile Prediction" (LAMP) chart for the current ionospheric conditions. It will
show you what frequencies are open at what times of the day for distances out to 600 miles.
It looks like 40m should be open for you for perhaps 7 to 8 hours per day, while this far north it
rarely opens for distances less than several hundred miles, and then only at the peak of the day.
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W7WX
Member

Posts: 4




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« Reply #5 on: December 19, 2010, 09:39:54 PM »

Just a thought to consider, but a friend of mine who runs the Sidekick shared with me he has to clean the coil / finger stock (spring?) connections every month or two.  Between the moisture in the air and heavy road spray apparently his collects more than it's share of road grime causing poor contact between the two.  Not sure if that's a possibility with yours or not...but I wouldn't think it would be hard to pop the cover and wipe down the coil just to see?  It would certainly explain the standing wave you are seeing.  Just a thought.

Best of luck.
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