Problem with an IC-706 & SWR spikes
 

IC-706MkIIG was working perfectly. Typical setup is 30 watts output,
PSK31 or RTTY, via short length of coax to an MFJ tuner, thence to
ladderline running to 250' low horizontal loop. Working with no problems
BEFORE I decided to rearrange my radio area. Rearranged my gear and ran
into trouble as soon as I fired things back up.

On two bands the SWR is never less than nearly 2:1, as indicated by the
MFJ meter, but much much higher by the 706's internal meter. Try to tune
the antenna system; if you dial in less inductor than it wants, or a
capacitor setting it doesn't like, SWR suddenly spikes to infinity and the
tx shuts off after a second. (Tuning is done at lowest power setting,
not 30 watts.)

The 706 works fine on 6, 10, 12, 20, 30, and 40. (I worked a guy in
California on 12, just checking things, and after we cleared a ZL called
ME on the frequency--ZL on 30 watts is clearly "working fine.") But on
15 and 17 meters, it will NOT achieve a low SWR, and sooner or later it
WILL oscillate or denooberate or whatever it is doing and spike the SWR,
and shut down.

I tried a lot of things--different coax, etc.; nothing made a difference.
(I was thinking at the time that it was the rearranging equipment that
caused the problem.) Then I did the systematic testing and found the
problem is only on 15 and 17 meters. (Fifteen's my favorite band, too.)
Now the only two things I can think of are A.) some problem with the big
loop, that presents some weird resonance on 15 and 17. Or more likely,
B.) some problem with a component in the 706, one in the output section
that is specific to 15 and 17 meters.

Thoughts? TIA!

_______________________________________________
Ken Kuzenski AC4RD ken . kuzenski at duke .edu
_______________________________________________
All disclaimers apply, see? www.duke.edu/~kuzen001

Problem with an IC-706 & SWR spikes
 

Ken,

This is a well known problem and is discussed in the following thread:

http://www.eham.net/forums/Elmers/108193

The Icom service bulletin 928 is @
http://home.comcast.net/~ad5x/images...ulletin928.pdf

An easier fix than 928 by AD5X @
http://home.comcast.net/~ad5x/images...bilityRevA.pdf

Good luck - Roger

Problem with an IC-706 & SWR spikes
 

wrote:
This is a well known problem and is discussed in the following thread:
http://www.eham.net/forums/Elmers/108193
The Icom service bulletin 928 is @
http://home.comcast.net/~ad5x/images...ulletin928.pdf
An easier fix than 928 by AD5X @
http://home.comcast.net/~ad5x/images...bilityRevA.pdf

Roger, I sent an email but would like to thank you here,
also, just in case you don't get the email. This info is
exactly what I needed--and didn't find in my quick google
search last week. I tried AD5X's version--it took about
ten minutes, all told, and when I was done the 706 once
again tunes up just perfectly on 15. THANKS, Roger!

_______________________________________________
Ken Kuzenski AC4RD ken . kuzenski at duke .edu
_______________________________________________
All disclaimers apply, see? www.duke.edu/~kuzen001

Problem with an IC-706 & SWR spikes
 

Ken,

Thanks for the update. Its always nice to know when something works
out. Phil (AD5X) has a good site - you can find lots of good stuff
there.

Roger