[NCARC] Ideas on HF vertical problem

[Steve]

Hi James-

Yikes , sounds like a very frustrating issue!  Did you try the procedure recommended near the end of the referenced article - measuring the traps (all of them) using your MFJ unit?  If so, how did the compare with the values the author presented?  If not, that might be good information to obtain to continue to troubleshoot the problem.

'73

Steve, N7GN



Sent from my iPad

On Jan 14, 2013, at 8:49 AM, James Cizek <jcizek at yuma.acns.colostate.edu> wrote:

>  Hi all,
> 
>  I have been racking my brain on this one for 2 weeks now and am giving in to
>  ask for assistance here.
> 
>  I have a very old Cushcraft R7 multiband vertical that I normally use on HF.  The other
>  day, something happened and now several bands won't tune.  I had one issue that I knew
>  about for sure, the 20 meter trap capacitor cover sun rotted and fell off, the trombone
>  style capacitor got water in it.  I carefully disassembled it, cleaned it, dried it, and 
>  reassembled / re-heat shrinked it.  Other than that, there is no visible damage to any 
>  other components.  
> 
>  The matching network is dry, everything is tight, and shows no signs of arcing.  I have 
>  measured DC resistance to verify that all connections are mechnically tight. I disassembled
>  the entire antenna this weekend and cleaned ALL the tubing with steel wool to clean up
>  any dirt/oxidation.
> 
>  The first and foremost problem is that it will not tune on 10 meters,  since this band
>  is the highest frequency band of the antenna, I am not even worrying about the rest until
>  I can get 10 meters working (though, some of the bands will tune, even though none of them
>  seem to be natviely resonant anymore) 
>  It's supposed to have a 2 MHZ bandwidth on 10 meters with under 1.5 : 1 SWR.   
>  Right now, I see 18:1 in the middle of the band.  The MFJ 269B is showing
>  a very narrow (5 khz) wide window where the antenna is measuring 50 ohms, but still has a 
>  very high SWR.
>  I do see a 1.7:1 spot in the band, but it's currently very narrow and sitting at 26 mhz.
>  Since 1" of tubing change = 50~100 khz freq change, that would be between 20 and 30 inches
>  I'd have to shorten the antenna.  Something else is fundamentally wrong (plus, I can't 
>  shorten it that much without removing large sections of tubing)
> 
>  I took the 10 meter trap off of the antenna and tried to couple to it using a grid dip
>  meter, but found that my grid dipper is now longer working, so no luck there. 
> 
>  The couterpoise is clean, and electrically sound, both between the 2 radial systems
>  and the matching network.  I also put a 50 ohm terminator on the coax outside and 
>  measured it inside (to make sure it wasn't the coax!) It's flat as a pancake reading
>  1:1 and 50 ohms on all bands. (The antenna measurements at the antenna seem to match
>  the ones taken in the shack also...)
> 
>  So, I am hoping that someone will be able to offer any suggestions on what to try
>  next, or what to look for.  This has been very frustrating!   I have followed the
>  great advide offered here: http://www.qsl.net/ei7ba/r7_vertical.htm 
>  to no avail.  Anyone got any ideas?
> 
>  Thanks for your time. -James   KI0KN
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