[Antennas] CushCraft R-7 problems

Wed Dec 30 21:16:28 EST 2015

All comments much appreciated. Some data...
The antenna is an R8 [not R7, my mistake]. It is brand new. With the 
several take-downs, it probably hasn't been "up" for more than a month 
or so, total. SWR readings were taken with the MFJ 256B at the antenna 
[2ft connecting cable], not at the shack end of a long piece of coax. 
That said, readings in the shack generally followed those taken at the 
antenna. Readings at a friend's house w/ the same antenna taken with my 
256B generally follow the curves at the back of the antenna assembly 
manual [under 2:1 and centered in the various bands]. Thus, there's 
something uniquely wrong with this particular antenna itself. I'm 
beginning to suspect that one or both of the traps may be bad/loose/etc. 
That would explain both the generally bad swr readings as well as the 
wide/wild fluctuations in readings that are observed with the wind 
blowing. I'm ready to take it down for the third time pending weather 
[snow and ice at this moment]. I haven't contacted CC after the latest 
go-around as I wanted to complete swr measurements under all possible 
conditions and compare with those at my friend's shack. Again, thanks 
for all comments and suggestions.
...robert
On 12/30/2015 22:43, K3SV wrote:
> Identical thing happened to me. The fracture is hard to see but needed to be repaired. I changed the guying points and have not had a problem.
> 73 Bill K3SV
>> Sent from my iPad
>>> On Dec 30, 2015, at 2:49 PM, Bob Nielsen <n7xy at n7xy.net> wrote:
>>>> I have a Hy-Gain AV-640, which is similar to the Cushcraft R8 and after several years the aluminum bracket which connects the matching network to the antenna fractured from the stress caused by the weather. This was hard to see except from up close but the SWR and signal levels were all over the place. Since the R7 matching unit is practically identical I would look there for a possible cause. I made a replacement bracket from a piece of aluminum of the same width but greater thickness which I found at my local Ace Hardware and hopefully it will hold up better.
>>>> Bob, N7XY
>>>>> On 12/27/15 3:42 PM, Robert G Strickland wrote:
>>> The house has aluminum siding. The antenna sits up on the roof, maybe 10ft above the siding and maybe 20ft away from it; the roof mounting spot is around 20ft above ground. I think the problem is with the antenna itself, not the installation context/environment. I had a SkyHawk beam, and the SWR never varied on that antenna, regardless of the wind/weather. So, the wide/wild fluctuations of the SWR when measuring it in a very slight breeze is suspicious of something mechanical.
>>>>>> ...robert
>>>>>>> On 12/27/2015 22:56, JK wrote:
>>>> How far away from ur house? Have aluminum siding. Any towers nearby? Any
>>>> vertical wires or metallic objects near the antenna?
>>>>>>>>>>>> Check continuity w/ohmmeter?
>>>>>>>>>>>> Jay...NE2Q
>>>>>>>>>>>>> On Sun, Dec 27, 2015 at 05:29 PM, Robert G Strickland wrote:
>>>>>>>>>> Hi, Jay...
>>>>>>>>>> Brand new!
>>>>>> ______________________________________________________________
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-- 
Robert G Strickland, PhD ABPH - KE2WY
rcrgs at verizon.net.usa
Syracuse, New York, USA