[TowerTalk] 80 m 4-square high SWR with no obvious reason why - using COMTEK ACB-80

[Michael Tope]

Hi Bob,

Does the VSWR (i.e. 800W forward, 350W reflected) remain the same when 
you switch directions with the array? Also, what is happening with the 
dump port load on the ACB-80 when you transmit? Is that dissipating a 
lot of power?

Mike W4EF.............

On 6/26/2022 5:22 PM, kq2m at kq2m.com wrote:
> Hi,
>
> Before WPXCW one month ago, my wire 80M 4-square using the COMTEK 
> ACB-80 was working very well, with ~ 1500 W out and 100 w reflected at 
> 3.5 mhz and ~ 1500 W out and 50 w reflected at 3.7 mhz.  The F/S and 
> F/B wer excellent and about as predicted when the DX station signals 
> were low angle.
>
> Between then and now (one month) we had two violent windstorms and a 
> few nasty T-storms, with gusts approaching 50 - 60 mph but tame 
> compared to what it has been through in the past.  2 wire elements 
> broke off, the F/B and F/S disappeared and the forward power dropped 
> to ~ 800 w with 350 w reflected from from 3.5 - 3.7 mhz. That's normal 
> and to be expected.
>
> However, when I fixed the two elements today, while the F/B and F/S 
> improved somewhat, the forward/reflected power did not go back to the 
> usual values. That is NOT normal.
>
> I checked each of the connectors and continuity at the bottom of each 
> element and everything appeared to be fine. I checked all the phasing 
> lines and they appeared normal.  All the elevated radials were in the 
> air at their normal elevations.  I could not find anything wrong.  
> There was one sketchy looking connection on the feedline to the shack 
> and I made a new connection with a new Amphenol pL259, but there was - 
> still ~ 800 w forward 350 w reflected from 3.5 to 3.7 mhz.
>
> I seem to remember something like this happening about 10 years ago 
> with high reflected power and loss of F/B and F/S as a result of 
> multiple COMTEK external relay box cold solder joints that were not 
> obvious.  DX Engineering checked it out found the cold solder joints 
> (that COMTEK did NOT find) and fixed them and priority shipped it back 
> to me so that I would get it before CQWWCW which I did!  But the F/B 
> and F/S was worse then than it is now so I am not sure that it is the 
> same thing.
>
> What is striking to me is that the forward power has uniformly dropped 
> and the reflected power has uniformly risen across the entire band as 
> though the entire array was detuned by 500 khz, suggesting something 
> systemic.  I suspect that the problem is in the relay box but I can't 
> figure out what may be causing this.
>
> Has anyone experienced a similar problem with their ACB-40, ACB-80 or 
> ACB-160?  Does anyone have any idea of what to do look for next?
>
> Tnx & 73
>
> Bob, KQ2M
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