[Top] [All Lists]

Re: [TowerTalk] 80 m 4-square high SWR with no obvious reason why - usin

Subject: Re: [TowerTalk] 80 m 4-square high SWR with no obvious reason why - using COMTEK ACB-80
From: Michael Tope <>
Date: Sun, 26 Jun 2022 18:57:59 -0700
List-post: <>
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, wrote:

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

TowerTalk mailing list


TowerTalk mailing list
<Prev in Thread] Current Thread [Next in Thread>