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

[Ignacy Misztal]

Bob,
Terrible problem with the splinter. We nearly always to remember to do
certain tasks with gloves, but sometimes we forget.

If money is available, the dxengineering 4sq is way above that of Comtek.
If you can reuse the controller, the switching unit is almost half price of
the complete package.

Ignacy NO9E

On Thu, Jul 14, 2022, 00:29 <kq2m at kq2m.com> wrote:

>
> My apologies to all for the extreme delay in responding.  I got a long
> wood splinter under my pointer finger  nail and it got infected and
> ballooned rapidly necessitating a visit to my internist and then to a
> hand surgeon who had to cut open the nail and remove some skin and the
> splinter.  Unfortunately he had to cut it open again 10 days later.  As
> you can imagine it was a mess, extremely painful and almost impossible
> to type with the multiple layers of bandages.  5 trips to the hand
> surgeon and 3 weeks later it is finally mostly healed.
>
> Many thanks to NO9E, NA6O, W5JMW, W4EF and N3AC for their thoughtful and
> very helpful responses.
>
> I had checked the coax, control cables, dummy load, Wire elements and
> feedlines just to be thorough and everything looked fine.  And then I
> opened the ACB-80 relay box and spotted a fully charred relay and partly
> blackened circuit board and then noticed that the other two relays next
> to it either had significant corrosion or lichen growth inside, or both.
>   Whatever was on the relays likely caused the relay immolation but it
> was surprising to see given that the relay unit was held in place with
> antenna ports facing down and then that was placed under a large heavy
> duty plastic bin to prevent water, leaves, etc. from getting inside.
>
> I am sending the relay unit back to DX Engineering for service along
> with the control box.  My understanding is that there is currently a 6 -
> 8 week backlog for repairs.  The unit is 27 years old.  It would be
> great to be able to get another 10 - 15 years out of it.  I won't need
> it after that.
>
> 73 and thanks for all of your help and information!
>
> Bob, KQ2M
>
>
>
> On 2022-06-27 14:17, Ignacy Misztal wrote:
> > If a mismatch in the 4 SQ should cause high dumped power but little
> > SWR change, it suggests that the Comtek box has a problem.
> > Perhaps during testing with the elements out of order something has
> > fried.
> > Comtek has a reputation of less reliable relays. My 2 year old Comtek
> > stack match stopped switching and a KW sent to the stack fixed the
> > issue.
> > Ignacy NO9E
> >
> > On Sun, Jun 26, 2022, 19:23 <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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