Greetings all,
Since completion of my AT11 kit, it has intermittently operated as desired.
The symptoms have been lack of repeatability of tune at a given frequency
with the same antenna and xmitter.
The AT11 would indicate a SWR of less than 1.5 but my TS140 foldback would
limit maximum power. A series SWR meter reading between the xmitter and the
tuner indicated an error with the AT11. But this too seemed intermittent.
Yes...I re-calibrated the AT11 SWR circuit. In fact tried several different
approaches to calibration in a vein attempt to remedy problem.
This weekend the AT11 indicated a SWR of greater than 3 into my 50 ohm dummy
load.
COOL! Finally a really solid failure..
With the cover off the AT11... everything checked out perfectly. I checked
the calibration at the center of each HF band and it could not have been better.
********************** WHAT I FOUND *********************
THE COVER SCREWS were so long they were touching/shorting the foil side of
the PC board when fully threaded. I shortened all four of them and so far
so good.
It looks like the outer foil track around the board perimiter is nothing but
ground but I haven't investigated further. Maybe some sort of ground loop.
If any of you have an AT11 I suggest you check the screws, even if you
haven't had any problems yet.
Hope this info is useful. 72 all
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