Well, after tweaking C31 to try to get the 10 Mhz signal closer; it
seems to be more or less behaving now... The jump on 30 meters is gone
even though I was unable to get the lock signal to match the other
bands. The 160 meter coil had to be adjusted in order to get the lock
signal to be stable. So far, FT8 signals on 40 meters is decoding every
time. Looks like the BFO trimmers need adjusting though. When I flip
between LSB and USB while tuned to WWV, the tone changes. Looks like
it's about 30 hz off on LSB and about twice as much on USB. Adjusting
those is kind of a pain since they seem to interact with one another :(
73
Stan
KM4HQE
On 06/28/2018 05:23 PM, Stan Gammons wrote:
Hi Gary,
I have the 10 Mhz signal. It seems to want to flop between 10,000.000
and 10,000.001 to 10,000.002 at times. For some reason it kills the
receive when I connect the counter, a Leader LDC-823S, to pin 9 of
U12. I have to turn the rig off and back on to get the receive to
work again.
I take it U13 is the MC145170P1 chip next to connector 88? If so, it
looks like I have 160 meter problems since the signal on pin 11 is
there for a fraction of a second, then it's disappears and reappears.
On all of the other bands, except 30 meters, the waveform looks nearly
the same. On 30 meters the waveform is wider. I haven't tried
adjusting the coil to see if I can get 30 meters to match the other
bands. Strange thing though on 30 meters is FT8 still decodes even
though it jumps about 100 hz for a very brief time. I'll try
adjusting the coil and pulling the board to see if it has any bad
solder joints. Still need to clean the connectors like Bob described
in another post.
73
Stan
KM4HQE
On 06/28/2018 08:40 AM, k4mt1950@charter.net wrote:
Stan:
I have had the exact same problem with my Omni VI. There is a
procedure to properly adjust band crystals. It is:
Omni VI Lock PulseRig should be on for at least 1/2 hour.Check 10MHz
REF at pin 9 of U12.Adjust 10MHz REF with C31.Check for lock pulse at
pin 11 of U13, Scope probe on x10 position; .2 volts per div, and .1us
time/div.Adjust L12 thru L21 on Xtal Osc. LO Mixer Bd. for the
narrowest wave form.
I did this but it did not help. I tuned in WWV and watched it on a
waterfall and you could see carrier drifting back and forth. I was
missing over half of the FT8 decodes as a result.
What I found is PLL circuit on logic board is very temp sensitive. I
tried to locate a part but the entire thing is that way. I found by
putting a very small fin blowing across logic board completely
eliminated the drift cycling.
FT8 now works perfectly. Put the fan along the right side (looking
from front) and not back panel. Back panel heats up during TX and when
I put my fan there the problem got worse when I went into TX.
Afraid its a design flaw and cant be fixed any other way.
Gary K4MT
-----------------------------------------From: "Stan Gammons"
To: "Discussion of Ten-Tec Equipment"
Cc:
Sent: Wednesday June 27 2018 7:38:42PM
Subject: [TenTec] Omni VI frequency jumping/drifting
Hi Everyone,
My Omni VI has decided to throw a few more fits. First the frequency
jumped on 30 meters, but FT8 signals still decode fine. So I let it
go
and didn't mess with it. Lately 40 meters has started throwing fits
and
it's much worse than 30 meters. Looking at the FT8 waterfall, at
times
it will drift during the 15 seconds and it's bad enough the FT8
signal
won't decode. I sent another email to the list with the waterfall pic
attached, but the message was too large and got rejected. I tried
tweaking the coils on the crystal oscillator board. It might have
helped 30 meters a little. Doesn't seem to have done much/anything
for
40 meters though. Crystals gone bad maybe? If so, anyone know a
source
now that ICM is no more?
73
Stan
KM4HQE
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