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[TenTec] Re: Omni 6, observations & questions

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Subject: [TenTec] Re: Omni 6, observations & questions
From: Peter A. Klein" <pklein@seattleu.edu (Peter A. Klein)
Date: Thu, 4 Sep 1997 11:58:39 -0700 (PDT)
Here's what Ten-Tec service said about my few problems with my demo-model
Omni Six:

On Sun, 17 Aug 1997, Peter A. Klein wrote:

> - The rig has one problem that will require fixing.  On the 10 MHz band,
> it tends to go through a drift cycle every ~18 seconds.  The rig will
> jump down maybe 30 Hz or so (guesstimate), then drift slowly up to the
> place where it jumped, them jump again.  This happens on both receive
> and transmit.  I checked all the other bands, and have not noticed it
> anywhere else.  

The 10 mHz band crystal adjustment is probably just at the borderline of
where is can be properly phase-locked.  (My suspicion is that they put it
dead zero-beat to WWV, and it needs to be a smidge off to lock properly). 

Fix:  Warm the radio up for a good 1/2 hour or more. Open the radio top
cover.  Open the oscillator board cover.  You'll have to remove a couple
of wire harness connectors because a couple of other boards are mounted on
the cover.  That's OK, the radio will still work enough to hear if the
adjustment worked.  Adjust the coil for the 30m band. Try turning the coil
1/4 turn clockwise.  If that doesn't work, return it to the original
setting and turn it 1/4 turn counter-clockwise from there.  It should lock
in solidly in one direction or the other.

I haven't done this yet.  The tech mentioned something about the 10 mHz
band's crystal being the third from the right, but I havn't confirmed this
yet.  Check your manual's diagram to be sure.  The tech said it was easier
to do than to describe.  

> - Signals dropped almost two whole S-units when switching in the 9 mHz
> IF's 500 Hz filter (NAR button).  Yes, the PBT was properly adjusted. So
> I checked the filter gain jumper on the 9 MHz board.  It has pins 1-2-3,
> with pin 1 closest to the optional filter.  It was set properly
> according to Figure 1-5 in the manual, which says that pins 1-2 should
> be jumpered for 500 and 250 Hz CW filters, and pins 2-3 for 1.8 and 2.4
> SSB filters.

> But when I moved the jumper to pins 2-3, the loss on switching in the
> NAR filter was reduced to only 1/3 of an S-unit.  So either the manual
> is wrong, or somthing's different about the radio. Has anybody else
> observed this?

As many of you noted, the manual may be wrong or outdated.  Use whichever
position on the jumper that gives you the most gain.

> - The PBT 12:00 center position is correct for LSB and CW.  But on USB,
> the signal centers at 1:30.  Is this normal, or am I out of alignment?

The BFO frequency is probably a little off on USB.  A frequency counter or
external general coverage receiver can be used to set it to the proper
frequency as per the manual.  

BTW, there is no need for 1 Hz or 1/10 Hz accuracy for this adjustment. 
The tech said my Radio Shack on-sale counter (least significant digit=100
Hz), or a good general coverage receiver zero-beated to WWV would probably
be fine for most adjustments in the radio *except* the master oscillator
frequency. In my experience, if you tune your gen coverage receiver *very*
slowly, and stop at the exact point where the least significant digit just
changes to the desired frequency, you really have 10 Hz accuracy.  Now I
have musical training and can match tones accurately, so your mileage may
vary.  But I've been doing this for years.

> - The radio runs warm.  Especially on RTTY--even at half power, the
> final's heat sink gets downright hot.
> . . .  I've stood a little computer power supply
> fan behind the radio blowing on the heat sink.  I figure it's like
> chicken soup--it couldn't hurt  :-)

> - I can't figure out how the SWR (reflected) meter is supposed to work.
> Is there a "set" point on the "forward" scale where the reflected meter
> is then accurate for SWR?  

The SWR meter is correct at full power (100w).  Otherwise, it's a relative
indicator only. 

> - When switching from fast AGC to slow, AGC sometimes jumps way high and
> hangs for over 5 seconds, effectively muting the receiver. This seems to
> happen only the first time I switch, and then it won't happen for a
> while.  

This is normal behavior.  In fact, it is mentioned in a review TenTec sent
me (The Peter Hart Review--British).  When you have been on fast AGC for a
while, a capacitor gets charged. It discharges when you switch to slow
such that the AGC thinks it's a *very* strong signal.  This hangs the AGC
for a few seconds.  While you can change the value of this capacitor to
modify the time constant, it doesn't eliminate the behavior.  Workaround: 
Turn off the AGC before switching to slow, then turn it right on again. 
Annoying, but no big deal, really.  The buttons are right next to each
other, so you can just use 2 fingers :-) 

> - I run CW at about 18-25 wpm.  The internal keyer, in Curtis mode B, does
> seem a little reluctant to generate the last element of "Q" or "K" 
> sometimes when I squeeze rather than move my fingers back and forth.  Does
> anyone know why this is? 

The response was, "what keyer problem?"  The tech mentioned that early
models had some microprocessor-induced speed variations, but that that's
been fixed.

Steve Ellington has said that there is a a few milliseconds' delay in the
Omni's internal keyer, and this throws a lot of people's rhythm off.  If
you look at the keying envelope scope traces from the QST review, there
appears to be about a 20 ms delay between what you do with the key and
when the RF envelope responds.  This 1/50th second--almost half the
duration of the dit.  

What this doesn't address is when the sidetone sounds.  Is this is just a
keyer issue, or an issue of the sidetone also being delayed?  Is the
Omni's sidetone also delayed when you use an external keyer?  I don't have
a dual-trace scope, so I can't check this accurately.  Steve, when you use
an external keyer, are you using the Omni's sidetone, or the external

I may piggyback my old MFJ keyer back on my Bencher paddle and play with
it, but my observations will have to be "by ear" only. 

--Peter (KD7MW)  

Peter A. Klein  (pklein@seattleu.edu)  :    -----==3==      ---      ---
Network Administrator, LAN/WAN/Novell  :   |    |  |  |    |   |    |   |
Seattle University, 296-5569           :  @|   @| @| @|   @|  @|   @|  @|

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