QSY'd the TXRe: [TenTec] RE: Omni V Fm'ing

MW0CDO MW0CDO" <gw7lhi@hotmail.com
Sat, 30 Mar 2002 18:22:16 -0000


Hi Carl.

Thanks for the input.

The 8.5v reg is working fine, according to my meter there is no change in
this supply when varying the RF output, even with a meter that can resolve
to 1mV when the 20v range is selected. Just for good measure, I changed the
723 and transistor as well.. made absolutely no difference at all.

As mentioned earlier, the 13.8v PSU exhibits a drop of 60mV between minimum
RF out ( 5w ) and maximum RF out ( 100w ), which is less than the drop
caused by the internal fuseholder and Molex connector in the radio.

I have just discovered something interesting, which I've not researched via
the schematic yet:
On 10, 12, 15, 17, 30 and 40m the carrier always QSY's down in frequency..
but on 20, 80 & 160m the carrier always QSY's up in frequency as RF out is
varied from min to max.
20m is the worst band for this, the QSY is around 3x greater than any other
band. Note that all tests have the same result whether a dummy load or real
antenna is used.

The actual amount of the QSY on all bands excepting 20m appears to be around
10Hz, ie: the beat note on a separate monitor RX changes by the same amount
as if I QSY'd the TX from say 28.100.00 to 28.100.01.
On 20m the effect is around 3x worse, equivalent to a QSY from  14.000.00 to
14.000.30.

I realise these are very small QSY's, but I'd like to get to the bottom of
it!

Cheers.. Paul MW0CDO

----- Original Message -----
From: "Carl Moreschi" <n4py@earthlink.net>
To: "Ten-Tec List" <tentec@contesting.com>
Sent: Saturday, March 30, 2002 12:46 PM
Subject: Re: [TenTec] RE: Omni V Fm'ing


> Paul,
>
> The problem is the 8.5 volt regulator needs about 3 to 4 volts above
> 8.5 to stay regulated.  When the main supply voltage drops below 12.5
> this regulator drops out of regulation.  It is very important for the main
> supply voltage to stay above 12.5 volts.
>
> Carl Moreschi N4PY
> Franklinton, NC
> ----- Original Message -----
> From: "MW0CDO" <gw7lhi@hotmail.com>
> To: "Ten-Tec List" <tentec@contesting.com>; <VE1BN@aol.com>
> Sent: Saturday, March 30, 2002 10:04 AM
> Subject: Re: [TenTec] RE: Omni V Fm'ing
>
>
> > Thanks for the info Don.
> >
> > Yes, I've double checked, and none of the oscillators I can find on the
> > schematic are powered directly by the incoming +Vcc, all are powered
from
> > REG+ 8.5v or 5v in the PLL compartment. Which ones in the OMNI VI+ are
> > powered directly from +Vcc? I'd have thought this wouldn't be good
> practice,
> > running an oscillator from the main power bus that is likely to
fluctuate?
> >
> > I will replace the screws that are missing, as you say this may be the
> > answer since TT use the mounting points as earth routes as well. I had
to
> > isolate the sidetone board from the chassis, as I was getting a lot of
> > talkthrough on the internal speaker and the headphones. This cured the
> > problem completely.
> >
> > I did buy the radio used, one previous owner. It was deaf on RX, due to
a
> > faulty external RX ANT switch. He's a good friend of mine, and did
mention
> > that he had sent the radio off a couple of times for repair. It was
cheap
> > tho'! :-)
> >
> > I'm still waiting for the agc hiss modifications from TT by mail.
> >
> > Once I have these 2 problems solved, the next step is one of Carl N4PY's
> v.9
> > microprocessor replacements. I'm looking for a source of the processor
> > MC68HC705C8ACP here in the UK, otherwise I'll have to order from Newark
> > Electronics.
> >
> > Thanks for your input!
> >
> > Paul MW0CDO.. another glorious sunny morning here.
> >
> > ----- Original Message -----
> > From: <VE1BN@aol.com>
> > To: <gw7lhi@hotmail.com>
> > Sent: Saturday, March 30, 2002 12:46 AM
> > Subject: Re: [TenTec] RE: Omni V Fm'ing
> >
> >
> > > Hello Paul -
> > >
> > > Thanks for the reply.
> > >
> > > Must admit I am still curious about a regulator for +8.5 volts. Don't
> > recall
> > > ever seeing one.  If your schematic says that, then guess I will have
to
> > > accept it (ha).
> > >
> > > About the missing screws, yes they should definitely be replaced. Two
> > sheet
> > > metal types hold the TX audio/BFO board mounting bracket to the back
> > panel.
> > > Better grounding and mechanical stability when you replace these!  May
> be
> > the
> > > fix you are looking for?  Ten-tec boards usually ground through
mounting
> > > screws to complete short earth paths.
> > >
> > > Odd they are missing, but then I seem to remember you saying something
> > about
> > > getting your OMNI from a previous owner.
> > >
> > > My OMNI is a 6+, not a 5.  The screws to be replaced on yours are in
the
> > same
> > > location.
> > >
> > > Hope this helps.  Good luck, Paul.
> > >
> > > 73  -  Don
> > >
> > >
> > >
> > _______________________________________________
> > TenTec mailing list
> > TenTec@contesting.com
> > http://lists.contesting.com/mailman/listinfo/tentec
>
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