[R-390] Frequency meter

Thu Sep 2 09:29:18 EDT 2004

Greetings Group,

        I have watched this thread for several days....interesting.  I have
had nothing of any real help to add...until I had an idea this morning that
took me back to the days of rock bound transmitters (Xtal) and "Spotting"
your transmit freq. on the receiver.

High quality signal generators with digital displays have become relatively
cheap in the last few years...why not pick up a nice HP-8640B signal
generator....set the TCXO reference on frequency (zero beat WWV on your
receiver) and the display and output will be dead on the money.  Generate a
spotting carrier with the signal generator on the desired receive frequency,
zero beat it with your receiver and there you are.  If you want to know
where you are tuned sweep the generator across the part of the band you are
in until it is zero beat the signal generator with your radio and read the
freq.

I use a similar technique when using my old HP-606A tube type Signal
Generator...I pass it's output through my frequency counter and pretty much
ignore the analog dial during setup, then reduce the output level and go to
aligning.

You could probably pick up a working 8640B for around $200 on one of the
auction sites and it can serve other duties around the shop as well....you
can even use it as a frequency counter by inputting a frequency to be
counted to a front panel jack.

Just a thought!

Cecil....
----- Original Message ----- 
From: "Dan Merz" <djmerz at 3-cities.com>
To: "Bob Camp" <ham at cq.nu>; "Charles B" <ka4prf at us-it.net>; "R-390 HF
Receiver List" <r-390 at mailman.qth.net>
Sent: Wednesday, September 01, 2004 10:44 PM
Subject: Re: [R-390] Frequency meter

> Hi,  I can't resist - maybe a pun is  intended - as Bob suggested taking
> care of the whole thing with a pto coupled variable resistor as an option.
>
> But since accuracy wasn't mentioned,  I would say just use the mechanical
> indicator on the radio and let it go at that.  If you want to do more work
> and want to know how accurate your radio is,  just make some notes using a
> notebook and pencil,  on how far the dial is off using a known signal or
> xtal calibrator for reference.  Pretty soon you'll know just where you are
> and you'll know more about your radio than anyone else,  which is hard to
> accomplish on this listing.   You'll have become an expert..   Eventually,
> you'll be unhappy because you'll hate having a radio that's that as good
as
> it could be.  This will lead you to tear open the pto and fix it - then
> you'll discover not all crystals are where they should be - life gets
> interesting.  But you're an expert enjoying a good radio.
>
> My opinion is to enjoy the radio as much as possible the way it was built,
> fix some things that you can't live with.  I left my 390a freq. readout
> as-is but
>  I added a digital frequency readout from AADE for about $60 +  to my
Mackay
> 3010C.
>  This is a programmable
> readout and works fine (all the programming was done by AADE and is
amazing
> in itself),  no noise that I can tell but I shielded and isolated it
pretty
> well.
> According to the online info the DFD3 works for a 390a. And I used the
> offered 20 preamp
> to give more isolation.      I have no experience with it's use
> for the 390a,  but I especially like it for the 3010 because it eliminates
> the backlash of the
> tuning mechanism belt mechanism,  ever so slight but makes tuning ssb
> tricky.
> hope this helps,  Dan
>
>
> ----- Original Message ----- 
> From: "Bob Camp" <ham at cq.nu>
> To: "Charles B" <ka4prf at us-it.net>; "R-390 HF Receiver List"
> <r-390 at mailman.qth.net>
> Sent: Wednesday, September 01, 2004 3:22 PM
> Subject: Re: [R-390] Frequency meter
>
>
> > Hi
> >
> > As the other posts have mentioned it's not a simple thing.
> >
> > A lot depends on how accurate you want to get. RTTY and SSB are the two
> > things that most people would like to tune accurately. With AM the
> > bandwidth of the filters makes a 10 or 100 cycle error a lot less
> > important.
> >
> > If you are going to tool up to do a full readout for SSB or you would
> > need to measure:
> >
> > 1) The first crystal oscillator
> > 2) The second crystal oscillator
> > 3) The VFO
> > 4) The PTO
> >
> > The digital stuff to do that isn't terribly expensive these days, but
> > it does make noise.
> >
> > Once you had all the frequencies measured then oddly enough you would
> > have to know what band you are set to. It turns out that several of the
> > crystals are used for more than one band so there is no direct and
> > simple way to guess the band in every case.
> >
> > That all sounds like a lot of work and I'm lazy. If I was going to do
> > it I'd fake it:
> >
> > No matter what you need some way to track the band switch. Say we slave
> > a pot to the shaft and measure the resistance.
> >
> > The 17 MHz ovenized crystal isn't going to drift much I would simply
> > measure it's frequency with a bench counter and store the result
> > somewhere.
> >
> > The same thing is true to a lesser extent for the crystals in the
> > crystal deck. They do drift but maybe by sixty cycles. I would just
> > measure them and store their frequency as well.
> >
> > That gets us to the BFO and the PTO.
> >
> > There is an old military mod that puts a multi turn gear drive and
> > readout on the BFO shaft. The net result is the ability to reset the
> > BFO very accurately. If you can lock down the BFO shaft fairly well
> > (maybe mechanical detents) you can get around reading the BFO.
> >
> > All that's left is the PTO. You can either count it's frequency or try
> > the slave a pot to the shaft trick.
> >
> > The cute thing about doing it al with pots would be that you have no RF
> > counters at all. You are dependent on the radio not drifting but that's
> > what the 390 is known for.
> >
> > Definitely a bit far from the "well enough alone" zone thought ....
> >
> > Take Care!
> >
> > Bob Camp
> > KB8TQ
> >
> >
> >
> > On Sep 1, 2004, at 9:37 AM, Charles B wrote:
> >
> > >
> > > Is there any place inside the R-390A where a frequency meter can
> > > attached to get a frequency reading?
> > >
> > > Chuck
> > >
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