[R-390] Frequency meter

[Dan Merz]

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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