[R-390] Solid State R-390, Why Not?

Mon, 12 Aug 2002 17:25:06 -0700

I've got the instrumentation and the degree and the methodology. You might
also read the website of Sherwood Engineering that discusses many receivers
and their measured performance. My numbers are consistent with those
numbers. Sherwood does competent work.

-----Original Message-----
From: [email protected] [mailto:[email protected]]On
Behalf Of Bob Camp
Sent: Monday, August 12, 2002 4:40 PM
To: [email protected]
Subject: Re: [R-390] Solid State R-390, Why Not?

Hi,

Not saying you are wrong, but those numbers are about 40 db better than
what's been published elsewhere on the R-390A.

    Bob

----- Original Message -----
From: "Bob Tetrault" <[email protected]>
Cc: <[email protected]>
Sent: Sunday, August 11, 2002 8:21 PM
Subject: RE: [R-390] Solid State R-390, Why Not?

> Dynamic range is pretty hard to beat:
> IP3=+10dBm at 10kHz separation
> IP3=+20dBm at 100kHz separation (the difference is in the tunable front
end)
> 4dB noise figure on all bands.
>
> One can buy receivers with better IP3 numbers, but they don't have a 4dB
> noise figure. It's debatable whether or not anyone can use 4dB, since it's
> commonly thought that the HF noise level is 10+dB, but that isn't always
the
> case...and we watch and wait for those openings...
>
> One could experiment with pushing the distortion levels even further down,
> but it requires pushing the tubes harder since the standing current
> determines their threshold of distortion. Turning up the juice means
they'll
> exhaust the cathode emission sooner.
>
> Having extra modules does give anyone the option to play all they want.
I've
> heard that ome people have replaced the first two mixers with 7360
designs;
> this is a double balanced tube mixer designed for SSB detection and
> generation. Rumor has it that they are noisier than the 6C4W, but I've
never
> seent the numbers or methodology. How much it improves the front end is
also
> anecdotal. There was a considerable body of literature about similar mods
to
> the 75A4, since that receiver was/is(to some, even now) considered one of
> the best DX'ing receivers around. Again, my exposure never got beyond the
> anecdotal level, though I'd relish a review of all that was published on
> that topic. If memory serves, there was quite a lot in QST and CQ back in
> the 60's and early 70's. Anyone got any numbers on this mod?
>
> The drawback to modifying an RF deck is the RF deck, as anyone who has
ever
> taken one out will attest.
>
> But let's remember that there were 50K of these made, and while there are
an
> uncounted number of them that were lost, stolen, spindled, stapled and
> mutilated, modifying one is a drop in the bucket.
>
> Imagine what a great exciter a 390 would make! Imagine a pushbutton where
> the diode load is so that you could zero-beat a carrier.
>
> pot-stirring in Portland,
>
> Bob
>
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>
>
>

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