[R-390] What is the difference between 390 and 390A

[Dan Merz]

Bob,  first,  I think all of these are excellent radios.  I've owned one of
each but don't have the 390 operating yet. My impression so far:  the HQ 180
is excellent for am and ssb as built and has very good agc for both of these
modes.  In that sense,  it is easier to operate over a wider range of signal
strengths and takes less manual tweaking of the rf gain. It is an easier
radio to surf bands with because the tuning knob covers the ground easier.
Of course,  the digital readout on the 390's is inherently more accurate
though I considered the HQ 180 to be good enough.   There is a very simple
mod for either the 390 or 390a that improves the agc characteristic but it
still isn't as good as the HQ 180 for ssb. The HQ 180 has pretty good audio,
as I recall.  The R390a and R390 have perfunctory audio amplifiers and a lot
of users want to make improvements.  There are a couple of obvious ways to
do that involving either modifications of the audio circuits or using an
external amplifier, easily connected to terminals on the back of the set.
The R390a uses mechanical filters and the audio suffers somewhat from that.
The 390 uses LC i.f. tranformers to attain selectivity and has a more
pleasing sound than the 390a as a result.  I believe the 390a is considered
easier to maintain,  one reason being that there seem to be more spare parts
and chasses available for the 390a.  One modification of the 390a is to
stick the 390 i.f. chassis in it(requires modification) to give it a more
pleasing sound.  I did this with my 390a and I modified the audio chassis to
improve the audio.  The audio chassis mod was the bigger improvement of the
two.  The nice thing about these mod's is that they are completely
reversible by sticking the original i.f. and audio chasses back in the
radio.  Of course this means that you purchase the extra chasses.  There are
other differences between the 390a and 390; the 390 has a more elaborate
power supply (more heat) and an extra front end rf tube/tuning circuit.  I
believe the 390 and 390a are capable of better sensitivity and resistance to
overload than the HQ 180 but I can't recall if this is documented as a
direct comparison.  I think from a practical point of view,  resistance of
the 390 and 390a to overload from nearby strong stations  is more important
than the differences in sensitivity.   The biggest difference in receiver
quality is obvious upon examinination of the guts of the 390 and 390a radios
compared to the HQ180;  the tuning of various stages as co-ordinated by the
gear train is unbelieveably elaborate.  Once you've seen it,  all the other
considerations take a back seat and other radios have a hard time competing
even if they hear every signal that the 390 picks up. Watching the gears is
almost as good as listening to signals.  Currently it is my radio of choice
and I doubt it will be replaced.  When I'm in a hurry and the 390a is not
on,  I'll fall back to the NRD-525 but the audio of that set always
disappoints me compared to the 390a with the 390 i.f. and modified audio
chassis.  I think the 390a had better audio than the 525 even before I made
those two mods. 

It took me about 10 years of serious radio tinkering before I owned a 390a,
mostly because I was more interested in older radios.  The thought of not
owning one (and now two with the 390 recently acquired)now seems
unacceptable. I think some of the guys in this group feel that the 390 is
the radio of choice,  a "real radio" and one owns a 390a because the 390's
aren't as available. When I bought my 390a about 5 years ago,  it seemed
that a lot more 390a's were being offered for sale than 390's.  I suspect
the popularity of the 390a is simply related to the fact that more of them
were made and it's a darn good radio.  I finally bought a 390 as well - to
restore it and see if I could appreciate the difference firsthand.
Surprisingly, I paid less for the 390 than the 390a but the 390a worked with
little fuss and the 390 so far has unknown problems causing weak reception
but sold as an operating set.   I'm sure I'll be back here asking more
questions once the power connector arrives and I bring it to life.

Which one is better for BCB dxing?  I would venture that the extra rf stage
in the 390 adds something,  namely better protection from off-frequency
strong stations.  And considering the i.f.'s, at narrow selectivity,  the
390 LC i.f. should sound better than  the mechanical filters in the 390a. I
have to think that the 390 would be better than the 390a in light of these
two aspects. But at this point realize that I'm inexperienced with the 390
and slightly biased - I have to think my 390 is going to have some pluses
over the 390a other than my being able to look at another set of gears go
around in a different fashion.
  
  Dan       

-----Original Message-----
From: r-390-bounces at mailman.qth.net [mailto:r-390-bounces at mailman.qth.net]
On Behalf Of ROBERT YOUNG
Sent: Sunday, April 10, 2005 8:55 PM
To: r-390 at mailman.qth.net
Subject: [R-390] What is the difference between 390 and 390A

Hi,

I'm new here, I'm a BCB dx'er and plan on buying a Collins within the next
year and was recommended to come here for help by a fellow member of the
NRC. I'll probably have a lot of questions and my first one is what is the
difference between the 390 and the 390A? Which would be better for BCB
DXing? Also I use a nice HQ-180 right now, can anyone compare the two for
me? thanks,

Bob Young
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