[R-390] Low gain 0.5 MC through 7 MC

[jkharvie]

 Excellent update!  

One can only think of the signals on 15 meters back when this receiver was initially placed into operation.
Nothing quite like resonance.  


John N3JKE

    On Monday, September 23, 2024, 1:59:13 PM EDT, Barry Scott <72volkswagon at gmail.com> wrote:   

 A preliminary alignment of the 2nd and 1st variable IFs has made a
significant difference.  The trimmers are stuck in the 1st IF's cans so I'm
going to pull, clean, and work those free before continuing.  If the 1st
IF's trimmers make as much difference as the 2nd IF's did, that will really
boost the sensitivity.

I actually heard signals on 15 meters - I think for the first time with
this radio!

Thanks,
Barry - N4BUQ


On Sun, Sep 22, 2024 at 9:25 PM Jacques Fortin <jacques.f at videotron.ca>
wrote:

> Barry, the troubles of your R-390/URR reminds me a lot of similar things
> I've gone thru with mine....
> Yes, it can be the first mixer tube: I just hope that is not a "dwarf"
> Raytheon 6C4W used there.
> Or it can be something around (any component in the plate circuit) Z221
> again ???
> The problem can also be the first crystal oscillator (V401) which do not
> have enough output...
> Check every component around and swap the tube for a known good one if you
> have spares.
>
> 73, Jacques, VE2JFE in Montreal
>
> -----Message d'origine-----
> De : r-390-bounces at mailman.qth.net <r-390-bounces at mailman.qth.net> De la
> part de Barry Scott
> Envoyé : 22 septembre 2024 20:37
> À : R-390 Mailing List <r-390 at mailman.qth.net>
> Objet : [R-390] Low gain 0.5 MC through 7 MC
>
> Sensitivity on the lower 7 bands is significantly lower than on 8 MC and
> up.
> I can see this very readily with the signal generator as input and, with
> the
> output level remaining the same, switching from any of the first 7 bands to
> 8 MC or higher shows a significant (approximately double) rise in the
> radio's dB meter.  It's also noticeable just listening to stations.
>
> The common factor seems to be V203 (1st mixer) and I suspect that tube
> might
> have low gain (possibly gassy?).  Is that a reasonable thing to start with?
> I don't see how something affecting the AGC would affect all the paths to
> V203's grid and so I was thinking the tube itself might be the problem.
>
> Thanks,
> Barry - N4BUQ
>
>
______________________________________________________________
R-390 mailing list
Home: http://mailman.qth.net/mailman/listinfo/r-390
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:R-390 at mailman.qth.net

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html