[R-390] Stage Gain Question

[Barry Scott]

Hi Jacques,

Yes, it's bypassed and the output is grounded.  That's why I don't
understand why there's a place in that table in the First Mixer column
that includes the frequencies above 8mc.

Thanks,
Barry - N4BUQ

On Mon, Oct 28, 2024 at 10:19 PM Jacques Fortin <jacques.f at videotron.ca> wrote:
>
> Hi Barry,
> The 1st mixer is bypassed in the 8-32 Mc range.
> See the Block diagram on page 141 of the TM 11-5820-357-35.
>
> 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 : 28 octobre 2024 22:48
> À : R-390 Mailing List <r-390 at mailman.qth.net>
> Objet : [R-390] Stage Gain Question
>
> After removing the RF deck (twice - don't ask..) and, other than finding one
> of the mini-banana connectors on Z221 had let go of its post (again), I
> didn't find anything of interest so I reattached that mini-banana (using a
> bit more heat and making sure it was solidly connected), I reassembled the
> RF deck.  After a touch-up on the realignment of Z219, Z220, and Z221, and
> resetting the RF gain, I can tell the noise level on BCB is down from the
> way it was.  Not dramatic, but I think it's an improvement.
>
> I then started back checking the stage gains and am still seeing low gain at
> the first mixer for all but the 0.5-1mc band; however, there's a few things
> about that process I don't understand.
>
> The table that defines the gain for Test Point E208 shows the acceptable
> signal generator voltage range to produce -7v at the DIODE LOAD for 0.5-8mc
> which makes sense.  It also shows the 9-18mc range and that part doesn't
> make sense to me.  In the circuit description for the First Mixer, it states
> that "In the 8- to 32-mc range, the front section of S210 grounds the output
> circuit of V203" and that can be seen on the schematic as well.  With the
> output grounded, then how is any output of that part of the circuit realized
> on those bands?
>
> 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
>