[R-390] R-390A IF and AGC

[Michael Murphy]

Hi Joe,

Back a couple cycles ago I took a stock SSB CB and used it as a tunable IF
for a 15 Meter Transverter Mobile Rig - worked great.

R390A SSB
The 6BE6 product detector mod is something I am working on right now with my
R390A. I built the circuit using the Electric Radio article (ER-58) parts
and am finding that it works pretty good. The injection is low and
distortion occurs during high signal conditions however. Before this, I did
the "competition grade" AGC mods that Ray N0DMS published in ER along with
the stock diode detector mod. The 6BE6 product detector easily beats that (I
kept using Rays AGC mod).

Instead of fooling around, I intend to build the product detector stage up
externally and characterize it "outside the box".  I have collected a spare
R390A BFO PTO coil assembly, tube socket, IF can etc.. and am mounting them
an a small BUD box. I also collected a variety of pentagrid converter
candidates which may outperform the 6BE6.

Mike
WB2UID

----- Original Message -----
From: "D. ball" <ke1mb@hotmail.com>
To: <r-390@mailman.qth.net>
Sent: Thursday, May 06, 2004 7:51 PM
Subject: [R-390] R-390A IF and AGC


> Hello all.
>
> I have been having great success by using the IF section of a SSB CB to
> demodulate the RF coming from the 390A's IF out. I cannot say how much fun
> it was to do this and watch it work so well. I can also feed the audio
back
> into the 390 by using the diode out. Now that I can hear SSB much better
> than the product detector mod someone installed I am considering reversing
> the mod to stock.
>
> Question 1: Does anyone think a tube diode makes for better AM audio than
a
> diode?
>
> The other is the ACG mods.
>
> Question 2: Would the stock AGC work better when the radio is used as a
down
> converter rather than the typical AGC mods found in these radios? The CB
has
> it's own AGC in the IF stage.
>
>
> On another note I removed a scary mod in the audio section. Someone had
used
> a line transformer as a plate transformer!!!!.. Did this guy know anything
> about voltage ratings?
> I removed that mod quickly and lucky there was no damage due to the mod.
The
> old caps were replaced with new ones for safty and all works well. I
bought
> a 500 to 4 ohm transformer and installed it in the speaker. No need to
mount
> a transformer on the back of the radio.
>
> thanks
> Joe
> KE1MB
>
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