[R-390] good product detector

[Michael Murphy]

Hi Roger

The R-11A does not have a BFO at all, so I built the whole product detector,
BFO and Audio outboard. I pulled V605 and V606 which have series heaters.

V-605 is a14A7 which is a dual triode (wired as a dual diode) one side as
the AM detector and the other some kind of ANL clipper. V-606 is the12A6
audio output stage. Now if I were a purist, I could have turned V-605A into
a triode product detector and the other section into a BFO and used a solid
state diode as an AM detector (with some clever switching for AM/CW) and
retained the 12A6 audio output stage. That would have been pretty nice. Of
course I would have had to shoehorn in a 85 kHz BFO coil somewhere.

Instead, I pulled the tubes and did everything on a solid state board
running on 28 VDC regulated down to 12 VDC. The board contained a simple
dual gate mosfet product detector right out of the Handbook, a diode AM
detector, a bipolar BFO with a home made 85 KHz hartley coil and an LM380 1
Watt Audio Amp. Not super but pretty good for the Q-5er. I could not find my
schematic- maybe there never was one.

More R-11A weirdness... The AVC is actually derived not in the (now missing)
detector, but in V-604, the last IF tube. This is a 14R7 which is a pentode
with two diodes stuck inside, probably meant just for AGC. I do remember
fooling with the AGC, but I can not remember what I did. I do remember that
the IF transformer had both a High Z and a diode tapped output on the final
transformer which was a deluxe setup for feeding the AM and CW detectors
separately.

By the way, you use the rig with all of the IF coupling rods pushed most of
the way in for AM (which really slices AM giving wonderfully steep skirts);
partially out for SSB, and all the way out for CW. It is not as hard as it
sounds.

I hope this helps.

Mike Murphy WB2UID


----- Original Message ----- 
From: <Flowertime01 at wmconnect.com>
To: <r-390 at mailman.qth.net>
Sent: Wednesday, April 13, 2005 7:04 PM
Subject: Re: [R-390] good product detector


> I stuck a good product detector in an R-11A and it really performed.
> Mike WB2UID
> ---------
> Mike,
>
> Do you have a schematic of the product detector circuit you used? If it
> worked good and you liked the performance I would like to give the circuit
a try.
>
> Roger KC6TRU
>
>
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