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LF: Re: AR88LF IF output

To: [email protected]
Subject: LF: Re: AR88LF IF output
From: "James Moritz" <[email protected]>
Date: Sun, 15 Aug 2004 12:52:22 +0100
Reply-to: [email protected]
Sender: [email protected]
Dear Bryan, LF Group,
Before hauling the AR88LF back to the shed, I tried using it as a tunable front end for another receiver tuned to 735kHz, as was suggested last week. I found a good place to tap off the IF signal was at the cathode of the first IF amplifier valve (V5 - 6SG7). On my unit this has a 100ohm un-bypassed cathode resistor between pin 3 and ground. Signal was taken from pin 3 to the second RX input through a 0.1uF DC blocking capacitor. This gave a satisfactory signal level for both my IC718 HF rig (which has somewhat reduced sensitivity at 735kHz) and RA1792 receiver. Obviously, selectivity was greatly improved, and sensitivity was good, as before. The AR88LF was operated with BFO and AGC switched off, and the selectivity switch in position 3 or 4. Having the second receiver connected did not seem to particularly alter the behaviour of the AR88 used by itself. The main drawback of this combination as a 136kHz receiver is the relatively poor frequency stability compared with a modern RX - but this would not be an issue for aural CW reception.
Can't help with Jane Russell, though ...
Cheers, Jim Moritz
73 de M0BMU
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