[Elecraft] loss of RX sensitivity

[Frederick Dwight]

Scott,
     The problem you describe is actually quite common in electronics.  In the telephone industry, especially in the “good old days” with wire cables, sometimes with many splices it was common to get drop outs.  These could be due to a splice, wire wrap connection, oxidized relay contact or whatever, especially with only low level signals.  If the circuit also had a DC voltage on it, the problem often did not exist.  In fact it was common on critical circuits for the FAA or military, or whatever to sometimes just put “sealing current” on certain circuits just to be sure it was reliable.  Often we used 24 volts DC or less with only a few ma of current.  At one time I had many phased verticals which were controlled by many relays.  Occasionally the received signal would drop by many S units.  Sending a single dot, even with QRP or QRPP power always cleared the problem, sometimes for weeks or months.  So it could be a connection in the antenna system, a plug on a circuit board, or even a relay.  I have never experienced trouble with Elecraft relays personally.  Sometimes PL-259 center pins are not correctly soldered, and can present similar symptoms.  You could try a random wire, or even something like an 80 meter dipole on 30 meters, just to see if it was anywhere in the antenna system.  Even a volt or two is often enough to punch through a poor solder or oxidized connection, but even something like a 0 dBm signal is just not enough.  I have identified problems with BNC connectors and adaptors purchased at ham flea markets which are just not reliable and are probably factory rejects.  So look into your antenna system before you dig into your rig.  You could also hook a signal generator to the rig and see if it receives OK on all bands with something like less than an S9 signal.  Be sure to not transmit into your generator, and/or set your tx to very low power.  Good Luck   Rick  KL7CW

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