[Collins] S-Line questions

[Dr. Gerald N. Johnson, electrical engineer]

Tuning the receiver preselector away from resonance will lower the LO
drive to the transmitter and so lower its output. You may find backing
off on the RF gain control is as effective at cutting down on the
background noise. I've done that extensively on multiple radios
including the S-line.

The stock D-104 element tends to have excess high frequencies that can
overdrive transmitter audio stages with syllibants outside the filter
pass band. The impedance of the crystal D-104 is very high and an
ohmmeter check won't be a valid check, and connecting an ohmmeter to a
microphone should be accompanied by a mentor screaming, "DON'T DO
THAT!!!!" or more violence. The microphone is made for very low currents
far lower than an ohmmeter supplies. It can be damaged by applying
voltage when its not made for it.

A dynamic microphone doesn't like an ohmmeter either but the DC
resistance will be smaller than the AC impedance. Same thing is true of
a speaker. Dynamic microphones are made quite similar to speakers but
the wires are much smaller in the microphone and more easily smoked.

Multiple dipoles mounted in parallel work, though most find they are far
easier to tune if spaced 4 or 5 inches apart.

73, Jerry, K0CQ, Technical Advisor to the CRA

-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.