[Boatanchors] SWAN 250C six meter rig question

[Drew P.]

Herman wrote:
   
"The downside of using heterodyning  (other than the expense of another
oscillator, more crystals, etc.) is that  additional filtering is needed to drop undesired mixing products to acceptable  levels."

I have a Utica 650 6 meter transceiver which has double conversion in the receiver section.  The first LO is crystal controlled and mixes the signal frequency down to the tunable first IF in the approximate range of 10-12 MHz. The second LO is tunable for a second conversion down to the second IF at 595 (figure that one out) KHz.  The scheme is rife with birdies and spurious responses, thanks to the single tuned circuit at the first IF, and unshielded at that.  And the radio still drifts.

Worse, it was highly susceptible to frequency pulling caused by B+ changes.  The power supply has poor regulation on receive as a consequence of the 6K dropping resistor feeding the entire receiver RF-Oscillators-IF section.  When I finally put up a beam antenna, using it was a two-handed affair; one hand on the rotator knob, the other on the receiver tuning knob. "Swinging the beam" would cause a signal to drift right out of the passband due to AGC-induced IF B+ current drain changes swinging the B+.  A couple of zener diodes (to regulate the second LO B+ only) fixed that.

Methinks that the Utica 650's only saving grace is its gleaming chrome-plated cabinet.

Drew