I had been experiencing problems with the receive on my 139XLR. Strong station's signals sounded crackly and distorted when propagation was high. My audio chain checked good. Ditto the receive AGC. Rig was totally recapped about one year ago. Started digging around with my 'scope, and found that the protection diode set at the input of the receiver front end transformer was clipping almost 100% of the time when a superstrong signal was detected. The garbage generated by this clipping (square waves and harmonics) was the cause of the distorted audio. So many operators are running really high wattage these days, and this, coupled with my high gain antenna, caused the diode clipping.
The solution was to install a 10db attenuator at the receive input. A simple three resistor attenuator works perfectly. I used a relay to switch the attenuator out when propagation is low.
Finally have clean receive audio again.
- J.J. 399
The solution was to install a 10db attenuator at the receive input. A simple three resistor attenuator works perfectly. I used a relay to switch the attenuator out when propagation is low.
Finally have clean receive audio again.
- J.J. 399
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