AW23 beat oscillator

[Lawrence E Edmister]

Hi everyone. I have a question about the beat oscillator in the AW23 . I have noise in the audio that stops if antenna is shorted out. All voltage checks look good except the plate of beat osc. Instead of 230 vdc as print says, it measures 82vdc. I'm tracking that down now { 1k resister may be open} . I'm not sure how the oscillator works or what it does really. holding the switch in and adjusting the pot seems to do nothing but I don't know what I should expect anyway. Any help is greatly appreciated.

[David C. Poland]

For the AW-15 and AW-23 Scotts, When tuning the radio while pushing the BFO button, as you near the station (carrier wave),  a tone or whistle descends into audible range and at the lowest tone/pitch you are exactly tuned.  As you pass the station, the tone ascends again. The tone can be rather low depending on the adjustment of that screw on the back of the receiver. (Read an AW-15 or AW-23 instruction manual section about  tuning on short wave.) Useful for short wave reception to find the carrier wave when there is no content - like dead silence between music selections, or a ham station not sending any code, or a foreign news station like BBC about to start a program in a minute or two after switching frequencies.

Adjusting the BFO screw recessed on the back of the chassis skirt is intended to select the "on station" tone to a desired or more pleasing pitch. If this control is way out of adjustment, the "low tone" may have been readjusted too  high to even hear the tone. You know - the same folks inclined to tighten down those loose screws on IF transformers and tuning capacitors.

Hope replacing the resistor fixes your problem. You may need to seek a tone because to had adjusted the screw.

Also, with the BFO button pushed,  you can also actually hear the voice of  ham operator broadcasts using SSB.

[Lawrence E Edmister]

Thanks David for the info. I think I get it. Is it only for use on shortwave or broadcast band as well? 

The 82v plate voltage turned out to be a wrong connection according to schematic. Problem is, it looks like it was always that way, not someones mistake. I'm not sure which is correct. Anyway, I'm still trying to track down the noise. Seems like it may be in RF or converter stages. This chassis is a little more complicated than I've worked on in the past but I like a challenge. At 71 years old, it helps to keep the brain sharp and I need all the help I can get with that!

David C. Poland said:

For the AW-15 and AW-23 Scotts, When tuning the radio while pushing the BFO button, as you near the station (carrier wave),  a tone or whistle descends into audible range and at the lowest tone/pitch you are exactly tuned.  As you pass the station, the tone ascends again. The tone can be rather low depending on the adjustment of that screw on the back of the receiver. (Read an AW-15 or AW-23 instruction manual section about  tuning on short wave.) Useful for short wave reception to find the carrier wave when there is no content - like dead silence between music selections, or a ham station not sending any code, or a foreign news station like BBC about to start a program in a minute or two after switching frequencies.

Adjusting the BFO screw recessed on the back of the chassis skirt is intended to select the "on station" tone to a desired or more pleasing pitch. If this control is way out of adjustment, the "low tone" may have been readjusted too  high to even hear the tone. You know - the same folks inclined to tighten down those loose screws on IF transformers and tuning capacitors.

Hope replacing the resistor fixes your problem. You may need to seek a tone because to had adjusted the screw.

Also, with the BFO button pushed,  you can also actually hear the voice of  ham operator broadcasts using SSB.

[David C. Poland]

The BFO functions on all bands, but you really don't need it on the broadcast band. But you can use it like a magic eye to get a broadcast station exactly on station.