Browning Golden Eagle mark IV LSB tx

[KneeBiter]

Browning mkiv. AM tx audio is full and normal. USB tx audio is full and normal. LSB tx audio is narrow and tinny sounding. My first guess is to replace the lsb crystal filter. Any other tips ?

 

[nomadradio]

The trimmer cap C201 on the carrier crystal is the only other thing that should have this kind of effect on the audio. Normally if this setting is tinny and weak on one sideband, it will have too much low audio frequency content on the opposite sideband. Carrier suppression frequently suffers as well.

And it certainly could be the LSB filter.

Check C201 and see if it can be set for an acceptable compromise between LSB and USB voice quality.

If not, that filter looks more likely the culprit.

73

 

[KneeBiter]

The trimmer cap C201 on the carrier crystal is the only other thing that should have this kind of effect on the audio. Normally if this setting is tinny and weak on one sideband, it will have too much low audio frequency content on the opposite sideband. Carrier suppression frequently suffers as well.

And it certainly could be the LSB filter.

Check C201 and see if it can be set for an acceptable compromise between LSB and USB voice quality.

If not, that filter looks more likely the culprit.

73

Thank you for that info. If I am able to get the audio balanced with c201 and I am a bit off frequency on lsb tx can I trim c122 the 6mhz a touch to pull it in?

 

[KneeBiter]

Ok, I aligned it to service manual spec with a calibrated frequency counter. Set the 6mhz voltage as stated in manual. Both LSB and USB sound about the same now. Not full like am but not tinny like it was. On ssb it's off a touch on freq. Is there a way to trim it in? If I use c201 then I am on the edge of the filter and this is where the tin can comes from. I know it uses the 2 filters to go up and down for the ssb using the 5.645 to get where it needs.

 

[nomadradio]

Ok, I aligned it to service manual spec with a calibrated frequency counter. Set the 6mhz voltage as stated in manual. Both LSB and USB sound about the same now. Not full like am but not tinny like it was. On ssb it's off a touch on freq. Is there a way to trim it in? If I use c201 then I am on the edge of the filter and this is where the tin can comes from. I know it uses the 2 filters to go up and down for the ssb using the 5.645 to get where it needs.

Okay, so let's say that the best-sounding compromise setting for C201 is 1 kHz high, 5.646 MHz. Setting the trimmer cap on the PLL master crystal will compensate, and get the transmitter on frequency.

You said 6 MHz. That means this radio really is a Mark 4, not a 4A. Best of luck keeping that setup on the air. I swore off of it decades ago. Couldn't make a high-enough percentage of them stay on the air to qualify as a professional-quality repair job.

73,
Chris

 

[KneeBiter]

Okay, so let's say that the best-sounding compromise setting for C201 is 1 kHz high, 5.646 MHz. Setting the trimmer cap on the PLL master crystal will compensate, and get the transmitter on frequency.

You said 6 MHz. That means this radio really is a Mark 4, not a 4A. Best of luck keeping that setup on the air. I swore off of it decades ago. Couldn't make a high-enough percentage of them stay on the air to qualify as a professional-quality repair job.

73,
Chris

Thank you Chris. I know how much you distance yourself from the mk iv. But for some reason I like the pain. Your tips got me straightened out. Much appreciated.