Ranger RCI 2950 weird crackling sound while transmitting on AM and SSB

[TigerOne]

Hello everyone,

I am currently struggling with a severe problem: My Ranger RCI 2950 produces loud crackling noises in the modulation when transmitting. This applies to all types of modulation, whereby FM occurs rarely but all types of amplitude modulation such as AM, USB and LSB are affected. It doesn't happen always but most of the times. The device may send crystal clear signals for a minute... but then crackles and squeaks so that nothing can be understood. Because the phenomenon is probably difficult to describe verbally, I made a video (modulation is monitored "backstage" with a second radio):



The most curious thing: when I change the SWR on the matchbox, the tone moves higher and lower, almost like a VCO. Mic Gain has no influence, and several mikes behave in the same way. It has to happen "in" the radio itself. I can also rule out antenna or cable because other radios work perfectly.

Is there anyone out there able to help me isolate the cause? My thoughts on this (and please correct me if I'm wrong): I suspect that it must be something with the ground / electrics or something with the power amplifier. Maybe a ceramic filter ... but which one? Electromigration? I have already re-soldered the audio IC. Does anyone know the symptoms?

Any help is highly appreciated!!!

73 + 55,
Tiger One

[Bombero]

Hey..

Take the cover off and check for cold solder joints, depending on the model and age of your 2950..that could
be the culprit.

Bombero

[jessejamesdallas]

If you have two radios too close together, then when you key one up, the other one is going to pick-up allot of RF and cause it to make all kinds of noises...(even if the receiving radio doesn't have a antenna hooked-up at the time)

[warlock35po]

Hello,for the age of those units (20/25+ years) I would check first for cold solder and maybe capacitors in the audio stage.Who knows,could be about anything, those units are well by their Best Buy dates and most of them were rode hard and put away wet.Good Luck,Regards,warlock35po. VE1-CSP