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RCI 2950DX... Slight Carrier Problem on SSB ,,,,,

H

High Miler

Active Member
May 30, 2005
298
6
26
Pennsylvania
On my 2950DX I have detected a slight carrier not even detectable by a good watt meter... VR7 has been adjusted for minimum Spurious emission...

Question now is... Is the carrier due to a Biasing problem... The radio sounds great on SSB ... But would like to get rid of the little bit of carrier that it produces... Probably will send radio out, just wondered if anyone had an idea what it may be...

If the signal I generate is less than about 10 to 20 over 9 the carrier is not even detectable..

Tnx much in advance.
 

High Miler said:
On my 2950DX I have detected a slight carrier not even detectable by a good watt meter... VR7 has been adjusted for minimum Spurious emission...

Question now is... Is the carrier due to a Biasing problem... The radio sounds great on SSB ... But would like to get rid of the little bit of carrier that it produces... Probably will send radio out, just wondered if anyone had an idea what it may be...

If the signal I generate is less than about 10 to 20 over 9 the carrier is not even detectable..

Tnx much in advance.
Click to expand...

Your problem is a balanced modulator issue, I'd be willing to bet the farm on.

Use a scope, and adjust the VR controlling the balanced modulator for minimum output with 0 modulation.

You could also have a "squeal" being generated in the audio circuit. At 1kC, it would do exactly as your seeing.

--Toll_Free
 
Tnx Much Toll Free... I adjusted VR 7 which is the balance modulator and No go... Still there...

I guess I will have to send it out to have it further diagnosed, It's definitely beyond my scope of know-how...

Thanks again for the input!
 
rci 2950dx

If you like the radio and want to keep it the best money you will ever spend will be when you box it up and send it to justin.I messed with my old yaesu ft101e for about two months with no results, finally I put her in a box and said goodbye, now I got 25 guys trying to buy it.But it would be like getting rid of one of the kids, kind of silly but I just like the old radio :D
 
High Miler said:
On my 2950DX I have detected a slight carrier not even detectable by a good watt meter... VR7 has been adjusted for minimum Spurious emission...

Question now is... Is the carrier due to a Biasing problem... The radio sounds great on SSB ... But would like to get rid of the little bit of carrier that it produces... Probably will send radio out, just wondered if anyone had an idea what it may be...

If the signal I generate is less than about 10 to 20 over 9 the carrier is not even detectable..

Tnx much in advance.
Click to expand...

could it just be your mic gain up to high on mic or radio ???
 
i'm a little lost as to how everyone even knows you have a problem. you never said how you detected the carrier (what type of equipment you used) nor how strong the signal is. you did say a wattmeter can not detect it so it is not very strong at all. btw, i did not follow the last part about generating a signal at 10 to 20 over s9..so maybe that too is why i'm lost.

i can say this with 100% certainty. you will -ALWAYS- have some leak through carrier power in ssb mode with any rci/galaxy type radio. when the balanced modulator is aligned right you will see around 50uw/-13dbm (as seen in average mode on a spec an) of carrier power in each side band. a wattmeter will not detect this but another radio very close by will.

the question is not if you have a carrier in ssb...but exactly how strong the carrier is. that is if you have a way of benchmarking the level.

you very well may have a problem with the balanced modulator. i personally don't see enough information to verify that you even have a problem at all. could you explain better how you tested this radio?

if you could better explain
 
I moved to a new location which is within' a couple miles of a local I talk too...

He said that I was giving him 3 S-Units with no Transmission... Just being keyed up which I am surprised he caught.

I than kicked on a radio above the one I was using and sure enough, On key-up, no modulation I was registering S-7 on my monitoring radio with no antenna hooked up.

Thinking this was a fluke, I took the 2950DX out to my blazer, hooked it up and keyed the radio with the D-104 Locked in transmit... Come inside and hooked my monitoring radio to my base antenna and there was the carrier...

Next day I called my friend that has Oscilloscope/Spectrum Analyzer etc hooked in line... He is able to listen 16 KC wide and is not far from me... From 1KC up from transmit frequency he could see and hear the carrier as he dialed his VFO up and down.

Yes there is a carrier comming from the radio, The Balance Modulator VR-7 has been adjusted for minimum carrier... There is nothing more I can do at this point.

You cannot hear the carrier on my transmission... I.E. - Dial the VFO up or down to HEAR the heterodyne UNLESS I am hitting that station with a 20+9 signal... Then you will hear the little Whirrr which you all know what I am talking about....

There is a slight carrier comming from the radio without question...

And yes I have tried 2 stock and 1 D-104 Desk Mic all with the EXACT same result...
 
I've found, on rare occasions, that 2950's seem to show some carrier leakage if they are out of alignment in areas other than the balanced modulator. I don't have a specific explanation for why, but if you've never had the radio completely aligned, I'd recommend doing that, not only for the carrier issue, but just to make sure its on freq everywhere.
 
DTB Radio said:
I've found, on rare occasions, that 2950's seem to show some carrier leakage if they are out of alignment in areas other than the balanced modulator. I don't have a specific explanation for why, but if you've never had the radio completely aligned, I'd recommend doing that, not only for the carrier issue, but just to make sure its on freq everywhere.
Click to expand...

That's called a lack of proper RF bypassing... Same thing Justin was referring to in another thread you had commented on, and I expanded. Check it out, and it might tell you why you see those "carriers".

Some people might call them "bad engineering".

--Toll_Free
 
Re: RCI 2950DX Carrier leakage.

Have you check TR40 this transistor can cause this problem and you should check that TR47 is not switch on in TX this will also give you a carrier leak.

Rick (Euro Radio Co).
 

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