1st gen CB squelch problem, splitter/duplexer

[Gearhead]

Hi, I'm posting this in 1st gen tech and also the Audio forum. Sorry for the repeat, but I wasn't sure which would be best.

 

My CB was working OK. I had dual short antennas. I recently switched to a single 3' Wilson Flex fiberglass antenna and a Firestik splitter, which should work better. I got it all hooked up and now the CB is stuck in receive mode whenever it is on. I disconnected the antenna and splitter and it stays in RX mode even with no antenna. It's like the squelch is turned to max sensitivity, but adjusting the squelch doesn't change anything (it used to function normally). It did work, now it doesn't. Timing is conincident with antenna change, but problem is independent of the antenna being connected. What could have happened?

 

Second, I've read that the Firestik splitter/duplexer is very efficient for signal transfer. The CB, while stuck in RX mode, is successfully receiving signals. But they are stronger (voices sound louder) when the antenna is connected directly to the CB, compared to when wired thru the splitter? What gives? Does the "Matching" pot affect receive strength or just transmit?

 

Thanks,

Jeremy

[lonestarmedic]

Check the plugs! I left off a plug on the bottom once and only got partial functions. Do the PTT switches seem to work?

 

JB

[Gearhead]

Hmmm, PTT works, but will recheck all connectors. Thanks.

 

My thought is that perhaps a Squelch pot solder joint has cracked - maybe?

 

Jeremy

[BOO]

Hi, I'm posting this in 1st gen tech and also the Audio forum. Sorry for the repeat, but I wasn't sure which would be best.

 

My CB was working OK. I had dual short antennas. I recently switched to a single 3' Wilson Flex fiberglass antenna and a Firestik splitter, which should work better. I got it all hooked up and now the CB is stuck in receive mode whenever it is on. I disconnected the antenna and splitter and it stays in RX mode even with no antenna. It's like the squelch is turned to max sensitivity, but adjusting the squelch doesn't change anything (it used to function normally). It did work, now it doesn't. Timing is conincident with antenna change, but problem is independent of the antenna being connected. What could have happened?

 

Second, I've read that the Firestik splitter/duplexer is very efficient for signal transfer. The CB, while stuck in RX mode, is successfully receiving signals. But they are stronger (voices sound louder) when the antenna is connected directly to the CB, compared to when wired thru the splitter? What gives? Does the "Matching" pot affect receive strength or just transmit?

 

Thanks,

Jeremy

 

Jeremy,

 

I posted on your other post so you know what I think, right or wrong.

Anytime you cut the coax and insert a fitting or any thing in the line there is going to be some losses. I would't think you could tell much difference by listening to the audio if the radio was hooked up direct or through the duplexer. Makes me think there is a lot of loss in that duplexer.

BUT I would say at this point your squelch problem is not related to the duplexer.

Can I presume the transmit does not work at all? And when you key the mic does the receive go away and you only have silence from the radio?

Jerry

[Gearhead]

Jerry,

 

I agree the duplexer is not the problem, perhaps a secondary issue.

 

Actually, keying the mic put the unit in transmit mode like normal. The RX indicator goes off and the TX indicator goes on, and yes, the unit goes quiet. I had no other CB present to see if I was actually transmitting.

 

Jeremy

[BOO]

Thanks Jerry. I'm not an electronics guy. I've seen these things referred to as a duplexer and as a matching box. To me, it "splits" the signal to the CB and radio. It's a Firestik box designed for that purpose, about the same size as the factory stock "splitter".

Yeah I went their site to see what they are selling and it apprears to be about the same thing that the orignal was.

 

Is overloading the front end permanent, and how does it happen?

Now like I said this usually happens to the am/fm radio when you transmit on the CB and the antenna is not disconnect to the am/fm side. and yes it can burn up something. I'm sure how this could have happen to the CB receive side though unles the PTT switch malfunctioned somehow.

Remember, now it is stuck in RX mode even with no antenna (or box) connected. I know it's bad to transmit with no antenna connected, but turning it on shouldn't be a problem, should it? Not a problem..

I'm probably making this a bigger problem than it really is.

Checking all the connections like that was suggested is a real good starting point.

Check the ones where the head plugs into the faring. All kinds of problems can be generated from there. Both sides CB and am/fm.

 

I should have went to the other post and read it before I responded above,

Sorry

Jerry

[Hugbare]

Hi Jeremy ... This is in answer to your email and some thoughts ... The Firestik splitter

should not be the problem .. The pots adjust SWR only and have no effect on the

receive side .. Do you have any volume control on the CB and I take it the squelch is not

doing its job, even when turned fully clockwise (Should get quiet up there at the stop, or

before) .. Since there are only 2 connections on the CB, coax and power/audio/PTT plug

make sure they are good and tight ... Sounds like maybe the squelch pot may have bit

the dust .. I really doubt very seriously that changing out the antenna would cause any

harm on the receiving side and you said you had set the SWR OK in your email, so that

would not be the problem either ... Check all your connections again coming out of the

splitter .. Should only be two, one to the AM/FM and the coax going to the back of the

CB ...

[BJB]

By what you describe, it sounds as it the squelsch is stuck wide open or completely counter clock wise? Why..I don't knowl.

 

Today in my 89, when I hit the PTT button, the 'TX' symbol came on, but nobody could hear me. They could hear that I keyed the mike...but no sound. I screwed around with this for 25 miles, before finally changind CB channels up and down. Went back to the original channel and everything worked perfectly. I don't know what I did, but perhaps it will work for you also. I think in these older bikes there are a lot of iffy connections etc. Good luck.

[Condor]

Sounds like you may have keyed the mike without a good antenna connection and blown the transmit finals???

[Gearhead]

Thanks all for your input.

 

I may have keyed the mic, BRIEFLY, with no antenna connected. Hmm...

 

I looked up the CB specs on p. 8-20 of the manual for 86+ bikes. It's p. 449 on the PDF manual available here. Under the Transmitter section, there is a line that says:

 

Output Protection.................5 minutes for all VSWR's

 

Does that mean it will tolerate 5 minutes with the mic keyed, even with no antenna? The thing is, it's not Transmit that's giving me a problem that I know of, it's Receive.

 

Marshall, I apologize if I misled you but I have not yet checked SWR with any of my antenna or duplexer setups. You asked about volume control; it may not be working either. I didn't put on my helmet / headset, just listened thru the speakers. The signals I was receiving were quiet in the speakers (I was probably a good distance from them), and the volume knob did not change them.

 

Keep 'em coming!

 

Thanks,

Jeremy

[Gearhead]

On the way home with the headset connected, I did some more CB testing. It was the same as described above, stuck in RX mode, but I verified that the volume knob is also not working. The on-off click on the knob does in fact turn the unit on and off, but the volume was one level regardless of where the knob was set. I listened in on some dudes' conversation for awhile to determine this. All buttons function normally, as do the remote controls on the left hand grip, but both knob pots are not working. This can't be coincidence. Weird. Maybe it's the twilight zone.

 

Jeremy

[BOO]

Jeremy,

How's the CB doing?

What was the problem if you figured it out?

Jerry

[GeorgeS]

Pull the top off, find the Pull apart plug , ( very near the duplexer unit ) Clean the contacts of this plug. Also, tug lightly on all the wires going into both sides of this plug.

I had some problem, and found 2 wires in this plug pulled out of their crimps.

I had to resolder them to the male and female pins.

 

Just a thought.

[Gearhead]

Hi guys. No, been out on vacation, not working on CB for a while. Now I'm back and sure would like to fix this thing!

 

George, what pull-apart are you referring to? Inside the CB unit or external? Is it the 4-wire (I think it's 4) that plugs into the back of the CB? Are you saying you had the SAME problem (volume and squelch knobs stuck wide-open)?

 

Thanks,

Jeremy

[Gearhead]

Hello. I took my CB apart over the weekend and found the problem! It turns out that both potentiometers, volume and squelch, were bad. Kinda weird that I found two unrelated bad parts. But it makes sense. Thinking back, the squelch knob was a little touchy and noisy when adjusting it before it died. And the volume - I don't think it has worked since before I bought the bike. The few times I've used the CB I noticed that the audio I heard was very quiet, even with the vol cranked.

 

I went to a local truck-stop-CB-shop and showed them what I needed. It turns out that the Venture CB uses totally standard pots (imagine that!) and they had some there with the exact same construction and cross-section. However, they only had them in dual-type. That is, the one pot is designed to be both on/off, vol and squelch, using two concentric knobs. It is really three switches stacked - the on/off clicker, the vol pot and the squelch pot, so it is a little longer than my originals, and the knobs are different. I used that configuration, one switch for all controls, and soldered the original little harnesses onto the new switch. There is enough depth where it goes to accomodate the longer switch. I installed it into the squelch side hole, and put one of the dead pots and knobs back into the vol hole to plug it. I used the chrome knobs that came with the pot, and arranged some o-rings under them to hopefully shed water like the original knobs did.

 

Now I just gotta set SWR and I'll be back in business!

 

Jeremy