This is bizzare

[Cahtrina]

Ok, what I’m about to tell you all is bizarre. Even doug from custom cb radio was baffled. I’m running a sr955 with a 500v behind it. This has been my setup for a little over a month. About 2 weeks ago, I noticed that my rx would cut out after I finished keying the mic. What i mean by cut out is lets say you have 5db of static, then after mic is unkeyed the 5db of static disappears and the people you were talking to can barely be heard, then about 4-5 seconds later the receive would pickup again with the 5db of static. This was only a intermittent situation which i payed no mine too. But now the problem is only getting worse. Every time the mic unkeys i lose the rx for about 4-5 seconds then back on again. I’m now at the point of throwing my setup away. Instead, i talked to doug and he says that it sounds like the delay switch on amp is getting stuck. Sounds logical but no where close to what was causing the problem. Amp was fine. Coax was fine. Antenna was fine. So I switched out the sr955 and put my back up radio (rci 63) up and it still was causing the same issue. So if it wasn’t the radio, coax, amp or antenna, then what the hell was it? Only thing I haven’t touched was the power cords. So i took the power cords off batteries, terminals were still clean, reattached the power cords and bam, no more rx problems, I’ve tested it for 30mins just unkeying the mic and no rx problems. So what was causing the rx problems? Yes the power cords but how???? Theres no relays, just a spade fuse and glass fuse. Like Doug said, it’s bizarre. If any of you have any possibilities of said problem, plz share with me.
Thanks for your time.

 

[Road Squawker]

Glass fuss are known to become "resistive" and an can cause a voltage drop. Often to the point of actually turning the radio off and then back on.

The question is, what will a voltage drop do to your radio.

You don't mention what your transmitted audio sounded like

 

[nomadradio]

A lot of intermittent problems will prove to have a mechanical sensitivity.

Just pressing the power and/or preamp buttons lightly might reveal an oxidized contact in one or both. Your receive signal passes through both of those switches.

The relay is the next suspect when this happens. Removing the amplifiers cover and tapping the body of the relay will reveal a mechanical sensitivity there.

Just sounds like a switch or relay contact point cutting in and out.

73

 

[Cahtrina]

Glass fuss are known to become "resistive" and an can cause a voltage drop. Often to the point of actually turning the radio off and then back on.

The question is, what will a voltage drop do to your radio.

You don't mention what your transmitted audio sounded like

There weren’t any complaints on the tx side other than turn down the echo....... also no complaints on sideband. Now when i key up my voltage does fluctuate, and how much depends on how i run the amp. It used to bounce around a lot until i moved the red wire to battery 1 and the ground to battery 4. The most it dips down to is 12.9 on ssb wide open. But it doesn’t hang at 12.9v, it’ll keep fluctuating between that and 13.9v

 

[Cahtrina]

A lot of intermittent problems will prove to have a mechanical sensitivity.

Just pressing the power and/or preamp buttons lightly might reveal an oxidized contact in one or both. Your receive signal passes through both of those switches.

The relay is the next suspect when this happens. Removing the amplifiers cover and tapping the body of the relay will reveal a mechanical sensitivity there.

Just sounds like a switch or relay contact point cutting in and out.

73

See doug thought it could be the relay too however when i took the antenna out of amp and directly plugged into radio it was still doing the same thing. Both run off different power cords which makes it even more bizarre.

 

[nomadradio]

So, the one thing this problem has in common with different setups is the antenna.

And the coax that feeds it.

Makes it sound like one, the other or maybe both.

73

 

[Cahtrina]

So, the one thing this problem has in common with different setups is the antenna.

And the coax that feeds it.

Makes it sound like one, the other or maybe both.

73

It definitely does sound like a rf problem however since i keep a spare antenna and coax with me, that was the first thing i tried to resolving this issue. There was no change. Who knows, i may never have this problem again. Only time will tell.

 

[Tallman]

Your amp could be oscillating and covering up your receive.

 

[nomadradio]

Hadn't thought of that.

A wattmeter or SWR meter in line with the amplifier output would settle that question.

And then again, he had the symptom without the amplifier in line.

Right?

73

 

[Cahtrina]

Hadn't thought of that.

A wattmeter or SWR meter in line with the amplifier output would settle that question.

And then again, he had the symptom without the amplifier in line.

Right?

73

That’s correct, i took the amp out of the equation and still had the problem.

 

[Shadetree Mechanic]

Intermittent problems just go away sometimes. Don't worry it will be back again some day so you can work on it some more.

 

[nomadradio]

Or is the wire inside the radio leading to the antenna socket center pin loose at one end?

73

 

[Cahtrina]

Or is the wire inside the radio leading to the antenna socket center pin loose at one end?

73

Took radio back off, all things were normal. What ever was causing the problem had to do with the power wires, that we already know. What exactly is the question.

 

[Tallman]

Reattaching the wire might have corrected the problem. I don't remember the first post being that long nor the radios swapped out and the problem was still there with the new radio. Might have been a low voltage problem because of the contact resistance. But with the radio swap it would indicate a problem with the amp,

Some times the keying circuits will oscillate and with no carrier input. I had a KL-1000 that did the exact thing. I tuned a capacitor in the HV area and that stopped it.

It could be a bad jumper in your set up.

 

[Captain Kilowatt]

Glass fuss are known to become "resistive" and an can cause a voltage drop. Often to the point of actually turning the radio off and then back on.

The question is, what will a voltage drop do to your radio.

You don't mention what your transmitted audio sounded like

Only ever had fuses cut a radio out when the radio went into TX not RX. The high current causes too much voltage drop but on RX the drop is negligible. I resoldered the crimp connections on both inline fuse holders and the problem went away. It was an Icom IC-735 HF rig.