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Clean sound on 27.3850 but warble on 27.4025

8113 Northern MN

Active Member
Aug 9, 2013
156
19
28
43
Virginia,MN
I have a small amp that ive been using when out at the hunting shack and firewood cutting place. I am reported to have a nice crisp clean sound on 38 when running the full 150 watts...but iof i go to channel 42 I am told I have a warble to my voice. Also, on 42 when talking I notice the relay cuts in and out alot while im talking....if there is a little pause between my voice it cuts out. So alot of clicking. I dont know what would cause these issues but would like to know what I can do to remedy this.
 

Instead of driving the amp wide open to distortion try backing down to about 75%. The change will make no difference on the other end and it may clean up your audio.
 
I am not familiar with that amp unless it is a knock off palomar/red devil amp ( 2 1446 transistors) but take that wide banded thing with a grain of salt.
Is the radio stable with the amp off?
Make sure it is not a radio problem first.

73
Jeff
 
You get 150 watts out of a 2 x mrf453 amp? Mrf 453 is rated at 60 watts each at 55% efficient . Thats never going to sound good. Disregarding that .Check your input vswr between the radio and amp .
 
Also look at the antenna system, on ch 38 VSWR may be "OK" but in ch what was it 42 or something the VSWR may be not so good and the amp and radio are having RFI or CMC issues.

If you sound good on one frequency and bad on another then antenna system OR if there had been a channel conversion to your radio it may need aligned.

Warble usually is lack of current on the radio especially in SSB since most "screwdrivers" tune a radio for max output and do not think about the limits of the components in the circuits.

Check vswr of antenna system if it is good put the radio on the bench see how it looks once aligned.
 
I was tinkering with a Cobra 148 GTL this morning( side mic/PC-412 ) that works "fairly well" on the normal 40 channels, but still has some drifty issues that a 148 should not have.
The cause, someone has added a crystal/switch/for a extra band of channels.
When the extra crystal is switched in, the radio becomes even more unstable.
This is because whomever did the conversion did not take the time to secure the added wires/ crystal well and were sloppy.
Removing the covers from the radio and just placing your finger near the crystal/switch or moving wires around was causing the radio to shift frequency......
His "tech" gave up because after trying to get the radio to stay on frequency on the second band, he found that when the covers were placed back on the radio, it would shift again.
It is not a good idea to have a crystal hanging off of the side of the switch, with long unsecured/unshielded wires floating around.
Even more so in a mobile radio.
I moved the crystal, soldered it to a secure location, grounded the outside of the crystal case, re-routed and shortened up the wires, used some cable ties and a few dabs of hot melt to keep everything in place.
Much better and the frequency shift problem with the covers back on has gone away.
It pays to be neat.

73
Jeff
 
Sounds to my like a low voltage issue. Where are you getting the power for the amp and how is it grounded? What Coax are you using for a jumper from the radio to the amp?
 
I fixed this issue today everyone! Last night the problem was getting worse and worse and worse even showing up on 38 and my locals I was talking with were constantly mentioning it. So i decided to dig in and not sleep until I found the issue. I started with the Capacitor next to the Relay in the mic. My thinking was...since whenever I key I could hear the relay clicking over and over perhaps the capacitor wasnt doing its job. Sure enough....changed it out and after that as soon as I key the mic I can hear the relay kick in rather then waiting for me to make a sound. All of the locals had gone to bed so I decided to just finish it out and change ALL the capacitors in the amp. Well, this morning I called out CQ on 38 and was told absolutely no warble. Then i went up to 42 and chatted with good ole 437 Operator Joe out of Louisiana and he reported that my sound was better then usual and absolutely no warble. So, im assuming it was the capacitor by the relay!
 
I was tinkering with a Cobra 148 GTL this morning( side mic/PC-412 ) that works "fairly well" on the normal 40 channels, but still has some drifty issues that a 148 should not have.
The cause, someone has added a crystal/switch/for a extra band of channels.
When the extra crystal is switched in, the radio becomes even more unstable.
This is because whomever did the conversion did not take the time to secure the added wires/ crystal well and were sloppy.
Removing the covers from the radio and just placing your finger near the crystal/switch or moving wires around was causing the radio to shift frequency......
His "tech" gave up because after trying to get the radio to stay on frequency on the second band, he found that when the covers were placed back on the radio, it would shift again.
It is not a good idea to have a crystal hanging off of the side of the switch, with long unsecured/unshielded wires floating around.
Even more so in a mobile radio.
I moved the crystal, soldered it to a secure location, grounded the outside of the crystal case, re-routed and shortened up the wires, used some cable ties and a few dabs of hot melt to keep everything in place.
Much better and the frequency shift problem with the covers back on has gone away.
It pays to be neat.

73
Jeff


Hey Jeff. I did the same thing with crystals in a radio but I made a small circuit board with a relay. My switch switched DC voltage to tje relay and the relay switched the crystals. It was nice and stable.
 

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