what the heck would cause this??

[dirtyjob]

friend of mine has an SBE console V and he hasnt used it for years, he brought it over to see if it still works and everything does, except one thing i noticed... when on lsb it throws out a carrier, usb works fine but when on lsb and not modulating into the mic, there is a carrier present as if your on am. when you talk on lsb it seems ok, i made a local contact on lsb with it, how ever, in between words it has a visible carrier, i turned dorn the mic gain to nothing and there it is, still a present carrier only on lsb.

what the heck would cause that???


also just hooked it up to my watt meter and plugged headphones into my audio monitor jack, interesting results, when on am/usb as reported it works perfect.

but when on lsb, and you turn mic gain off, you have a carrier putting out .5 watt also when you turn up the mic gain and talk on lsb, while listening through my monitor jack i hear what sounds like half am, half ssb audio.

Im no repair guru so i leave it to you guys, any clue on whats happening with this radio ??

[Circuit Breaker]

I'm not an expert but it sounds like the low pass filter isn't completely removing the carrier. A low pass filter is an RC circuit that consists of a resistor and capacitor looking something like this:



The values of the components determines the RC time constant - which determines the cutoff frequency. Frequencies below the cutoff are passed through while frequencies above are sent through the capacitor to ground and, thus, filtered out. In most cases, the resistors, being carbon based, don't go bad...although it does happen. It's more likely that the capacitor is an electrolytic type and could be leaking considering the radio is probably 30 years old. A bad component in the low pass filter could change the cutoff frequency and allow some of the carrier through. This, of course, is just a possibility but a great deal of that depends on HOW the Console V generates SSB signals. Filtering is just one method.

[MDYoungblood]

Cb Tricks has a service manual for the SBE, I would print out a copy for him, check out step 20 on the transmitter alignment.
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I would go through it and get everything right, they were great radios, mods on them were a little difficult for the average CB'er but it would make it a powerhouse.

3's

Greg

[dirtyjob]

thanks for the response, would adjusting the carrier balance points to the lowest voltage be the solution???

***edit***

well we went ahead and adjusted the 2 carrier balance points for lowest reading and low and behold the radios lsb issue is fixed.

thanks guys for the help.