hi josh,
those are nice little radios, but it is very old, and the hum on transmit probably means that a capacitor is drying out.
USB, and LSB are different modes of modulation.
they are still the same 40 channels.
when you are on channel 38, AM mode, you are on 27.385mhz, and when you key the mic, you create a carrier.
when you speak into the mic, you "modulate" this carrier with your voice.
that is called AMPLITUDE MODULATION (AM).
when you are on channel 38 and you are in LSB mode (lower sideband), you are on 27.3835mhz, and when you key the mic, no carrier is created (needle on meter doesn move)but when you speak into the mic, you modulate the radio.
USB is upper sideband, and on channel 38, it would be 27.3865mhz.
this is a cool thing about sideband mode; you can be on 38LSB and not mess with a conversation on 38USB.
so, SSB (single sideband) is a mode, just like AM and FM are modes. OK?
the CLARIFIER knob on your radio allows you to tune the receiver while in SSB mode (USB or LSB) for the best voice quality.
you will find that after talking to someone on LSB or USB, and then trying to talk to someone else on the same channel, that you may have to tweak the CLARIFIER knob a bit because the two people were on slightly different frequencies.
this is just the nature of the beast, and thats why they put a "fine tuning" control on the radio. to allow you to "clarify" someones voice.
you dont need to use the clarifier on AM, and should just leave it in the middle until you need it in SSB mode.
as for the CAL knob, that has to do with your SWR feature.
to get an accurate SWR reading on the radios meter, you first need to CALibrate the meter, so, turn the mic gain down so extraneous noises dont make the needle bounce around.
set the switch to the CAL position.
key the mic and look at the big meter.
on the far right side of the meter, you will see the word CAL next to one of the indicator lines.
there will be a mark on the line near the word CAL, and most of the time its right at the end of the line.
with the mic keyed (SWR readings only work in AM mode),
turn the CAL knob until the needle lines up with the mark on the CAL line on the meter.
unkey the mic.
now switch the switch to SWR position.
key the mic again, and look at the line on the meter that has the SWR numbers on it. (probably the same line as the CAL marker is on)
if your SWR reading is below 2, you are fine.
if it is approaching 3 or more, then you have an antenna problem and should not transmit more than a few seconds, as you could damage the radio.
(the CAL knob is only a calibration control and has no effect on the actual SWR of the antenna system. SWR stands for Standing Wave Ratio)
BTW, S/RF position on that switch means that in this position, on receive, the meter is showing the "S units" of how strong someones signal is.
when you key the mic, the meter shows the RF power out, or RFO.
when you want to know how many watts you are putting out, look at this line on the meter while you are transmitting.
that NB/OFF switch is for your Noise Blanker.
it cuts out some static and pulse noises from your receiver.
i always leave mine on.
ok, good luck.
remember that radio is old and may not last long, so you may want to think about buying a new radio if the bug bites you hard.
later,
LC
