Subj : Re: CB experiments
To : Ginger1
From : Weatherman
Date : Sat Feb 15 2025 12:44 am
-=> Ginger1 wrote to Weatherman <=-
Gi> Re: Re: CB experiments
Gi> By: Weatherman to Ginger1 on Sat Feb 08 2025 02:36:00
> SWR = Standing Wave Ratio. Compares the signal output to the RF returning
> along the coax. A tuned antenna system will have a low SWR, meaning more
> signal is transmitted compared to what is returning through the coax. SWR
> of 1.5:1 are good, 1.0:1 is perfect. SWR of 3:1 or below is acceptable.
Gi> Thank you - that makes some sense!
Gi> Is this different to the meter on the CB radio itself? Mine has a meter
Gi> with a single needle, but two gauges - one labelled signal, the other
Gi> power.
I've been made aware that you're located in the UK, so regulatory issues are
definitely different between there and the US.
Generally the CBs here have one meter, it's referred to as an S/RF meter.
When transmitting it shows the output signal strength as referenced against an
internal standard and when receiving it shows the receive signal strength -
again referenced against an internal standard. When I refer to "internal"
standard, I mean it. There is no industry standard I know of that defines
exactly what an S9 received signal is or what a "5" output strength is. Too
many variables to go into here to try to explain it. On your radio, with two
meters, I can only guess that "signal" would indicate the strength of the
received signal and "power" would indicate the transmitter output. Not knowing
the model of the radio and then looking up the manual, this is just a guess.
Gi> And I've been reading about tuning the antenna - but what is there to
Gi> tune? Does this mean the direction it is pointing in? I have a
Gi> car-mounted whip antenna - and I can adjust the angle it points at, but
Gi> not much else. I've only tried it perpendicular to the car roof.
Tuning refers to altering the length of the driven element of the antenna.
Making it shorter to try to match the desired operating frequency. When
fabricating an antenna we tend to make it a bit longer than needed so that it
can be trimmed down to match the frequency. Your car-mounted whip antenna
probably has a set screw to hold the whip in place. Loosen it and you can
adjust up and down as needed (to a small extent) to fine-tune your SWR.
Gi> Do Squelch and RF Gain have a role (I have knobs for these on the
Gi> radio).
Squelch is used to raise the noise floor of the radio's receiver so that only
signals above a given level will be heard. It's essentially used to adjust the
receiver so that background static is not heard and so that signals stronger
than the squelch setting will be heard.
RF gain adjusts the receiver's sensitivity. Best use of the RF gain is when
you are trying to hear a signal but a weaker signal on the same frequency is
interfering. By adjusting the RF gain you can make the receiver less
senstitive so that the weaker signal is attenuated to the point where it no
longer interferes with the signal you're trying to listen to.
Gi> Apologies for the newbie questions!
Not a problem. It's how you learn, and it's good for me to review some of
these myself. I've been off the air ever since I relocated and miss this
stuff. Need to get some coax buried out to my antenna site and put some
equipment on the air!
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