rashleigh at sympatico.ca
Mon Oct 27 23:12:34 UTC 2008
Hi Dave, thanks for the report.
I would suggest you check out the deviation level setting on your radio.
An FM receiver designed for +/- 5 KHz deviation will normally accept no more
than +/- 7 kHz before the energy is outside the bandpass of the receiver and
the squelch begins to shut down on modulation peaks. And since all
communications transmitters have a nominal 6 db per octave pre-emphasis of
modulation, a modulating signal at 2 kHz will inherently have double the
deviation as a 1 kHz modulating signal. Of course, the deviation control is
typically a "limiter" circuit, and if properly set, should limit the
modulation at +/- 5 kHz. Now, there may be differences between one
repeater and another. This may depend on relative squelch setting of the
repeater, the amount of signal into the repeater, the amount of hysteresis
designed into the receiver squelch circuitry. or whether a repeater receiver
is using CTCSS or not. With CTCSS control, the sub-audible tone is
transmitted at a low level and thus would not necessarily be over-deviating
in itself and therefore may hold the squelch open even though the voice
modulation is over modulating.
Please note that the "modulation acceptance" of the 2 mtr Daniels receiver
was tested before ve3mpc was put into operation and was confirmed to accept
+/- 7 kHz deviation.
So. I recommend you check for over-deviation on your radio and turn it down
if necessary. You should also check your transmitter frequency, an
off-frequency signal can also shut down the squelch circuit on modulation
>From listening to the repeater, your problem does not seem to be
experienced by others using the new VE3MPC.
Regards and 73
----- Original Message -----
From: "David Green" <dave.green at ncf.ca>
To: <ve3lc at rac.ca>
Cc: "David Green" <dave.green at ncf.ca>
Sent: Saturday, October 25, 2008 1:35 PM
> Hello Norm,
> Good to see VE3MPC back on the air. I just had a QSO with Pat, VE3PM via
> the 2m VE3MPC repeater. Pat reported that my audio was cutting out and
> suggested that perhaps I was over-deviating. He said the drop-outs seemed
> to be most noticeable at the higher end of my voice spectrum. He suggested
> that I move the mic away to reduce my transmit audio level. That resulted
> in proper operation of the repeater. We then switched to VE2CRA and tried
> a follow-on QSO. With the mic at a normal distance (about 6"), Pat
> reported no problem with repeater operation. This suggests that the
> problem may be at the VE3MPC receiver. It's as if the deviation gain, if
> there is such a thing, is set too high.
> Hope this helps.
> Dave VE3TLY
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