Well for a week I sat on 145.000 Mhz 2M FM and call CQ and what I did was use
my scaner to listen to my self and try to see if I was not over driving the FM,
and if it sounded clean I was happy, I had no takers for the hold week and the
rig was a Icom 706mk2g. GL Russell NC5O
1- Whoever said nothing is impossible never tried slamming a revolving door!
2- A government big enough to give you everything you want, is strong enough to
take everything you have.
- Thomas Jefferson
" IN GOD WE TRUST "
Russell Blair (NC5O)
Skype-Russell.Blair
Hell Field #300
DRCC #55
30m Dig-group #693
________________________________
From: Warren Moxley <k5...@yahoo.com>
To: digitalradio@yahoogroups.com
Sent: Mon, November 16, 2009 9:37:23 AM
Subject: Re: [digitalradio] Re: Digital on 2M FM: Audio settings ?
"That can be tricky without a deviation monitor but it can be done by comparing
your own digital modulation to other known good signals."
Comparing your own digital modulation.. .
How do you do that? Please explain.
K5WGM
--- On Mon, 11/16/09, Gary <grwes...@yahoo. com> wrote:
>From: Gary <grwes...@yahoo. com>
>Subject: [digitalradio] Re: Digital on 2M FM: Audio settings ?
>To: digitalradio@ yahoogroups. com
>Date: Monday, November 16, 2009, 8:51 AM
>
>
>
>Hi Andy,
>
>I suppose this would be confusing to someone not used to FM operation on a
>multi-mode rig. In all modes, ALC is a function of transmitter output power.
>In SSB modes we keep our transmitted digital signals clean by running our
>transceivers below the power level that causes ALC to be generated. In FM,
>however, the transmitted signal is a constant level carrier. The audio
>modulation from the sound card causes the frequency of that carrier to
>'deviate' above and below its unmodulated frequency. What we care about on
>digital FM is how clean the audio at the receive end is. The ALC reading
>reflects only how much RF we are putting out, not what the modulation looks
>like at the receiving end. Remember that essentially all voice FM transmitters
>use some sort of peak audio clipping to limit how wide our modulation
>'deviates' to keep it inside the pass band of the receive IF filters. When we
>run digital FM, we need to keep the audio drive low enough that we are
not driving the transmitter audio section into clipping.
>
>Setting the audio drive level for digital operation with an FM transmitter is
>not quite as simple as for SSB. We really must monitor the actual transmitted
>signal while we make that adjustment. That can be tricky without a deviation
>monitor but it can be done by comparing your own digital modulation to other
>known good signals.
>
>That said, though, a little extra distortion is not quite the problem on FM it
>is on SSB. On FM, audio distortion will generally not interfere with other
>stations. It may look bad on the water fall and may not decode quite as easily
>as if the level was correct but it will likely still work OK. That is why we
>can get away with just holding a handy talkie up to the computer speaker to
>operate digital modes on VHF FM.
>
>That make sense?
>
>Gary - N0GW
>
>--- In digitalradio@ yahoogroups. com, Andy obrien <k3uka...@.. .> wrote:
>>
>> Hmmm. Well I thought it would be simple enough to transmit digital
>> modes on 2M FM but one issue I just ran in to is the ALC is very high
>> and my usual method of lowering it has no effect. I also lowered the
>> mic gain but that had no impact. Something simple I am not taking in
>> to account when using FM ?
>>
>> Andy K3UK
>>
>
>
