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From: jhs%Mitre-Bedford@d3unix.ARPA
Newsgroups: net.ham-radio
Subject: Re: Motrac,Mocom,Mastr?
Message-ID: <10917@brl-tgr.ARPA>
Date: Wed, 22-May-85 12:26:22 EDT
Article-I.D.: brl-tgr.10917
Posted: Wed May 22 12:26:22 1985
Date-Received: Sat, 25-May-85 08:36:32 EDT
Sender: news@brl-tgr.ARPA
Lines: 36

1. (Re: audio quality) I would think that loudspeaker response would be an
important part of it, but possibly IF filter response would be another.
For transmit audio, the microphone is very important and you can even hear
big differences among ham type transmitters.

For external speakers, by the way, it's HARD TO BEAT the Radio Shack
"CB Extension Speaker" which sells for about $12.95.  Add this to even an
HT with low audio power output capability, and you can hear radio calls from
30 feet away from your vehicle (if you put the speaker on the roof or
something), even beside a busy highway.  (I am NOT exaggerating!) This speaker
has excellent frequency response shaping for FM voice communications use.

As for microphones, buy a Turner or Shure mobile dynamic mic and you can't
go wrong.

The IF filter is harder to fiddle with.  Also, you should be careful, because
the "pros" (meaning Motorola) found out early in the game that you DON'T want
a nice square-topped filter -- you want a nice stoop-shouldered Gaussian one
because its IMPULSE RESPONSE is also stoop shouldered and short in duration
so IGNITION NOISE doesn't ring on into the middle of the 21st century as it
would with a sharp-edged filter.  Maybe you could buy a 455 KHz IF filter from
the "Big M" and substitute it for the one in the el cheapo rig.

I dunno about audio shaping, but maybe you could analyze the offending ham rig
with an FM generator and audio voltmeter and plot its frequency response at
various points to see where the loss occurs.

2.  Six meters.  I am not a 6m user, but I have noticed that the ARRL Repeater
Guide lists quite a few 6m repeaters.  You might want to look at it for hints
and maybe get on some of the repeaters and ask for further information.

Good luck!

						73,
						John Sangster, W3IKG
						jhs at mitre-bedford