Scott,
After you pulled and bypassed the final, what was the lowest power you
could get out of it while still being stable? I'm thinking about doing
the same to a VHF maxtrac to use as an exciter for a cont duty PA, but
it only needs about 400mw to drive it to full output. Thanks.
Kevin
K2KMB
-Original Message-
From: wn1b8 [mailto:[EMAIL PROTECTED]
Sent: Wednesday, October 06, 2004 11:03 AM
To: Repeater-Builder@yahoogroups.com
Subject: [SPAM] - [Repeater-Builder] Re: Motorola Radius/GM300 - Email
found in subject
--- In Repeater-Builder@yahoogroups.com, "Steaven Rogers, W4YI"
<[EMAIL PROTECTED]> wrote:
> Has anyone here used a Radius or GM300 to make a repeater? I have
a
> pair of Radius (M120) UHF mobiles wired up and working, but I
would like
> to add a third one to use as a link to a second repeater. Can
anyone
> give any input on how to go about hooking up the third radio to
make it
> work properly?. This will be used for temporary installations
only.
> Aside from the heat issue are there any other pitfalls or concerns
I
> should look at for. These will be run on LOW power when being
used to
> help with the heat.
>
> Thanks,
> Steaven, W4YI
Hi Steaven,
I have been playing around with the GM300s for a couple of weeks now
with plans to use them as UHF link radios. In my humble opinion, they
are a nice little radio and should do a good job. This, of course, will
be proven or disproven in due time. Here are some of my
observations:
The heat issue can be a problem. Turning the power output down only
adds to the heat problem. Instead, I took Kevin's (and others') advice
and pulled and bypassed the final. The radio does about 3.5 watts this
way. The output is very clean (I looked -70 dB and didn't detect a
thing) and stable. I observed this into load with a
1:1 SWR as well as a 2.5:1 SWR. Aside from the (still) moderate heat
produced, there were no detectable problems during a 35 minute keydown
period. To overcome the heat issue, I simply added a computer processor
fan to the back of the radio pair that triggers on from the receiver's
COR (or tone squelch) and shuts off one to two minutes after the carrier
or tone drops. (See Kevin's web site for the circuitry)
My radios didn't display any significant drop in power until I tuned
down around the low end of 433 MHz.
The 16 pin connector has descriminator output, mic input, and PTT
available on it making interfacing quite easy.
The one drawback I have detected is the built in Tx delay. When added to
the inherrent delay from an aftermarket tone decoder, which I am using
on the VHF receiver married to this transmitter, the overall delay
borders on the undesirable. I have a GM300 service manual and schematic
en route, but without it I haven't determined a work-around. I suspect
this delay is intentional and can be altered through minor component or
circuitry changes.
I hope this helps. Good luck.
Scott Madison, WN1B
Yahoo! Groups Links
Yahoo! Groups Links
<*> To visit your group on the web, go to:
http://groups.yahoo.com/group/Repeater-Builder/
<*> To unsubscribe from this group, send an email to:
[EMAIL PROTECTED]
<*> Your use of Yahoo! Groups is subject to:
http://docs.yahoo.com/info/terms/
