*** Mobile Repeater Design ***

From:	 JHowel@aol.com
Sent:	 Friday, June 26, 1998 8:12 PM
To:	 sar-l@listserv.islandnet.com
Subject: Re: Comms: Mobile repeater for SAR
In a message dated 98-06-26 21:44:22 EDT, you write:

>On the subject of SAR radio communications, has anybody had any experience
>using a mobile or portable (backpack) duplex repeater for SAR? The problem
>I see is finding an input frequency separate from out state SAR frequency.
>  
>We may try a simplex repeater (it records what it receives and then
>retransmits it on the same frequency). I have heard that simplex repeaters
>are ackward to use.

I don't have first-hand experience with the simplex repeaters, but I would
venture a guess that it would be best to stay away from them because, as
you say, they are (or appear to me to be) awkward, to use.

As for using an on-site repeater, that is certainly a viable option, with
several methods of putting a repeater together. There are a couple
(however, I apologize, I don't recall the companies' info) of companies
that make "repeater builders" or "repeater makers." With these small
devices, you plug them into two H/T's which, ideally, are located at the
highest point in your incident area, program one H/T for the receive freq.
and the other for the transmit freq. and, viola, you have a portable
repeater. Again, I have no first-hand experience using one, so I don't
know how well they work.

For those who are or who use Amateur Radio, you can use a crossband
repeating mobile radio to effectively "build" an on-site repeater. Or,
put two back-to- back (appropriately spaced to eliminate interference
between the two radios) and you have a "true" single-band repeater.

Oh, and as for the additional frequency you mentioned to use with a
portable repeater, the FCC has set aside a handful of frequencies that are
intended for low-power "vehicular repeater" operation (150.775 is one of
the freq's). Simply add that freq to your license, and you're set.

Finally, it is possible to build a portable repeater from many of the
"surplus" commercial radios such as the older trunk-mount mobiles. These
radios are built with seperate transmitters, receivers, and power supplies,
enclosed in one container. You "simply" input the receive audio from the
receiver into the microphone audio of the transmitter, add a controller,
and you have a repeater. A bit more than a "backpack" repeater, but a
viable alternative to no repeater at all.

Best thing is to get with your Amateur Radio Ops who (I would genuinely
hope) are involved in your SAR group, and get them to work it out.  

Jeff
EMT, W9SAR, et al


From:	 Bruce Barton [rescue@keyinternet.com]
Sent:	 Wednesday, July 01, 1998 1:12 AM
To:	 sar-l@listserv.islandnet.com
Subject: Re: Comms

The most common bands are ham and VHF 155.160 or other 155 Mhz freq.
Our team NESAR has gone to UHF commercial (462 Mhz) as we use 6 repeaters
over a 14 county area. Ham repeaters provide a great backup.

Our team has about 50 Digital and voice keynote pagers on a commercial
paging system that covers about 2/3 of our area the rest use there own
private pagers. The voice I feel is still the best as we can give up to 60
sec of message and directions and back that up with callout codes on the
display.

The FRS and CB's are being used everyday and as I say in my new
communications manual every team needs to have one at the CP in case.  

The FRS radios make a great training and CP radio. They are only 1/2 watt
but work well for short range operations (1/2 to 1 mile). It is legal to
use them for such operations. RI has designated FRS Channel 7 with tone
118.8 as the SAR channel, Channel 1 as the general calling channel and 6
as the Emergency Calling channel (with no tones) for wilderness use.

On the repeater topic the cross band system works very well. A portable
repeater or cross band base  can be made by a number of means. The best
and a not to costly way is to get two motorola Radius or maxtrac mobiles
and a RIC (radio Interface controler) from motorola ($225) it will allow
you to make a crossband base or a repeater from the mobiles, all can be
gotten used for about $700 up.

The GE MVP mobile or desk top base can be converted to repeater operation
for just about $200-$300 as it has seperate TX and RX sections, just add
the tone controller and a used duplexer.

The other great way to make a crossband base or portable repeater is to
get a unit called a Transpeater controller from Transcript Intl. I had the
pleasure to be involved in it's design in the late 80's. It is widely used
in the US forest service and allows two portables to be used to make the
base or repeater by pluging into the jacks on the radios. We have used
this unit with great results all over the world under all types of
conditions with both the disaster team and in business applications.

If any one is interested we have a communications list server on the
rescuenet domain, please contact me by private e-mail if you want to join.

Thanks and I hope this helps.