Oh grief ... here we go ... again ... ;)
Mike Morris WA6ILQ wrote:
>
> At 05:07 PM 1/3/05, you wrote:
>
> > Hey Mike,
> >
> > Thirty plus years ago, I built up a portable 2 meter repeater
> > for one of the Baja 500 off road races in Baja California.
>
> If I recall that was the race where you tore the exhaust system
> out of your CHP 1960s Polara going up the hill to place the
> repeater, then one of the racing crews rebuilt it, then you tore
> it out again getting the repeater down...
Uh huh ... almost ... but I will spare you the corrections ...
> Now repeat after me... CHP chase cars are not high-clearance
> off-road vehicles...
Yes sir !! ... ducking ...
> >I used a pair of Motorola Motrans - U43MSN - rated at 30 watts
> >out - continuous duty. I tuned them up so each could replace
> >the other in case either the receiver or the transmitter should
> >quit.
>
> I never trusted the continuous duty rating on the Motran...
> never tried running one at 30w, but they were clean at the
> levels I ran them at (10-20w) and that's where I used them.
> Never needed any more, anyway.
After I moved to Oregon in 1976, I frequently used the Motran as
the hidden transmitter for T-Hunts. I never had a problem with
them - part of that was knowing how to tune one up - correctly.
After inserting the Channel Element on the correct frequency, and
tuning the exciter and following multiplier stages according to the
manual, you just leave it keyed and tune for maximum output power
on your Bird Wattmeter. Next?
Re T-Hunts, I frequently fed the output of the Motran to a 12
element KLM log-periodic fed Yagi pointed at something such as an
elevated steel water tank (Woodburn, Oregon) or a steel bridge
(I-5 Bridge, Portland, Oregon. RF was everywhere.
(You don't want me to hide a transmitter hunt for you ... ever.)
> Always had high ground available for the event's porta-peter,
> and never had a need for high power. The one time
> I needed penetration I just used the KLM two-port power
> splitter, ran one side to the stationmaster on top of the
> tripod, and the other side to the KLM 16-el beam mounted
> on a second tripod. Gave me an omni pattern with a large
> lobe pointed at the control point.
That works!
> BTW did I ever tell you about the 220 mod for the U43MSN
> TX ??? just chop out 5 caps, insert a channel element for
> 149.000 and tune it up on 223.5 ... gives a perfectly clean,
> continuous duty 10w. (220 freq / 3) then x 2 gives the 2m
> freq you order the rock for...
149.000
--------- = 12.416666 x 18 = 223.49998
12
> The M series RX took some work to push to 220 but
> wasn't much more difficult than a Micor RX today.
Yes, the M Receiver front end will pose a couple problems on
that QSY ...
> Somewhere around here I have a MSN with a
> "U43.5MSN-3190B" serial plate. I ordered a blank
> one before Moto stopped selling them as spare parts
> and had a local engraver make it up. Quite a few folks
> did double and triple takes when they saw it -
> complete with the 223.34 - 224.94 and 223.5 channel
> elements (complete with International Crystal style
> labels). Never got a chance to show it to Ray Grimes.
At last report, Ray is still around. (I just looked him up, he's
almost as old as you are Mike.)
> > If one end quit, swap units and Channel Elements and back
> > on the air. The interconnect was one pair of wires - included
> > the transmitter keying and audio.
>
> Yup. The T-1200 transformers and those out of the DC
> wireline panels in the A-strip base stations came in handy.
Yup. I have a few of those transformers around here. The last
time I looked up the price - was $130 or so.
> > Nothing ever quit ... and I still have the audio/transmitter
> > adapter keying boxes in the garage.
>
> Porta-peters are handy items.
> Who was it that made a repeater by cutting a UHF HT-220
> board in half with a jewelers saw?? cutting between traces?
> And then added a 2m HT-220 as a porta-mote?
One of the guys at the Beaverton Oregon Tektronix Plant.
The whole package is about 8 inches high, a foot long and about 7
inches deep ... has 1 antenna on top and a handle to carry it with.
Includes the following:
440 MHz repeater (a Motorola HT-220 cut in half),
a HT-220 on the 2 meter band as a base station,
the duplexer for the UHF repeater,
a diplexer to combine the VHF and UHF,
the touch-tone decoder and repeater controller as well as the
battery pack to run this package for long periods of time - in
hours.
Is totally self contained. This was done in early 1970's
technology.
> Mike WA6ILQ
Neil - WA6KLA
>
> >
> >
> >
> >Mike Morris WA6ILQ wrote:
> > >
> > > Dakota...
> > >
> > > Can your operational requirements be met by a
> > > station in a parked vehicle, or does it have to be
> > > operational while in motion?
> > >
> > > Can your 2m repeater requirements be filled by a single
> > > channel solution?
> > >
> > > Twenty years ago when UHF was not in use locally by the
> > > average ham we had a portable 2m repeater that in the first
> > > incarnation was made usable by two notch cavities - one for
> > > RX and one for TX.
> > > The radios then were 30 or 40w (I forget which) Motorola
> > > Motran mobiles, which would survive continuous duty at
> > > the 10w level. With the cavities in line the antennas could
> > > be as close as 20 feet.
> > >
> > > Later on we needed to use it and the cavities were not
> > > available, so we tried it anyway and by placing the RX
> > > radio and it's antenna 75 to 100 feet away it was usable
> > > with careful placement of the RX and TX. In one case we
> > > put a full-size RV between the two and grounded the metal
> > > skin of the RV.
> > >
> > > In your situation, if an im-mobile solution would work, I'd
> > > put a 2m antenna on a tripod mount coupled to an RX
> > > powered by a gellcell (maybe even with a solar panel
> > > plugged in). A 100' cable would carry audio and PTT
> > > to the vehicle where the 10-30w TX would be. And
> > > without cavities it could be frequency agile. If you could
> > > scare up a couple of cavities you would limit yourself to
> > > one frequency but the performance would go up
> > > tremendously.
> > >
> > > I could build it with stuff on the shelf - a Motrac M-series
> > > receiver, and a split winding audio transformer would fit
> > > into a 50-cal ammo box. If the Motrac RX was used (it
> > > has a passive front end and for a 20+ year old RX is really,
> > > really, really overload resistant) the biggest expense would
> > > be the crystal. For the TX I'd use a GE MVP, Mastr II or
> > > Exec II.
> > >
> > > How much of a controller do you need? You could probably
> > > get by with an ICS Basic at about $80....
> > > See http://www.ics-ctrl.com
> > > Mike WA6ILQ
> > >
> > > At 01:45 PM 1/3/05, you wrote:
> > >
> > > >Cant drop the 2M side of things as a lot of hams don't
> > > >have 70CM around here and 2M will do what 70CM wont
> > > >in the mountains when runs and races require 2M am
> > > >looking at a few suggestions for the van right now that
> > > >might work.
> > > >Couple of emails on Motorola gear, either one or two
> > > >channel radios and a controller and duplexer for the
> > > >rigs that I need.
> > > >Thanks for all the help!
> > > >Dakota
> > > >
> > > >-----Original Message-----
> > > >From: Jim B. [mailto:[EMAIL PROTECTED]
> > > >Sent: Monday, January 03, 2005 1:50 PM
> > > >To: Repeater-Builder@yahoogroups.com
> > > >Subject: Re: [Repeater-Builder] Mobile Repeaters?
> > > >
> > > >
> > > >Dakota Summerhawk wrote:
> > > >
> > > > > Is the best way to have a mobile repeater up and running with two
> > > > > mobile radios and a duplexer? Looking for a way to be able to run a
> > > > > couple of repeaters, one VHF, one UHF for a mobile communications van.
> > > > > Can anyone recommend ways to cut down on weight and space? Thanks
> > > > > Dakota
> > > > >
> > > >
> > > >Best way to cut space-forget about the VHF unit. For UHF, get a Kenwood
> > > >TKR-850 and a mobile duplexer. Keep the transmit power down to 20W or
> > > >less, more then that will cause problems with other radios in the van,
> > > >and get the antenna as far away from other antennas as possible,
> > > >preferably on a 30' or more mast.
> > > >
> > > >--
> > > >Jim Barbour
> > > >WD8CHL
>
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