[50mhz] 6 Meter Repeater

[Ray Brown]

----- Original Message -----
From: "Larry E Himes Jr" <ecentric@earthlink.net>

<< I am wanting to set up a QRP 6 meter repeater in the northern Indiana area.
Could anyone help me with the information and sources for equipment that I
would need.  I am wanting to achieve a range of 25 miles radius and an
offset of 455KHZ.  The offset selected is so that the homebrew handie
talkies can used the same oscillator for transmitting and receiving.>>

  Greetings! Since I'm the proud owner of a new 6m repeater here in EM27,
aka Joplin, MO, I think I might be able to answer some of your questions.

  First off, with that narrow an offset, you will almost certainly have to have
a split-site repeater, or an extremely efficient and costly duplexer (the device
that allows repeaters to share an antenna). I don't have all the figures in front
of me, but to avoid "desense", aka the ability to hear weak signals because
the output of the repeater is reducing the receiever's ability to hear, you would
need to have the input and output antennas at least a mile apart horizontally,
or at least 200' vertically. Maybe more.

  Second, I don't think you'll get much usable range on your repeater by keeping
it at QRP levels. Actually, it's more of your walkie-talkies I'd be concerned with.
If they have efficient antennas, then you might stand a chance. Bear in mind that
an efficient antenna would be a dipole, 5' a side. Otherwise, you have to deal
with some kind of loading coils on the antennas to get them to resonance. I have
one of the Cherokee 6m handitalkies here. They have a nearly-constantly-loaded
antenna (with a BNC mount) so that they're resonant on 6m. I can get into my
repeater (input is about 5 miles as the crow flies) on 5 watts but not on 1.

  So, to run split-site, you'll need 4 radios and antennas. One pair will be 6 in >
link out (I'm running coordinated on 440-something), going into a link in > 6 out.
Links can be 220 MHz or higher, please do NOT consider linking with 2m!
I'm running Motorola radios myself. One interesting solution is to consider GE
Mastr II mobile radios.Basically, get 2 radios, one on 50 MHz, one on 450 MHz,
make sure they work first (that means first, make sure they work BEFORE you
start modifying them!), then modify them for the right frequencies, then swap the
receievers in them and make all the right connections. :-) Also, at least 1 vendor
makes an interesting repeater controller that drops into a slot on the radios,
thus making you legal (IDer, time-out timer). You still have to rig up 4 antennas,
and power supplies, but that would work. Just be ready to move them further
apart if you get desense. And I still think you'll need to run at least 20 watts out
to be heard at 25 miles.

  Frankly, I've never heard of anyone putting a repeater together on a .455 MHz
split. You may have a hard time getting it coordinated. You *will* try to get it
coordinated, won't you? Otherwise, you might be causing harmful interference to
other repeaters. When the band opens, you may strongly wish to consider running
an input PL tone, otherwise you may have other repeaters that are on your
frequencies interfering. But it'd be interesting to see you try. :-)

  I just went and found my 2002/2003 ARRL Repeater Directory. Hmmm. There
are some *weird* listings there for Indiana. The majority of 6m repeaters listed
have a split of 1.0 MHz, there's a couple of 0.5 MHz, but there's at least 2 6m
repeaters listed that have a split of only 240 KHz. Those are certainly linked,
but they don't say. Also, IMHO, climbing up on a soapbox for just a minute...
*shame* on the folks that are running a "repeater" on 52.525 there, and shame
on the coordinators that allowed that to happen. But that's my soapbox.
Enough of that. :-)

  Last but not least, if you're serious about this, you need to join another listserve,
mailto:Repeater-Builder@yahoogroups.com and start reading the messages there.
I'm there, have been for 3 years, and it's a wealth of info on all kinds of repeaters.
Most of the folks there are hams, altho there are some Public Service and
commercial repeater folks there too.

  Finally, hope you have a deep pockebook... unless you get very lucky, you'll be
out at least $500, maybe up to $1,000 or more, just to get it on the air. If you have
to rig up a duplexer, you may be out another $1,000 (4 copper cylinders, each
1.5 meters tall).

  But don't let me discourage you at all. Go for it. Keep us posted.

  And, in case anyone's interested, mine (again) is 53.25 out, 51.55 in. :-)

                _Ray_        KB�STN