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Author Topic: simplex repeater  (Read 610 times)
KC0UWS
Member

Posts: 1




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« on: October 09, 2005, 08:27:46 PM »

where can I find a cheap, used simplex repeater? I want to put it on 2m FM simplex.

 73 de kc0uws
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WA4PTZ
Member

Posts: 528




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« Reply #1 on: October 10, 2005, 08:38:23 AM »

There are a number of repeater controllers on the
market that can  make a plain rig act as a simplex
repeater. All you need to do is a little research.
We used one at Dayton several years but I can't recall
the name or maker.
73 - Tim
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WB2WIK
Member

Posts: 20543




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« Reply #2 on: October 10, 2005, 12:01:17 PM »

A simplex repeater is nothing more than a digital recorder and controller.  It records what the simplex "repeater" receiver hears, and then at the end of that transmission, it keys the transmitter and replays it so others can hear.

Unless people keep their transmissions very short, it's kind of silly -- you never hear anything in "real time," it's always time delayed by the system and as such not of much use in an emergency.  

Is this really what you mean??  There isn't any other sort of "simplex repeater."

If so, you can homebrew the recorder/controller easily and plans for doing so are well published.  Do an archive search of QST and QEX on line (arrl.org) and I think you'll find a couple of articles.

WB2WIK/6
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WB6BYU
Member

Posts: 13027




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« Reply #3 on: October 11, 2005, 12:37:34 PM »

I was on a Search and Rescue team where someone set up a
simplex repeater and we used it ... just once.  They
really are annoying, and quite different from normal
radio operation.

The first problem was that, if you could hear the calling
station directly, everyone's immediate response is to
answer their call when they finish.  Except that, when you do
so, the repeater is also repeating their call on top of
your signal.  So nobody (including the repeater) hears
you.

Of course, if you wait to listen to the message the
second time around, and you were out of range of the calling
station, then it doesn't repeat, because you were hearing
the repeater the first time, not the other station.

Anyway, it can really be confusing to use one, though
there might be situations were it would be useful.

But the other thing to remember is that you still have
to maintain control of the station (on a frequency higher
than 220 MHz) and provide an ID.  Do a careful reading
of Part 97 - I suspect you will find that this does NOT
qualify as a "repeater station".  You will need to choose
a frequency that doesn't cause interference, and think
about what happens when other stations using the frequency
get repeated through it also.

The one time the SAR team tried their portable repeater
it was left unattended on top of a high mountian.  Not
only did it relay transmissions from team members, but
it also picked up - and re-transmitted - communications
of a group 200 miles away, with the result that our
repeater covered up their field units when they tried
to respond to their base station.  Needless to say,
they weren't amused...
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K7AAT
Member

Posts: 414




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« Reply #4 on: October 14, 2005, 07:25:01 PM »


   "Its this really what you mean?? There isn't any other sort of "simplex repeater."

    Actually, there can, and have been, true simplex repeaters.... retransmitting in real time on a simplex frequency.  The requirements are that the transmit antenna and receive antenna have attenuation path between them enough to prevent Rx from hearing the Tx.  Usually this involved the top of a hilltop providing the attenuation, with no close hills to provide any reflections.  Separating the Tx and the Rx by long wire control/connection is the usual method.

   Ed   K7AAT
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WB6BYU
Member

Posts: 13027




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« Reply #5 on: October 17, 2005, 01:45:09 PM »

Getting more sophisticated, they have been built as integrated
units in the 300MHz range, but this isn't the type of
thing that one would find a cheap used one for 2m!

In this case, the transmitter had a vertical whip and the
receiver had an adaptive antenna array (for example, four
independent receive antennas spaced around the transmitting
antenna.)  When the receiver heard a signal it would key
the transmitter with an added tone, then adjust the relative
amplitude and phase of the signal received from each of
the separate inputs to null out that tone on the received
signal.  So, whatever direction the input signal came from,
the receiver would essentially phase the receive antennas
to pick up this signal while nulling out the transmitter
(which was transmitting on the same frequency.)

They managed to get 1 watt out of the transmitter without
excessive desense to the receiver.  Needless to say
this was a military project where expense was not an
impedement.
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N8GNI
Member

Posts: 29




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« Reply #6 on: October 17, 2005, 02:03:50 PM »

Here's one on Ebay. The radio shack ones should run about $40 to $50. I wouldn't buy or bid on this one, his shipping is $30.
Do a search on Ebay once a week and you'll find one.
Harry
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N8GNI
Member

Posts: 29




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« Reply #7 on: October 17, 2005, 03:08:15 PM »

OOPS
This might help.
http://tinyurl.com/9ycx8

But DON'T buy this one, he want's $30 to ship a1 pound package!
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