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Author Topic: Manpack repeater (Help pls)  (Read 18253 times)

KG6RYR

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Manpack repeater (Help pls)
« on: July 18, 2011, 01:58:01 PM »

I am going to make a "manpack" repeater by two HTs (4Watt UHF)., and a repeater controller (by Radio-Tone).

I have mounted the RX and TX vertically oriented , one above the other. But I experience some interference (the receiver losses its sensitivity when the Tx operates).

Now my questions:

Is it important to mount the Rx over the Tx or vice-versa?

How much far should I mount the radios to get rid of the problem?

Does a duplexer (or diplexer; I couldn't figure out which one is which) is good for my problem? or is it better to just mount the radios a little bit farther?

73
KG6RYR
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WB6BYU

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RE: Manpack repeater (Help pls)
« Reply #1 on: July 19, 2011, 07:00:55 AM »

You can mount the RX and TX with vertical separation, but it will take far more separation
than will be convenient to carry in a backpack to make it work.

You need several things to build a repeater in a small physical size:

good shielding on the transmitter and receiver

good receiver that can tolerate strong off-frequency signals

some sort of duplexer ("duplex" meaning transmitting and receiving simultaneously) to provide filtering
of the transmit signal at the receiver.  Actually they serve two functions:  to filter the TX signal
out of the RX, and to filter out any spurs or noise that the transmitter generates on the RX frequency.
You need BOTH functions to make it work, and the rigs have to be well shielded or the RF will bypass
the filters.


Fortunately for you the UHF "cans" are smaller than those used for 2m.  I know of several portable
repeaters that are built from a single Motorola mobile rig with separate transmitter and receiver in
a single case, plus a duplexer, allowing them to be used with a common antenna.

AD4U

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RE: Manpack repeater (Help pls)
« Reply #2 on: July 19, 2011, 10:47:23 AM »

I don't understand if you are taking this repeater "man packing" or hiking as I call it, or if you are planning to "man pack" (carry) this repeater to a permanent location.

If you plan to use it hiking, may I recommend that you use a cross-band repeater.  All you will need is a suitable VHF / UHF transceiver to be configured as a cross band repeater (a walkie talkie will work) and a dual band antenna.  This will eliminate the need for a duplexer, separate antennas, and all the other things mentioned in the previous post.

Dick  AD4U
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KG6RYR

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RE: Manpack repeater (Help pls)
« Reply #3 on: July 21, 2011, 02:53:10 AM »

well, by "manpack" I mean a simply made, small size repeater that I can mount on the roof for a limited time (and maybe battery operated).
I do not intend to "carry" it.
I prefer to mount the HTs with their own antennas.

what is the best configuration (vertical/horizontal/oblique)
the required distance of the radios (3-4 meters adequate?)
Tx or Rx on the top?
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WB6BYU

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RE: Manpack repeater (Help pls)
« Reply #4 on: July 21, 2011, 12:53:03 PM »

Quote from: KG6RYR
...
I prefer to mount the HTs with their own antennas.

This is unlikely to give good results, but perhaps you'll learn a lot from playing with it.


Quote
what is the best configuration (vertical/horizontal/oblique)
the required distance of the radios (3-4 meters adequate?)
Tx or Rx on the top?

I'd guess you'll need a vertical spacing of 20 to 50 feet, depending on the radio design and
how well it can handle strong signals off frequency.  Without any filtering you may also
have transmitter phase noise appearing in the receiver passband.

That assumes that there is no RF current flowing on the wires connecting them together, which
is very difficult to achieve using built-in antennas (especially with vertical separation.)  You may
end up mounting the lower HT upside down so the audio and control cables don't run along the
antenna.

Or a few hundred feet of horizontal separation might be adequate.

I'd suggest putting the RX antenna on top to maximize received signal strength to help overcome
the desense problems.

KG6RYR

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RE: Manpack repeater (Help pls)
« Reply #5 on: July 22, 2011, 04:21:27 AM »

Very informative reply; thank you.

I'm going to conclude that a "simplex" repeater is more convenient for my purpose.
I've had excellent coverage by a simplex repeater.

Sirous
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AE6RV

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RE: Manpack repeater (Help pls)
« Reply #6 on: July 30, 2011, 12:21:40 PM »

You don't mention coordination, so can we assume this will be a sort of "pirate" repeater?  If you do choose to just name your own frequency, please don't use the satellite sub-bands.  It can take forever to track down a well-meaning device that is locking up one of the satellites and denying its use to a large number of hams.
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KG6RYR

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RE: Manpack repeater (Help pls)
« Reply #7 on: July 31, 2011, 12:41:04 PM »

well, it's not a quite pirate repeater !
I'm out of the US right now. Where I live, there are no hams for hundreds of kilometers!!
Besides, I'm not going to install a permanent repeater. It will be operating occasionally just for test and experience.
« Last Edit: August 19, 2011, 04:00:36 AM by KG6RYR »
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W3LK

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RE: Manpack repeater (Help pls)
« Reply #8 on: July 31, 2011, 02:12:45 PM »

Yes, it is pirate repeater !
But, I'm out of the US right now. Where I live, there are no hams for hundreds of kilometers!!
Besides, I'm not going to install a permanent repeater. It will be operating occasionally just for test and experience.

ROFLMAO!!!!

If there are no hams within hundreds of kilometers, who is going to talk on your 5w repeater? :)
« Last Edit: July 31, 2011, 02:18:16 PM by W3LK »
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KG6RYR

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RE: Manpack repeater (Help pls)
« Reply #9 on: August 01, 2011, 09:35:53 AM »

Actually there are a few unlicenced hams and they are not in the feild of sat work.
Besides, i can try simplex repeater in which i can check my voice echo.
I want to get experiece about antennas, cables, etc and their effect on the range.
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W3LK

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RE: Manpack repeater (Help pls)
« Reply #10 on: August 01, 2011, 11:06:17 AM »

No such thing as "unlicensed" hams. There are illegal radio operators though. :)

I hope whatever country you are operating in doesn't decide to take an interest in your activities. It's entirely possible that getting nailed for illegal radio activity in another country could give the FCC cause to revoke your US license.
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N0FPE

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RE: Manpack repeater (Help pls)
« Reply #11 on: August 01, 2011, 07:51:42 PM »

Keep it up please!!  This is the funniest thing I have read in weeks!!! well besides the congress critters playing with our money...


Dan/NØFPE
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W3LK

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RE: Manpack repeater (Help pls)
« Reply #12 on: August 02, 2011, 10:17:58 AM »

Keep it up please!!  This is the funniest thing I have read in weeks!!! well besides the congress critters playing with our money...


Dan/NØFPE


I tend to agree with you. :)
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WY3X

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RE: Manpack repeater (Help pls)
« Reply #13 on: August 14, 2011, 09:24:27 AM »

This is the funniest thing I have read in weeks!!!
Dan/NØFPE

I'm glad you quantified that Dan! I think the FUNNIEST thread on here (eHam.net) was
the socially defective Captain Underpants guy trying to upgrade to General! HAW!!!!
(That thread also generated the most replies EVER, 322!)

http://www.eham.net/ehamforum/smf/index.php/topic,66488.0.html

73, -WY3X
« Last Edit: August 14, 2011, 09:28:26 AM by WY3X »
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