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Author Topic: Help with setting up a small cross band repeater.  (Read 5126 times)
KD8MJR
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Posts: 1991




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« on: February 11, 2011, 05:33:39 PM »


Any help on this would be greatly appreciated.

I have the following

A Kenwood TM-701A Mobile and I am modifying it to do Cross Band Repeating.

A Diamond MX-72D Duplexer

A Diamond 50A Antenna that can do 440 and 2M.

My Question is can I hook the Diamond Duplexer into both Antenna ports and use the One Antenna to do Cross Repeating between 2m and 70cm ?

I see they call the MX-72D a Duplexer but I know a duplexer to be like a cavity and those things are monstrous in size while this thing is small like a Diplexer!  I am fearful it will blow out the Receive end of the Rig so I am hoping for some advice on this before doing anything.

BTW the specs on the MX-72D say 60db of isolation.

Thanks
Robert

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VA3WXM
Member

Posts: 277




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« Reply #1 on: February 11, 2011, 07:00:00 PM »

Yes, it's a diplexer.  And yes, it'll work without blowing up your radio. Smiley

Keep in mind, pretty much all recent dual-band mobile radios have a single coax connector so the diplexer is built in to the radio.
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KD8MJR
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Posts: 1991




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« Reply #2 on: February 11, 2011, 08:25:02 PM »


Thanks so much for the information. Thats great, now it's off to have some fun  Grin Grin
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KQ6EA
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Posts: 608


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« Reply #3 on: February 13, 2011, 03:41:56 PM »

I'm using a D710 and a Comet GP-3 to do that.\One feedline, one antenna, one radio, works perfectly.
Your D701 should do the same.....
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VA3WXM
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Posts: 277




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« Reply #4 on: February 14, 2011, 06:06:20 AM »

Don't think the OP has a "D701".  It's an older TM-701A which has separate V and U.  In order to use a dual-band antenna a diplexer is required.
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KQ6EA
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« Reply #5 on: February 14, 2011, 09:15:44 AM »

DUH!
My mistake.....
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KB5ZAU
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Posts: 12




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« Reply #6 on: February 14, 2011, 10:51:01 AM »

Here in Sioux falls we have a pretty strong 2-meter repeater. Serves the main area well. I can hit the repeater from any basement in the city. Utilizes several uplink recieve statations across town.

I would like to test crossband repeat to see just how far it would serve. Let's take an emergency situation such as a flood south of here. We needed someone to access the flood area by foot and report back to the city over a 3 hour period. I know on a handheld the repeater can be accessed with a HT and mobile antenna 30 miles south. The flood area is an additional 12 miles.

If I were to have the crossband mobile (20 watts or more) at that 30 mile point, I am guessing I could get the HT to serve the extra 12 miles which would have been impossible to reach the Sioux Falls repeater before. It would probably work even better on 220 than 440.

Thanks for the thread. I would like to test this sometime soon.

What are some other common uses for crossband repeat? Another I though of would be assisting a car club rally. Anyone want to volunteer for the Corvair Convention in Denver this summer?  Smiley
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K8SOR
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Posts: 55




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« Reply #7 on: February 14, 2011, 01:36:29 PM »

Got out the flame proof suit, etc.  Before you get too involved into the cross band repeater, figure a way for the thing to ID the 440 transmitter.  When you use your 440 ht, you will id and that in turn will id the 2mtr output of the cross band rptr. But, when the cross band rptr hears a 2 mtr signal, and re-transmits it on 440, it won't id with your call, thus it is illegal.
A lot of people will say "who cares", because it's just a local thing.  Right is right, wrong is wrong.  I guess I grew up "old school".
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VA3WXM
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Posts: 277




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« Reply #8 on: February 15, 2011, 07:44:57 AM »

Kenwood has addressed the ID issue to a certain extent in the TM-V71A (and maybe the TM-D710 but I don't know for sure).  In the radio menu you can program in your call sign and set the radio to ID at regular intervals.  That should deal with the legal aspects of ID'ing the crossband repeater.

Many Kenwood mobiles also can be controlled remotely using DTMF so that deals with the legal aspects of controlling the "remote" station.

As far as common uses for a crossband repeater I personally use mine to extend the range of my handheld.  The reality is many ham repeaters were never designed for portable coverage and if you want to maintain reliable handheld communications you often need the extra oomph a crossband repeater with it's higher power and (usually) better antenna provides.
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KB9TMP
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Posts: 58


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« Reply #9 on: February 24, 2011, 05:44:12 PM »

Got out the flame proof suit, etc.  Before you get too involved into the cross band repeater, figure a way for the thing to ID the 440 transmitter.  When you use your 440 ht, you will id and that in turn will id the 2mtr output of the cross band rptr. But, when the cross band rptr hears a 2 mtr signal, and re-transmits it on 440, it won't id with your call, thus it is illegal.
A lot of people will say "who cares", because it's just a local thing.  Right is right, wrong is wrong.  I guess I grew up "old school".

I got around that using a Byonics PicCon and cheap 2m HT set on low power. Worked like a champ and IDed my crossband every 10 minutes.  If he uses the crossband radio in a locked band repeat mode. (RX only on 440 and TX only on 2m) there isn't a problem with the ID, just possible reception problems of the 2m repeater directly using the HT.

WW KB9TMP
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K9KJM
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Posts: 2416




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« Reply #10 on: February 24, 2011, 11:09:15 PM »

To be fully "legal" with cross band repeat, You DO need a dual band hand held with both of your cross band frequencies in it, So you can easily  go "reverse" to properly I.D. both of your cross band repeater sides.......

You do NOT have to have it done automatic.....    I.D.ing manually is just fine.

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