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New Project, "Tactical" Repeater


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So I had this interesting idea while looking at some "Tactical" repeaters owned by the Texas Department of Transportation. Basically they are VHF boxes with Li-on battery packs about the size of your average Pelican handgun case, a 5W full duplex board and a notchplexer.

 

Then I started running some power draw numbers with the Maxon data radios…then the Ritron data radios, and then Tecnet released a new line of smaller data radios along side their Maxon line at IWCE this year.

 

Then 11 Motorola RNet 450's plopped in my lap from a SK's estate. Crystal controlled, single channel data radios that'll run 4W out (on what is probably a 10% duty cycle) with some other junk in the case that isn't actually needed for "repeater" duty.

 

So I've though about throwing a repeater (or two) together in an ammo can, adding a small duplexer (the 20W rated Jensen duplexer will fit nicely in a 30 cal can), adding some external heat sinking and a battery and seeing how it runs. Just gotta track down the service manual for the radios if I'm going to use the RNet radios…

 

Any thoughts?

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Yeah...

 

Where do you find a 20 W Jensen Duplexer??? LOL

 

I made a portable field deployable repeater repeater out of a .50cal amo can.  Did it V/U for a ham/scout thing.  Two antennas using the ammo can as a ground plane.  Here's a couple of things I ran into.

 

Battery life...

Used batteries on the radios the first time.  Second time used a 14 amp hour SLA battery hooked to battery eliminators.  First time had about 8 hours of use, then the batteries died.  Second time got Friday evening until Sunday noon out of it. 

 

Heat... 

On the first go around I think the heat really messed with the LiPo batteries on the radios, the second time by using the battery eliminators the transmit radio was warm, but didn't get as warm as the first time. Also, on the second time I drilled some holes on the sides and a couple on the bottom to allow for air flow.  i also put some "flanging" over the holes so when it rained water wouldn't get in the holes.

 

This thing was pretty slick.  Had four eye bolts mounted to the lid, so I could run it up a tree with some 550 cord.  I can also leave it sitting on the ground and run two lines of RG-8X from the SO-239 connectors on the top to two roll-up J-Poles.  NOW "theoretically" if I space the J-Poles out far enough, I can run this thing on V/V or U/U without problems.  So that's my next experiment.

 

73

James

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Either the 409 Radio shop or the Radio shop 888 for the duplexer.

 

Heat is a concern but after spending a year taking various classes covering the subject of thermodynamics, you figure out ways to move heat without unsealing your watertight ammo can.

 

I think I calculated a battery life of roughly 23 hours at a 15% duty cycle but how that actually plays out... Who knows. Also looked at adding a 10 or 20 watt amp but for the first one I think I'm going to keep it simple.

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Interesting project and thanks for sharing.   Our Chaplain Responder group tried something similar with a Kenwood TKR820 desktop repeater with internal duplexer. We had better luck running mobiles and portables on simplex because of antenna height limitations for the portable repeater.

 

Good luck on your project and testing and please let us know how yours works out.

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Take a look at these links as they might work a little better, and best of luck. I own the UV-5R and was very happy with it for both HAM and GMRS.

 

Karen

WQND308

WB5GEO

 

http://www.amazon.com/dp/B00CWPAIBW/ref=wl_it_dp_o_pd_nS_ttl?_encoding=UTF8&colid=328MRQRKIYLOZ&coliid=I230BESDB4I7K1&psc=1

 

 

http://www.amazon.com/dp/B00IUFUNO0/ref=wl_it_dp_o_pC_nS_ttl?_encoding=UTF8&colid=328MRQRKIYLOZ&coliid=IB9VW5VW2P7HJ

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The only thing I've never been too fond of baofengs of is the squelch settings. Either too much or not enough (to the point tones don't make a difference). The other big problem, I try and design my repeater's to run 25% duty at a minimum. It's not something that can be accomplished without dropping the power (lower than what the PA is actually speced at) or tearing the unit apart to add some heat sinks.

 

 

Sent from my iPhone using Tapatalk

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I built a VHF one for our local SAR team in a small pelican box. We utilized 2 ICOM portables that we had with battery eliminators. 20 W duplexor from ebay and a 7AH gel battery. We use the repeater for standby events and other uses. Only issue we have had is heat. We now leave the lid open some if we cannot get it in the shade. I wanted to find some data type radios just to make it even more error proof. Right now they need to turn on both radios and controller, hence errors happen. The data radio idea is flip a switch and leave. Keep us posted on the outcome. I was thinking a similar project for when i go camping in an ammo can.

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The only thing I've never been too fond of baofengs of is the squelch settings. Either too much or not enough (to the point tones don't make a difference). The other big problem, I try and design my repeater's to run 25% duty at a minimum. It's not something that can be accomplished without dropping the power (lower than what the PA is actually speced at) or tearing the unit apart to add some heat sinks.

 

 

Sent from my iPhone using Tapatalk

Hey Zap!

 

Sorry I've been out for a while, been planning the JOTA (Jamboree On The Air) here plus a couple of side projects kicking my butt.  

 

ANYWAY, just a side not on the BaoFengs, the latest daily builds of CHIRP lets you adjust the squelch levels under the "service" tab.  It's made a HUGE difference in mine. I've also found that a separation of about 15' on VHF and 8' on UHF keeps the radio's clear of desense while running.  Also I switched out my transmit radio to a BF-F8HP set on Medium power (5 watts) and I've been pretty impressed with the performance.  

 

I know a lot of that info is ham related, but the UHF separation of about 8' is noteworthy for GMRS ops when setting up a "tactical" system.

 

James

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One of my project radios is a Motorola APCOR box. Basically a 463 mhz EMS portable repeater, like the orange box you see int he old TV show Emergency. The only issue is that the duplexer is connected with real small rigid coax and it is upside down frequency-wise. It receives 463, transmits 468. But the duplexer isn't symmetrical, it's like 4 notch cavities one side and three teh other. In a duplexer you (most of the time) need to keep the frequency sense the same, one port always the lower, one the higher, regardless what's hooked to it. But the point is that these are self contained and have nicads in them. If you can find an APCOR unit it can be a pretty good portable repeater. They came in 1 watt and 12 watt versions. Oh yeah, the radios are a pair of MX300's. And those are plentiful on ebay, for making portable repeaters.

 

George Csahanin

W2DB

WQEU782

Cedar Park, TX 

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