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Creating a portable repeater with a mobile transceiver

WA3MED

Member
Joined
Apr 13, 2021
Messages
6
Hello all!

I have returned to seek expertise on a project I am creating.

Task: Create a simplex repeater for search and rescue operations using a mobile radio.

I am trying to find a way to boost coverage of team communications in a remote area. I currently have a 25w AnyTone AT-778UV which I would like to use as the base station.
I am thinking about purchasing a LATNEX RC-S120 Simplex Repeater Controller to connect to the mobile radio; however, the input/output on the repeater controller is 3.5mm AUX and the input/output on the mobile radio is the well known RJ45 connected speaker mic.

If I purchase a RJ45 to headset adapter show in the picture below (and the necessary coupler/male-male adapter), will I be able to make the correct connections to create this repeater?
1619370657382.png

If anyone has created this project before and has a parts list, that would be even better.
 

prcguy

Member
Joined
Jun 30, 2006
Messages
11,542
Location
So Cal - Richardson, TX - Tewksbury, MA
If the RJ45 headset adapter is made for your specific radio then you have a chance of it working. Otherwise there is no standard for RJ45 mic wiring and it would be a miracle if it happened to work.

I have a few simplex repeater controllers here and in my opinion they are one of the most annoying things to use that I can think of. Everyone using it has to adopt a new way of thinking like very short transmissions and always wait for the repeated message. That lasts a few minutes then most people who can hear the direct broadcast respond immediately and collide with the repeater message and it becomes a mess.

A much simpler approach is a dual band radio with cross band repeat function. You use it just like a regular repeater and when everyone is set up with the correct frequency pair and tone it works great.

Hello all!
I have returned to seek expertise on a project I am creating.




Task: Create a simplex repeater for search and rescue operations using a mobile radio.

I am trying to find a way to boost coverage of team communications in a remote area. I currently have a 25w AnyTone AT-778UV which I would like to use as the base station.
I am thinking about purchasing a LATNEX RC-S120 Simplex Repeater Controller to connect to the mobile radio; however, the input/output on the repeater controller is 3.5mm AUX and the input/output on the mobile radio is the well known RJ45 connected speaker mic.

If I purchase a RJ45 to headset adapter show in the picture below (and the necessary coupler/male-male adapter), will I be able to make the correct connections to create this repeater?
View attachment 102751

If anyone has created this project before and has a parts list, that would be even better.
 

kayn1n32008

ØÆSØ
Joined
Sep 20, 2008
Messages
6,315
Location
Sector 001
Hello all!

I have returned to seek expertise on a project I am creating.

Task: Create a simplex repeater for search and rescue operations using a mobile radio.

I am trying to find a way to boost coverage of team communications in a remote area. I currently have a 25w AnyTone AT-778UV which I would like to use as the base station.
I am thinking about purchasing a LATNEX RC-S120 Simplex Repeater Controller to connect to the mobile radio; however, the input/output on the repeater controller is 3.5mm AUX and the input/output on the mobile radio is the well known RJ45 connected speaker mic.

If I purchase a RJ45 to headset adapter show in the picture below (and the necessary coupler/male-male adapter), will I be able to make the correct connections to create this repeater?
View attachment 102751

If anyone has created this project before and has a parts list, that would be even better.
Buy a simple controller, a pair of 25w mobiles, a mobile duplexer and build a full duplex repeater. Get your antenna up minimum 2 full wave lengths(on VHF) or better. It's going to be mostly portables using the repeater, so keep your power down. Less than 10w into the duplexer. Add low noise, 3dB gain preamp to overcome feedline and duplexer loss. Keep the antenna gain low, no more than 5-6dBd gain. Ideal would be a unity gain exposed dipole, for large vertical beam width. Use PL/DPL for access control. Ensure all your connectors are high quality, avoid adaptors at all cost. Ensure jumpers are RG-142/400. Do not have excess feedline. Use minimum length as possible.

Excess power is not going to be your friend. Strategic repeater placement is going to be key to effective use of a portable repeater.

A simplex repeater has got to be one of the most annoying things ever created.
 

mmckenna

I ♥ Ø
Joined
Jul 27, 2005
Messages
16,579
Location
From the land of sky blue waters!
Simplex repeaters might be fine for amateur/hobby use, but have no business in any sort of life safety communications. If this is for a search and rescue group on Part 90 frequencies, take the time to do it correctly.

I agree, get two good low power mobiles and a separate controller. Simplex repeaters get very tiresome after a short while. It delays communications and that may be dangerous.

I've got a remote site at work that I inherited that has a couple of the low cost Bridgecom repeaters on high ridges running about 10 watts off solar panels and batteries. A single folded dipole antenna covers the deep canyons below very well.

It's a bit more of a challenge to build, but the people using the radios will greatly appreciate it.
 

WB9YBM

Active Member
Joined
May 6, 2019
Messages
1,392
A "mobile extender" typically used in police squad cars--if find-able on the used market--might make a good starting point. Alternatively if you have two mobiles (preferably on different bands to avoid conflicts) with the squelch of one radio used to key the second radio (and vice-versa) can be used (I've done it myself with good results, once from 220MHz to two meters and also 220MHz to 10M FM).
 

kb2ztx

Member
Feed Provider
Joined
Jul 29, 2012
Messages
789
Location
South West Virginia
I have built many repeaters for the SAR world. We started 20+ years ago with a simplex repeater. Lasted one event and was shelfed. As other said spend some time and research. Most of our repeaters are now 2 VHF mobiles, a duplexer and power source in a pelican case. Basic antenna on a mast works well. Low power works fine as its only portables talking to it anyway. In the end this is the best way to do this in the LMR world. I even have one repeater that uses a pair of HT1000's with a cheap controller. ITs not idea but is the backup or a backup and is light and runs on batteries. I can carry to a hill top throw a VHF antenna in the tree with 20' of cable and get something on the air quick until a better system can go up.
 
Joined
Jun 16, 2013
Messages
3,685
Location
Texas
I was actually discussing this topic with someone yesterday. Mentioned what I found with simplex repeaters is they tend to operate more efficiently if they are configured like a regular repeater (RX on one frequency and TX on another) as it's less apparent to the casual user that they are running on a half duplex system. If you are listening to the repeater output...you only hear the message from the repeater. If you send a message to the repeater, you will hear the message on the output from the repeater but you will be the only one who hears the message twice.

That being said, for SAR application I would personally go with a full duplex repeater based on some small radios. I really like the Maxon SD series radios and actually just sent a pair of to a friend who is wanting to package two SD-170's with a duplexer into a small Pelican case and fly it via a tethered weather balloon (I suggested a cheaper proof of concept using a lifting kite). Portable and can get enough altitude to make up for low transmit power.
 
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