Setting up a repeater

[thames]

I'm fairly new to GMRS and decided to buy a Motorola Radius GR300 UHF repeater off ebay. It is in working order with a duplexer and the Motorola RICK. I had some questions about the basics that I would appreciate some help on...

 

First off, I have successfully be able to program both the Tx and Rx for each unit (Motorola M10's). When programming I saw the original frequencies programmed were Rx 469.56250 and Tx 464.56250 on both M10's. I want to changes these to be Rx 462.57500 and Tx 467.57500.

 

Knowing this unit was in working order before, I assume the duplexer was tuned to the previously programmed frequencies. Being new to this, I am not sure if the the frequencies I want to change to will require re-tuning the duplexer.

 

Additionally, I am not sure I completely understand how having each M10 programmed to the same Rx and Tx between units works when it comes to repeating a signal... mentally it's not clicking for me.

 

Any information you can provide is greatly appreciated!

[Jones]

You need to have the RX programmed to the HIGH SIDE on a repeater - 467.xxx. The transmitter will then repeat what it hears on the repeater's output frequency, which is the 462.xxx that your radio is listening to.

 

You WILL need to have the duplexer re-tuned regardless.

 

:...not sure I completely understand how having each M10 programmed to the same Rx and Tx between units works:

 

Both units are programmed to the same RX (high side) and TX (low side) so that the units can be swapped out if a final amp blows out or something.  One unit is always the receiver, and repeater controller.  It never transmits.  The other unit is the transmitter, and is NOT used for receiving or control of the repeater.  ...but the 2 units are swap-able for service purposes.

[Jones]

.... original frequencies programmed were Rx 469.56250 and Tx 464.56250

 

Since these are ending in .5625 rather than .565 or .560, there is a very good chance this is also programmed for narrow band operation.  You'll want to change it to wide-band for GMRS use.

[marcspaz]

Edit: Jones be me to it. LOL  Drawback of typing on my phone instead of the PC.

Just briefly, you have the transmit and receive transposed. You want the repeater to listen to 467.575 and transmit on 462.575. Radios that will use the repeater listen on the repeaters output 462.575, but shift up to 467.575 when they transmit. This is how the channel pairs are setup.

Also, you will need to tune the duplexer. The band pass and band reject filters are extremely tight. You're either going to need to hire someone with the right tools to do it or spend some decent time and money buying and learning how to use a spectrum analyzer, tracking generator or VNA and some other tools.

The only benefit I can think of to having the two units programmed with the same in/out values is that they can switch roles if needed. Such as if a decoder fails or a transmitter final amplifier starts to go bad, you can reverse which system does what job while waiting to do repairs.

I have only worked with diplexers which are similar. Hopefully one of our other members with experience with tuning the duplexer can give e you some more refined information.

[coryb27]

I just have to ask, why would you set up a repeater if you have no idea how to program it or how it works? I highly recommend reading my post here. https://forums.mygmrs.com/topic/1402-you-just-got-your-gmrs-license-now-you-want-your-own-repeater/

[berkinet]

I highly recommend you visit (and bookmark) http://www.repeater-builder.com/ They have the answers to all your questions, plus much, much more.

[thames]

I just have to ask, why would you set up a repeater if you have no idea how to program it or how it works? I highly recommend reading my post here. https://forums.mygmrs.com/topic/1402-you-just-got-your-gmrs-license-now-you-want-your-own-repeater/

 

Because I can't help myself... I like to learn new things and after using some local repeaters in my area I thought it would be fun to set one up. I also have access to a facility where a repeater being located there would be very useful for my friends and family.

[thames]

Thanks everyone! I will be diving into this project some more this weekend. I hope to have it up an running soon... One of the guys I spoke to on a local repeater has a guy who can help out with tuning the duplexer using a spectrum analyzer. Unless there is a way for me to do it without one, I'll be asking for some help. If all else fails maybe buy an analyzer... just to ensure my wallet knows who's boss.

[Ian]

Happy hunting, Thames -- I look forward to your inevitable success, new friends, and new skills.