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Amateur Radio Equipment - For general and technical discussion of Amateur Radio equipment such as transceivers, repeaters, controllers and receivers.

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Old 03-18-2013, 7:38 PM
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Default Ritron RRX-450 Repeater on Amerateur Bands?

Can a RRX-450 be tuned to 440? It programs in to the band fine and all but the status light blinks green.

Its obviously a 450-470 Repeater, But i would like to know if it can be done or how to move it to function on 440
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Old 03-18-2013, 8:54 PM
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If the green light is blinking, this means the VCO is out of lock. You can adjust the VCO to lock at lower freqs at the expense of loosing the higher freqs. A voltmeter is all it takes.

Also to consider is the duplexer as they are pretty wimpy. I don't how many threads are left on the tuning slugs after you go below 450MHz.

I have never tried to take a Liberty down to the ham bands, so I cannot speak on the performance nor the bottom limit. Experimentation is the only answer.
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Old 03-18-2013, 9:59 PM
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Smile Exactly the answer i was looking for

Ok. I adjusted the VCO, and it adjusts fine at 460.000

But i tried programming to 450.000 and it wont lock. The test point stays at .19 to .20v and it wont move

At GMRS Frequencys it adjusts fine....

Last edited by centuryvrproductions; 03-18-2013 at 10:51 PM.. Reason: Further infermation was found
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Old 03-19-2013, 1:53 PM
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It doesnt seem to do down past 450. It wont tune so it will lock
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Old 03-19-2013, 10:51 PM
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I had to dig out my service manual. Don't do many Ritrons, so I had to dig.

What you want to do is put the voltmeter on the indicated tie point and adjust to 4 volts on both the transmitter and the receiver. The transmitter needs to be keyed up to adjust and you tweek L207. On the receiver twist C180.

Links are to diagrams of locations...

https://dl.dropbox.com/u/2991846/TX.pdf
https://dl.dropbox.com/u/2991846/RX.pdf
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Old 03-20-2013, 12:24 PM
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Yes, While it is on Frequency 460, It will transmit. and it will tune to 4 volts no problem.

It will not Key up at the frequency that I want to use, So How should I tune the VCO to my frequency (444)?

I have adjusted it to 4v just fine at the frequency 462, But i tried to tune it anywhere under 455, It just flashes and the voltage reads .10-.11v
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Old 03-20-2013, 3:36 PM
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Talking

I Got it!

I Basically programmed in the frequency pair. (444)+5. Then Tuned the Reviever VCO. As well as the Transmitter.

With a bit of tweeking back and forth... it works well.

Thanks for the Help
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Old 03-22-2013, 10:29 AM
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The repeater works but The Transmitter VCO will not stay locked. I got the pot tuned so it will transmit but it will not tune even up to a volt at the test point on the transmitter.

The pot screw is all the way out and will not go far enough...


Could i possibly add a larger or smaller value POT in there to be able to tune it to these frequencys?
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Old 01-31-2017, 3:55 PM
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I have been successful with getting a repeater down into the 440 MHz amateur band, and just got it installed a few days ago.

These repeaters are nice in that they are self-contained and have most of the functions you need on 440 MHz amateur repeater, and will accept external controllers. I started with 2 I picked up cheap at a Hamfest (the original RRX-450 is wideband only, so it is fine for Amateur use. The current RRX-452 is narrowband. Many of the RRX-450s were surplus when public safety/commercial users were forced narrowband.)

Issues:
1) The transmitters seem to go into the 440 MHz band without too much difficulty. Note that you need to activate the PTT via a local mic to tune the VCO to 4V, and it is the one changing of the 3 voltages when you diddle you need to worry about.

2) The receiver VCOs are more touchy - I was able to get 1 of 2 I had into the 440 MHz band. The other simply would not ever lock up, in fact, I could not get the VCO to lock much below 460 MHz. Not certain if there was a build where there were separate receivers for different UHF sub-bands. I did have the advantage that the input frequency for the repeater I was building was in the 449 MHz range, so not too far out of the manufacturer's specs. There are no frequency-dependent parts I could find on the schematic, but I suspect an RF engineer could identify parts that might aid in tuning outside the specified band.

3) For the receiver where the VCO did lock, I could never quite get the VCO all the way to 4V, it seems to work just fine at about 3V.

4) The built-in duplexer (4-cavity notch type) was not designed to go below 450 MHz. With longer screws (I replaced the provided 1" screws with 1.25" screws), I could get an adequate notch (about 70 dB) on the 449 MHz receive side, but not enough notch on the 444 MHz transmit side to be effective (could only get about 45 dB). I ended up just removing the internal duplexer, building a set of cables, and using an external set of pre-owned commercial cans, which works great.

5) The nominal output power of the RRX-450 is 8 Watts (Ritron's market is low-power single-site systems for malls, golf courses, and industrial sites). While this might fall short for system intended to cover a large metropolitan area, it is enough for a small to medium sized town, or even farther if you have an elevated site. If most users are on portables, this should be fine. Keep in mind that 8 Watts into a 9 dB gain antenna means you have an ERP of 64 Watts, which is respectable. Recall, however, that such a gain antenna may have coverage holes "under" the pattern of the antenna.

6) One of the repeaters came with a 30 Watt amplifier. At least on 444 MHz this proved very difficult to keep properly tuned and after a few days would drift off its ideal tuning and become a current hog, source of broadband noise, and not reliably increase the on-frequency transmit power. Taking the amplifier out of the repeater resulted in significantly better performance on both transmit and receive and far less power draw.

7) The built-in CW-IDer will not transmit the "/" required for the CW ID of amateur repeaters. This is especially frustrating, since the "/" is listed as an available character in the Ritron programming software; I contacted Ritron to ask and they confirmed that this is an error and the "/" is not supported. Thus, a simple ID-er or repeater controller would be needed to have a legal amateur repeater.

So, the overall answer is that the RRX-450 can be moved into the amateur band, but pick up a few if you can so you will have enough transmit and receive modules that you will have a few that will actually tune into the 440 band.
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Old 02-01-2017, 10:39 AM
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Although you've resurrected an "ancient" thread, I am just as happy that you did, since I happen to have two RRX-450 repeaters I bought at auction over a year ago. I need to send both of them off to Carmel, IN to have them fixed though.
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Old 02-01-2017, 12:30 PM
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I'm not sure that Ritron has anything left in Carmel. I think they moved all the engineering, and maybe the whole shebang, to Florida.
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Old 02-01-2017, 1:18 PM
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Quote:
Originally Posted by W9BU View Post
I'm not sure that Ritron has anything left in Carmel. I think they moved all the engineering, and maybe the whole shebang, to Florida.
If they have, then they haven't updated their website...
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N4GIX - Ham / WQWU626 - GMRS
Leixen VV-898, Kenwood TK-840(N), 2xTYT-7800, 2xUV5R v2+, Home Patrol 1, BCD436HP, Kenwood TMV7A, Ritron RRX-450 Repeater, MD-380, 2xCS800, Bridgecom BCR-40U Repeater
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