Radio repeater methods?

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AllN
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Posted by AllN: Wed. Aug 22, 2007 - 05:34 PM
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I use FRS radios as an intercom system for boating. Now, I have linked the base station into my PC and using it for a voice recognition system that listens and processes user commands. I would like to add a (voice directed) switcher/repeater to send and receive from the FRS to my boat’s VHS radio, using it’s like a repeater. (Note: Changing to GMRS if that matters)

There are more requirements but I know so little think it will be easier for me to learn bit by bit.

Questions:
1) Do you know of an existing commercial solution? Or at least what search term should I use to look for it.
2) Do you know or have a circuit for it.
3) What are the know problems as I have no clue – everything seem possible?

Any insight at all would be helpful,
John

Resistance is futile…… You will be compiled!

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Learning and Information, General Electronics
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ka7ehk
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Posted by ka7ehk: Thu. Aug 23, 2007 - 02:00 AM
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Well, this is quite a bit like the ham repeaters. Since the two radios are on very different frequencies, there should not be much problem unless one just happens to be a harmonic of something happening in the other.

It would take some analog switches to route FRS audio to/from the VHF marine radio. The switches would be controlled by the voice detection software in the PC. This might be an AVR that is driven by the PC through serial or USB. The AVR would just convert serial commands to audio switch actions and assert the push-to-talk on the marine radio. Not much to it. You would need a method to terminate the link and unkey the radio.

Oooops, the marine radio is half duplex. It cannot transmit and receive at the same time, Neither can the FRS radio hooked to the marine radio. So, you need to establish a priority (which one links through to the opposite if both have an active receive). Then you have to key the right radio to transmit. Its not easily done without access to carrier detect logic signal or an audio detect. The AVR with ADC COULD do this, I think.

Jim

Resistance is futile, it is lossy.
But Reactance is lossless.
So, don't just resist. REACT.

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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AllN
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Posted by AllN: Thu. Aug 23, 2007 - 02:11 AM
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Jim to my rescue, I knew you would know!!!
That’s what I thought but usually when I think it’s this easy it has some unknown catch.
Thanks Jim!!! I’ll proceed with the fun part.

John

Resistance is futile…… You will be compiled!

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AllN
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Posted by AllN: Thu. Aug 23, 2007 - 02:13 AM
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ka7ehk wrote:
....

Resistance is futile, it is lossy.
But Reactance is lossless.
So, don't just resist. REACT.

I love that!!!
Thanks,
John

Resistance is futile…… You will be compiled!

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AllN
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Posted by AllN: Thu. Aug 23, 2007 - 02:20 AM
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Edited:
Sorry you added more and already answered it!! Thanks

Lets forget the voice switch for now.
Check my design. Yes simplex or half duplex for both.
1) Once the audio is transfered to the AVR switcher I was hoping to sense when the carrier was received or dropped to key the mic or receive.

Like any carrier over a threshold?

John

Edited:
Sorry you added more and already answered it!! Thanks

Resistance is futile…… You will be compiled!

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ka7ehk
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Posted by ka7ehk: Thu. Aug 23, 2007 - 02:30 AM
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Both of these radios are FM.

The classic "Motorola Squelch" uses a high-pass filter to pass only audio above about 5KHz (maybe a bit higher). When the radio is not receiving anything, the audio AT THE DETECTOR OUTPUT has a huge amount of high frequency noise. When the carrier comes on, this noise disappears and you only have audio (or quiet). These radios probably have such a squelch. Well the marine radio ought to; FRS/GMRS might not. But those will have an internal squelch of some sort that you shoud be able to tap into.

Jim

Resistance is futile, it is lossy.
But Reactance is lossless.
So, don't just resist. REACT.

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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AllN
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Posted by AllN: Thu. Aug 23, 2007 - 02:32 AM
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I can get to the audio and the signal strength meters on both radios. I'm going to try these for my output to ADC.
Being an explorer in electronics it’s all fun until I let the magic smoke out of a radio or two.
John

Resistance is futile…… You will be compiled!

Last Edited: Thu. Aug 23, 2007 - 02:49 AM
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AllN
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Posted by AllN: Thu. Aug 23, 2007 - 02:37 AM
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They both have squelch's I'll investigate further.
I've heard the squelch behavior that you just described so well.
Thanks,
John

Resistance is futile…… You will be compiled!

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ka7ehk
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Posted by ka7ehk: Thu. Aug 23, 2007 - 04:23 AM
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If there is a signal strength voltage, then use that to sense when a signal is received, The radios could use either that or the "noise squelch". it is usually implemented in the FM detector IC so you get what you get.

I may be able to provide some more detailed assistance if you need it.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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AllN
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Posted by AllN: Thu. Aug 23, 2007 - 04:57 AM
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Thanks Jim!!!

Resistance is futile…… You will be compiled!

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ka7ehk
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Posted by ka7ehk: Thu. Aug 23, 2007 - 07:07 AM
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Send me a personal message on this board and I'll provide my home e-mail for direct contact.

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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AllN
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Posted by AllN: Thu. Aug 23, 2007 - 02:47 PM
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PMing Jim Freaks are the best!!!
Thanks
Jim

Resistance is futile…… You will be compiled!

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