Civilian Aviation Band Repeater Question

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gwpettit

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I'm having a bit of trouble explaining our communication system differences to a coworker. We primarily utilize a UHF radio system with a repeater. So naturally we have 2 frequencies licensed to our program. We have a backup VHF system that is also repeated. We monitor UNICOM (123.050MHz) for military as well as other medical rotorcraft inbound to our facility that do not have UHF capabilities. We also utilize that frequency to activate our traffic control devices around our helipad. We hear traffic on a fairly regular basis from aircraft calling FBO's 50-100 miles away (depending on the weather). They may not be able to hear us (I think we have a 10 watt transmitter) but we can hear them. Last night we had a total console radio failure due to unscheduled facility maintenance. We switched over to portables for UHF and UNICOM & were essentially fine because our repeater was still working. However, UNICOM is not repeated. Our dispatch console is on a lower level, fortunately it has a window so we get some reception, but its range was dramatically decreased since we were then transmitting from the 2nd floor of a 9-story downtown building instead of off a rooftop antenna that the radio console connects to. My coworker thought UNICOM was repeated. I'm having trouble explaining why it is not and why it cannot be.

Can anyone help me out here a little?
 

kma371

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Tell him UNICOM is one frequency. When you talk, it is not amplified on a secondary frequency with more power like a repeater would be.
 

gwpettit

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Thanks. I tried but I guess the early morning hours wasn't allowing things to sink in. She finally understood.
 

popnokick

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Aviation communications such as UNICOM use AM mode, not FM. And it's not that it wouldn't work, but AM modulation does not lend itself well to repeater operation. That of course draws the question, "Why does most aviation use AM instead of FM or SSB?" That is a different question and a longer answer.
 

jaymatt1978

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Leave the radio out of it. Explain it as if you were talking with someone with or without a microphone and speakers. With the microphone and speakers make the sound louder and travel further than just using regular voice.In basic terms the repeater amplifies the radio signals
 

bharvey2

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If you're trying to explain repeaters, I think I'd use the term channels rather than frequencies. As most people are familiar with TV channels, the analogy would be better understood. e.g. portables talk on channel A, and listen on channel B. Repeater listen on channel A but talk of channel B but have the benefit of more power and range due to antenna height.
 

riveter

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If you're trying to explain repeaters, I think I'd use the term channels rather than frequencies. As most people are familiar with TV channels, the analogy would be better understood. e.g. portables talk on channel A, and listen on channel B. Repeater listen on channel A but talk of channel B but have the benefit of more power and range due to antenna height.

NAAAAAAAH None of that mix-and-match terminology *shudder*

Anyway, OP got it sorted out with the co-worker, so never mind me. That just made me cringe though. Don't mix and match terms... please. :(
 

902

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I'm having a bit of trouble explaining our communication system differences to a coworker. We primarily utilize a UHF radio system with a repeater. So naturally we have 2 frequencies licensed to our program. We have a backup VHF system that is also repeated. We monitor UNICOM (123.050MHz) for military as well as other medical rotorcraft inbound to our facility that do not have UHF capabilities. We also utilize that frequency to activate our traffic control devices around our helipad. We hear traffic on a fairly regular basis from aircraft calling FBO's 50-100 miles away (depending on the weather). They may not be able to hear us (I think we have a 10 watt transmitter) but we can hear them. Last night we had a total console radio failure due to unscheduled facility maintenance. We switched over to portables for UHF and UNICOM & were essentially fine because our repeater was still working. However, UNICOM is not repeated. Our dispatch console is on a lower level, fortunately it has a window so we get some reception, but its range was dramatically decreased since we were then transmitting from the 2nd floor of a 9-story downtown building instead of off a rooftop antenna that the radio console connects to. My coworker thought UNICOM was repeated. I'm having trouble explaining why it is not and why it cannot be.

Can anyone help me out here a little?
That's because it's not repeated at all. Unicom is simplex. Your base is probably close to the roof and is using an antenna that's roof mounted. That's why you hear further. Your lighting system was probably working because the radios themselves were powered up and so was the lighting interface. The console is the weak link here.

What I would do is figure out what kind of signaling you have going to the aviation radio, then install a stand-alone desktop remote unit that has nothing to do with the console. This way, the console can go away - literally - and as long as you have power to your roof and no one's cut the control line, you can stay informed of inbound with zero reduction in range.
 

ecps92

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And to add confuzzlement, there have been Unicom Radios [AM] patched to UHF [FM] Simplex and Repeater pairs, to allow folks to listen, while also maintaining normal airport Ops without being strapped to a Desk, using a 2nd PL/DPL to talk to the Planes from the FM Portable and a different PL/DPL for the Non Aircraft chatter YMMV and without knowing his set-up, we are all guessing

That's because it's not repeated at all. Unicom is simplex. Your base is probably close to the roof and is using an antenna that's roof mounted. That's why you hear further. Your lighting system was probably working because the radios themselves were powered up and so was the lighting interface. The console is the weak link here.

What I would do is figure out what kind of signaling you have going to the aviation radio, then install a stand-alone desktop remote unit that has nothing to do with the console. This way, the console can go away - literally - and as long as you have power to your roof and no one's cut the control line, you can stay informed of inbound with zero reduction in range.
 

bharvey2

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I understand that UNICOM transmissions aren't repeated. If you can explain what a repeater does and why it is used, it will probably become evident that installing one to communicate with an aircraft at 10K ft + would be futile.
 

ecps92

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Repeaters are Generally (FM) and used to RELAY transmission from (one Frequency) a low spot to (second Frequency) which is usually place on a HIGH Spot (Hill, Mountain, Tall Bldg)

I would suggest you talk to your local Radio shop, as patching FM to AM if not done properly could create some (AM) aircraft issues

I understand that UNICOM transmissions aren't repeated. If you can explain what a repeater does and why it is used, it will probably become evident that installing one to communicate with an aircraft at 10K ft + would be futile.
 

bharvey2

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Repeaters are Generally (FM) and used to RELAY transmission from (one Frequency) a low spot to (second Frequency) which is usually place on a HIGH Spot (Hill, Mountain, Tall Bldg)

I would suggest you talk to your local Radio shop, as patching FM to AM if not done properly could create some (AM) aircraft issues

I'm not disagreeing with you and understand fully why AIR comms aren't (or need to be) repeated. I thought the purpose of this thread was that the OP was trying to find a way to explain that to his coworker. If the coworker understands what a repeater does and why, an explanation of why one isn't used for ground/air comms would make sense to him.
 

nr2d

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Repeaters are Generally (FM) and used to RELAY transmission from (one Frequency) a low spot to (second Frequency) which is usually place on a HIGH Spot (Hill, Mountain, Tall Bldg)

I would suggest you talk to your local Radio shop, as patching FM to AM if not done properly could create some (AM) aircraft issues

Patching can cause problems on the FM side also since the AM side in our system here at ACY in noise squelch only just like standard aircraft radios. We have had problems on the AM side from the FM side. Even though the FM side uses digital squelch we have had problems of other FM transmitters getting into the system and causing problem on ACY ground control.
 
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