Posted: 5/30/2011 1:49:54 PM EDT
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could i set my HT at xxx.xxx and my mobile at xxx.600 and run a dual headphone jack from my HT audio-out to my mobile audio-in? and set the mobile to vox?
of course this wouldnt be the ideal set up but in a pich or emcomm situation it could be very usefull if your mobile doesnt have cross band repeat. question 2- if possible what would be a good mobile to do this with i.e. audio in and some kind of vox? would the yeasu 7800 do it? thanks eta- or without an audio in can you wire a mic on one side and 3.5 jack on the other? and make a signal going from the audio+ turn on the ptt? |
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Quoted:
could i set my HT at xxx.xxx and my mobile at xxx.600 and run a dual headphone jack from my HT audio-out to my mobile audio-in? and set the mobile to vox? first, read this, paying close attention to the diagram: http://www.ar15.com/forums/topic.html?b=10&f=22&t=604477#10323265 now then, the basic problem you will be facing in the setup you describe above is the same as EVERY repeater operator/club faces: achieving adequate TX and RX isolation. it can be simplified as follows: if there is too much of the "repeated" signal (output) leaking into the "received" signal (input), your "repeater" will be deaf and for the most part listening to itself. it won't work the way a repeater is supposed to work. and your HT and mobile radio, with their wide-open front ends, do not provide enough selectivity to provide adequate isolation without significant external help. the TX will overload/saturate the RX and you will get nowhere. there are a couple of ways to get sufficient TX and RX isolation, with the best way (a mechanical cavity duplexer) also being the most expensive and having the largest size. another way to get close is to use separate TX and RX antennas, use low power (around 5-10W), and locate one antenna about 20-40 feet directly above the other. even this is difficult to pull off successfully as the coax for the top antenna has to pass directly through the RF field of the bottom antenna; you will need the best double-shielded (foil and braid, 100% coverage) coax that you can purchase. a variation on this is to put the complete receiver+antenna pair at the top, which means you just need to run the audio cable down to the transmitter. again, shielded high quality audio cable with bulkhead feedthrough LC filters are mandatory, otherwise you are going to couple (RF-wise) the TX and RX antennas using the audio cable. yet another way is to separate the TX and RX sites by, say a hundreds of yards to a half mile, and carry the audio over twisted pair like a phone line (dry POTS). but again, preventing RF from getting on the twisted pair is a real pain. you can also use a separate "backhaul" RF link (e.g., on 440) but the overall equipment complexity is going up. ar-jedi ETA: example 2m repeater cavity filter setup... 
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To avoid the need for a cavity filter you could also do cross-band repeat - the repeater listens on 2m and transmits on 440.
It gets a little more complicated but you can also build a simplex repeater. Radio shack used to sell a controller for one a long time ago but I think the FCC put a stop to it. Not sure if it was due to people using it on CB/FRS or what. |
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Quoted: Quoted: could i set my HT at xxx.xxx and my mobile at xxx.600 and run a dual headphone jack from my HT audio-out to my mobile audio-in? and set the mobile to vox? first, read this, paying close attention to the diagram: http://www.ar15.com/forums/topic.html?b=10&f=22&t=604477#10323265 now then, the basic problem you will be facing in the setup you describe above is the same as EVERY repeater operator/club faces: achieving adequate TX and RX isolation. it can be simplified as follows: if there is too much of the "repeated" signal (output) leaking into the "received" signal (input), your "repeater" will be deaf and for the most part listening to itself. it won't work the way a repeater is supposed to work. and your HT and mobile radio, with their wide-open front ends, do not provide enough selectivity to provide adequate isolation without significant external help. the TX will overload/saturate the RX and you will get nowhere. there are a couple of ways to get sufficient TX and RX isolation, with the best way (a mechanical cavity duplexer) also being the most expensive and having the largest size. another way to get close is to use separate TX and RX antennas, use low power (around 5-10W), and locate one antenna about 20-40 feet directly above the other. even this is difficult to pull off successfully as the coax for the top antenna has to pass directly through the RF field of the bottom antenna; you will need the best double-shielded (foil and braid, 100% coverage) coax that you can purchase. a variation on this is to put the complete receiver+antenna pair at the top, which means you just need to run the audio cable down to the transmitter. again, shielded high quality audio cable with bulkhead feedthrough LC filters are mandatory, otherwise you are going to couple (RF-wise) the TX and RX antennas using the audio cable. yet another way is to separate the TX and RX sites by, say a hundreds of yards to a half mile, and carry the audio over twisted pair like a phone line (dry POTS). but again, preventing RF from getting on the twisted pair is a real pain. you can also use a separate "backhaul" RF link (e.g., on 440) but the overall equipment complexity is going up. ar-jedi ETA: example 2m repeater cavity filter setup... http://oh3tr.ele.tut.fi/~ftp/repeater/filter/2m/oh2raa_duplexer.jpg how the fuck do you know all of this???? |
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correct, although this is not a "realtime" repeater and doubles the amount of time it takes to get a message across. the one time that my ham club tested it we found it "marginally" useful for SAR. it is extraordinarily easy to end up doubling. ar-jedi |
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Quoted:
To avoid the need for a cavity filter you could also do cross-band repeat - the repeater listens on 2m and transmits on 440. true but the OP specified not having access to a cross band repeater capable radio. i thought of one more approach, and in fact i think one of the folks here in the HRF has done it before –– use frequency hopping radios in the 900MHz ISM band. these types of radios aren't exactly prevalent in the amateur community, but the TriSquare eXRS radios are supposed to work pretty well. http://www.trisquare.us/products.htm ar-jedi |
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Just a note, this is also a lot easier if you are not tied to 600 kHz spacing. I've run several such repeaters without cavities with vertically spaced antennas (recieve on top for best coverage). It seems to be important to be on a tower, away from obstructions. If the transmitt signal is reflecting off near by buildings, it will get back into the receiver.
I put up a cool emergency repeater in PR one time with a 600 watt transmitter on the top of El Yunque, and a reciever on top of our hotel with a UHF link between them. The cool feature was the transmitter could be heard in parts of St Thomas, so we could call crews there, and 5 minutes later they would call on the sat phone. I know someone else (government agency) that uses back to back land mobile radios to extend a phone line 60 miles off shore. There is a TX and RX on land (each feeding yagis with vertical seperation), a repeater (two TX and two RX) , and another pair of radios on the island. 4 frequencies for one phone line. But if their VSAT goes out, this is their only link. Ar-Jedi's pics of cavity filters are typical for good ham repeaters, but are much higher performance than are installed in many commercial applications because their spacing is so much larger. We "tie" multiple VHF and UHF radios together all of the time for emergency operations. Almost every major city these days has an ACU-1000 for tieing different radio networks (though in some cases, they are tieing talkgroups on the same trunked radio system together. The result is indistinguishable from the repeater you mention. |
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good info above.
Quoted:
There is a TX and RX on land (each feeding yagis with vertical seperation), a repeater (two TX and two RX) , and another pair of radios on the island. this works even better by cross-polarizing the two opposing unidirectional links. e.g. at one site mount the TX antenna in vertical polarization and the RX antenna in horizontal polarization. at the other site, reverse it. ar-jedi |
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Quoted:
Quoted:
To avoid the need for a cavity filter you could also do cross-band repeat - the repeater listens on 2m and transmits on 440. true but the OP specified not having access to a cross band repeater capable radio. i thought of one more approach, and in fact i think one of the folks here in the HRF has done it before –– use frequency hopping radios in the 900MHz ISM band. these types of radios aren't exactly prevalent in the amateur community, but the TriSquare eXRS radios are supposed to work pretty well. http://www.trisquare.us/products.htm ar-jedi I described doing it but haven't...  An ebay parrot repeater would be ideal...
The Trisquares are good for fairly secure coms but don't perform quite as well as the FRS ones -in our experience. Yet if you're compromised by not having 'secure' commo, the TriSquares might an answer. I just went over using them in an 'emergency' w/ my SO a moment ago. The one problem I see is they beep a lot and I don't know how to change that w/out Googling the menu. |