Posted: 11/30/2007 8:18:54 PM EDT
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this may be a real dumb question, but I thought that someone made a moble 2meter that could be used as a short range (50 watts or less) repeater. Am I just not remembering right?  |
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Are you talking about in-band repeating? (say 146 to 147 or 443-448)??? It's possible to do, but at lower frequencies it's a lot more difficult because of space and other factors. AR-jedi's ham radio 101 thread has some very good repeater info, plus the rest of us can try to answer more if you have any questions. I was in the process of building a mobile 440 repeater, but funds are needed for important things so I'm selling the gear I had acquired for the project. www.ar15.com/forums/topic.html?b=10&f=22&t=604477 |
Here's a repeater that runs on 4 AAA batteries, is the size of a pack of cigs, works with most W/T's. I got several when they were cheap aditl.com/ham/polly.html Ebay is a good source now, but they cost.  k0swi.microlnk.com/REVIEW/RS/RADIO%20SHACK%20SIMPLEX%20REPEATER%20REVIEW.htm www.craigwilliams.com/radio/miss.htm And one more link for a repeater made by MFJ www.mfjenterprises.com/products.php?prodid=MFJ-662 |
first read here... 2nd page, about 80% of the way down, section is titled "Building your own repeater" --> www.ar15.com/forums/topic.html?b=10&f=22&t=604477&page=2 then read here... 1st page, about 60% of the way down, section is titled "Crossband repeat with a dual-band mobile radio" --> www.ar15.com/forums/topic.html?b=10&f=22&t=604477 ar-jedi |
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Here is another option to throw into the mix www.arrowantennas.com/uconrtoller.html |
You're still not going to be able to do inband repeat without some serious duplexers (especially on VHF) That's just a controller. |
well...  if you have a 100' tower handy, you can mount the TX antenna about halfway up, and the RX antenna directly above it at the top of the tower. oh, and you have to use the best coax possible (e.g., dual foil/braid shield RG8) to prevent leakage into the receive coax as it passes by the TX antenna. this setup will give you about 30-40dB of isolation. so the receiver won't be *totally* deaf from the transmitter output, but it will be nowhere near the performance of a true duplexer setup. it will make a "couple of blocks radius" repeater. the TX output will be heard for miles but the RX setup will be too deaf for far away radios (esp HT's) to bring up the system. there will be other issues as well; for example, the duty cycle on the HT will be limited to about 10% -- they simply don't dissipate heat fast enough. of course, if you have a 100' tower and 300' of dual-shielded RG8 coax on hand, i don't know why we are having this conversation about using 2 HT's and an inexpensive control box for a repeater. ar-jedi |
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The main technical problem at 2 meters is the narrow 600 khz difference between the repeater receive frequency and the transmitt frequency. This requires six two foot tall cavity filters to allow use of one antenna. I think this was caused by the limiting of repeater operation to the upper 2 mhz of the band in the late 1960's and early 1970's. Most VHF public safety (police, fire. EMS) repeaters (operating just above the 2 meter band) have better than 2 mhz separation of the frequencies. Mobile repeaters are much easier in the 440 band, since the "mobile" duplexers are the size of a large textbook. I am thinking that NWRuger might be talking about a crossband setup using a 2m/440 mobile? RS |
OP asked "this may be a real dumb question, but I thought that someone made a moble 2meter that could be used as a short range (50 watts or less) repeater." How could he run a 100' tower moble w/o having troubles w/ power lines and bridges? |
by "moble 2meter that could be used as a [...] repeater" i inferred he meant "mobile 2meter radio that could be used as a [...] repeater" -- not that the repeater itself would be mobile perhaps instead of needling me about my answer you should ask the OP whether he meant a fixed or mobile repeater application. ar-jedi |
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so sorry for not getting back for a while. father in-law had a heart attack and by pass surgery. He is doing well now. so I have time to get back on-line. My original intent was to find a radio that could be used as a repeater in a small area for the use of handholds (so the 100' antenna is not out of the question.) but I would like to be able to move it also I would prefer a mobile system. although it would not need to move once activated. I did first mention a mobile due to a thought way in the back of my head that was a little fuzzy about a mobile that could do in band repeating. thank you for all the input so far. could you cross band repeat and then cross band repeat back. say you setup a cross band repeat on an antenna at house A 146.200-440 and then 5 blocks away cross band repeat back to 600khx from the OG 2 meter at house B 440-146.800?  
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it is not permissible to crossband repeat with your end station on 2m. it must be 70cm. said another way, the control link to the relay station (the X-band repeater) must be on 70cm. moreover, the setup you envisage has many legal issues with respect to lack of FCC-required ID on repeated transmissions. ar-jedi |
did not know this thanks.
aren't there auto ID transmitters? for this |
Wasen't there a recent change in reference to the bands you could remote control from? |
I had planned on building either a crossband or UHF only repeater. Right now all I have left is a pair of motorola maxtracs, one a 40w 32ch and a 2w 16ch. The 2watt version would be great for to uses. If I ended up building a crossband 2 meter to 440 repeater, then the UHF side would not need to be transmitting too far anyway. If I ended up building a 440 or GMRS repeater, then I would use the 2watt as the TX and use an amplifier behind it to keep from burning out the finals under harsh conditions. It's easier to replace an outboard amp than teh finals in a hard to find mobile. But money being what it is, I gave up on those plans and have a buyer for the 2watt and possabily for the 40w. Money problems suck
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| Ah my friend money problems are not that bad at all, it's health problems that suck and no amount of money can fix them. We are trying to get a couple of repeaters online over here in North East TN since our little county has none. Kinda hard with only two active hams in the county and one of can't seem to stay well. Good luck on your projects. BallGroundBoy |
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I think what NWRuger is asking about rxing on 2m, link on 440 to a nearby 440 then 2m out. I think that is legal. I have tried that setup and it will work if the freqs used are at the band edges. Like 147.995 in-441.00 out-in then 145.110 out. It didn't used to be legal to link/control below 222mhz, but seems like Kenwood got their Sky Command 2 meter setup approved by the FCC. I don't know the particulars since I don't own any SkyComm radios. Repeater-builder has some guys listed that can make you a 2 meter repeater on the cheap. I have an old Motorola Micor converted to 2 meters with a Sinclair flatpack duplexer. The input is 147.600, the output is 145.110. [Depending on who your repeater coordinator is, there may be a portable repeater freq pair for mobile/portable repeaters (SERA does not)]. The sensitivity is no where near as good as a 90 db duplexer setup used on sited 2-meter repeaters. What it can do with a good "tall" antenna is extend the range of your portable radios to at least double or triple what you normally would get. If you put it on a hill, you can talk a lot further especially to the back side of the hill. Whether it is worth the trouble in a SHTF situation is a good question. I need to test it on a 12 volt car battery to see how long it will run. If the crystal heaters are connected, probably less than 12 hours. As our forum experts have said, 440 mobile/portable repeaters are much easier. I think my repeater transmit power is set to 15 watts, with about 8 coming out of the flat pack. RS |