I recently put up a 45 foot repeater tower with 2 antennas that are separated both vertically and horizonally at least 15feet. It sits on the highest plateau. Using the surecom 328 and a UV5R on the RX and UV82HP on the TX. In the 134mhrtz band with a full 5htz spread. The radios work OK… inbound and outbound but only short range… less than 1000 yards. The surecom has terrible directions… do I need to activate VOX on any of the radios, adjust squelch… ??? what ? Thanks
Almost certainly the problem is desense. Keep in mind that Baofengs are not too sensitive, and worse still they are not selective, so with a 5MHz (I assume, not KHz!) split, as soon as the transmitter fires up, it’s power output makes the receiver deaf - this is what’s probably causing your limited range. What you need to do to confirm this is find a weak signal close to your selected frequency, and then fire up the transmitter. If the weak signal vanishes, then you’ve confirmed it’s desense. The solution are filters - cavity filters, either really big single ones or perhaps a multi-cavity version. They’re going to be more expensive than the radios, of course.
More important is that you are aware 134MHz is inside the VHF airband. Your repeater will be heard by many aircraft, and while they use AM, they’ll almost certainly report you to the FCC or CAA (in the UK - no idea where you are)
Interference to aircraft is really bad news.Desense might be the least of your worries! They might even decide you are doing it on purpose meaning to cause a crash - the authorities are a little quick on the draw nowadays.
We just tested in that freq to see if it was related to that… we first tested in the GMRS band which we are licensed for. Even tried cross band VHF to UHF. Tried different VOX settings, squelch, volume, TX power output, with tone and without… different radios UV5r+ and 82HP’s… we were getting the repeater kick back from up to 4 miles away but no audio. The audio worked only about 400 yards away from the tower… THEN, I removed the radios from the antennas… moved it to another place away from and metal buildings on top of a 400 ft hill… (this is a Texas ranch) again, the repeater kicked back but no audio past a few hundred yards. The Surecom has very litte troubleshooting info… poor directons. Are there any special settings on the radios that I am missing? On the surecom? THANKS!
If you get RF, but no audio at a more than a certain distance, I can think of nothing at all that makes your system break the laws of Physics!
The box is really very simple - it’s extremely difficult to find anyone technical who has looked at one. The reports and reviews I found suggest it is NOT a vox system, then another confirms it is, and then another determines that background noise (presumably hiss, rather than silence) triggers the TX. No idea at all.
There is nothing at all that can make a radio close to the tower receive audio and a distant one receive a carrier and no audio - that plainly cannot happen, so your testing must be flawed. Perhaps at certain times, you get the carrier and no audio, and at other times you get repeater audio - and as it’s an intermittent fault, you’ve come to the conclusion audio is based on distance - which just n’ happen.
These devices simply take the received audio and then use it for detecting DTMF tones, and then feeding it at a lower level to the audio in on the transmitter.
You need a more systematic testing routine. If the audio, on any setup comes and goes, then that should be the same at any distance where the signal strength is enough to open the squelch. If you are using tone squelch, the TX unit is obviously sending it - and the audio in is being interrupted. It could be RF getting into the switching unit I suppose, but unlikely. If you are trying in band and cross band then your next step is to give the unit and your radios to somebody who has the competence to do some proper testing. Have you experimented with different volume settings on the receiver? Did this make a difference? A bit more systematic fault finding needed.
What frequencies are you using now and are you operating legally?
I have tested in all bands… but this will be set up under our GMRS license as a GMRS repeater. We have adjusted audio etc… every possible test… Now I have heard that these Surecoms will not work with UV-5R + has something to do with the mic cable input. The directions say nothing about this. I know the audio works short distance… but nothing beyond 3-400 feet. Like I said… I get RF up to 3-4 miles away. So, it does not make sense to just have short range audio. emailing surecom is interesting. I don’t think they understand actual english since this is a chinese company and just said. “please send video of problem” lol. I did. No reply as of today…
thanks for your help!
Tim - as I said, RF does not have a property to be able to only send audio a limited distance - if you get a reading on the meter and the squelch opens, the the audio MUST be there - how you are describing it is impossible, so something else is going on.
If your electronics is a bit rusty or non-developed there is a method that is much simpler as a repeater controller. A TTL controlled relay - 5V at very low current switches a relay. You can buy these little modules online for around $10 or so? It needs you to be willing to open the radio though - but most radios have an LED that lights ups when he squelch opens - so you use this to trigger the relay. A cable between audio out and audio in, and the relay contacts making the circuit. The only other component being an inline pot to trim the speaker level down to mic level. Cheaper than the repeater controller, and much more reliable.
These repeater controllers have no technical spec, they have lots of youtube reviews by non-technical people and no reviews I can find by people who know their subject.
something to do with the mic level input?
This makes no sense if the thing works at all. Think about it. Something comes in on the receive line, the device detects it, shifts into TX, and you hear audio from some other radio listening. It works. What makes you think it doesn’t?
Your testing MUST have a flaw in it somewhere. The device could be faulty - certainly possible, but your results contradict. Let’s examine the audio vanishing with distance, yet RF remaining strong. I assume you confirmed this with TWO receivers - so one is reporting the audio gone, but a closer one (at the same time) confirming it is present. If you simply move a single receiver, your test conditions have changed. Could it be the receivers, not the transmitter? Could it be RF getting back into the receiver? Loads of other questions.
If you are out of your depth, why not seek out the local ham community and ask for their assistance? You might discover a bunch of helpful folk who will sort it in a flash. Clearly - you are doing sensible best guess testing, but if you don’t understand the theory, your conclusions could be pointing you in totally the wrong direction. RF has audio on it or not - there is NO function that allows audio to drop but RF strength to remain - that is impossible, yet your conclusion is glued to this as at the fault symptom. I don’t doubt this is what appear to be happening - so it suggests that there is another function at work here.
Seek out some outside help from people who understand the subject.
I’d bet the system can be made to work.
Potential problems will simply be frequency split, wide open receivers and desense. Cheap radios make rotten repeaters - usually systems that seem really insensitive and have limited range.
I have here quite a few Kenwood repeaters, plus a little TYT that contains 2 medium price handhelds, with the cases off and lots of tacked on pickup points and a small controller. The Kenwoods can transmit full power on my frequency with no filters, using two stacked aerials on my mast. Range is pretty good, even though the antennas are not very high. Swap the Kenwoods for the TYT and range is across town, that’s all - unless I add in external filters to cure the desense. At best, I can get the TYT nearly as good as the Kenwoods.
I’ve just found a light activated relay on ebay - for less than ?3 - so I have ordered one. It comes with a little cable with a photocell on the end - I’ll see if the light of an LED will activate the circuit - if it does, that’s a very cheap and simple way to activate the transmitter!
Paul, thanks for all your help. We tested again with different radios on both the RX and TX. We adjusted volume, squelch etc… Also using 25watt mobile 2501’s in the ranch. The UV5R+ in the vicinity of the repeater setup (100 feet) could be heard clearly up to 5 miles away on the 2501. But as soon as you move to 300-400 feet, it goes mute. Keys up but no audio Surecom has asked for the controller to be returned. We are now considering the Kenwood TKR-750/850. Again thanks for your help. I am old, I used to build radios and linears when they used tubes and crystals…
No problem - but this is extremely odd! The kenwoods are solid devices and perform very well - the software has a few oddities - took me ages to work out why I could not programme in a CW ID, until I realised that to do this you needed to NOT use certain other options - but they also have the very useful facility to have multiple CTCSS tone groups - so you can have two users (or more) on one repeater, totally unaware of each other - other than if they tried to access at the same time.
I have this exact same problem. If one of my radios are with half mile of my repeater the audio will retransmit to all other radios within several miles. If the closest radio is more than one half mile, the repeater will key up with RF but no audio goes out to any of my radios farther away, even though I can still key up the repeater for several miled. So, in other words, one of my remote radios has to be fairly close to my repeater for audio to go out even though the repeater keys up. I’ve used several brands od radios, even high quality Motorola Sabers on GMRS but still the same problem as Tim. Any other ideas? Its very frustrating becausevit doesn’t make sense. Even used different duplexers, LMR400 cable straight up 40’ and changed N connectors. There is nothing else I can do.