Batboard

OK, here is the situation. At the company I work for, we use a tone remote setup. We have a VHF MSF5000 in Quitman GA, and the tone remote to control it in Albany GA (about 40-45 air miles). The console and radio are currently linked by a leased telco line that we are paying through the nose for, as we actually go through two different carriers. The thought that I have is to do away with the leased line by using UHF radios to carry the signal instead of the twisted pair. Does anyone know of any readily avalible equipment to interface the remote console, and the radio, to, say, an M1225 or equivilent? Or maybe a way to do this simply? Any other ideas? We do need to keep the ability to use the tones, as we are using a multi-channel setup. Thanks!

Is the radio you are trying to control a repeater or simplex base?

I knew I was forgetting to include something! All simplex. Four channels on the MSF5000, and a fifth through a "remote chassis" controlling a Motorola "RF Link" unit.

45 miles??? eesh. too far for a quick microwave link, right ?

It depends on thr terrain but
GOOD yagi antennas and UHF may work fine
as point to point LINK.

Are you trying to control channel selction with this too?

The MSF5000 tone control can be configured for two or four wire operation, meaning you can have a separate path for transmit tones and audio, and receive tones and audio.

The transmit circuit is a piece of cake. You can use a pair of radios to relay all the tones plus mike audio from the control point to the MSF5000. When it sees the tones, the transmitter will act accordingly, which includes selecting frequencies, disabling receive PL, and transmitting. The console would need to provide a way of keying the link radio, although you could use a VOX circuit, possibly.

The receive part is more problematic. The MSF5000 just sends its receive audio down the pair. No tones, no other indication that it's receiving something. Usually the remote control unit just amplifies the audio on this pair of wires and the user hears it. What you need is an indication of receive activity to key a radio to send that audio back to the control point.

The tone board, by itself, does not provide any such indication, BUT the system controller does, and that would be a signal called RSTAT or RxSTAT, which would go high or low (depending on which pin is used) when there's some activity on the receiving channel. This would drive the PTT line of your link radio, and the tone remote's RX audio could then be transmitted to the control point. A VOX circuit might work here, too.

You'd probably need some form of ID on both transmitters being used on the control link, as well as getting an official call sign and coordination of a pair of frequencies.

45 miles is quite a haul. Why is it so far away?

Bob M.

We are using a uhf RF Link (simplex). The max distance is about a 4 mile shot. We run it at about 2 watts on a yagi antenna. We have multiple dispatch centers that use the remote base station. Works great. The company that installed it said they have had success over 30 miles with a mere 2 watts on a link. Best of all.......no monthly expense.

Why is it so far away? I like that one. You're right, we'll just move the tower a few miles closer. Actually, the overall distance is about 70-75 miles, with a relay point along the way. We may be able to, and may have to, add another relay along the way. I would think that I should be able to use plain radios for the RF portions of the system. Like maybe a pair of Maxtracs, tied together with the acc. connector, for the relays. I would think that there should be a COR line avalible somewhere at the MSF5000, or that I should be able to make one there. That takes care of keying the link for the return trip. Now I need some way to interface the tone remote with a radio, like a Maxtrac, at the dispatcher's end.

You probably would be better served using 72-75mhz link equipment. I am not sure what the FCC requirements are today, I did have a sysytem in the late 80's for my business paging system, and 70mhz will definitly go the miles. As far as using tone control over links there is some adjusting you need to do. The tone key sequence and or function tone sequence must be delayed untill the RF link is up and running completely, and if you are using PL on you links you would have to add an additional delay so the PL could open the audio at the other end. If you are llooking for just keying up a transmitter on a single channel, you can set the transmitter for guard tone key only.
There are probably a lot of equipment on 70 mhz available with the shut down of most of the larger paging comanies. Also I would recommend a 70mhz repeater at the main site so that the receiver could not lock you out of transmitting.

Don't want to do all the mods for the receive? Add a second radio on the VHF frequency for receive on the other side of the room and the UHF for transmit then your set. Just keep the volume down on the VHF when Tx.

CHART

That's not a bad idea. You could even use the PTT circuit on the transmitting radio to mute the speaker on the receiving radio to prevent feedback.

If you are looking for a cos/cor type indication in conjunction with the 2/4 wire you can use the following:

On J2 25 pin D-Sub system connector located on the side of the repeater cabinet... Pin 23 which is RDSTAT (if iremeber it as pin 23) will provide you a constant +/- 5.5 volts DC and when a carrier with proper Pl is detected will drop to almost zero volts when set correctly.


I will confirnm this later with my paperwork at home. Happy Holidays, Rob

yeah, this is pretty easy... just use good equipment on each end. 45 miles should be no problem via radio, but be prepared to spend some money.

get about a seven element yagi at each end, make sure you're in a different band than the radios you're supporting, make sure TX at both ends can handle 100% TX, and turn the power down to about 5W or less. It's more than doable, but you may have to be closer to the top of the tower, depending on distance and terrain inbetween.

PM me if you want more info or care to give me HAAT, etc.