Radio Gods please help me

[brandon@se-coop.com]

I am trying to learn a few things, and understand what is going on with our Radio
we have an old 2 wire DC Midland Radio FCC Licensed and it is working correctly. my question is I am trying to hook up a remote link from a working microwave remote site, link has been tested and is working.

The equipment between the connection on my side of the microwave and my radio are as follows:
microwave 4 wire punch down ---> 4 to 2 wire converter ---> remote input of CPI TTP1N-C tone remote termination panel ---> Radio side terminal connection of TTP1N-C ---> side output of CPI DR30 deskset ----> radio bottom input of DC30 ---> DC radio termination block ---> Radio

when it worked properly our truck radios could hear and talk to the remote microwave site and vise versa. No they can only hear and not talk back to the remote microwave site and I am not sure what is wrong. I just need some pointers if anyone is willing new help a newbie out, it is hard to google some of this older equipment, any reading material links would also be appreciated! (I am unsure what a tone remote termination panel does)
Thank for any help,
Brandon

[Bill_G]

Have you been to the site and verified the radio works? Maybe the microwave link and tone remote adapter is working fine, but the radio doesn't transmit. Got a spare to swap in?

[brandon@se-coop.com]

yes both Radios are in working order, just some where in the link is the problem. I don't have any spares though.
thank you for replying!

[ve3nsv]

You are trying to use a DC Remote across a MUX?

[brandon@se-coop.com]

yes I think so, but I think my termination panel is tone if that helps, I am kinda unsure what I have. Just trying to learn all of this

[brandon@se-coop.com]

one end is tone one end is DC

[KI4M]

Trying to decipher what you have up top and I am coming up with a few ideas. Sounds like you have a Tone remote on the deskset/dispatch end and DC at the base station end. Sounds like the audio from the base station is passing back to the deskset over the microwave. I am assuming the base station is setup for DC keying. If it is then more than likely you will need to provide a ground to the station to get PTT. You can do one of several things here as I see it.

You can either get a tone to DC converter at the base station end to key the station when it receives the correct tone over the wireline or convert the base station to tone remote if it allows such and avoid the Tone to DC converter. If you do not want to do that the easiest thing to do would be to figure out how to get an M lead out of the deskset into the microwave then use E&M signalling if you have a channel bank. That would then allow you to have an E lead at the far end which can be wired to go to earth/ground when the deskset generates an M lead.

Just a few ideas if I have deciphered the above correctly.

[brandon@se-coop.com]

thank you!!! all of this is starting to make a little sense now, I think you are correct, I have a small understanding on what you are are saying. I am going to look some of this equipment up. Yes you are correct on my setup remote microwave connection is 4 wire tone and my base station is 2 wire DC all with 2 wire DC desksets. Thank you for taking the time to help me! much appreciated!!

[Bill_G]

Then how did it ever work? DC keying requires a DC path, and microwaves don't pass DC. I think you're using tone control.

[Jim202]

All microwave is set up for 4 wire audio. One direction is a pair for TX and the other direction is a pair for RX.

You could be using E&M keying where the microwave is supplying a ground to key the radio from the same input at the dispatch center where the console is supplying a ground on one of the wires. In your case it would be the M wire that is being grounded if that is what your using.

The other common way of doing it is with tone remote control like Bill is saying. Your TX audio path at the dispatch end becomes the RX pair at the remote tower site. The TX pair at the tower site becomes the RX pair at the console end.

Another place to poke into is the setting of the audio levels. The sort of depends on the type of microwave and what levels it uses. Many of the microwave systems have pad attenuation switches built into the audio out put and input ports so you can make like 6 db adjustments. Then there is a level adjustment pot to fine tune it from there.

You need to get a hold of a TIMS unit so you can measure the audio levels going into the microwave and coming out the distant end. It needs to be used in the bridge mode so you don't load the line down while your trying to measure it. There is no simple way to do it. Will take 2 people and 2 TIMS units. Set one up in the dispatch center and send a 1004 Hz. tone at the level used to adjust the microwave. Set the input of the Microwave audio port to the level it needs to be at. At the tower site, measure the RX pair that is feeding the radio and adjust the level to what it should be. The reverse the connections and go the other direction. Do the same thing. N

Now that you have proved the microwave is at the correct levels, use a service monitor at the tower site and inject a signal into the radio receiver and put in a 1000 Hz. tone at a 20 db quieting level, at about 85 to 90 percent modulation. Look at the input of the microwave and adjust the radio line output to be at the desired audio level. On the dispatch end you should get a good RX tone level on the console for the channel your working with.

Now using the alert tone on the console, measure the level going into the microwave and adjust it to what it should be. Note, the alert tone should be slightly lower than the normal dispatcher audio with a loud, long AHHH or fiiiiiiiive from the microphone. Do this with the remote transmitter disabled so you not sending this tone over the radio transmitter. Now enable the transmitter and set the service monitor to measure the transmitter deviation. Again key the alert tone from the console and set it to about 85 percent modulation.

Now that everything is set audio level wise, do a test transmission with a mobile and see what you get. Should sound good in both directions.

One of the other tricks I have used many times is if you have a tone remote controlled radio, you can use the low level guard tone of 2175 Hz. from the dispatch end to make your TX level measurement with. This way your not driving the field troops mad with long tone transmissions while doing the alignments. You just need to find out what the low level guard tone level should be. Once you find that number, write it down and use that for your adjustments in the future.

Jim



This might sound long and convoluted, but it works well.

[brandon@se-coop.com]

Thank so much for that very detailed write up! Very informative and detailed!