QC-II & Multiple Towers

J_L_COHEN · Post by **J_L_COHEN** » Sat Oct 25, 2003 1:06 am

this is a question regarding the recieving of QC-II tones
I have a pro 9150 v3.1.03
what i am trying to do i don't even know if this is possable it should be but hey, in our county we have three towers (3 diff vol fd's) Newton, Harrison, Falls, which talk to our county fire dispatch, 3 diffrent freqs, 3 diff pl tones, so i set up all three in my radio,3 diff channles ect , here is the probliem i can only recieve our fire/ems tones on our tower (newton) if i am on one of the other towers i can here the tones but the radio does not respond to the QC-II. so i went in and made sure that QC-II was on all the channels that i wanted and still no luck, nor does the answer mode pick these other towers up. I am lost on this one

any help would be great
thanks Jeffrey
Newton Twp Fire Ems

p.s i forget to add this i dont know if this will matter or not
the towers are vhf and county fire is low band, we use a vhf maxtrac & maxtrac lowband tied togegther with a RICK so it kinda looks like this. I don't know if this has some effect on the transmiting of the tones or not.

lowband----rick----vhf----tx

nmfire10 · Post by **nmfire10** » Sat Oct 25, 2003 12:54 pm

Could be one or both of the following:

1. The tones are programmed wrong in your radio.

2. The RICK repeater thing is clipping the beginning of the A tone which throws the timing off and therefore NO DECODE.

Could be other problems but those two come to mind.

jim · Post by **jim** » Sat Oct 25, 2003 5:57 pm

Are you getting a "clean" signal from the other 2 towers? If there is alot of static, the radio may not be deconding properly.

Do you have to use a PL on receive? If not, run the frequencies opened.

J_L_COHEN · Post by **J_L_COHEN** » Sat Oct 25, 2003 11:04 pm

Jim,

Yes the signal is very strong and clear, I also checked my tones to make sure that they were the correct setting and it was correct, i was close to one of the other towers today and we had a run, my maxtrac lowband in the truck went off for our tones but my portable (on that tower) did not even acknowlege the tones

, only thing it can be is like matt said something with the RICK that is not passing the tones.

well thanks for your help guys!

Jeffrey

Jim202 · Post by **Jim202** » Sun Oct 26, 2003 5:05 am

Your first message was unclear about just how the different repeaters are connected. Let me ask this question in a more direct way.

Do all the repeaters get activated at the same time from the same paging encoder? If the answer is yes, then there is a problem. I would go and start right at the dispatch point and look at the transmitter they are using to key the repeaters with.

Take a service monitor and look at the normal voice deviation level. You should see the level be around 4.5 to 4.8 Khz. Then do a test page and make sure the page tone level is about 3.0 to 3.5 Khz. max. If the tone levels are the same as the voice levels, look no more. The paging encoder tone level needs to be turned down.

It is important to not put paging tones into compression. That is have the radio system cause audio gain while sending paging tones. This causes distortion to the tones. It can also cause audio twist if it is bad enough. The audio twist is the difference in the audio level from low to high tones. It can actually cause a phase change between tones. This also is not good and pagers have a hard time decoding the tones.

Another problem that that is very common is the setting of repeater audio throughput. This is the difference between the audio deviation level coming into the repeater and the audio deviation level going out of it. The best way to tell if it is set wrong is to listen to someone talking on the repeater and listen for how much background your hearing. If it is set high, you will be able to hear everyting being said by others for 10 to 20 feet. It won't be real loud, but you will hear it. It will also be hard to hear the conversations around a fire truck with the engine running. Most of what you hear is the roar from the engine.

Anyway, again you need 2 service monitors this time. One to generate a signal into the repeater and another to look at the output deviation. Use the better of the 2 for the output. Calibrate the input deveiation with it to 3.0 Khz. Measure the output deveiation. If it is set correctly you should see no more than 3.5 Khz. including the PL tone. If it is higher than this, adjust the repeater throughput down until you get to this level. Note that your not adjusting the transmitter deviation. Your adjusting the the voice level of the audio through the repeater. They are 2 different adjustments.

This all assumes that you looked at the voice deviation level from the repeater transmitter. Again it should be set for no more than the max of 4.5 to 4.8 Khz.

When your all done messing with everything, you will notice 2 major changes. First and most important, the pagers will work better. Matter of fact, they should decode signals almost into the noise. Second, you won't be able to have people leave the mic on the dash of a truck and reach over, key the radio to talk. You won't hear what is being said anymore. You won't be able to hear all the road noise moving down the road anymore. It will sound clean and not distorted. People will have to get use to holding the mic close to their mouth.

Jim

J_L_COHEN · Post by **J_L_COHEN** » Tue Oct 28, 2003 2:14 am

Jim202

let me go into more detail of what we have, I may have mis led some (sorry)

about 4 yrs ago our department carried moto sp50 lowband radios 33.98
of corse they were bulky and the antena was a pain (foot long) so in the wisdom of our cheif ect we decided that we would go to a vhf radio (p-110 gp300) of course that was a great idea , that would give us the ability to have a channel that we could talk to our fire dispatch and a channel that we could call our own (ya know a bs channel) ect, so all was good BUT oops we forgot that the county fire dispatch is on a freq of 33.98 and our portables are in the 154.055 range!

so now what do we do

So our local moto dealer to the rescue "why don't you but in a cross patch"

so to make a long story short we use a cross patch system we are able to talk cross bands from vhf to lowband, lowband to vhf using a RICK, in all reality we don't have a repeater on the lowband side just out own dept freq

the way it works is at the tower we have a maxtrac lowband and a maxtrac vhf tied togeather with a rick,

our portables are set up like this
ch 1 154.055 freq with a tpl of 103.5 when we transmit on this freq it actuly is talking on 33.98 with the maxtracs and the rick, our county fire dispatch hears us great,

as for recieve the channel is set up the same ch 1 154.055 freq with a tpl of 103.5, in this sutiuation we are listining to county dispatch 33.98 , so this eliminates the need for lowband portables.

so other departments followed in our footsteps, but each dept has there own freq and pl, so when county pushes there transmit button on the mic all the towers at Dept A, Dept B, Dept C, here the message in lowband form and re broadcast it through vhf via the rick, on there own channels.

here is what i want to do, my dept A is at one end of the county,dept B's tower is at the other end of the county, both is just a 45 watt output so on a portable reception gets bad the further you get from the tower, so when i am at the mall ect at on the Dept B's end of the county i will switch my channel to Dept B's tower, and be able to here county dispatch, and i also want my radio to qc-II when our tones go off. here is the kicker my radio does not here my tones when i am on Dept B"s tower WHY? even our local tech of 15 yrs dosent know why. I can talk fine to county dispatch on there tower and here fine but my radio just doesn't here the tones.

wow that was a mouth full, hope that explains it a little better (I hope)

jeffrey

nmfire10 · Post by **nmfire10** » Tue Oct 28, 2003 4:54 am

Are all these towers on the SAME low band frequency? Your saying they all key up at the same time when the tones go off?? You don't get lots of really odd noises with multiple transmitters going at the same time... or are they far enough apart and low enough in power that it doesn't happen??

Most of the usual causes of QC-II not working couldn't apply here, otherwise the other department's own tones wouldn't work either. It isn't going to front-end clip your tones and not theirs. It couldn't be an audio problem on the repeater because again, the other department's own tones wouldn't work right either.

Are you sure (as in, someone has actually checked) that the other channels have QC-II enabled and programmed correctly?? Do other portables have this problem or is it just yours??

J_L_COHEN · Post by **J_L_COHEN** » Tue Oct 28, 2003 7:48 am

Matt,

yep, when some bodys tones drop from dispatch the final tx, rx for these towers all are on the same lowband freq.

our tower is only 45watts, and about 15 miles away from one of the other towers and 5 miles from the other. but if i stand at our station and change channels to the other tower i can Rx and Tx fine. some times you can get a squell or two if you are in just the right place with all the towers going, oh yea the county tower is a 250 ft twr with a 500 watt transmitter! and the next county to us is assigined the same fire band freq as us 33.98 so we are walking all over each other,

as for programing i have done it my self and all the channels are set up correct with qc-II, i an going to try my gp-300 to see if it is just the 1550

jeffrey

Will · Post by **Will** » Tue Oct 28, 2003 12:15 pm

The time that the low band receiver takes to decode PL and the RICK to key the VHF TX and for the portable to "hear" it can "drop" some of the first QCII tone. There needs to be some delay at the originating point, County Dispatch, before the QCII is transmitted AFTER the TX is keyed, usally a full second to offset all the cumlative delays.

RICK's do also clip and add resulting audio distortion to the "mix", causing the portables to fail to "see" the tones as QCII.

Jim202 · Post by **Jim202** » Tue Oct 28, 2003 1:17 pm

Jeffrey,

If you read the post that Will made, it gives you another issue that you didn't explain clearly before. There is a time delay between the time your low band base comes up and the time that the department B low band receiver decodes it. Then it takes time for the VHF TX to come up after the rick gives it the command to key.

I wouldn't be surprised if there wasn't close to a 1 second delay before your pager actually sees the RF. Then it takes time for the QC-II to decode. Back at the dispatch center, the paging encoder was never set up for any delay. It worked just fine for the original low band simplex.

You need to get the paging encoder to delay the time before it starts to send out any of the paging tones. Most of the paging encoders have this option built into them. You just need to activate the delay.

The next problem is the audio through the rick. It needs to be adjusted just like I was giving you the information in my last post, for setting up a repeater. That is what a rick is doing.

Remember, you can't distort paging tones. You need to delay the tones at the encoder when going through a repeater. It takes time for all the RF equipment to come up to speed and be heard. You may not hear the delay, but take it from all the radio techs that have worked on repeaters and paging problems, there is a time delay.

Jim