Batboard

i had a meeting today with some of the bigshots and we discussed a few issues one of which being the possibility of splurging for a voting system.

background info: we currently have a conventional UHF repeater (MTR2000) with the antenna on a 17 story building. generally good talk-out to most of the city. a few gray areas that are probably shadows of other large buildings, but it's generally ok receiving a signal from the repeater, even inside most buildings. talking into the repeater is another story. 90% of our field units are portables (HT750's & EX600's). the rest are mobile CDM's. the mobiles have no trouble at all hitting the repeater. the handhelds are almost perfect if you're outside, but start to lack when inside a building. the buildings are schools so we're talking concrete, brick and steel bunkers!

at the meeting i suggested a voting system would be one of the best ways to solve this problem. only 1 other guy (IT department, and amateur ham radio operator) at the meeting was familiar with any kind of radio equipment. it was basically us two who called the meeting to convince the other department heads to put this in their budget. anyway, i started explaining what a voting system is and how it works in laymen's terms to the other department heads. i got to the part where i suggested that we keep an eye to the future and when we install the telco lines at these locations, we should get 2 sets installed so we can convert our other channel & repeater to a voting system when money allows. then the IT guy said he doesn't want to be dependant on telco for voting, he wants to have it run more like a mini-repeater with a yagi or some other type of beam antenna aimed at the main repeater site. i pointed out that this would require twice as much hardware and more frequencies.

i am by no means an expert on voting systems, but i said i think that you'd need a distinct frequency for each voting location and as many separate receivers at the repeater site. the way i understand a voting comparator is that it needs distinct signals coming in so that it may compare their strength/quality/etc and choose the best one. the IT guy was saying that it would only require ONE additional frequency for the up-links and the comparator would filter the junk out and let the strongest signal through. i don't see how this is possible if all the voting sites are transmitting in to the comparator on the SAME frequency.

wouldn't that be one big heterodyne mess?

am i missing something or is the IT guy smokin grass?

The IT guy is out of his realm of expertise, for sure. He seems to know enough that sure, the comparator will choose the signal with the best signal to noise ratio & pass it.

He isn't taking into account that the signal normally arrives at the comparator via phone lines, which means no mixing of RF signals, resulting in distinct audio sources to compare.

By having all voting sites sending in the signal on the same frequency, the single receiver will get all signals at once, resulting in a big heterodyne mess, as you say. The resulting input to the comparator will be crap, which it will have to pass, since there won't be any other better signals to compare it to. Or, it won't pass anything, depending on your comparator model & settings.

He's probably envisioning multiple receivers on the same frequency...he hasn't taken into account just because 'receiver A' is meant to receive 'transmitter A', it can't block out 'transmitters B,C,D, etc'). Then he'll just get crap on multiple receivers, resulting in the comparator not working once again.

Essentially, you are correct, multiple frequencies would be needed.

Todd

ok thanks, that's what i thought. oh and thanks for moving this post, i thought i was in the system infrastructure forum, but obviously i wasn't. :/

so now here's another question. if we're going to do it my way and use telco service, is there going to be a problem with losing service during emergencies? for example, when there's a big crisis (9/11) and the phone company is so overwhelmed that all you get is that stupid "all circuits are busy" message, are our voters gonna get booted off the switchboard as well? cuz basically, our main goal here is for crisis management and children's safety. it would kinda suck if the system works good until there's a crisis, then it takes a crap.

is there any special type of service that phone companies offer for this? i'm sure the local police voting system is better than your standard phone-line, right? we're a government agency too, so if there's something available, we're probably eligible to receive it. question is, what's available? how do i find out more about this?

The type of circuit used for voting receivers - a leased line dedicated circuit - is not affected by call volume induced outage issues.

These circuits are vulnerable to outage from accidents, e.g. construction worker cuts burried cable, etc. - but can be pretty reliable - it depends on the telco.

There are two facets to having these circuits installed. First is facilities, i.e. are there physical pairs available at the intended sites? Solving that would be OK to procede with at any time.

Activating the service is another matter. Once you do that, the telco will begin charging you a recurring [monthly] charge. These are usually specified in their tarriffs and may include termination charges [for the drops or endpoints] as well as mileage charges based on the distance between the drops [plus taxes, etc.]. You really want to get quotations from the telco to know what the install and monthly charges will be for these circuits.

Your alternative is RF. Yes - discrete frequencies will be required for each path if RF links are employed. If your paths are not too long and line of site is available - there may be some low cost 'license-free' RF solutions available in the 2.4 or 5.6 GHz bands. You would have to compare the cost of this equipment and its installation and maintenance vs. the telco costs over the life cycle of the system.

Also, some agencies have an easier budget process for one type of cost vs. the other, i.e. purchases of assets vs. recurring 'expenses'.

Obviously, the leased line solution is the easiest - you just make one phone call to your telco rep and you're done.

Here's something else to concider. If your remote sites are not constantly transmitting a status tone when they are not receiving anything on the input, you will have no supervision of the link.

One a wireline link, you have a constant audio path 24/7. When there is no RX audio, there is a 1950hz "status tone" on the line. The voter hears this and knows that there is nothing to receive and that the line is intact. If this status tone goes away and there is no RX audio, the voter knows the line has failed and indicates a fail for the dispatcher.

One the RF link, if you make them all little repeaters on their own link frequency back to the voter, you will not have that constant audio path to supervise. If a link transmiter or receiver craps out, you won't know it until someone notices a lack of RX, probably when they need it the most.

If you make an RF link that is constantly transmitting to maintain the supervised audio path, you will be spending a lot of money. I don't think there is anything in VHF or UHF that allows that anyway so it would have to be something else. Microwave comes to mind but that's going to be a huge expense.

eboe wrote:I had a meeting today with some of the bigshots and we discussed a few issues one of which being the possibility of splurging for a voting system.

Had you considered using IP to backhaul the traffic to the transmitter site? Your employer does have it's own network if I recall correctly.

If the IP remote receivers were to go bad, you could fail back to the system you have in place now.

Got to be cheaper then leasing pairs from Verizon from each school to the Courthouse.

Martin

xmo thanks. a leased line dedicated circuit. i didn't know what they called it. I'll have to call to see if i can get a quote for installation and monthly fees.

nmfire i knew about the status tone, but that's a good point. i hadn't realized that you would not have that luxury with the RF link. i'll point that out to them.

spareparts that's a pretty good idea i hadn't considered. as a matter of fact the IT guy suggested something like that for the supervisors to be able to monitor radio traffic from anywhere in the world. (just what we need) apparently voip is the latest craze in the ham radio world.

we do have our own network, but it goes down alot. and it's also not connected to the courthouse, other than over internet. but i'm sure that could be arranged. i suppose that's a possibility we can look in to. and also, i wasn't planning on having a voting site (is that the correct term?) at each school. we have about 30 schools and some are pretty close to each other. i was doodling on a map and i think i can swamp the whole city with no more than 10 sites. especially if we put the antennas up nice.

alrighty then, clearly i need to sit down with some of these folks again. especially my doobage-puffin IT friend. thanks

10 sites is going to get very expensive very fast. You basicly need at least 2 voters chained together for that. The JPS and older GE voters are all 6 channels. For some reason, I don't remember how many the AstroTAC receivers are but I suspect it is 6.

10 sites plus the main receieve = 11. Also, 10 leased lines is going to make you want to rob a bank.

the JPS SNV-12 says it supports from 2-12 voter sites. would this one work for me?...

http://www.jps.com/downloads/PDFS/snv12.pdf

i'm also wondering if i would still be able to use the MTR2000. can i loop the RF signal out of the receiver section and into the voter, then back out into the transmitter section? that way in case all the remote voting sites were dead, i'd still fall back on the original configuration with x-mit and receive from the courthouse roof, being that the MTR would be the only vote left. can it be hooked up like that?

as for the expense, i'm not trying to get 10 sites out of them all at once. that's just insane. basically i want them to spring for the comparator and enough hardware to get at least 2 or 3 sites up in our worst parts of town. then each year for the next couple years we can put up 2 or 3 more. i was also thinking of using the PTG-10 pilot tone generator so i can use regular mobile receivers instead of high-dollar voting receivers. should cut the cost a bit, eh? what's a ball-park cost on leasing a line from the phone company?

The IT guy is wrong about needing only 1 other frequency; it indeed would be a hetrodyne mess. This stuff doesn't work like his IP world.

Now, onto design topics:

You need to be cautious when using leased lines. In particular, most long copper circuits have a significant "roll off" at the higher audio frequencies. Most voters, including JPS in the FM mode, sample high frequency noise and choose the site that has the least noise. So, what can happen is that the system can mistakenly vote the leased circuit due to the lack of white noise even though it doesn't have the best audio.

You will need to "set up" the squelch settings on each far end receiver such that they only unsquelch with really good audio.

That said,

You might consider converting your MSR2000 into a wireline controlled repater with status tone output.

Then, the MSR's audio out goes to one module on the voter. The voter's audio out is programmed (with JPS) to have function tone keying. The voter audio out is connected to the MSR's wireline audio input.

You then program the MSR so the following keying priority: Local PTT =P1 Wireline PTT = P2 and Squelch-Gate(repeater PTT) = P3.

So, what happens is that even if the voter dies the repeater still functions on priority 3 internal repeat PTT. If the voter is alive the voted audio gets repeated through the Priority 2 wireline PTT. It also protects against loss of wireline if the voter isn't co-located with the repater.


If you do want to use radio linking instead of leased telco lines it's quite costly. You license the links as FXO (Fixed Operational) stations. The links stay keyed and on the air all the time; status tone is fed into the link Tx audio input on the far end.

We provisioned our systems with T1's, channel banks, and we own our own transport. It makes the second channel near free.

Do you use this channel for dispatch? If so, running a 4 wire circuit from a new console module to the voter's console audio in will allow for full duplex audio at the console. In this case the dispatcher can tone or talk even if there is a stuck mic in the field. It also allows an IC to interupt (god forbid really doing this) the dispatcher mid sentance if there is a life safety kind of problem.

The dispatch control station can still be a backkup and can be cross muted against the voter control.

Lastly, the voter doesn't have to be co-located with the repeater in this configuration.

This article tells more about our system: http://mrtmag.com/mag/radio_jps_communications_case/

But, candidly the article applies more to law enforcement than to fire due to the higher level of activity.

Good Luck! Bob

Single chassis digitac and astrotac comparators are 8max each. They can be chained togeher. Max is 64 (off the top of my head.)

tpg

One other thing to try is the doug hall voting equipment...

They are priced much lower than the moto or jps stuff, and don't utilize the status tone to work.

http://www.dheco.com/voter.htm

Have I got the solution for you. Get your feet wet in voting without too much pain. I have some mint condition 8 channel Astro-tac voters and Astro-tac Recievers (uhf). To keep it simple place a new rx'er at the tx site. That way you dont have to mod the current machine and it keeps the audio freq response the same with all the rx'ers. Plus you could give the exiting repeater a remote command to "self-repeat" in the event of a voter failure or maintence.

8 channels should be more than enough. Some people keep adding RX'ers rather than properly designing and maximizing each site. Good heliax, band pass filtering, and a low-noise preamp go a long way.

Phone lines: Pain in the A**, but for a small system it's the easiest, unless you're rural and can use RF links uhf or 900. Costs around here are $700 installation and about $50-75 per month.

Astro-tac 8 channel voter $800 ea
Astro-tac UHF Rx'er $1200 ea

Doug Hall and STG (I think) make very good voters if your system doesn't use status tones for supervision. I would recommend you exhaust all supervised options before you settle on something without it to save money.

And that is a hell of a deal for the astroTAC system.

I too like the Doug Hall system. It works great! But if you're going to use status tone, I'd go with the Astro-Tac or GE. Unless you have the money to blow, the JPS in sweet too. The Astro-Tac gives you many, many options.

We are using an RF-based voting system here in Colquitt Co., Georgia. The volunteer FD, Sherrif's Dept., and E-911 (kind of a county backup repeater) repeater are all on voters with 5 RCVRs. They all utilize a DB224, as all three repeaters are VHF, for RX, and a small Yagi to XMIT a UHF signal from an M1225 to the repeater site. There are 4 voting systems, each haveing a RCVR for each repeater, and the RCVR at the repeater site. All are using the RCVR in the actuall repeater for the 5th RCVR. The system also utilizes a constant tone from the voters to the main repeater. Of course, as was stated earlier, each site uses a seperate frequency for each RCVR at each site, for a total of 12 frequencies needed.

eboe wrote:spareparts that's a pretty good idea i hadn't considered. as a matter of fact the IT guy suggested something like that for the supervisors to be able to monitor radio traffic from anywhere in the world. (just what we need) :roll: apparently voip is the latest craze in the ham radio world.

we do have our own network, but it goes down alot. and it's also not connected to the courthouse, other than over internet. but i'm sure that could be arranged.

I
think you would actually find the network & routers stay up, but the servers go down <grin>

Anyway, It's kind of a toss up on which of the campuses are closer, but I'd be willing to bet if you back hauled everything back to the Main Campus or the special Ed Campus via IP voted it there & RF linked it back to the courthouse, you would be fine.

ok, you guys are great. giving me alot of info to chew on. i'm gonna look into some of the equipment mentioned above and i'm also going to look furthing into the IP system. any sugestions on who's stuff i can take a look at and read up on? brand names or even model #'s would be appreciated. i wonder if the IT guy can give this voip voting system it's own server. it's not like we have just one now anyway, they're all over the place. and i'm not sure how they're is all connected like if they all go through a hub somewhere, but i'm just trying to think how it could be as isolated as possible from any other type of network problems.

I would think the voip would be unacceptable for the audio link. I would assume that the comparator would be located at the main RX/TX site. The audio from the VoIP linked receiver would lag behind the locally received audio. This would cause the switching between receivers to be very noticable.

The delay with 2 hops of analog microwave is noticable if listening to yourself talk into the most distant receiver, like a slight echo. It's not noticable when the voter swaps RX sites, but too much delay would be.

I have been working on both a Spectra TAC system on microwave and wireline, and a GE system with microwave and RF linked sites.


Josh

P.S. Don't forget to equalize your audio!

http://www.ldgelectronics.com/rvs-8.html is my favorite voter, and the one I'll be buying if I win the lottery and build the 33cm repeater I want to. Major caveat is iirc, no 1250hz detection. But it is affordable, tells you what reciever is strongest, and which port voted the most/last.

IP for backhaul? That's utterly retarded. You'd have radio talking over the ip remote and a mixing nightmare. Do that and you'll make nextel look absolutely error-free. I know that sounds harsh, but let's be realistic -- KISS. VoIP really doesn't need to be used in public safety comm. DES and trunking is about as complicated as it needs to get. Anything else is kinda useless. And yeah, your IT guy is out of his league on this one. IT is not RF. He may be a backup voice, but don't let him be a voice of dissention in the meeting.

eboe wrote: spareparts that's a pretty good idea i hadn't considered. as a matter of fact the IT guy suggested something like that for the supervisors to be able to monitor radio traffic from anywhere in the world. (just what we need) apparently voip is the latest craze in the ham radio world.

we do have our own network, but it goes down alot. and it's also not connected to the courthouse, other than over internet. but i'm sure that could be arranged. i suppose that's a possibility we can look in to. and also, i wasn't planning on having a voting site (is that the correct term?) at each school. we have about 30 schools and some are pretty close to each other. i was doodling on a map and i think i can swamp the whole city with no more than 10 sites. especially if we put the antennas up nice.

alrighty then, clearly i need to sit down with some of these folks again. especially my doobage-puffin IT friend. thanks

Also, any time you touch the internet, you introduce an entryway for an unpopular visitor. I STRONGLY recommend you not touch any network for this reason. Use RF. But for godsakes, don't cross your radio and your network or you'll be sorry.

If your network goes up and down that often, it may be a good time to start shopping for another IT guy because obviously he's a waste of time.

SlimBob wrote:IP for backhaul? That's utterly retarded. You'd have radio talking over the ip remote and a mixing nightmare. Do that and you'll make nextel look absolutely error-free. I know that sounds harsh, but let's be realistic -- KISS. VoIP really doesn't need to be used in public safety comm. DES and trunking is about as complicated as it needs to get.

Just to point out, that EBOE's employer owns the whole network, with a single gateway router to the Internet. The radio backhaul would never hop off onto the public Internet. The traffic would travel over the existing leased T1's back to the central point. QOS can be assured if the routers are set up right.

The reality is this is not a public safety communications system (think of it as corporate) and to his credit, his boss is checking with the end users, looking at options and gathering data before going to a high dollar consultant.

BTW, I'm using Cisco IP wireless phones & they work fine, but per our IT Guys, the routers were a *itch to get right. And, you are right - during the turnup, they sounded worse then NextHell.

Martin

ok then, so everybody knows (it's no secret) we're talking about a school system here. our repeater is currently on the courthouse which is obviously not one of our buildings. i wouldn't call it public safety, but if you have kids in one of our schools during an emergency, you might call it that. so i'm treating it as if it were as important as life and death.

here are the pro's and con's as i understand them:

while the IP system sounds attractive, and i'm sure it would sound even more attractive to the IT guy, i'm concerned with the fact that it's kinda complicated. i too, subscribe to the KISS theory. servers crash, computers freeze-up, etc. it does however let us control the entire system and be self-sufficient, but a hardline is always vulnerable to damage.

the RF linked system also let's us be self reliant, but getting that many frequencies and we might as well go to a trunked system. we're kinda limited for space in the penthouse of the courthouse so that many receivers and equipment would be difficult to fit. it does however relay the signal from each site to the voter with no hardlines and seems most resistant to any kind of system-crippling damage.

leased telco lines (still my favorite i think) have a downside of being expensive by having initial and recurring fees. audio quality was mentioned as being questionable, I'd like to hear more opinions on this. telco lines are easy as far as we're concerned cuz somebody else does that part of the install, but we don't control the line and it's subject to failure that's out of our control. this is probably the simplest system configuration though, and fits the KISS theory most closely.

we have two main requirements for a voting system:

1) it has to work reliably and consistently.
2) it has to be able to work during disasters such as power failures.

KISS takes care of #1.
back-up power supplies take care of #2.

question about telco lines... do they rely on power from anywhere like a telephone company switching junction, or are they just a point A to B wire? I can easily implement back-up power supplies at the voting sites and courthouse, but if the telco lines go out during a city-wide power-failure then that's very bad.

Audio quality should not be a problem. Leased lines, like any other telephone circuit. are designed to pass the same voice frequency band that is necessary for two-way radios.

There can be issues with illogical voting, however, if the frequency response characteristics of your lines vary greatly from one to another. This can particularly affect the local receiver which is connected with a short piece of wire which has much better high frequency response than the leased lines, thereby passing more noise.

In that case, the local receiver, which could even have the best signal, is the last to vote. Older Motorola voters, e.g. Spectra-TAC had an available module called a roofing filter, which was used to equalize the frequency response of the local line to match the leased lines [or microwave circuits]. I have not seen this for newer voters which leads to the conclusion that their more sophisticated circuitry samples noise differently.

There is one other option that I would personally prefer. It was suggested that there are already T1 lines in place to these facilities for the computer network. I assume these connect directly to T1 cards in network devices like routers.

I would install a channel bank at each location. I would install a V35 high speed port and an E&M port card in each channel bank. Then I would replace the T1 cards in the routers with V35 cards

Then you map 23 of the 24 time slots to data and steal one for voice. The data users will never notice a 5% loss of bandwidth. It will probably have less impact on data users than a continuous VOIP stream necessary for the status tone.

This gives you defined frequency response, eliminates variable latency issues between paths, and keeps the radio and data sides a separate as possible. If either side has trouble, there is less chance of finger pointing at the other guy. T1 traffic, channel banks, and E&M circuits are all easier to test and qualify than VOIP.

Best of all, once you buy the hardware, there's no increase in monthly line costs over the existing T1 costs.

Eboe,

You've got two choices for the satellite receivers ... either the Astro-TAC T5589A or the MTR T5731A (sold by /\/\ Reps) or T5769A (sold by a /\/\ Dealership) but the T5731A/T5769A are the identical product.

The Digitac Comparator Model numbers are as follows:

Q2980A 1 Input Module that supports 4 separate satellite receivers
one Chassis
Q2981A 2 Input Modules that supports 8 separate satellite receivers
One Chassis
Q2982A 3 Input Modules that supports 12 separate satellite receivers
Two Chassis
Q2983A 4 Input Modules that supports 16 separate satellite receivers
Two Chassis

These Digitac comparators can be ordered with or without a cabinet or open relay rack mounting.

When you go from the Q2981A to a Q2982A, a Q2984A or a Q2986A the order adds an additional chassis to house the necessary modules and the additional cables to daisy chain the chassis together in the comparator system.

Since you will be using the Digitac comparator in a UHF repeater configuration, you will be required to order the C175AGSP option for Console Priority and the TRC Keying function for the MTR2000 UHF Base Station / Repeater.

All of the Satellite Receivers will be software programed for the same receiver channel frequency and PL as the repeater's receiver is programed on and they will require either a RT2002 or T1 Telco line pair between the remote receiver site and the comparator. Any programming in the Digitac comparator requires only PROCOMM software.

Depending on where you decide to locate the Digitac comparator will determine what additional Telco pairs are required in the system configuration. A lot of end users colocate the comparator with the repeater but it's not always necessary to configure the system this way. You could locate the Digitac comparator adjacent to the console, configure the MTR2000 for the necessary 4 wire Telco circuit so one pair handle the MTR Base Station / Repeater receiver's audio back to the comparator and the second pair handles the TRC and transmit audio.

You need not worrying about the audio Roofing Filter because the Digitac Audio Input Modules has a special circuit built into them that prevents the unwanted audio bandwidth that was associated with the "Down Voting" problems. The MTR2000 can be set up for "Fall Back In Cabinet Repeat" in case there's a major malfunction with the comparator. The repeater's receiver and all of the remote satellite receivers will be software programed for the 2175 Hz Status Tone output at -13 dBm to enable the link between the receivers and the comparator. On your remote satellites receivers, I would not recommend anything higher that a +5 dBm Gain antenna and 1/2" Heliax RF Cable therefore reducing the "umbrella effect" with the RF signals.

Dan

the KISS principal is a good thing to keep in mind. With phonelines, usually only one goes down at a time, not all of them unless someone cuts a cable, that leaves the other rx'er working fine. If the main TX line gets cut, you can give the main base/repeater a remote command to "repeat". Simple. Easy.

As far as the audio quality, newer voting rx'ers (like the Astro-Tac) have equilizers built-in to compensate for line freq roll-off.

The Astro-Tac voters that I have are best way to get your feet wet in voting. But I just checked and the Rx'ers are currently in the 400-440 range and new rx modules would need to be slid in. Maybe someone here has some range 2 quantar rx'ers they will help out with. So I dropped my price on the rx'ers to $400 ea. New modules from the factory are ~$850.

Project costs:
2 astro-tac voters, 8 channel, priority keying $800ea $1600
6 astro-tac Rx'ers 400-440mhz $400 ea $2400
6 Quantar Rx'ers 450-470 $900ea $5400
1 DTMF "self-repeat" misc module $200
1 19" rack $100
1 Misc cables and blocks $200
3 DB408 antennas $400ea $1200
3 Polyphasors $50 $150
300' 1/2" superflex $350
3 19" cabinets for rx'ers $100ea $300
Misc, oops, forgot, ect. $500
Now add the phone lines

there are out-of-the-box 2.4 & 5.6 systems with phone line emulators that can take the place of leased telco lines - telco quality audio
cost approx: $750-20000 per pair (dep. on type & manuf.)
can run from 2-20 @ the same location (depending on manufacturer)
range 5-60 miles (dep on manufacturer)

note: even the 20k units seem cheap after paying leased lines for 10 yrs.

...Z

cheap units: I-Will trailblazer phone line extender
good units: Vytek

xmo, i didn't understand a word you said! LOL

which means that this system would be under the control/supervision of the aforementioned IT guy. :/

ok, so if audio quality is good with the astro-tac/digitac combo, then that's great. i was thinking about going with the raytheon jps stuff using a mobile radio like a cdm750 and the ptg-10, but i don't know if a mobile radio would still offer such good audio quality since there aren't any kind of audio equalizing circuits built into it. or does the svn-12 do that? i think i'll call them.

so maybe the only thing left to discuss at the next meeting is whether or not to rf link or telco link the voters. most of the potential voting sites do not have a line of site with the courthouse, that's partly why those areas need help in the first place. so i guess that leaves microwave out. besides, there's no way we'd be able to put 1/2 dozen microwave antennas on the courthouse roof. there's no room left as it is. i'm lucky to have 2 feet of space on the railing to mount my mast.

i really doubt the supervisors would want to erect towers at all the voting sites either so the best we could do is a uhf or 8-900 mhz link right off the school's roof with a yagi in the general direction of the courthouse, through the treetops and maybe an apartment building or two.

we're probably looking at getting at least 3 sites up initially. two in the field and one at the main site since i understand that it's best to have everything similar and it would also allow the MTR2000 to have the "fall-back in cabinet repeat" feature. that's mandatory.

as a side note, we do NOT have a console to operate this system. for now, it's a stand-alone repeater. i'm trying to get them to pop for something like a deskset controller like the MC2500. that would be able to command the MTR2000 for fall-back repeat, right?

The SNV-12 has a very impressive digital signalling processor system that can equalize your audio and cook breakfast simultaneously. It can do just about anything under the sun. Trust me, you won't be losing anything by getting the SNV-12.

I wouldn't use a CDM750 for a receiver though. You can use anything you want for a receiver, even the AstroTac receivers. The voter doesn't care what it is as long as there is audio and status tone. The only thing is you should keep them all the same. Don't mix AstroTac's, CDM's, maxtracs, and a Kenwood. Keep all the receivers the same so the audio is as similar as possible.

thanks, now depending on which way prices out better, that's probably the route i'll go. so why do you say you wouldn't use the cdm? is it just a dislike for the waris line, (very common indeed) or is there something specific that would make it not a good choice? the only reason i mentioned that particular radio is because that's what we have in our fleet and i'm familiar with it and i already have the cps and cables. if you were to choose a mobile for this application, which one would you pick?

If it helps, I can ship you what I have for a no obligation test for 60 days. As far as the CDM's go, I don't think the RX will have enough selectivity for good performance. The Astro-tac RX'ers are fairly simple and straight forward.

If there are already T1's between buildings for inter/intranet access between schools, then your golden.

A full T1 Curcit is 24 channels. You can use those channels for voice (telephone) or network. What XMO is suggesting is that you can buy a box or get the phone company to set up a system where you have 23 channels of that T1 dedicated to the computer network, and one channel dedicated for a voter.

This would be an ideal solution. Your already paying for the T1 curict, you wouldn't have any more reoccuring costs above and beyond that curcit that you pay for already. No additional $$ required / month for the backhaul back to the repeaters, except for the cost to reconfigure the routers, and some hardware, but that's a one time cost.

Here's the other problem - you have to know the network topology for this to work.

Is it a star topology, or do all the building connected in a line - you loose a building, it breaks the chain.

If it's a star, and your central link is the courthouse, you have yourself a leased line solution at a very low cost.

-Alex

hey eboe I have a leased line replacement soloution and our company is located in Brick, NJ.. we would like to showcase what we have to solve your coverage issue. I must note that it is an iP solution, but it is currently being used by many high profile customers and their testmonials are available. This system is very cost efffective because it can use anywhere from a 19.2kbps connection or higher to talk across the internet, 100% AES encrypted for free. It's resiliency is high due to the fact it can use regular telco lines in the event of high speed network failure or power loss. These things save a ton of cash. If you want PM and me and I can tell you more....my name is Steve BTW.

regards,
Steve

alex, i kinda understand now. ..and i'm pretty sure our topology would be like a star, but i'd have to check on that to make sure.

i had a message on my phone today from our AT&T regional rep and he mentioned something about a T1 to the courthouse as opposed to the leased lines. i plan to call him in the morning to see what he's got for me. he rattled off a monthly fee of about $350/mo for the example address i gave him. he didn't mention an install price, but he did say something about there being "fiber" (optic?) in the building already, so maybe that makes installation a snap? i gotta call him back.

so then tell me, if it were to be connected via the T1, exactly what pieces of equipment would be between the astro-tac and the digitac? lay out the chain for me so i can understand. i'm miserably below par on computer networking, so i'm not sure if the signal would be passing through routers, or servers, or whatnot. i'd like to know how many potential points for failure there are in the chain.

the AT&T guy also said the leased lines do go through their switching system, but they don't "switch". they pass straight through. when i asked him about power failures he pointed out that it is dependant on power, but they have generators so as long as their location doesn't get blown-up, my leased lines should stay up and running.

if the T1 requires other pieces of equipment to stay up and running, i need to know this so i can determine some sort of cost/effectiveness of having UPS power supplies everywhere and also take into consideration the actual reliability of the network equipment itself.

oh lord help me. lol

My $0.02 (to quote Bernie).

WHY are you guys discussing putting ANY AstroTac equipment in this system? If you don't need P25 capability (ever), why spend the additional money on it?

A DigiTAC comparator will not handle Astro signals (it handles analogue voting and SECURENET only), so you're buying receivers that you can only use the analogue portions of. Seems like a waste to me unless you REQUIRE P25 compatibility from the get-go, or anticipate it sometime down the road.

If you don't plan on going P25 EVER, the MTR 2000 can be ordered in a receive-only configuration with no transmitter. This is for 2nd receiver and voting receiver applications.

OR, if you don't mind a crystal-controlled receiver and can rustle up a few of them, there's still nothing wrong with the original MICOR SpectraTAC receivers... They work just as well in the 21st century as they did in the 20th.

Seems to me if you compared them "new from Motorola", the MTR 2000 receiver would be a hell of a lot cheaper than an AstroTAC receiver.

Just keeping your budget in mind.



Off-topic QUICK question though: Can the AstroTAC 3000 comparator handle analogue voting, or is it STRICTLY P25?

eboe -

Your going to want to seriously talk with your IT person and find out more about your infrastructure. Don't think of T1's as strictly for internet - they are widly used as telephone trunks as well.

Regardless, you need to figure out how your infrastructure works. If you have T1's from every building to your courthouse, then that's pretty good. If they don't all lead back to the same place, your going to have a bit of a problem, and using a single channel off the T1 for the line connection for the comparitors/recievers isn't going to work all that well.

Another example of how a T1 is setup is think of it as 24 seperate phone lines (channels) dumped into a single 4 pair wire. You can buy a device where out of those 8 wires, you can seperate out 24 unique phone lines, or, divide up the T1 so that all 23 channels are internet, and 1 voice, or vise versa.

Regardless, you need to figure out your T topology, and see if it's practical from a cost standpoint to do. I would highly suggest calling your vendor and setting up a meeting to get the details on the hardware required to do this using what is already in place. They will know how to do this for you, and will know what hardware is involved.

-Alex

If you are going to use any of the "older" spectra-tac receivers remember they where designed for 25khz channels. Is your system still 25khz and do you plan to narrow band soon.

Just dont want you to build something that will need replacment a few years after it's done.

thanks for the heads-up on getting MTR2000's for receive only. you're right, we have no need for P25 so the MTR's would do all we need them to do for less money. that helps.

After reading some of the posts here and talking with the AT&T guy today, i understand a T1 a little better now. I'll have to check with the IT guy on some details to see where everything comes together. it's definately not the courthouse though, but as was mentioned earlier, i could have the comparator somewhere and then T1/telco/RF that up to the transmitter. according to the AT&T guy, the T1's will require a UPS power supply at each end to power the panel. so let's say the topology of my network is like a starfish and i have 5 sites that come together at one point. then i'd be looking at 6 UPS power supplies. is that right?

OR i could just have telco installed from anywhere i want to exactly where i want for free. yeah, that's what my regional rep told me. sounds a little odd which is why i asked him twice, but that's what he said. installation of point-to-point lines would be free and based on the one location i gave him which is probably the longest run, monthly rates would be like $350/mo. shorter runs are supposedly a lower fee. plus the telco lines draw their power from the hub [or whatever he called it]. no UPS's necessary. that's not sounding too bad because it's easier for me to get approval for monthly bills than a lump-sum purchase.

either way looks about equally reliable though, wouldn't you agree?

a smaller initial investment is why i'm looking at only getting 2 or 3 sites up at first. how many receivers can you connect to a digitac?, 6? it'd be okay too if i can get just one digitac and 3 MTR's and then as we add more sites (next year's budget) i can get that adapter and another digitac, right? or if that option is internal i'll just get it from the beginning and be ready for the 2nd comparator whenever it's needed. i'll definately make sure our local sales rep pays attention to those details.

as far as the spectra-tac's go, they'd never approve buying used, so they're out. we are currently 25Khz and don't plan to go narrow unless it's mandatory. with all the help i'm getting from you guys, i'm gonna have all the answers at the next meeting. i appreciate it.

thanks

The only reason I mentioned the Astro-tac stuff is that I have it available and that if you're not completely satisfied, or the project doesn't fly, you can return it. The voter does 8 channels. The reason for 2 is for a spare. You can't buy a spare module for close to the price of the whole unit. I'll drop the price of voter by $100 ea if you buy 2. If someone can help you out with some spare UHF quantar Rx'er modules, you can drop the cost even more. Sorry I don't have any. If you go the way of the MTR2000, make sure you get the preselector option.

My quick math shows the UHF MTR2000 RX'er retails for $3600 ea. Does someone have some used ones for this guy?

2 astro-tac voters, 8 channel, priority keying $700ea $1400
4 astro-tac Rx'ers 400-440mhz $400 ea $1600
4 Quantar Rx'ers 450-470 $900ea $3600
1 DTMF "self-repeat" misc module $200
1 19" rack $100
1 Misc cables and blocks $200
3 DB408 antennas $400ea $1200
3 Polyphasors $50 $150
300' 1/2" superflex $350
3 19" cabinets for rx'ers $100ea $300
Misc, oops, forgot, ect. $500

Hello d119,

Here's your answer to the OT Astro 3000 Comparator:

The Astro 3000 Comparator is strictly a Digital signaling comparator. It is capable of Astro, Astro-Secure and Analog modes but it'snot capable of interfacing with a MTR2000 Analog only repeater. If you were to install the Astro-TAC T5589A Receivers to the Astro 3000 Comparator, you would be required to use RS232 Telco T1 circuits on each remote satellite receiver so they would establish the required digtal link. The way the Link works is it established the RS232 Digital communications and remains in the Astro/Digital mode till an Analog signal is detected in the Astro-TAC receiver. The comparator then switches to Analog mode on the RS232 link, then Votes the best signal passing the audio through another RS232 Digital link between the comparator and a Quantar Base Station / Repeater out over the air and down to the console through the DIU. This product is not backwards compatible with the Analog Base Stations. It may be a superior comparator but it doesn't mean you can mix and match different Base Station products with this unit.

EBOE,

You could order a single Q2980A 4 Channel (Receiver) DigiTac Comparator initially and ADD another 4 Channel (Receiver) Module QRN4306 from AAD 1-800-422-4210 in the future.

A NOTE to everyone:

The older Spectra-TAC T1786 & T1787 Comparators (APC 273) were CANCELED & are OBSOLETE as of JUNE 30, 2005. This was the single longest manufactured product by Motorola for 30 years!

Dan

OK, I'm feeling kind of stupid right now. I've been calling my Digitac voters "astro-tac" voters. They are in fact DIGITAC Q2980A's with 8 channels and Transmit board. The unit does analog and DES/DVP.

For those hams using logic high/low COR to validate signal, you can do a simple modification to the status tone detect curcuit to use those types of control signals.

What is nice about this voter, is the AGC on the input. not a lot of level setting.

Again, sorry about miss stating the model name. The RX'ers are definitely ASTRO-TAC.

Have you considered having an inbound coverage study done? This would involve measuring building penetration loss for the buildings you would want to cover then running coverage prediction software. That way you will have a good idea how many receiver sites you need. You might be able to cover the city with 4 or 5 receive only sites.

The money you would save in equipment and monthly leased line expenses would more than pay for the study.

George