maratrac as a repeater?

olderookie · Post by **olderookie** » Wed Oct 27, 2004 7:34 pm

I have seen the maxtracs hooked toghether as a repeater why if a maratrac is a maxtrac in a case with an amplifier( simplified explination ) could you not make a nice repeater from them?

I would love to hear your thoughts?

wx4cbh · Post by **wx4cbh** » Wed Oct 27, 2004 7:49 pm

Got two UHFers working as a standby repeater, and it gets 32 to 40 hours use per month (8 hours each Saturday). 5+ years and no problems so far. Do have them mounted in an enclosure that has a temp controlled cooling fan with the t-stat element on the heatsink of the TX unit. TX power is turned down to about 80 watts, BTW. Antenna is 35 feet up on a tower on a mountain and is 1800 feet AGL.

olderookie · Post by **olderookie** » Wed Oct 27, 2004 8:30 pm

was this very technical? I would assume you need pwr supply to handle the wattage and the heads for both of them I guess the first thing I need is a manual to find all of the connections. and I am really thinking of using a real contoller and doing this right. I might just be ahead to sell the maratrac's and use that money to get a dedicated repeater? waiting for more input?

wx4cbh · Post by **wx4cbh** » Thu Oct 28, 2004 10:03 am

Unless you're lucky enough to have the parts and pieces we had and are Maratrac techwise and are willing to make the mods, you might wanna go for the sell and buy routine. There are a coupla simple minor mods ya have to make to the radios which are easy to do, and there are several different options as to how to accomplish the task, depending upon what pieces and parts are readily available to you for a decent price, or better, free.

For us, the two Maratracs were 8 channel clam shell units that had been taken out of service and were basically going to surplus, and I had a controller from a dead-lined repeater available to me. I made the mods to pick up COR, discriminator audio, etc, and shortened the two control cables to connect up to the Zetron controller. There are other ways to do it , and those will depend on what your individual circumstances are regarding the parts and pieces you've got to work with. For our situation, it was a no-brainer and took no real expertise.

You could do it with a RICK, or build your own interface from info on this board (search Maxtracs, I believe), or purchase a relatively inexpensive controller from the amateur market. The interconnection diagrams you would need are in the model specific info on this board. The power supply is definitely necessary and for repeater use needs to be adequate to handle the duty cycles. And you WILL need to provide cooling for the TX PA unit, BTW.

Max-trac · Post by **Max-trac** » Thu Oct 28, 2004 12:34 pm

I think there was info on how to run them with no control head at the batlabs site.
That would make it simpler.....

JAYMZ · Post by **JAYMZ** » Thu Oct 28, 2004 1:42 pm

I've actually been tinkering with the idea of doing this lately. With any kind of luck in the next few weeks I will have a few parts and pieces to do something with so I may pick up a couple of maratrac UHF drawers to mess with...

But it is mentioned below for the Maratrac repeater. wx4cbh touched on it a bit. The 16 pin connectors inside the trunk unit of the Maratrac/M400 are not configured the way your maxtracs/radius mobiles are. You'll need top make a jumper to get COR.. It actually looks to be an easy mod to do. The more and more I think about it... the more I am feeling like trying it.

http://www.batlabs.com/maratrac.html

Max-trac · Post by **Max-trac** » Thu Oct 28, 2004 2:04 pm

All the Maratracs I have seen were 5 pin logic boards.
What models had the 16 pin and are they programmable in RSS like the Maxtrac?

olderookie · Post by **olderookie** » Thu Oct 28, 2004 3:56 pm

yes but I did forget when we get an input freq it is most probabaly going to be narrow band then I will be up the proverbial creek with out means of propulsion.

the more I think about it , the more I am apt to sell those radios and look at a medium duty repeater. the desktops seem a little light for what we want.

what does mother M make that I should look at?

replies, flames, all forms of input welcomed

wx4cbh · Post by **wx4cbh** » Thu Oct 28, 2004 9:46 pm

Yes, the 5 pin board is there, but Macs have more stuff to manage, so there is actually a 16 pinner, too, but it's not exactly the same as what you find on the Maxtracs. The 16 pin connector is in the front of the drawer on the left side next to the lock. In fact, there's more than one and they're together there, so ya gotta know which pins go to what. I may be way off but I believe the info for that COR mod is on this board somewhere, but I haven't done a search.

Since you already have a "wideband" UHF channel, you may be granted an input freq that is the same. Don't see why not because it would merely be the 5.000 mHz offset companion freq for the one you have.

olderookie · Post by **olderookie** » Fri Oct 29, 2004 2:12 am

I will have to look in uls see who has it if anyone?

olderookie · Post by **olderookie** » Fri Oct 29, 2004 4:45 pm

ok who has a less confusing version of the Frequency Allocation Table so I can even figure out to look and see if there are any freqs availabe?

tvsjr · Post by **tvsjr** » Fri Oct 29, 2004 5:41 pm

olderookie wrote:what does mother M make that I should look at?

Mother Moto doesn't make any cheap repeaters. Take a look at a Kenwood TKR-750/850. 50-watty intermittent duty, 25-watts continuous. 3U rack mount. 16 channel. Provisions for battery backup (charging/automatic switchover with ID change). Integrated controller (simple, yet functional). Etc. Should be $1000-$1200.

I'm currently building a VHF repeater for our RACES group. TKR-750, 300 watt power amp, TX/RX duplexer, battery shelf, etc. Doing it the right way, rather than taking the hamsexy approach.

Of course, I've already been called sacriligious for installing a Kenwood repeater into a Motorola cabinet!

olderookie · Post by **olderookie** » Fri Oct 29, 2004 9:42 pm

I am seeing that as I was on moto.com and they dont list anything other than high end.

who has used Icom to me kenwood is the next step below moto?

help me I need to get info so I can sell this deal?

still can't tell about the input freq simplex is 155.xxx need the spread to make it work what aboout input on that I think I see there is a large enough slit but I need guidence?

olderookie · Post by **olderookie** » Sun Oct 31, 2004 11:48 am

anyone see a 5 mgz slpit that I don't? I see 4 but not quite 5 the freq part is kinda new for me unless I am looking for an assigned freq?

thanks good replies so far keep em comming

wx4cbh · Post by **wx4cbh** » Sun Oct 31, 2004 4:40 pm

Sorry, my mistake. I assumed (dumb move) that you were talking UHF freqs. It's the UHFers that are 5 mHz apart. In the VHF ranges you might well find it hard to get an input freq since there are no set offsets, and especially if the freq you have now and want as a repeater output is one that is not usually utilized as a repeater freq. And if you do manage to get one, you're right about the probable insistance that it be "narrowband." Anyway, a good coordinator can try to get you a sort of "dual" license that is "wide" for now and "narrow" for both by some date specified in the future. There are several out there like that now, so shoot for that perhaps.

olderookie · Post by **olderookie** » Sun Oct 31, 2004 10:00 pm

I think like I said the best route looks like selling the maratracs and buying a repeater. looks like with the cost I will end up with a desktop but I think that will suffice due to the duty cyle not being all that high. but I would like a duplexer but I can use 2 antennas oh well we will see. first priority is to get the 10 new ht1250's up and running.

thanks for all the input

Dan562 · Post by **Dan562** » Mon Nov 01, 2004 11:02 am

First of all I'm having a difficult time understanding which application you're attempting to utilize a repeater in .... Public Safety or Business and then would it need to be on VHF or UHF. You refer to narrow band width or splinter channel spacing but are using Analog or Digital signaling.

On the UHF Band 450 to 470 MHz is a standard 5 MHz split, above 470 to 512 MHz is a standard 3 MHz split between T & R. On VHF the narrowest frequency split is 1.6 MHz between T & R and I believe the widest is 4 MHz between T & R. To request additional frequencies or RF Channels, you may want to consult a frequency co-ordinator or RF spectrum consultant. If your going to use the frequencies for Public Safety, I would consult with APCO because of their requirements and the APCO P25 Digital Standard.

/\/\ sells three types of Base / Repeater Products: MTR2000 Analog only and can be set up for 12.5 KHz Channel Spacing, Quantar Analog, Digital FDMA or CAI (Common Air Interface) being able to switch between modes 12.5 KHz Channel Spacing and the newest being STR3000 APCO P25 Digital 6.25 KHz Channel Spacing currently being configured as 700/800 MHz Trunking but within a year the product should be ready and backward compatible on VHF Lowband 30-50 MHz, Highband 150-174 MHz and UHF 450-512 NHz.

There's also one thing to consider about VHF Highband, the manufactures are settting up the stations for the Trunking feature which could change the whole band plan as it is known today.

Dan

olderookie · Post by **olderookie** » Mon Nov 01, 2004 3:14 pm

ok here is what I need ....

I need a VHF anolouge repeater with the output in the 155.xxx , it is for public saftey, and its duty cycle will not be that high. a R1225 was used by a former induvidual and it worked well but we no longer have it. I do need to get a freq assiged to our dept for repeater input. and I have talked to apco about this and I am going to pursue it from there. I was trying to find out what piece of equipment I wanted to look at in order to do this. I belive there is a cdm variation using 2 mobiles and I will have it in place for at least 5 years until any anticipated changes

this is not a primary channel so as I said the duty cycle will be low. that is why I was thinking of 2 mobiles and a controller. I think a desktop might be a much better solution to my needs.

I do know I need that input freq before I can really go any further.

is that a clearer explanation?

if not I would like to here more thus far it has been great feed back

Dan562 · Post by **Dan562** » Mon Nov 01, 2004 4:19 pm

Well, I'd get APCOs approval in writing for the Analog Repeater. If there's any Homeland Security government grant or dollars involved I'd make an educated guess they'll require the Digital capability on the repeater ... just a gut feeling. Depending on where you would place the repeater station might warrant a Receiver Band Pass Filter / Preselector to prevent front end overload besides using the duplexers. On the MTR2000 Base Station / Repeater (Analog ONLY) this would be a X265 Preselector option and the X182 duplexers option.

I read through many different post that it is possible to take a pair of ASTRO mobiles & configure them back to back through a repeater controller to provide both modes of operation Analog and ASTRO Digital as a non-wire line repeater. I would not mount the mobiles very close to each other otherwise the internal synthesizers have a tendency to interfer with each other. Sending you out chasing a ghost problem that should have been dealt with while building the configuration.

I've read about the GR1225 repeater but don't have any experience with this low tier product.

Dan

olderookie · Post by **olderookie** » Mon Nov 01, 2004 5:12 pm

as far as digital that will be handeled very soon by our county wich handles our dispatching. there is a lots of post on the internet referencing this so I only need to expand our channel for about 5 years to work in a larger area we already have a remote reciver on one of our buildings and there is a meeting in dec wich I will attend in reference to the 800 / 700 changes. so I am dealing in all reality with 2 different systems. mine and theres for now.
five years or so I will be dealing with talkgroups. whole new system as I understand.

this is a VHF simplex for now and the amount of intermod I hear is killing me!!!! on the dispatch channel.

we want a larger area of coverage and we know with the location we have it will work very well.

I also am trying to pass an ordinace that any cell site in town will have to have a location on the tower for any public saftey antenna and associated equipment.

lots of work to do

Dan562 · Post by **Dan562** » Mon Nov 01, 2004 11:35 pm

Okay I understand why and what you're trying to accomplish on the VHF band. I noticed that you already have a satellite receiver to enhance your coverage but you didn't mention if this additional receiver and the Base Station feed into a voting comparator.

If you've got some type of an analog voting comparator you could re-crystal the second receiver for the new RF receiver channel and utilize both receivers in a voting system. You haven't mention what you are currently using as a base station and if you are intending to continue using that simplex configuration. Since you understand the advantages of a repeater, Why would continue to use the simplex channel .... as a redundant back up or inter-agency point to point frequency?

It appears as if all Public Safety is being directed to Trunking systems with Talk Groups ... I hope the powers to be built in enough RF channels to prevent over loading of the system causing system busy conditions.

I see that you want the Public Safety systems to have access to Cellular towers. Well, keep this in mind as you switch to the 700/800 MHz frequency bands, look at the Tx/Rx Inputs & Outputs and compare what either the Cellular or Nextel providers are using for their Tx/Rx Frequency combinations. If I'm not mistaken they use the reverse of standard Trunking frequencies and this does cause interference and desense to the Public Safety frequencies.

The younger generation of designers fell into their own trap thinking Digital is not affected by interference, not so! I don't care if they are using FDMA, CDMA or TDMA Digital signaling, interference & desense happen on all of these modes of operation. The only problem you will face is trying to determine, who is now interferring with your system because all signals will be digital? The interferring audio signals can not be decoded on your receivers like the older analog systems.

A few years ago I overheard a couple of young engineers discussing interference at a Public Safety site that Nextal erected a tower with a 99 Year lease (this is very common for the Nextel people to do) and put their antennas on with the 800 MHz Public Safety antenna system.

These two engineers theorized if they could tilt the Nextel antennas, it would Null out the interference. The unfortunate thing about tilting Nextels antennas, they would require 90 degrees, thus laying the entire tower on a flat bed truck and moving it a mile down the road to provide enough isolation. A word to the wise, you may want to reconsider where you're mounting the 700/800 MHz Public Safety antennas especially if they are on the same Cellular or Nextel towers. It could be a very costly mistake.

As you have stated, "there's a lot of work to do!"

Dan

maratrac as a repeater?

maratrac as a repeater?

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