Repeater Interface Cable for Motorola Maxtrac

[WhiteThunder]

Hello,
I am new here and new to amateur radio. eBay seems to be the place to buy cheap equipment for beginners. I have come across numerous listings for "Repeater Interface for Motorola Maxtrac" on eBay. They are very inexpensive (cheap) and I would like to know what they really are and what they do. I take it that the people selling these things would like us to believe that if you happen to own a couple Maxtracs, that all you have to do is join them together with their $10.00 or less cable and VIOLA you have a repeater. I am guessing that is not the case, but I have been wrong before. Can anyone tell me what these are and how (do) they work? I am thinking that there has to be some other equipment involved, or at least some form of duplexer. Has or is anyone using one of these things, that can fill me in on what they are, what they do, and whaty other equipment is required.
Thanks,
DB

[jhooten]

They do what they say they will do. Whether that makes a useable repeater or not is open to debate. Be careful of the basic/less expensive ones. They only have the circuit to detect the carrier and key the other radio, no time out timer or other protection to keep the transmitter from staying keyed long enough to do damage.

[kayn1n32008]

Wirelessly posted (Mozilla/5.0 (BlackBerry; U; BlackBerry 9780; en-US) AppleWebKit/534.8+ (KHTML, like Gecko) Version/6.0.0.600 Mobile Safari/534.8+)

As well, you will need duplexers or have proper vertical antenna seperation. But yes those cables do excatly that, they link the cos, ptt, receive audio and transmit audio between two maxtrac/GM300's and turn 2 radios into a very simple repeater.

[WhiteThunder]

Thank you for the information. Sorry to ask so many questions, but I am really green and I guess the only way to learn is to ask.
If this is used with the Maxtrac, will there be a squelch trail or courtesy tone or anything like that?
Is there any particular duplexer that should be used or would one of the roughly $100. duplexer from Hong Kong be okay.
Is there a better way to go without spending alot of money? The reason I am wondering is because I have 4 Maxtracs that I would like to put to some kind of use, more as an expierment than anything.

Another thing I would like to learn about is the VERY BASICS of Motorola programming. I can find lots of info on how Rss software is expensive and the legal issues. I can find all the info in the world on RIB boxes and cables. How you need a slow computer like a 486. I can find stuff on YouTube that shows me how to program once I have the computer up and running in MS DOS. However I am looking for the VERY BASICS. How to get into DOS, how to start the software, what files and how do you start them from the floppy? I would like to purchase the RSS for the Maxtracs and just expierment and learn.
Thanks again.

[GSPD]

It's really easy to get a copy of DOS. Do a search and download it to a disk. Hook up the RIB and cables, insert the DOS disk and power up the computer. With your radio connected, insert the RSS, turn the radio on(you may have to type in radio software name) and a programming menu should appear. That's the basics of it.

[WhiteThunder]

Originally Posted by GSPD

It's really easy to get a copy of DOS. Do a search and download it to a disk. Hook up the RIB and cables, insert the DOS disk and power up the computer. With your radio connected, insert the RSS, turn the radio on(you may have to type in radio software name) and a programming menu should appear. That's the basics of it.

Thank you so much for your help. I don't know for sure if I will ever spend the money to buy the rss, as I understand it is around $300. through Motorola, but it might be a good learning experience and I think I would enjoy it. I sure appreciate the kindness and information you folks have offered.

[jhooten]

Can't buy Maxtrac software from them. It shows NLA on the website.

[WhiteThunder]

. . . . . and it is against the law to purchase it elsewhere???? So perhaps my best bet is to find a local dealer to program them and they can die a slow life as an eBay built repeater.

[Thayne]

Originally Posted by WhiteThunder

Thank you so much for your help. I don't know for sure if I will ever spend the money to buy the rss, as I understand it is around $300. through Motorola, but it might be a good learning experience and I think I would enjoy it. I sure appreciate the kindness and information you folks have offered.

Just diligently keep looking once you determine what exact RSS you need and you will find it. MOTO doesn't sell it anymore so no need for you to get needlessly ripped off---

[WA0CBW]

It may also be a good idea to check with your local Repeater Frequency Coordinator to find out what frequencies are available in your area. In many places all the repeater pairs have been assigned and there is a waiting list. Also a quick review of the the FCC's rules on operation and control requirements for repeaters would also help. Much information can be found on the repeater-builder dot com web site.

Building, installing and maintaining a repeater will expose you to a whole new learning experience.

Good Luck!

BB

[WhiteThunder]

Thanks again.
I guess it doesn't really matter at this point. I am going to have to find another option as my Maxtracs are all 5 pin and those cables are for 16 pin. I have found some other controller boards on eBay that would probably work better anyway, as I don't believe these cables would ID the repeater which is a requirement here. I have learned alot already, and it only cost me $7.00 LOL. I really appreciate all of the information you folks have offered. It is nice to have this kind of support, when you are new to a hobby. Thanks.

[kc0swg]

When making a repeater out of a couple of Maxtracs, you need to make sure that 16 pin connectors on both radios are configured for what you want to plug into them. This is done via the RSS. If you just plug something into that connector that the radio isn't expecting, things can go bad in a hurry. I know this from experience. Have fun, and welcome to the hobby.

[kb0nly]

Easy to do with five pin radios also, a quick mod inside and you use the mic jack for your interfacing.

Interfacing a MaxTrac, MaxTrac 50, MaxTrac 100, MaxTrac 300, or Radius GM-300 mobile to a repeater controller

I would go with a basic controller. NHRC Repeater Controllers is a good choice, i have used a lot of their -4 models, the -2 is a good and slightly cheaper unit as well.

Those back to back cables are ok, but if you use one you would have to add a CW ID unit to it, and also make sure you set the radio which is the transmitter for a time out timer of say 180 seconds, three minutes, to protect it if the keying interface fails.

[WhiteThunder]

I was just looking at those controllers tonight. As well as the "LINK PORT CW ID" controller. I already purchased the cable, and seeing as how I haven't got a clue what to do with it and there is ZERO information on them anywhere, I will save it and use it in the event of a local emergency. Both the NHRC and the LINK PORT seem to have alot of information available to help newbies like me, so I think I will go with that. Does anyone know anything about the $100 or less duplexers on eBay? They say they are a 6 cavity, but don't look much bigger than a duplexer you would use for your TV cable. Are they safe to use or do they have some other mystical application. There is so much stuff on there from China and some of it just doesn't work. I have had nightmare issues with programming cables from there. Well, not so much the cables but the drivers to run them. Thanks for all of your help and suggestions. I appreciate it all.

[mm]

If your using the high power, 45 watt VHF radio you'll want to put a fan on it and a 1 minute or less time out timer.

I don't know what the UHF version is like since all my experience with maxtracs is with 10, 6 meters 220MHz, 2 meters and 900 MHz and of all of them the 45 watt VHF model is the most sensitive to blowing PA's if not modified and cared for.

The high VHF has been known to melt the Collector DC feed choke of the output transistor when the radio gets really hot, actually the choke is under rated for even 25% duty cycle and a larger size inductor will fix it to a degree but that's beyond this posting.

When it starts to melt it un-solders itself from the circuit board and falls over and shorts out so you'll also want a good power supply with output short circuit protection, none of those cheap Pyramid power supplies either, you'll need a good linear Astron supply with 35 amps or greater rating for repeater service.

A better option is to use a low power model, such as the 2 watt version, then use an outboard power amp made for repeater service.

There are other mods that the radio needs such as disabling the internal Carrier controlled software power cutback timer which will fool you into thinking that your radios transmitter has died after several minutes of use.

If you really want to use a maxtrac then be prepared to do all the required mods for repeater service or you'll be spending a lot of time repairing the radio and your power supply if you skimp.

Repeater builders page has all of the required Maxtrac conversion information.


Mike.

[rescue161]

Originally Posted by WhiteThunder

Does anyone know anything about the $100 or less duplexers on eBay? They say they are a 6 cavity, but don't look much bigger than a duplexer you would use for your TV cable. Are they safe to use or do they have some other mystical application.

They are safe to use if they are adjusted correctly. Those type are called notch filters and essentially "notch" out a frequency for receive on three of the cavities and one for transmit on the other three. I wouldn't put more than 25 or so Watts through one. I used one with pretty good results years ago.

I have a band-pass/band-reject duplexer now that is much better. It has 4 cavities and you adjust it to pass the receive frequency and reject the transmit on two of the cavities and to pass the transmit frequency and reject the receive on the other two. There is MUCH less chance for interference on this type of duplexer.

If you are in an RF friendly zone, then you can get away with using the notch duplexer. If you are thinking about putting this setup at a repeater site with other repeaters and transmitters, then a notch type probably won't cut it and could interfere with the other stations on site. Furthermore, the tower owner more than likely will not allow the use of a notch filter alone.

[WhiteThunder]

Thank you very much for all of the information. You have all been very helpful.

[kb0nly]

I usually take the VHF 45w radio and set it to about 20w and let er go.. I haven't had one fail yet in link radio or exciter duty. But then i usually put two 80mm fans on a bracket on the heatsink of the radio.

[oemctx4]

Radius radios work better for repeaters. Maxtracs automatically turn down the output power of the radio as time transmitting. Repeater builders has a simple circuit to override this issue. I have a link radio it was cool as a cucumber with a 4inch fan but still it backed off it power to milliwatts. I also recommend band pass/reject duplexers too and circulators too cleans up transmitter noise and reduce possible intermod with other near by transmitters.
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