Maratrac Help Please!!!!!

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cm9
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Maratrac Help Please!!!!!

Post by cm9 »

Recently bought a used engine/rescue with a low band Maratrac radio installed in it already. Bought a used VHF high band Maratrac to install in place of the low band. Changed the antenna and installed the high band radio. The radio turns on with no problems. When we try to call our communications center they cannot hears us. The radio transmits loud and clear around the station and also recieves fine. When the radio is put in scan mode it will not recieve our communications center on any channel. We took the same radio out and put it in another fire truck and they can hear us loud and clear. We also hooked the antenna up mounted on the engine/rescue to the radio on the other truck and they can hear that as well. We have switched out A-7 control heads and mics and nothing works. Traced all wires and checked incoming power without any problems. The engine/rescue has a Motorola black box mounted by the pump panel with a speaker that connects to a regular mic and also has a seperate hook up for a headset. You cannot change channels on it. I have a pic of it if it will help anyone out. The same wire that runs to the back of the A-7 control head also runs to the black box with a plug on it. We have also tried disconnecting the black box and transmitting without any success. Also the low band radio was scanning and picking up communications before we took it out. Unkown if it transmitted. The guy we have bought the radio from thinks it may be a programming issue with the radio because the black box is acting like a second radio head or the only othertthing is the cable is bad to the control head. Anyone else ever run into anything like this? I am pulling my hair out!!!!!
Someone help me please...
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Bill_G
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Re: Maratrac Help Please!!!!!

Post by Bill_G »

I suspect a bad antenna connection at the mount.
cm9
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Re: Maratrac Help Please!!!!!

Post by cm9 »

We tried the same antenna mounted on the truck with the radio problems with our other maratrac radio mounted in our engine,,,the cable was long enough to reach and that radio worked fine. I also tried a magnetic mount antenna and that didn't work either.
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Bill_G
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Re: Maratrac Help Please!!!!!

Post by Bill_G »

Let's review, and you can tell me if I'm misunderstanding -
The radio turns on normally.
You can transmit and receive locally to another truck in the bay, or a portable, but not to dispatch.
You can put the radio into another truck and talk to dispatch.
You can run the antenna cable over to another truck and talk to dispatch.

That leaves the A+ fuse, or possibly a rusty ground. I don't recall if the main fuse runs the receive audio in a Maratrac, or not. I suspect not. I would put a voltmeter on the main A+ and key the radio to see what happens. A wattmeter would be handy too, but after you verify the main power is good.

Wait. I recall a problem with the Maratracs needing the green ignition line and the main A+ at the same potential. If there was a .7v (or so) difference, you could get a no transmit condition.

None of this would explain why you can't hear dispatch. Something is missing from the story.
fchrist16
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Re: Maratrac Help Please!!!!!

Post by fchrist16 »

Bill I agree about the green ignition line having to go to the same A+ source.

Regards,

-Frank C.
cm9
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Re: Maratrac Help Please!!!!!

Post by cm9 »

[quote="Bill_G"]Let's review, and you can tell me if I'm misunderstanding -
The radio turns on normally.
You can transmit and receive locally to another truck in the bay, or a portable, but not to dispatch.
You can put the radio into another truck and talk to dispatch.
You can run the antenna cable over to another truck and talk to dispatch.

Yes this is correct. We have checked all wiring nothing wrong there and the green and red fused wire both go to the battery post. Ground is fine as it looks brand new and is on a dedicated grounding post inside of the cab. We have changed everything except the wiring itself in the truck. I checked the voltage coming into the radio itself and it is at 12.3 volts.
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Bill_G
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Re: Maratrac Help Please!!!!!

Post by Bill_G »

Excellent. Sounds like you did some good diagnosis.

Doing a Columbo - sir, just one more thing - I forgot to ask this -
You swapped Maratracs between trucks - the "new" fire/rescue always doesn't work, but the other truck does.

If this is true, then it's time for a tech to do a laying on of the hands with a wattmeter, service monitor, and manual. It's a good problem that logical trouble shooting through the interwebs isn't going to resolve. I highly doubt a programming issue. There may be some incompatibility between the control heads of your existing trucks and this "new" truck, but my experience is that only limits the number of modes you can operate on - it doesn't cause a full no tx/rx condition. I could be wrong. Won't be the first time.
cm9
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Re: Maratrac Help Please!!!!!

Post by cm9 »

Yes the radio will work in our engine fine but not in the engine /rescue. We also took the Maratrac out of the engine and put that one in the engine/rescue and that did not work either. I am starting to think it is a wiring problem and may just install a brand new cable.
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Bill_G
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Re: Maratrac Help Please!!!!!

Post by Bill_G »

Depending on how well it's installed/hidden/impossible-to-reach, I'd inspect the installed cable first. At least do a pin for pin continuity check.
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jackhackett
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Re: Maratrac Help Please!!!!!

Post by jackhackett »

It's a bit unclear whether the radio was receiving from dispatch when not in scan mode.
The transmit problem sounds like it is transmitting, but at reduced power.
I haven't dealt with a Maratrac in quite a while, but I believe this might happen if the radio has power through the green and orange leads, but not from the main red lead (is my memory correct that the A+ lead mainly feeds the RF PA?)

I would measure the voltage right at the RF PA. A good test point would be the current sense shunt R813 which should look like a long metal strip bent down on each end and soldered into the PA board. Measure with the radio both unkeyed and keyed. If you have no or low voltage unkeyed the A+ lead is open somewhere, if you have 12V and then it drops very low when keyed there is probably a high resistance in the A+ lead, such as a poor connection or corroded wire.

Also look at the pins of the cable connector that plugs into the radio to make sure none of those are smashed up. Sometimes a slightly bent pin on the radio would damage those.
Jim202
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Re: Maratrac Help Please!!!!!

Post by Jim202 »

Me thinks it time for some tools to go any further. Take a volt meter and make sure you have 12 volts on the
heavy power cable pins. You either have a bad or corroded fuse or your missing the ground on the large black
wire to the frame of the vehicle if there is no voltage.

You need to check that you have TX power leaving the radio in the bad vehicle. Put a watt meter in series
with the antenna cable. You will need a short jumper to do this. If you have the correct or near correct
power going out of the radio box, rotate the power slug and see what the reflected power is. If it is high,
then you probably have a bad connection at either the antenna end or at the radio.

Take your test meter and put it in the Ohms scale and short the 2 meter wires together. You should see
zero Ohms or just a very small value. This proves the meter is working. I have gone down the drain a number
of times with a bad meter. Take and measure the coax connector center pin to the outer shell. Depending
on the type of antenna, you should see an open or a short. If your using a screw on loading coil type antenna,
remove it and do the test again. You now should see an open or infinity on the Ohm meter. If not, then fix
the coax cable.

You need to give us some more feedback to go any further.

Jim
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maxkelley_kc2spy
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What radios do you own?: XTS2.5K-Q, ASpectra, MT2K

Re: Maratrac Help Please!!!!!

Post by maxkelley_kc2spy »

I would check to make sure that the big red lead has power... A Maratrac will transmit without this connected, but it will do it at very low power (only like... 1 or 2 watts). That would explain being heard around the station and stuff. The wiring harness in the other truck may have that red lead connected and that would be why the communications center can hear you, while this "new" truck doesn't have it properly connected.

So... RED LEAD! :)
Max Kelley KC2SPY
http://www.maxkelley.com
MT2000 VHF & UHF A7, Visar UHF, ASII UHF, Maratrac UHF, Astro Spectra UHF, MCS2KIII 900, XTS2.5K-Q
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Bill_G
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Re: Maratrac Help Please!!!!!

Post by Bill_G »

We're all having the same train of thought about the xmit. Does anyone have a speculation why this radio cannot receive?
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jackhackett
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Re: Maratrac Help Please!!!!!

Post by jackhackett »

Like I was saying, he didn't really make it clear about the receive...
cm9 wrote:The radio transmits loud and clear around the station and also recieves fine. When the radio is put in scan mode it will not recieve our communications center on any channel.
That could be read as the radio receives normally until it's put in scan mode.
I think we need a clarification here...
1) Does the radio receive the comm center okay when not in scan?
2) Does the radio receive the comm center both scanning and not scanning when it's in the other vehicle?
cm9
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Re: Maratrac Help Please!!!!!

Post by cm9 »

Actually believe it or not it was the antenna. We changed to a 18" 1/4 wave antenna and it works fine. We were using a 36" antenna and I noticed this morning when I took it off that the wire seemed awful brittle inside and broke easy so I am thinking it may have a broken wire in it and when we stretched it over to the other engine it made contact and worked fine but when we brought it back over it didn't make contact. The magnet mount antenna I tried was the same style but I am thinking that one is junk too. Also the scanning problem was in the way it was programmed as I had to select every channel that I want to scan. Thanks for everyones help as it was greatly appreciated!!!!!
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Bill_G
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Re: Maratrac Help Please!!!!!

Post by Bill_G »

Mmmm - good point. I see what you're saying. It could be receiving just fine when not scanning. I see my mistake in thinking it was the antenna mount. Many hands, light work. Thanks Jack.
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Bill_G
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Re: Maratrac Help Please!!!!!

Post by Bill_G »

(sitting here this morning wondering how I missed his response last night, then realized he is still on probation and his messages are moderated)

Excellent. Broken wire in the antenna mount. That never happens to anybody else. Never. Ha!
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