I've Googled this problem to death without success, so I'm hoping someone
here will be kind enough to please point me in the right direction.



I work at a small company that uses the UHF Radius M1225 in its Ford
vehicles powered by the Powerstroke diesel.



Not long after beginning to use the newest vehicle (a 2004 model) we started
having problems hearing the person using that vehicle. Its signal would
drop from the repeater intermittently. Sometimes this happens for long
periods, and then again the radio will work the next day.



When this is happening I've listened to the output of the radio using a
scanner and the transmission seems normal. Yet at the same time, people in
the other vehicles never hear some of these transmissions that should be
coming from the repeater.



Of course we suspected the radio. But when we swapped radios, the same
problem still occurred in the 2004 vehicle.



Anyone care to venture a guess, or point me to a forum that might have some
Motorola techs in it?



I'm beginning to wonder if voltage to the radio may be playing a part in
affecting the signal going into the repeater.



BTW, the business that installed the system can't figure it out, so I'm
grasping at straws.



Many TIA!

Steve

In article ,
says...
Not long after beginning to use the newest vehicle (a 2004 model) we started
having problems hearing the person using that vehicle. Its signal would
drop from the repeater intermittently. Sometimes this happens for long
periods, and then again the radio will work the next day.

When this is happening I've listened to the output of the radio using a
scanner and the transmission seems normal. Yet at the same time, people in
the other vehicles never hear some of these transmissions that should be
coming from the repeater.

Not really enough information for a diagnosis, but my first
guess would be that alternator whine or other noise in the
radio's signal may be interfering with the repeater's abilty
to decode subaudible tone or digital squelch. The M1225
seems a little more susceptible to power noise getting into
the transmit audio than some of Mot's other models.

Steve:

Things to check:

1. The repeater requires a subaudible private line tone (PL/CTCSS) or
digital private line data word (DPL) for access. If it is corrupted or
distorted, the mobile audio won't pass through the repeater. That is why
to your scanner and ear, the microphone audio sounds ok. The tone if
good should be a sinewave of 500 to 750 Hz deviation, while if it is
DPL, the code word should be fairly clean squareish wave with symmetry,
flat topped with some visable shoulders (rise and fall). Because it is
data, don't expect each cycle to look like the last! The DPL deviation
should be 500 to 750 Hz deviation. By the way, you need a service
monitor or a receiver and scope with DC coupling on the discriminator to
see these waveforms properly.

2. Cheap mobile radios often have poor filtering on the DC power input.
If the alternator or other circuitry (electronic injectors) are imposing
any noise on the DC power into the radio, the CTCSS or DPL might be
getting distorted by whine or noise impulses. Check this first by
turning the engine off, second by powering the radio from a seperate 12V
battery, finally by observing with an oscilloscope the vehicle power line.

3. Cheap mobile radios (yes I said it again) often have microphonic
(sensitive to mechanical vibration) voltage controlled oscillators (part
of frequency synthesizer) which if subjected to mechanical vibration
(that power stroke engine knocking) will distort the CTCSS or DPL. Check
this by removing the radio from it's bracket and setting it on a pillow
while the engine is running.

4. Finally, Yes it could be a voltage problem, check with a voltmeter,
the radio should work at 13.8 volts +/- 20%. But that would be too obvious!

"The RFI-EMI-GUY"




Steve wrote:

I've Googled this problem to death without success, so I'm hoping someone
here will be kind enough to please point me in the right direction.

I work at a small company that uses the UHF Radius M1225 in its Ford
vehicles powered by the Powerstroke diesel.


Not long after beginning to use the newest vehicle (a 2004 model) we started
having problems hearing the person using that vehicle. Its signal would
drop from the repeater intermittently. Sometimes this happens for long
periods, and then again the radio will work the next day.


When this is happening I've listened to the output of the radio using a
scanner and the transmission seems normal. Yet at the same time, people in
the other vehicles never hear some of these transmissions that should be
coming from the repeater.


Of course we suspected the radio. But when we swapped radios, the same
problem still occurred in the 2004 vehicle.


Anyone care to venture a guess, or point me to a forum that might have some
Motorola techs in it?


I'm beginning to wonder if voltage to the radio may be playing a part in
affecting the signal going into the repeater.


BTW, the business that installed the system can't figure it out, so I'm
grasping at straws.



Many TIA!

Steve





--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"

The Lost Deep Thoughts By: Jack Handey
Before a mad scientist goes mad, there's probably a time
when he's only partially mad. And this is the time when he's
going to throw his best parties.

Steve:

Things to check:

1. The repeater requires a subaudible private line tone (PL/CTCSS) or
digital private line data word (DPL) for access. If it is corrupted or
distorted, the mobile audio won't pass through the repeater. That is why
to your scanner and ear, the microphone audio sounds ok. The tone if
good should be a sinewave of 500 to 750 Hz deviation, while if it is
DPL, the code word should be fairly clean squareish wave with symmetry,
flat topped with some visable shoulders (rise and fall). Because it is
data, don't expect each cycle to look like the last! The DPL deviation
should be 500 to 750 Hz deviation. By the way, you need a service
monitor or a receiver and scope with DC coupling on the discriminator to
see these waveforms properly.

2. Cheap mobile radios often have poor filtering on the DC power input.
If the alternator or other circuitry (electronic injectors) are imposing
any noise on the DC power into the radio, the CTCSS or DPL might be
getting distorted by whine or noise impulses. Check this first by
turning the engine off, second by powering the radio from a seperate 12V
battery, finally by observing with an oscilloscope the vehicle power line.

3. Cheap mobile radios (yes I said it again) often have microphonic
(sensitive to mechanical vibration) voltage controlled oscillators (part
of frequency synthesizer) which if subjected to mechanical vibration
(that power stroke engine knocking) will distort the CTCSS or DPL. Check
this by removing the radio from it's bracket and setting it on a pillow
while the engine is running.

4. Finally, Yes it could be a voltage problem, check with a voltmeter,
the radio should work at 13.8 volts +/- 20%. But that would be too obvious!

"The RFI-EMI-GUY"




Steve wrote:

I've Googled this problem to death without success, so I'm hoping someone
here will be kind enough to please point me in the right direction.

I work at a small company that uses the UHF Radius M1225 in its Ford
vehicles powered by the Powerstroke diesel.


Not long after beginning to use the newest vehicle (a 2004 model) we started
having problems hearing the person using that vehicle. Its signal would
drop from the repeater intermittently. Sometimes this happens for long
periods, and then again the radio will work the next day.


When this is happening I've listened to the output of the radio using a
scanner and the transmission seems normal. Yet at the same time, people in
the other vehicles never hear some of these transmissions that should be
coming from the repeater.


Of course we suspected the radio. But when we swapped radios, the same
problem still occurred in the 2004 vehicle.


Anyone care to venture a guess, or point me to a forum that might have some
Motorola techs in it?


I'm beginning to wonder if voltage to the radio may be playing a part in
affecting the signal going into the repeater.


BTW, the business that installed the system can't figure it out, so I'm
grasping at straws.



Many TIA!

Steve





--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"

The Lost Deep Thoughts By: Jack Handey
Before a mad scientist goes mad, there's probably a time
when he's only partially mad. And this is the time when he's
going to throw his best parties.

They don't build radios like they used to. I remember testing the heck
out of these things. 12M specs, TIA-603 etc. What in the world happened?
Try to get "real" specs for a cellphone or FRS radio! give it up!

Ol' Duffer wrote:

In article ,
says...


Not long after beginning to use the newest vehicle (a 2004 model) we started
having problems hearing the person using that vehicle. Its signal would
drop from the repeater intermittently. Sometimes this happens for long
periods, and then again the radio will work the next day.

When this is happening I've listened to the output of the radio using a
scanner and the transmission seems normal. Yet at the same time, people in
the other vehicles never hear some of these transmissions that should be
coming from the repeater.



Not really enough information for a diagnosis, but my first
guess would be that alternator whine or other noise in the
radio's signal may be interfering with the repeater's abilty
to decode subaudible tone or digital squelch. The M1225
seems a little more susceptible to power noise getting into
the transmit audio than some of Mot's other models.




--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"

The Lost Deep Thoughts By: Jack Handey
Before a mad scientist goes mad, there's probably a time
when he's only partially mad. And this is the time when he's
going to throw his best parties.

"Steve" wrote:

}Not long after beginning to use the newest vehicle (a 2004 model) we started
}having problems hearing the person using that vehicle.

Descibe what antennas are being used; brand, where they're mounted, etc.

Could be a ground plane problem.

Also, does the problem change depending on whether or not the engine
is running?

Stan.

The obvious question is "Did you try the suspect radio in a vehicle that
had no known problems" (Without even getting close to test gear yet).
If that proves out ok, suspect the antenna/cable/installation of same as
a common denominator......after checking basic supply voltage at the
radio first.