I have a Motorola Radius (maxtrac) that has a receive problem. The best I can get is about 2 uv (That is a 2, not a .2). It is a 30-36 MHz. Model number: D51LRA9732AK. Radio performs fine otherwise; TX at 60 watts and good deviation. Any ideas or how does one adjust the receive on these?? I have a service monitor and all the adjustment tools.
The 14.400 crystal is working as are the 10.700 ones. I also verified the 455KHz is receiving quite well. Just some added info.
Maxtrac lowband receive
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radiocat37
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Maxtrac lowband receive
Brian Griffin: Ah, if my memory serves me, this is the physics department.
Chris Griffin: That would explain all the gravity.
.
Lois: Peter, you're drunk again.
Peter: No, I'm just exhausted because I've been up all night drinking.
Chris Griffin: That would explain all the gravity.
.
Lois: Peter, you're drunk again.
Peter: No, I'm just exhausted because I've been up all night drinking.
Re: Maxtrac lowband receive
radiocat37 wrote:I have a Motorola Radius (maxtrac) that has a receive problem. The best I can get is about 2 uv (That is a 2, not a .2). It is a 30-36 MHz. Model number: D51LRA9732AK. Radio performs fine otherwise; TX at 60 watts and good deviation. Any ideas or how does one adjust the receive on these?? I have a service monitor and all the adjustment tools.
The 14.400 crystal is working as are the 10.700 ones. I also verified the 455KHz is receiving quite well. Just some added info.
Have you tried moving the antenna coax connector around some? Loosen up the locking ring and move the coax cable up, down, side to side and see if the reception changes.
Those mini UHF connectors are prone to damage. It only takes a larger center pin on the connector or too much solder left on from making it up to damage the female center pin in the radio side of the connection.
f this turns out to be the issue, then you can try a simple method to fix it. I take a flat screwdriver blade and rest it on the edge of the nylon insulator. Rap the end of the screwdriver with something to attempt to bend the center pin. You might have to take a sharp scribe tool to open up the bent pin if you hit it too hard.
Now go back and see if you don't have a better RF connection after attempting to tighten the center female connection. Point of caution here. If you hit it too hard, your going to damage the female center pin connector beyond repair.
There also is a very slight chance the RX coax cable has come out of the RX feed to the front end filter. To check this out, you will have to dissect the radio slightly. If you have a front dash mount, you will need to remove the 2 screws that hold the PA onto the main radio frame. Slowly move the 2 sections apart and see if the RX cable is secure. If so, then that was not the problem.
You could have a bad switching diode in the TX, RX antenna switch. Good luck on that one. One cause of blowing them is too much RF power coming in the antenna in RX.
Jim
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radiocat37
- Posts: 210
- Joined: Mon Sep 22, 2003 9:59 am
Re: Maxtrac lowband receive
Jim,
Thanks for heads up. Can you direct me to the switching diode and I can test it? The antenna connections is good. Thanks Mike
Thanks for heads up. Can you direct me to the switching diode and I can test it? The antenna connections is good. Thanks Mike
Brian Griffin: Ah, if my memory serves me, this is the physics department.
Chris Griffin: That would explain all the gravity.
.
Lois: Peter, you're drunk again.
Peter: No, I'm just exhausted because I've been up all night drinking.
Chris Griffin: That would explain all the gravity.
.
Lois: Peter, you're drunk again.
Peter: No, I'm just exhausted because I've been up all night drinking.
Re: Maxtrac lowband receive
1 to 2uv sensitivity is often the first mix. You'll need a schematic to fix it.
Re: Maxtrac lowband receive
radiocat37 wrote:Jim,
Thanks for heads up. Can you direct me to the switching diode and I can test it? The antenna connections is good. Thanks Mike
If you go to the repeater builder site, go to the Motorola section and then near the bottom of the Maxtrac info, there are some manuals that you can download. You will need these to be able to work on the radio.
Jim
Re: Maxtrac lowband receive
The lowband Maxtrac has much the same RF board.
Re: Maxtrac lowband receive
A fast check of the pin switch is to inject your receive signal directly on the RF board. With the top cover removed and the front facing you look to the left rear and you should see 9 variable can/coil forms in a row, just towards the front of the first 2 coil forms is the receive coax which is gray color and inserted into a metal shield can at a 45 degree angle.
Simply pull the gray coax out and move it aside so it doesn't short to any components.
You can make up a short pigtail coax from a piece of RG-174 or similar coax and insert the center pin where the gray coax fits in and the coax ground to the shield can.
Inject your signal Gen thru this temporary pigtail and measure the receive sensitivity this way directly at the receiver front end.
If the sensitivity is around .3uv or better then the pin switch is probably bad. If the sensitivity is still 2 uv then it could be the pre-selector tuning or even the 4 IF variable coils being misaligned, there are no variable tuning for the lo injection.
The 9 shielded coils in the row near the rear are the receive pre-selector tuning.
Closer to the middle of the RF board you will see 4 variable shielded cans/ inductors, the 2 towards the right are the first IF tuning and the two towards the left are also IF tuning but these are also fed in parallel with the noise blanker gates.
Inside the inner shield are the VCOs to the right and the noise blanker is the smaller section with 3 tunable coils in it.
Before tuning anything however; download the manual so you understand how the IF coils and the blanker need to be tuned.
As to the 9 preselector cans you can try carefully tuning them to see if you pick up any sensitivity but again be careful on the 4 IF coils and the 3 noise blanker coils.
Mike
Edited: to fix FU@#%ng android autotyping, I hate FU$%^ng androids
Note: Also If you need any more help in digging deeper then there are a lot of us on here plus I'm presently in the process of moving a mid split radius down to 10 meters so my radio is wide open at this time for any needed measurements.
Simply pull the gray coax out and move it aside so it doesn't short to any components.
You can make up a short pigtail coax from a piece of RG-174 or similar coax and insert the center pin where the gray coax fits in and the coax ground to the shield can.
Inject your signal Gen thru this temporary pigtail and measure the receive sensitivity this way directly at the receiver front end.
If the sensitivity is around .3uv or better then the pin switch is probably bad. If the sensitivity is still 2 uv then it could be the pre-selector tuning or even the 4 IF variable coils being misaligned, there are no variable tuning for the lo injection.
The 9 shielded coils in the row near the rear are the receive pre-selector tuning.
Closer to the middle of the RF board you will see 4 variable shielded cans/ inductors, the 2 towards the right are the first IF tuning and the two towards the left are also IF tuning but these are also fed in parallel with the noise blanker gates.
Inside the inner shield are the VCOs to the right and the noise blanker is the smaller section with 3 tunable coils in it.
Before tuning anything however; download the manual so you understand how the IF coils and the blanker need to be tuned.
As to the 9 preselector cans you can try carefully tuning them to see if you pick up any sensitivity but again be careful on the 4 IF coils and the 3 noise blanker coils.
Mike
Edited: to fix FU@#%ng android autotyping, I hate FU$%^ng androids
Note: Also If you need any more help in digging deeper then there are a lot of us on here plus I'm presently in the process of moving a mid split radius down to 10 meters so my radio is wide open at this time for any needed measurements.