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APX7500 Receiver Issues

This forum is dedicated to discussions pertaining specifically to the Motorola ASTRO line of radios (those that use VSELP/IMBE/AMBE), including using digital modulation, digital programming, FlashPort upgrades, etc. If you have general questions please use the General or Programming forums.

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loband
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What radios do you own?: APX7500 plus too many to list

APX7500 Receiver Issues

Postby loband » Mon Oct 28, 2013 9:54 am

We have 2 APX7500 mobiles installed in 2 different vehicles. These are 110watt VHF/UHF R1 with 05 heads and RX Preamp option. Both radios are deaf on VHF compaired to Astro Spectra or XTL5000. The latter will hear a readable signal were the APX is silent. Or a noisey signal where the latter hear clear. Seems to me a -3db difference by ear. UHF is perfect. Both check out fine on the bench and were sent to the Depot, all that was done was a reflash of the firmware. If this is Motorola's best then I will go back to 2 XTL5000 instead because these are junk for fringe areas in my opinion. Any thoughts? Thanks Rob

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escomm
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Re: APX7500 Receiver Issues

Postby escomm » Mon Oct 28, 2013 11:04 am

Yes, have you checked your infrastructure to ensure the transmitting signals are comparable to the bench signals you are generating?

Jim202
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Re: APX7500 Receiver Issues

Postby Jim202 » Mon Oct 28, 2013 3:33 pm

loband wrote:We have 2 APX7500 mobiles installed in 2 different vehicles. These are 110watt VHF/UHF R1 with 05 heads and RX Preamp option. Both radios are deaf on VHF compaired to Astro Spectra or XTL5000. The latter will hear a readable signal were the APX is silent. Or a noisey signal where the latter hear clear. Seems to me a -3db difference by ear. UHF is perfect. Both check out fine on the bench and were sent to the Depot, all that was done was a reflash of the firmware. If this is Motorola's best then I will go back to 2 XTL5000 instead because these are junk for fringe areas in my opinion. Any thoughts? Thanks Rob
Last edited by Jim202 on Mon Oct 28, 2013 3:37 pm, edited 1 time in total.

Jim202
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Re: APX7500 Receiver Issues

Postby Jim202 » Mon Oct 28, 2013 3:37 pm

loband wrote:We have 2 APX7500 mobiles installed in 2 different vehicles. These are 110watt VHF/UHF R1 with 05 heads and RX Preamp option. Both radios are deaf on VHF compaired to Astro Spectra or XTL5000. The latter will hear a readable signal were the APX is silent. Or a noisey signal where the latter hear clear. Seems to me a -3db difference by ear. UHF is perfect. Both check out fine on the bench and were sent to the Depot, all that was done was a reflash of the firmware. If this is Motorola's best then I will go back to 2 XTL5000 instead because these are junk for fringe areas in my opinion. Any thoughts? Thanks Rob


Have you tried putting a test cable on the roof antenna connection point and run it back to a service monitor? You could have an antenna problem you don't know about.

Jim

loband
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Re: APX7500 Receiver Issues

Postby loband » Tue Oct 29, 2013 5:04 am

Yes both antennas test fine. Not fixed infrastructure related. It is all vhf systems including federal, local and weather freqs. As I said put XTL5000 or A/S is the same vehicles in place of the APX and antennas and big difference in vhf receive. We have a large fleet and only these two APXs and we are not impressed at this point with fringe area receive. I guess if they are used within a limited coverage area then they do work as designed.

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escomm
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Re: APX7500 Receiver Issues

Postby escomm » Tue Oct 29, 2013 7:48 am

You haven't checked the infrastructure but you know it's not infrastructure related.

You bench test the radios and they test within spec.

OK, so you don't want to actually fix the problem, just complain about the APX. Gotcha

loband
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Re: APX7500 Receiver Issues

Postby loband » Fri Nov 01, 2013 8:35 am

Escomm,

How would you like for us to check the "infrastructure"? It is all signals received on VHF.

Changed the radio box and control head with an XTL and the problem is gone. So...common sense the problem is with the APX.
Roof top NMO antennas are PCTEL no tune wide band and are less than 2-1 swr. Even tried other mounts on the trucks and 1/4 wave antenna. Just because it has a batwing logo doesn't make it the best product....So what I'm gathering from the comments here is nobody has any experience with the APX mobile and this type of problem. I will do more than complain about the APX, I will tell every agency I'm in contact with considering them not to. It won't be the first dog Moto put on the market. For a cost of over $6k these should be the absolute best of the best.

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escomm
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Re: APX7500 Receiver Issues

Postby escomm » Fri Nov 01, 2013 10:55 am

Uh, go to the hilltop and get your service equipment out and check the infrastructure. You know, things like deviation, frequency error, transmit power, and so forth.

That you have "bench-checked" these radios and found them to be within spec, coupled with the radios passing Motorola's autotune & autotest procedures, only points the finger at the radios NOT being the problem.

Curiously enough, another user had a very similar problem to yours: viewtopic.php?f=1&t=107060

Turns out the radio system had never been narrowbanded!

Now, I am not saying the problem is with the infrastructure. Only that a comprehensive analysis of the problem inherently requires ruling the infrastructure out.

Keep in mind that the more modern digital radios will have much less tolerance for poor signals than older digital radios, and older digital radios will have less tolerance than older analog radios.

It's certainly ostensible there's something with the VHF RF boards in the radio. But if the receiver is opening up with .25uV or so of signal on the bench then something is not right elsewhere. I still think there are issues with the infrastructure but of course only a detailed analysis will say for sure.

Jim202
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Re: APX7500 Receiver Issues

Postby Jim202 » Fri Nov 01, 2013 12:52 pm

I had a comment passed along to me today that basically indicated the front end of the APX radios on VHF seems to not like strong signals nearby, like in miles. It causes the receiver to become deaf. Maybe this is what is going on with your radio.

Do you have any VHF pagers within several miles of where your working on this radio?

Maybe try a bandpass filter on the radio input and see if it knocks out the pager problem. Let us know how this turns out.

Jim

loband
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Re: APX7500 Receiver Issues

Postby loband » Fri Nov 01, 2013 5:25 pm

All your suggestions are appreciated.
Ok more trial and error came up with more insight to the problem. The 05 control head appears to be radiating strong spurs. Here is what it is doing....
If you take a portable in this case an APX7000 and set it to receive a strong vhf broadcast and the APX7500 is set for open squelch it desenses the portable. Now if you turn the volume on the 7500 off the desense is gone, crack the volume, the portable AND the FM stereo in the truck desenses along with the 7500's receiver. This only occurs when the audio amp is active. Unfortunately when the radio was sent to the depot the head was not.

tvsjr
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Re: APX7500 Receiver Issues

Postby tvsjr » Fri Nov 01, 2013 6:37 pm

You might also check:
Radio Wide/General/Ultra Narrow Intermediate Freq Filter - try 5.76K rather than the default 7.8K
Conventional Personality/Advanced - try standard or enhanced, if currently set to disabled

loband
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What radios do you own?: APX7500 plus too many to list

Re: APX7500 Receiver Issues

Postby loband » Sat Nov 02, 2013 2:35 pm

Ok after much experimentation and reading the service manual I think the problem maybe solved or at least identified.

The yellow ignition sense wire is radiating the vhf band spur from the 05 head micro processor.

It's access of wire was originally coiled up, it is now shortened. While receiving a weak off the air signal, I repositioned the remaining wire to where the APX received the best and tie wrapped wire in that position.

It is still radiating the spur to a vhf portable in or near the truck and on the FM stereo but at least the APX seems hear weak signals.

Gees...the things we have to go through to make this new stuff work. I wish we still had the Mitrex .....they are bullet proof.

Jim202
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Re: APX7500 Receiver Issues

Postby Jim202 » Sat Nov 02, 2013 3:37 pm

loband wrote:Ok after much experimentation and reading the service manual I think the problem maybe solved or at least identified.

The yellow ignition sense wire is radiating the vhf band spur from the 05 head micro processor.

It's access of wire was originally coiled up, it is now shortened. While receiving a weak off the air signal, I repositioned the remaining wire to where the APX received the best and tie wrapped wire in that position.

It is still radiating the spur to a vhf portable in or near the truck and on the FM stereo but at least the APX seems hear weak signals.

Gees...the things we have to go through to make this new stuff work. I wish we still had the Mitrex .....they are bullet proof.


Go find some of those snap on ferrite cores and put one or two on the yellow wire. Use them all the time on USB cables so that VHF portables don't kill things when you transmit.

Jim

tvsjr
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Re: APX7500 Receiver Issues

Postby tvsjr » Sat Nov 02, 2013 6:25 pm

Jim202 wrote:Go find some of those snap on ferrite cores and put one or two on the yellow wire. Use them all the time on USB cables so that VHF portables don't kill things when you transmit.


I've got lots of USB running around the truck and have never experienced any issues. Care to elaborate?

Jim202
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Re: APX7500 Receiver Issues

Postby Jim202 » Sun Nov 03, 2013 3:55 am

tvsjr wrote:
Jim202 wrote:Go find some of those snap on ferrite cores and put one or two on the yellow wire. Use them all the time on USB cables so that VHF portables don't kill things when you transmit.


I've got lots of USB running around the truck and have never experienced any issues. Care to elaborate?



I work for a company that builds radio interoperability gateways. We found that VHF portable radios when they transmitted near the usb cables would cause it to sometimes crash the laptop software and interface connections. Adding the ferrite cores on the USB cables took care of this problem.

Am just suggesting that if the control head is generating the noise coming out of the yellow and maybe the red power wires, put a ferrite core on the wires to cut this noise from being transmitted over the wires. It is a simple engineering practice used all the time. Not saying to put the cores on the USB connections in the vehicle, but on the noise source as was stated earlier.

Jim

tvsjr
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Re: APX7500 Receiver Issues

Postby tvsjr » Sun Nov 03, 2013 10:00 am

Jim202 wrote:I work for a company that builds radio interoperability gateways. We found that VHF portable radios when they transmitted near the usb cables would cause it to sometimes crash the laptop software and interface connections. Adding the ferrite cores on the USB cables took care of this problem.

Am just suggesting that if the control head is generating the noise coming out of the yellow and maybe the red power wires, put a ferrite core on the wires to cut this noise from being transmitted over the wires. It is a simple engineering practice used all the time. Not saying to put the cores on the USB connections in the vehicle, but on the noise source as was stated earlier.


Interesting. Yeah, I understand the principal of ferrite cores - just curious what you were seeing as far as real-world issues.

loband
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What radios do you own?: APX7500 plus too many to list

Re: APX7500 Receiver Issues

Postby loband » Sun Nov 17, 2013 6:35 pm

Update.....waiting for a new replacement control head from Moto to see if it takes care of the problem.

fineshot1
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Re: APX7500 Receiver Issues

Postby fineshot1 » Tue Nov 19, 2013 6:48 am

loband wrote:Ok after much experimentation and reading the service manual I think the problem maybe solved or at least identified.

The yellow ignition sense wire is radiating the vhf band spur from the 05 head micro processor.

It's access of wire was originally coiled up, it is now shortened. While receiving a weak off the air signal, I repositioned the remaining wire to where the APX received the best and tie wrapped wire in that position.

It is still radiating the spur to a vhf portable in or near the truck and on the FM stereo but at least the APX seems hear weak signals.

Gees...the things we have to go through to make this new stuff work. I wish we still had the Mitrex .....they are bullet proof.


Sounds as if the control head could be radiating wide band noise.
fineshot1
NJ USA

loband
Posts: 108
Joined: Fri Nov 25, 2005 7:29 pm
What radios do you own?: APX7500 plus too many to list

Re: APX7500 Receiver Issues

Postby loband » Tue Nov 19, 2013 7:02 am

Yes it could be. I am working with Moto engineers to solve this. Seems to effect other APX7500 05 as well. Something in the Audio Amp circuit.
Most users would probably not notice anything is wrong. But working with weaker signals it is very noticable.

The test is very easy to do.

1: Set the APX 7500 05 to open squelch with the volume turned off. Or set the mobile to receive a signal. Does not matter what band or frequency.

2: Take a portable vhf and set to receive a distant weather broadcast.

3: Now turn the volume on the mobile up slightly and the portable gets desensed. This also desenses the vhf mobile receiver through it's roof top antenna and thus the problem we are experiencing. (A service monitor straight to the APX receiver will of course mask the issue.)

4: Turn volume off and desense is gone. Audio amp issue?

loband
Posts: 108
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What radios do you own?: APX7500 plus too many to list

Re: APX7500 Receiver Issues

Postby loband » Sun Dec 01, 2013 8:31 am

Update.

New replacement head arrived and the problems are completely solved. We will be replacing our other 05 APX heads as well. Seems to be a problem will older heads. I am very impressed it turned the 7500 into a "new" radio. RX sensitivity is hot and speaker audio louder.
Bravo to Motorola for working with us on this frustrating issue.


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