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.
I have an Astro Spectra W3 which I have been using to monitor the digital police comms. It works absolutely flawlessly on analogue conventional, which is what I mainly listen to. However recently I have been monitoring more digital conventional channels and I noticed that the digital audio is actually quite bad. That is, it's distorted and sounds as if very small chunks of the digital data is missing. I can understand what they are saying most of the time, but it does get very annoying.
I have checked the antenna & coax, and everything is ok. It even suffers this problem when I'm in the middle of an area which I know has a good digital repeater coverage, so I don't think it's a reception issue.
Does anyone know what this could possibly be, and is it fixable? I am not a radio tech and don't have service equipment to test it thoroughly. I also don't particularly want to send it off to motorola as I believe they aren't too keen on members of the general public owning these radios over here where I live. I'm hoping it might be somehow tweaked or fixed in the CPS or Tuner software. Can anyone give me some ideas as to what it could be and how to fix it? I know it's a bit of an ask from a motorola n00b, but any help would be much appreciated. Thanks
Start with giving us some information about the radio like :
Model #
Flashcode
Host
DSP
Any encryption installed
Which reminds me are you sure they are not running encrypted digital. I know from my experience it sounds like the older donald duck type encryption and actually once in a while it sounds like you can understand a word here or there.
It has DES-OFB encryption board installed but not active in the software. The police don't currently use encryption much and everything is in the clear. They will go over to DES-OFB within the next half year to year.
So looking at that info, does anyone have any idea as to what it could be?
I sat in the car last night and listened to it. The voices sometimes sound ok, and sometimes they sound very uhhh digital? Almost robot like you could say...
To me it sounds like they are using encryption. Is it like this all the time when one person is talking or does it go in and out during a single transmission?
I'm certain they aren't using encryption. It is most of the time, but it's not completely losing the audio. I can pretty much hear everything they are saying and most of the time it's quite clear, but sometimes it fades in and out of the digital sounding distortion, or chops a small part of the transmission off. It sounds as if it would if you monitored a digital transmission from far away and weren't getting all the P-25 data.
Is it possible you are in a multipath area? Are they perhaps using simulcast and you are not in the area it is "engineered" for? Both of these conditions will disrupt digital audio in the manner you describe.
Another possibility would be a simultaneous analog transmission on the channel - which would interfere - can you listen to the channel "analog only" to see if this is the case?
There are settings in the Astro Spectra that will affect digital reception - but I would NOT attempt to adjust them without proper test equipment!
73 DE Hartley
p.s. You are correct - if you are able to make out real words, then they are NOT encrypted!
HJG
It would be nice if you could record what you are hearing as an audio file so we could hear it. There are indeed settings in the cps/rss that can affect how the radio handles weak signals, etc.
I would like to comment further on the encryption issue. With your further description in may or may not be encryption. I can tell you that I have a dual encryption module in my radio, I use one type but the other one is not keyloaded. There is an agency on digital in my area that uses the encryption type that I do not have keyloaded. Most of the time when they are encrypted I can not understand what they are saying but sometimes I can make out a word here or there. I know that is strange.
During the hard to understand conversations is the receive light on steady or flashing? Also I would be happy to look at how your codeplug is set up if you want to send it to me.
If the comms were encypted you wouldn't hear anything without the key loaded in the radio. Its all or nothing. (This would be for the normal DVP/DES etc typed of encyption - voice inversion etc may be different).
Try chaning the ASTRO type to WIDE, or CPSQK? (or whatever) and see what happens. Also they could be running narrowband while you have it on wide or vice-versa.
Lowband radio. The original and non-complicated wide area interoperable communications system
We recently had an XTL5000 come in suffering from the same problem...the digital comms were sometimes sounding like you were in a fringe area, with the error correction being tested to the max. This results in vowels/words sounding 'stretched out' & robotic, with a few beeps & buzzes thrown in for good measure. Sound like your issue? Alignment didn't help ours, Motorola fixed it under warranty, but all the paperwork showed was "replaced defective part MHUF". Not sure what that actually is...maybe someone else here does?
Todd
No trees were harmed in the posting of this message...however an extraordinarily large number of electrons were horribly inconvenienced.
Hi guys, thanks for the replies. Todd, what you described is pretty much exactly the problem that I have. I don't suppose they mentioned the part and labour cost in the job sheet? Since my radio is definitely not under warranty, I fear that it will set me back quite a bit to fix it. I might have to just put up with it. Eventually when they go encrypted, the digital comms will be useless for me and it will just become my personal conventional analogue unit (that is unless I get my hands on the key somehow). The XTL5000 is a relatively new model, so I wonder why it would have that problem in the first place. Hrmmm...??
Oh, also, is it possible to adjust the bit error correction? And what would be the best way to adjust it? Is there a max correction setting? I was wondering if I should take a screen shot of all the settings, and then adjust it and see if it's made a difference. What do you guys think?
