Digital scanning

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Blaine

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Still can't figure out why at times my GRE PSR500 will stop on a frequency, say.. 165.2875, and show a NAC of 650, yet NO AUDIO will pass through. Anybody know what the deal is? I am assuming it is just the signal strength going into the radio, but I also feel that if it can decode the NAC why can't it decode the audio. It should be the same, right?

I was listening the other night to the frequency 170.100 and only getting one side of the conversation....the other side was just the P25 buzzsaw. Guess it was just too faint to get the radio to decode it. This is one of the major frustrations of todays digital communications and scanners, I think. At least with analog there seemed to be a middle ground, and let's say you had a faint simplex comm you were listening to..yeah, you might have had some picket fencing but you still might be able to pick out the conversation, and bits and pieces of what they were saying. With digital, and the decoding process, there is no middle ground. Either it's strong enough to decode the audio with the scanner, or you just get nothing at all, or the buzzsaw. Very annoying.

What I wonder is if there are any tweaks in the EXTENDED SETTINGS option in Win500 that could alleviate this problem, or make weaker
signals where they could be decoded better...

Any ideas?
 

troymail

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Still can't figure out why at times my GRE PSR500 will stop on a frequency, say.. 165.2875, and show a NAC of 650, yet NO AUDIO will pass through. Anybody know what the deal is? I am assuming it is just the signal strength going into the radio, but I also feel that if it can decode the NAC why can't it decode the audio. It should be the same, right?

I was listening the other night to the frequency 170.100 and only getting one side of the conversation....the other side was just the P25 buzzsaw. Guess it was just too faint to get the radio to decode it. This is one of the major frustrations of todays digital communications and scanners, I think. At least with analog there seemed to be a middle ground, and let's say you had a faint simplex comm you were listening to..yeah, you might have had some picket fencing but you still might be able to pick out the conversation, and bits and pieces of what they were saying. With digital, and the decoding process, there is no middle ground. Either it's strong enough to decode the audio with the scanner, or you just get nothing at all, or the buzzsaw. Very annoying.

What I wonder is if there are any tweaks in the EXTENDED SETTINGS option in Win500 that could alleviate this problem, or make weaker
signals where they could be decoded better...

Any ideas?
Every situation is different but I've noticed on my local system - which is half digital and half analog - that all of the voice frequencies are not of the same quality when it comes to reception... in fact, there has always been at least one frequency in the group of 15-16 that, when an analog conversion appears there, it's almost always more scratchy than all the others. I could imagine that the control channel frequency might be of decent quality for decoding but the voice channel maybe not so much... of course, this is but a guess on a possible reason why....
 

N8IAA

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Joined
Dec 19, 2002
Messages
7,074
Location
Fortunately, GA
Still can't figure out why at times my GRE PSR500 will stop on a frequency, say.. 165.2875, and show a NAC of 650, yet NO AUDIO will pass through. Anybody know what the deal is? I am assuming it is just the signal strength going into the radio, but I also feel that if it can decode the NAC why can't it decode the audio. It should be the same, right?

I was listening the other night to the frequency 170.100 and only getting one side of the conversation....the other side was just the P25 buzzsaw. Guess it was just too faint to get the radio to decode it. This is one of the major frustrations of todays digital communications and scanners, I think. At least with analog there seemed to be a middle ground, and let's say you had a faint simplex comm you were listening to..yeah, you might have had some picket fencing but you still might be able to pick out the conversation, and bits and pieces of what they were saying. With digital, and the decoding process, there is no middle ground. Either it's strong enough to decode the audio with the scanner, or you just get nothing at all, or the buzzsaw. Very annoying.

What I wonder is if there are any tweaks in the EXTENDED SETTINGS option in Win500 that could alleviate this problem, or make weaker
signals where they could be decoded better...

Any ideas?
A VHF frequency that is analog, P-25, and encrypted. Are you listening to federal frequencies? A VHF trunked system? You are not giving enough info for us to answer your questions.
Larry
 

ChrisP

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May 20, 2002
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1,176
Location
Portland, OR
Blaine,

In your post you gave two different examples, and I think you are dealing with two different situations.

First, in the case of the BATF frequency you posted, remember that P-25 radios offer the option of transmitting digital data, not just voice. This data could be GPS information, alarm information, status reports and I have confirmed that some federal P-25 users have the radios programmed to "announce" their presence on the frequency when the radio is powered up or channels are changed. The dispatch console can record the radio ID and note that it is on a particular frequency without the radio operator doing anything. I have noted on both conventional federal systems and trunked federal systems (the IWN) a lot of what you have noted - a repeater keys up, a NAC is noted but no voice is heard. That likely indicates a data transmission, or non-voice information was transmitted.

In your second example, especially dealing with simplex communications, you just don't get enough signal strength for the scanner to decode the P-25 information into voice. The only solution is to get more signal, i.e., higher antenna or such. There are some adjustments to the P25 settings in most digital scanners, but I don't know how much they would buy you in the case of a weak signal.

- Chris
 
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