BCD996T: Programmed freq fair quality, but OK during QS

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Airdorn

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Hi. I have a BCD996T.

If I QUICK SEARCH a frequency that has a P25 CC, say, 380.0750 it comes in loud and clear.

But if I program a trunked system and use 380.0750 as the CC, then during scan that frequency seems to come in weaker... IE, I hear a noticeable hiss. This is true even if I HOLD on the CC frequency.

The 996T still recognizes the CC and shows the site ID, etc..

But the hiss is there and Unitrunker reports a lower 'health' value, than if I simply quick searched the frequency.

Why is that?
 
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jonwienke

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A P25 control channel is constant digital noise. Unless reception is really marginal, you should never hear static or hiss over the digital buzz. Are you sure you have a control channel, rather than a voice channel (which does not broadcast continuously)?
 

Airdorn

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Yes, 380.075 is a P25 control channel for US Dept of Defense.

When I hold on it, the scanner displays the site id, something it can only do with a control channel.


And yes, control channels, just like any other monitored frequency, can have all kinds of noise overlayed on them because of distance to the source, interference, etc. I am listening to the control channel noise itself -- it sounds like an idling boat motor.

I'm listening to all this via the discriminator tap.
 

jonwienke

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Which is why I caveated marginal reception. With a good signal, the digital noise is the loudest thing you'll hear.

If you're using a discriminator tap, you're probably overloading the tap point. The hiss you describe is obviously not part of the original RF signal. Use a device with a higher input impedance to process the tap signal, or add a resistor between the tap point and whatever you're connecting to it. If one is already there, replace it with a larger one.
 

Airdorn

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Thanks! I'll try that.

Sent from my SAMSUNG-SM-G890A using Tapatalk
 

Ubbe

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The discriminator tap shouldn't behave differently if you scan or quick search.
The only thing I could think of is that the IF filters are changed during scan or search, FM and NFM mode.
In search you use the value set in the bandplan by Uniden, if you haven't edit it, and in scan it can be differently set when you manually program the frequency, or let the RR database do it for you.

/Ubbe
 
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