700 mhz trunking system (on a 396T)?

[ampulman]

Came across what sounded like a Motorola Type II control channel on 794.75xx on my PRO-106 (yes, I know). I realized it could have been an image.

I tried programming the CC into my 396T, using the MOT 800 Std mode and kept getting out of range errors. Tried using lower frequencies, but same result.

My firmware is the latest: 3.02.02. I was under the impression that that version included 700 systems. Am I wrong? Is there a way?

Yes, there is a way. Just found out that they are all P25 systems. Put in the CC and it's scanning, but probably just an image. Will update if any info.

Amp

 

[nd5y]

It is an image. 776-806 is the mobile/input part of the band. Base and control channels are 30 MHz lower. The 396T will work on 700 MHz P25 systems.

 

[Cmcadet]

I am in the DFW area and trying to listen to the new NCTCOG system on 770.83125. Apparently I have missed the part where my 396T allows me to put 3.125 Mhz steps into it. I have programmed 770.8312 into the scanner, but it doesn't work quite right. Does anyone know how to get the 396T to accept a 3.125 step or if Uniden will ever release a firmware that will allow this?

 

[nd5y]

You have the correct frequency entered.
The 396T display only shows 4 decimal places and it tunes 6.25 kHz steps not 3.125.
If it doesn't work right then something else is wrong.

 

[Cmcadet]

I went back and checked the frequency in the system and it still shows that I have 770.83125 programmed in, but the display while scanning only shows 770.8312. The control channel is a little scratchy but it says that it is searching for ID's no problem. What I am noticing is that when I connect the discriminator audio to Unitrunker the health of the signal ranges widely between 0 and 15, it never gets high enough to do anything with. I was just curious if there was a way to get the actual frequency plugged in so the audio would be better.

 

[mancow]

nd5y mentioned already that it doesn't display the last digit but the receiver is actually tuned to the correct frequency.

You discriminator issue sounds as if you are loading down the demod/discriminator circuit. Did you use a capacitor in the tap?

 

[Cmcadet]

No I didn't use a cap. I just have a straight wire. The discriminator audio works great on the Fort Worth Public safety system (800 Mhz Smartnet).

What else should I try? I have heard that Unitrunker really likes a strong clean signal for P25 systems, I have 3 to 4 signal bars on the 396 display, which should be enough.

I have attached a copy of what the scope looks like, not the traditional "Square Wave."

 

[Ablice]

I went back and checked the frequency in the system and it still shows that I have 770.83125 programmed in, but the display while scanning only shows 770.8312. The control channel is a little scratchy but it says that it is searching for ID's no problem. What I am noticing is that when I connect the discriminator audio to Unitrunker the health of the signal ranges widely between 0 and 15, it never gets high enough to do anything with. I was just curious if there was a way to get the actual frequency plugged in so the audio would be better.

The poster above you indicated the correct answer.

Your scanner cannot acquire the correct frequency because it cannot tune to a step that small.

EG: If you go in the HOLD screen, enter in 44.1. Now turn the mulitfunction knob clockwise. You'll see the step size is .01MHz (10kHz). This new 700MHz system would be the equivalent of having 44.1050MHz -- something you can't tune to because you have either 44.1000MHz or 44.1200MHz.

You could fiddle with the frequency and see which one works best, or get a scanner that can tune to that low of a kHz step. There was a new 700MHz system (I believe CHP) in CA which has a similar small step size. This is because of crowding and heavy competition along radio users for channels. Older radios are not as efficient as modern ones and cannot tune to such small steps accurately.

The higher the frequency, the smaller the step size (typically). Also, the reason for 4 digit decimal is for frequencies like 858.6125MHz. Although the 396T can't really resolve anything less than 12.5kHz at 1252.0000MHz (1.252GHz) range, that may not mean that there exists freqs with a smaller step than it can attain (such as 3.125kHz in the 700MHz band).