Need help getting accurate Rx here, advise please.

[Baskt_Case]

OK, just now hearing occasional comms from Green Co. first responders on 155.5500 but showing up as KY-11 Air Methods with a found DCS 025.

Something in my programming is causing goofy results here, I need someone to help me sort this...

1. Green County EMS (Analog)....155.557500....FM......DCS 025
2. Green County EMS (Digital).....155.557500....NFM ...NAC 556
3. KY-11 Air Methods Bedford......155.550000....NFM....found DCS 025 (Getting occasional Green Co. first responders here)

I feel like I need to change mode(s) on some of these but not sure what to do. Staring at it, I'm tempted to change 1 to NFM and 3 to FM, would this fix this situation?

Note: This is part of a longer thread already in the Kentucky Forum, just need some help on this particular situation.

 

[UPMan]

Likely that the 155.5575 transmssions are falling within the passband of your scanner when it is monitoring 155.55. If the KY-11 Air Methods group really doesn't use a tone, then the best you can do is either attenuate that channel or lock it out.

 

[Baskt_Case]

Likely that the 155.5575 transmssions are falling within the passband of your scanner when it is monitoring 155.55. If the KY-11 Air Methods group really doesn't use a tone, then the best you can do is either attenuate that channel or lock it out.

"Falling within the passband..." Thats why I was wondering if using NFM would help to remedy that situation. Would it not narrow the scope, focusing in on the desired target?

I'm still learning the technicalities of narrowband, it was my understanding that 155.5575 is inherently narrowband anyway, by nature of the 25KHz stepping being used. Or am I looking at this wrong?

 

[UPMan]

Your post says that you already have it set to NFM.

 

[Baskt_Case]

Ok UPMan, I think I understand...

Scanner is "looking" for 155.5500 NFM but "hearing" 155.5575 FM anyway and with no tone designated it has no other way to reject the "hit". Is that correct?

I will set the Attenuator flag for the Air Method group and see if that helps.

 

[n4yek]

I'm still learning the technicalities of narrowband, it was my understanding that 155.5575 is inherently narrowband anyway, by nature of the 25KHz stepping being used. Or am I looking at this wrong?

Your understanding of it is growing, but you still need some more help.
the step size is 7.5 KHz not 25 KHz between 155.5500 and 155.5575.

A 25 KHz step would look like this:
155.5000
155.5250
155.5750
155.6000

7.5 KHz step size looks like this:
155.5425
155.5500
155.5575
155.5650

Being that is the case, the frequency of 155.5575 will hear the frequency of 155.5500 and vice-verse when you monitor in analog mode. If they were both digital signals, you might be alright if they both were using 6.25 KHz bandwidth. But if they were using 12.5 KHz digital, they would still interfere with each other.
Have a Merry Christmas.

 

[Baskt_Case]

Thankyou N4YEK, I'm coming to better grip with these things everyday. I do understand so many of these concepts as they are explained to me but its more of trying to organize and memorize all of these things in my brain so that I can properly apply knowledge to pertinent situations. I guess what I'm trying to say is, the last few days I have been experiencing major information overload!

That being said, having the offending channel set to NFM and setting the Attenuator flag to ON for that channel as well, did not work. My HP-1 still occasionally stops on that channel while receiving other traffic. I do not know of any tone being used by said agency either, and transmissions from them being so far and few between, I will probably never discover it either.

Simple solution, dont monitor it. I've deleted it from my list. No biggie, at least I learned a few things.

 

[n4yek]

I learn something new everyday so don't expect to one day have all the knowledge you will ever need.