ILMRadioMan
Member
Picking up some law dispatch on 475.15
Any ideas?
Any ideas?
475.15 Dispatch?
- Thread starter ILMRadioMan
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whitehelmet1202
Member
Interesting...
Perhaps what you are hearing is an image?
What is the IF of your receiver?
It is possible that you could be receiving Bladen County SO Dispatch, which is on 453.775, which could produce in image at 475.175 using a 10.7 Mhz IF in your receiver...
Holden Beach does have a repeater licensed for 453.750 which would work out to an image of 475.150.
Just a thought.....
Perhaps what you are hearing is an image?
What is the IF of your receiver?
It is possible that you could be receiving Bladen County SO Dispatch, which is on 453.775, which could produce in image at 475.175 using a 10.7 Mhz IF in your receiver...
Holden Beach does have a repeater licensed for 453.750 which would work out to an image of 475.150.
Just a thought.....
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ILMRadioMan
Member
Excellent point.
I hadnt even thought of images.
Man, this is why I am glad I picked up that old scanner...it gives me an oppurtunity to think about all the RF characteristics that you just never mess with when you are working with these engineered systems.
I mean, yea it can happen...it just rarely does.
I hadnt even thought of images.
Man, this is why I am glad I picked up that old scanner...it gives me an oppurtunity to think about all the RF characteristics that you just never mess with when you are working with these engineered systems.
I mean, yea it can happen...it just rarely does.
KE4ZNR
Radio Geek
nozman hit the nail on the head...If I was Pete Rose and a betting man I would put money on an image...it happens...hopefully the better filtering in the radio the less images but it happens in even triple conversion radios...
Marshall KE4ZNR
Marshall KE4ZNR
ILMRadioMan
Member
Well like I said, this is a Pro-2056. Its old. I have no idea what the filter is.
But also like I said, I love it. It gets me to flex my mind muscle to use these specific RF theories that you just dont use as much.
But also like I said, I love it. It gets me to flex my mind muscle to use these specific RF theories that you just dont use as much.
whitehelmet1202
Member
See, I am good for something. I haven't used alot of my radio skills lately, but this one got me going again,
The Pro-2056 has a first IF of 10.8 MHz and a 2nd IF of 450 kHz.
So, with a receive frequency of 475.15, minus twice the IF, you have the following:
f=475.150
if=10.8
af=actual frequency
use the following equation: af=475.150-(if x 2)
you have a true frequency of 453.550, which is the UHF side of the Pender County Law Dispatch system, a simulcast of dispatch traffic from the Viper TG 21856 (5560).
Mystery solved....
Man, I wish I was still a radio tech....
The Pro-2056 has a first IF of 10.8 MHz and a 2nd IF of 450 kHz.
So, with a receive frequency of 475.15, minus twice the IF, you have the following:
f=475.150
if=10.8
af=actual frequency
use the following equation: af=475.150-(if x 2)
you have a true frequency of 453.550, which is the UHF side of the Pender County Law Dispatch system, a simulcast of dispatch traffic from the Viper TG 21856 (5560).
Mystery solved....
Man, I wish I was still a radio tech....
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ILMRadioMan
Member
I agree with your science, but here is the thing.
I listen to Pender Law regularly, and the call signs for the units AND for dispatch were not Pender.
So I am sure the IF has ALOT to do with it, now that I think about it, but I am positive it wasnt Pender.
Dispatch was called as T-Com or C-Com...I couldnt clearly make it out.
I listen to Pender Law regularly, and the call signs for the units AND for dispatch were not Pender.
So I am sure the IF has ALOT to do with it, now that I think about it, but I am positive it wasnt Pender.
Dispatch was called as T-Com or C-Com...I couldnt clearly make it out.
whitehelmet1202
Member
453.55 is the low side image, with the high side image being 496.75, depending on how the receiver is designed.
This one has me thinking now.
I no longer listen to Pender Law on the UHF side on a scanner, since I monitor them on VIPER now.
I know there has been some distant stations coming in on 453.550 this time of year and sometimes their signal is stronger than Pender's...
SOme random thoughts/bits of info:
I know Robeson County has a repeater on 453.550 with a PL of 85.4, listed as Law 1 (I think they used to use C-Com as the name for dispatch)
Davie County has a repeater on 453.550 with a PL of 173.8, listed as Law Dispatch
Fayetteville PD used to have a channel on 453.550 back before they switched to their TRS.
The CIty of Nashville (Nash Co) has a freq of 453.550 licensed as well...
Stokes County also has some stuff licensed on 453.550...
I would assume the scanner is designed with low side conversion, since high side conversion would bring the actual frequency to 496.75, and I don't know of anything around here on that frequency...
This one has me thinking now.
I no longer listen to Pender Law on the UHF side on a scanner, since I monitor them on VIPER now.
I know there has been some distant stations coming in on 453.550 this time of year and sometimes their signal is stronger than Pender's...
SOme random thoughts/bits of info:
I know Robeson County has a repeater on 453.550 with a PL of 85.4, listed as Law 1 (I think they used to use C-Com as the name for dispatch)
Davie County has a repeater on 453.550 with a PL of 173.8, listed as Law Dispatch
Fayetteville PD used to have a channel on 453.550 back before they switched to their TRS.
The CIty of Nashville (Nash Co) has a freq of 453.550 licensed as well...
Stokes County also has some stuff licensed on 453.550...
I would assume the scanner is designed with low side conversion, since high side conversion would bring the actual frequency to 496.75, and I don't know of anything around here on that frequency...
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