NYPD coming thru on 446.100mhz

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m1k3e221

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Hi all,

Heard something strange for the past few weeks. While scanning the 70cm band, I've been hearing the NYPD 120/121 station on 446.100mhz. Signal seems pretty weak but I clearly heard the station identify as WIM576. What's going on here?

Mike
 

ecps92

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Taxachusetts
Make/model of your scanner ?
I'm going for an Image [IF] of the actual frequency.
Hi all,

Heard something strange for the past few weeks. While scanning the 70cm band, I've been hearing the NYPD 120/121 station on 446.100mhz. Signal seems pretty weak but I clearly heard the station identify as WIM576. What's going on here?

Mike
 

wtp

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Port Charlotte FL
more questions

roughly how far away from you is the transmitter ?
is it a 24/7 thing or just some transmissions ?
that would take two receivers parked on the frequencies.
if you take the antenna off your radio, can you still hear the 482 freq ?
 

RFI-EMI-GUY

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Dec 22, 2013
Messages
4,328
Hi all,

Heard something strange for the past few weeks. While scanning the 70cm band, I've been hearing the NYPD 120/121 station on 446.100mhz. Signal seems pretty weak but I clearly heard the station identify as WIM576. What's going on here?

Mike
What model receiver do you have? What is the IF frequency? Which frequency from WIM576 is active when you hear this, is it 482.8875? You might be receiving an image frequency.

It would be odd that someone would re-transmit at 446.100 when they could tune it directly with most radios.
 

m1k3e221

Newbie
Joined
Jan 26, 2012
Messages
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Location
Staten Island
Make/model of your scanner ?
I'm going for an Image [IF] of the actual frequency.
BCD325P2, but I also heard it on my VX8GR. I’m not too far from the Staten Island Mall, maybe there’s a transmitter somewhere around here? I must be close because the original frequency comes through even without an antenna attached.

Mike
 

m1k3e221

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Jan 26, 2012
Messages
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Location
Staten Island
What model receiver do you have? What is the IF frequency? Which frequency from WIM576 is active when you hear this, is it 482.8875? You might be receiving an image frequency.

It would be odd that someone would re-transmit at 446.100 when they could tune it directly with most radios.
Yeah that’s the frequency I’m hearing. I must be close, the original frequency comes through even without an antenna attached. Also happened on my VX8GR.

Thanks to all for the replies!

Mike
 

RFI-EMI-GUY

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Yeah that’s the frequency I’m hearing. I must be close, the original frequency comes through even without an antenna attached. Also happened on my VX8GR.

Thanks to all for the replies!

Mike
I can't find the IF frequency for that model. Try this, check the manual for a feature called Intermediate Frequency Exchange (IFX) and toggle it. If the problem goes away it might be an image response.

If it doesn't, and given the actual 482.8875 MHz is so strong, it could be a signal mix with something around 36.7875 MHz (or any of several dozen possibilities) and reradiating at 446.100.

Questions,

Do you have another scanner operating at same time this occurs?

Does the signal on 446.100 have exactly the same "hang time" as 482.8875? If not, it could be a repeated signal.

Does the signal at 446.100 persist or go away? Does it ever sound garbled like a mix of other voice or tones ? (multiple transmitter IM)
 

m1k3e221

Newbie
Joined
Jan 26, 2012
Messages
4
Location
Staten Island
I can't find the IF frequency for that model. Try this, check the manual for a feature called Intermediate Frequency Exchange (IFX) and toggle it. If the problem goes away it might be an image response.

If it doesn't, and given the actual 482.8875 MHz is so strong, it could be a signal mix with something around 36.7875 MHz (or any of several dozen possibilities) and reradiating at 446.100.

Questions,

Do you have another scanner operating at same time this occurs?

Does the signal on 446.100 have exactly the same "hang time" as 482.8875? If not, it could be a repeated signal.

Does the signal at 446.100 persist or go away? Does it ever sound garbled like a mix of other voice or tones ? (multiple transmitter IM)
I think you figured it out. To clarify, I don’t hear the signal coming through on the VX8GR (but I am able to hear the original frequency without the antenna attached). When I enable IFX on the BCD325P2, it immediately stops coming thru. Didn’t know about that feature, pretty cool! Thanks for helping to explain things.

Mike
 

RFI-EMI-GUY

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Dec 22, 2013
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Glad to help. I wonder what the first IF frequency is for that scanner.

Sent from my SM-T350 using Tapatalk
 

N9JIG

Sheriff
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Far NW Valley
Glad to help. I wonder what the first IF frequency is for that scanner.

Sent from my SM-T350 using Tapatalk
Just ran across this thread...

I assume that the IF freqs are the same as the 996P2, while they are not listed in the 325 manual they are listed in the 996P2 manual as:

1st IF: 380.75 MHz. (for 25-320 and 806-1300) and 265.55 MHz. for 320-806
2nd IF: 10.8 MHz.
3rd IF 450 Hz.
 

RFI-EMI-GUY

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Just ran across this thread...

I assume that the IF freqs are the same as the 996P2, while they are not listed in the 325 manual they are listed in the 996P2 manual as:

1st IF: 380.75 MHz. (for 25-320 and 806-1300) and 265.55 MHz. for 320-806
2nd IF: 10.8 MHz.
3rd IF 450 Hz.
Definitely sounds like some sort of spurious response.So I ran some reverse IM calculations and the numbers are not revealing anything obvious using the expected LO frequency. I tried high and low side injection possibilities,The OP said he can receive the repeater on the desired frequency with the antenna removed, so the desired signal is strong enough to punch through the housing. It could be mixing with other oscillators in the radio, or perhaps even nearby equipment and radiating.
 

Analogrules

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I have heard FDNY rebroadcasted on 449.025 (the FDNY Ham Repeater Net) at times. But never public safety on 446.100. Also, 446.900 is an old N2BEI repeater out of Newark, NJ. But, I believe that repeater is still offline. The PL for that repeater was 141.3. Under which PL were you hearing NYPD?
 
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