CHP and a 996P2

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amoking

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Friends,

WHAT IN THE HECK AM I MISSING HERE?

This is in my truck. Reception on P25 channels are rock solid but VHF (40 MHz) reception of CHP is non existent. This is certainly not my 1st rodeo as I have been scanning for years but this specific scanner is new to me. Even with squelch zeroed out I will get an occasional and static filled reception. I know there is chatter because I can hear the transmissions on my app on my phone...just hardly on my radio. I never seemed to have the issue with my 325 or 396.

BCD996P2 with current firmware.
Larsen NMO40B whip. Not cut to 40/42 however.
All of my freqs came right off of the RR database and loaded using freescan.
Quick keys are 'on'
RG8 cable on a 15' run
 

Whiskey3JMC

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Does reception differ if you remove the radios from the truck? Vehicles present numerous sources for RFI, this is particularly important as low band frequencies have a higher noise floor and are more susceptible to undesired interference generated by your vehicle
 

amoking

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Does reception differ if you remove the radios from the truck? Vehicles present numerous sources for RFI, this is particularly important as low band frequencies have a higher noise floor and are more susceptible to undesired interference generated by your vehicle
Interestingly, it seems that when I shut the truck off the reception increases. Still a lot of noise. This could be a coincidence however as now that the truck is off again for a 2nd time, there is no chatter.

I don't believe that an analog channel needs to 'settle in' like some digital channels do.
 

Randyk4661

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I have the same problem. My 996P2 won't pick up local CHP on the stock telescoping antenna, however sitting right next to it my 796D picks up CHP with no problems using the same telescoping antenna. will even pick up Los Angeles area CHP from Orange County.
I haven't tried the scanner in the car yet.
Seems like the 996P2 has poor sensitivity on low band?
 

gmclam

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Damn. An antenna designed for low band and having issues. I see the RF sensitivity is 0.3uV for all bands (NFM) except 72MHz.
(NFM) 40.840 MHz 0.3μV
(NFM) 53.980 MHz 0.3μV
(WFM) 54.050 MHz 0.6μV
(FM) 72.515 MHz 0.2μV


The only thing left is the coax and connectors from the antenna. Either the signal is not getting to the radio or the radio has issues.
 

amoking

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Damn. An antenna designed for low band and having issues. I see the RF sensitivity is 0.3uV for all bands (NFM) except 72MHz.
(NFM) 40.840 MHz 0.3μV
(NFM) 53.980 MHz 0.3μV
(WFM) 54.050 MHz 0.6μV
(FM) 72.515 MHz 0.2μV


The only thing left is the coax and connectors from the antenna. Either the signal is not getting to the radio or the radio has issues.
Again, on the 700/800 P25 stuff it's crystal clear. Maybe it's just the reception where I'm at today. Perhaps out on I-5 it'll be clearer.
 

jonwienke

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Any antenna designed for 700MHz isn't going to work well on low band.
 

jonwienke

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When scanning VHF low I use a whip. I have a different antenna for p25 stuff
Then this statement is invalid:
Again, on the 700/800 P25 stuff it's crystal clear.
The reception you get with a different antenna on a different band is irrelevant. It's possible your radio has low band reception issues, but much more likely that your low band antenna, coax, or connectors have a problem Especially if it's a mag mount.
 

gmclam

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Again, on the 700/800 P25 stuff it's crystal clear. Maybe it's just the reception where I'm at today. Perhaps out on I-5 it'll be clearer.
You could simply be in a dead area. Or there could some anomoly in the antenna which reduces its effectiveness on low band (shorted coil?). I could also see, although highly unlikely, some "short" in the coax/etc which effectively disconnects the antenna and turns the downlead into the antenna. It would work for 700 reasonably well.

To get to the bottom of this you need to switch things out, one at a time, and note the difference. What kind of reception do you get on a rubber ducky? Can you try some other antenna (with its own coax)? How about a different receiver on this antenna?
 

amoking

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Then this statement is invalid:

The reception you get with a different antenna on a different band is irrelevant. It's possible your radio has low band reception issues, but much more likely that your low band antenna, coax, or connectors have a problem Especially if it's a mag mount.
it's a hard mounted NMO now. I pulled the mast out of the base and re seated it. It dropped in a bit further beyond the 2 set screws. Seems to be a bit better. Sometimes the smallest tweaks can make a difference.
 

jonwienke

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A VNA/analyzer is probably a good idea at this point.
 

Elpablo

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I have the exact antenna and it works great on my hard mounted, NMO on my SUV with my SDS200 for CHP low band. Things to check are your CTCSS tones and your Service Types (Law Dispatch). I know this sounds basic, but I have been burned by these before. The mount could be an issue if you're not getting a significant ground plane (metal in all directions from the NMO). Mine is on the roof which provides a large ground plane.

I understand your frustration as I bought a base/NMO ground plane kit to use this antenna and I get so much noise on low band due to short (20") radials. The signal is great, but there's too much noise on the channel to understand what is being said. I am looking to add longer radial to fix it hopefully. Good luck and I hope you find a solution.
 

celbaseman

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Been using this to check out my antennas.
 

jonwienke

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Been using this to check out my antennas.
So am I. Highly recommended.
 
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