Another CHP question - explain how this happens!

[gmclam]

I am running a discone into my VHF low band scanner and picking up CHP from Chico to Merced and Truckee to San Francisco. I pick up cars in the Sacramento area most of the time as well. I only get signals on the EXTENDER frequency when a car is close to me. So far so good.

When this first happened I didn't think anything of it. Today it is happening almost non-stop. I am getting traffic on the EXTENDER frequency which does NOT appear on any Sacramento channels. I can hear the dispatcher ID herself as Sacramento.

I have a second scanner connected to the same discone (split 3dB to each scanner) and it does not have CT decoding. I get nothing on that scanner either while the EXTENDER channel chats away. In other words, it is not an issue with a missing CT or my receiver's decoding of such.

So how is this possible? I can ASSUME that there is a CHP car in my neighborhood and that's how/why I am receiving on the EXTENDER channel. But THAT car has to be receiving on a frequency which I am not. I have checked ALL CHP frequencies, mobile or base, regardless of where in the state they are assigned. I even tried a search in VHF low band. I can't receive 72MHz, but cars don't receive that anyway do they?

I am open to ideas or things to check. Thanks!

[antfreq]

Originally Posted by gmclam

I am running a discone into my VHF low band scanner and picking up CHP from Chico to Merced and Truckee to San Francisco. I pick up cars in the Sacramento area most of the time as well. I only get signals on the EXTENDER frequency when a car is close to me. So far so good.

When this first happened I didn't think anything of it. Today it is happening almost non-stop. I am getting traffic on the EXTENDER frequency which does NOT appear on any Sacramento channels. I can hear the dispatcher ID herself as Sacramento.

I have a second scanner connected to the same discone (split 3dB to each scanner) and it does not have CT decoding. I get nothing on that scanner either while the EXTENDER channel chats away. In other words, it is not an issue with a missing CT or my receiver's decoding of such.

So how is this possible? I can ASSUME that there is a CHP car in my neighborhood and that's how/why I am receiving on the EXTENDER channel. But THAT car has to be receiving on a frequency which I am not. I have checked ALL CHP frequencies, mobile or base, regardless of where in the state they are assigned. I even tried a search in VHF low band. I can't receive 72MHz, but cars don't receive that anyway do they?

I am open to ideas or things to check. Thanks!

Do the transmissions have that ticking noises like typical repeater freqs. I'm in the Carmichael-Arden Arcade area, what freq are you getting the transmissions?

[gmclam]

Originally Posted by antfreq

Do the transmissions have that ticking noises like typical repeater freqs. I'm in the Carmichael-Arden Arcade area, what freq are you getting the transmissions?

I get the "clicking" sound so I know it is the EXTENDER I am hearing - 154.905 MHz. I am near Hazel & Madison in Fair Oaks.

I will also note, that depending on which site they transmit from, I can pick up Black & Gold CHP base via Signal Stalker on my discone.

[antfreq]

Robertson / Eastern area - Not hearing anything at all.

[gmclam]

The EXTENDER frequency is short range. You must be near an office or a CHP auto to be receiving anything. At this moment there are no cars near me as well.

However, often during weekdays, I will pick up transmissions on the extender frequency which do not appear on any other assigned low band VHF frequency (regardless of CT). I am wondering how this is possible, unless the cars are receiving 72MHz or something like that.

[duster]

Originally Posted by gmclam

The EXTENDER frequency is short range. You must be near an office or a CHP auto to be receiving anything. At this moment there are no cars near me as well.

However, often during weekdays, I will pick up transmissions on the extender frequency which do not appear on any other assigned low band VHF frequency (regardless of CT). I am wondering how this is possible, unless the cars are receiving 72MHz or something like that.

Is the traffic "regular" traffic such as stops, status changes, etc, or is it just POSSIBLE that a special assignment unit is working off a discrete frequency pair that is not showing up in the database?

[gmclam]

Originally Posted by duster

Is the traffic "regular" traffic such as stops, status changes, etc, or is it just POSSIBLE that a special assignment unit is working off a discrete frequency pair that is not showing up in the database?

Yes it is regular traffic.

Keep in mind I also did a search function during this condition to try and find the frequency being received by the car, and repeated by the extender, and didn't find anything (so far).

I originally thought that perhaps they were just using a different CT, but that idea failed. Also, FWIW, I monitor the LIME and TAC channels as well as all of the "color" channels". My scanners are pretty much programmed statewide.

[avtarsingh]

i would check the BLUE


the blue channel is used a lot for saccats and many other ops - you might have had a car / undercover vehicle that was near you for a long period of time

so next time you hear it - also make sure you check the blue

[avtarsingh]

i forgot to explain my reasoning....

when they have ops on the blue there will be a dedicated dispatcher for the blue

and they do id as sacramento

[gmclam]

Originally Posted by avtarsingh

i forgot to explain my reasoning....

when they have ops on the blue there will be a dedicated dispatcher for the blue

and they do id as sacramento

I did check the BLUE frequencies (both car and dispatcher) with no required CT and there was nothing there. I am fairly certain this happens when there is a car in my neighborhood. But it is puzzling how the car is picking up the dispatcher and I am not. Keep in mind I am able to hear base channels for quite a distance in all directions and cars for a good distance too.

[avtarsingh]

hummm

i am sure you checked the gold and black

what about the green?

thats all thats left that is dispatched by sac

[gmclam]

Did you read all of my posts? Not only did I check all known channels & frequencies, and did so without requiring a specific CT; I also used the SEARCH function to look for new frequencies.

As I pointed out I am able to hear CHP for quite the distance, that's why I'd like to know the method/frequency of reception for a car down the street - at least what's being emitted on the extender frequency (154.905 MHz).

[avtarsingh]

the only way to find out what it is - is to listen closely and hope the dispatcher gives out the call sign

and search the call sign

[inigo88]

There's no reason the cars would be receiving 72 MHz - as far as I know these are limited to linking the dispatch center or area offices to the mountain top remote base transmitter/receivers. I could venture two guesses:

1.) Besides simulcasting, the dispatchers can individually select remote base transmitters. There's a *chance* they selected one out of range of you but not of the car. It could have been on the Blue running lower power or from a different mountain top than the other colors. However, this doesn't make much sense to me considering how well low band propogates and how flat Sacramento is...

2.) One of the new 44 MHz secondary channels? However you said normal traffic, and that you did a band scan of that area.

Interesting find!

[gmclam]

Originally Posted by inigo88

There's no reason the cars would be receiving 72 MHz - as far as I know these are limited to linking the dispatch center or area offices to the mountain top remote base transmitter/receivers.

It does not make sense to me either, unless it is not a standard patrol car I am picking up, but some sort of portable command post.

I could venture two guesses:

1.) Besides simulcasting, the dispatchers can individually select remote base transmitters. There's a *chance* they selected one out of range of you but not of the car. It could have been on the Blue running lower power or from a different mountain top than the other colors. However, this doesn't make much sense to me considering how well low band propogates and how flat Sacramento is...

Flat? LOL! I am in Fair Oaks, about 300 feet above the American River. I've got a good 'view' of the valley below me. This is one reason I get so good of reception including digital TV from San Francisco.

While I haven't jumped in my truck to check it out when this happens, I can just about guess where the car is parked which I am picking up on extender. It is 2 blocks from here as the radio waves travel. Considering that I am running a discone about 20 feet above the ground, and my house is on a slight hill, there's no where around here that a car could be higher than me to pick this signal up while I am not able to.

2.) One of the new 44 MHz secondary channels? However you said normal traffic, and that you did a band scan of that area.

Interesting find!

Actually, I have programmed the new frequencies in as well. I have not picked any traffic on them yet (but lots of atmospheric noise) but I keep monitoring. I don't expect regular traffic to appear on them before they make their line-up change next month.

[karldotcom]

Okay I reread the entire thread. This happened on Furlough Friday? Could you be picking up CHP units checking the closed DMV offices in Carmichael or Folsom? That are using the old State Police frequency of 460.375. There is a transmitter in Sacramento. I have heard them patch to a 42.xx frequency in SoCal from time to time...and during special events such as the Rose Parade.

ULS License - Public Safety Pool, Conventional License - WPMF457 - CALIFORNIA, STATE OF - Frequencies Summary

[gmclam]

Originally Posted by karldotcom

This happened on Furlough Friday?

It did but I've experienced the same thing on other days in the past.

Could you be picking up CHP units checking the closed DMV offices in Carmichael or Folsom? That are using the old State Police frequency of 460.375. There is a transmitter in Sacramento. I have heard them patch to a 42.xx frequency in SoCal from time to time...and during special events such as the Rose Parade.

Thanks, I'll check that one out. I do have the UHF CHP frequencies programmed, but did not specifically check to see if that was what was coming through the extender. Next time it happens I'll check them first.

[dougr1252]

The VHF extender signals can travel a lot farther than a few blocks under the right conditions. The extender(s) that you're hearing could be several miles away or more, especially if it's up in the foothills above you or if there are inversion layers. With a discone and a splitter your lowband reception may not be not good enough to hear whatever that CHP car is repeating. The radios they use are far better than any scanner too. Try a dedicated lowband antenna connected directly to a dedicated scanner or maybe an HF receiver and see if that solves the mystery.

[gmclam]

Originally Posted by dougr1252

The VHF extender signals can travel a lot farther than a few blocks under the right conditions. The extender(s) that you're hearing could be several miles away or more, especially if it's up in the foothills above you or if there are inversion layers.

The Gold channel is used at my immediate location, the Black channel is used less than 2 miles away, and up the hill they use Green. If I was getting the extender frequency from cars (not to mention offices) from those locations, I would know it. Most of the time, even during inversion layers, the extender channel is quiet here for me. It only becomes active when someone drives into my area.

During this condition I have paid a great amount of attention to the extender channel. The first thing I wonder is why my scanners stopped there and not the "home" channel. I have the CHP local channels programmed first, and the extender last. That means someone has to key up precisely between when my scanner leaves a local channel and before it leaves the extender channel. It does happen, but rarely.

In this situation I'll just lock one scanner on extender and go surfing with another. I typically get no CHP traffic on ANY low band frequency while the extender chats away " ... Sacramento ..."

With a discone and a splitter your lowband reception may not be not good enough to hear whatever that CHP car is repeating. The radios they use are far better than any scanner too. Try a dedicated lowband antenna connected directly to a dedicated scanner or maybe an HF receiver and see if that solves the mystery.

I do not doubt there are better setups for dedicated low band reception. But I am not buying into the fact that the signal being received nearby and repeated on a low power extender frequency is so low I am not picking it up. Keep in mind, as posted earlier, I have no problems picking up Golden Gate, Chico, Merced and Truckee as well as cars in the regional area.

[benca]

I'm just north of you (Hazel/Greenback) and all I've found on the extender ch from here is North Sac units, corresponding to the Gold.
When you hear the extender in question, are you hearing id's for 46 units, or 112 units or 107? or others?