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CHP Radio System Question

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pepsima1

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#1
So when I am in certain parts of Orange County I am having such a hard time picking up CHP Santa Ana and several other channels like San Juan Cap and Westminister.

Wouldn't you think that VHF low band would have a strong signal and bounce that signal all over the place?

Now if I am at home I have an antenna up 30 feet in my tree and I am able to receive all of the Orange County CHP and alot of the Los Angeles CHP channels too with no trouble.

Does anybody else have this trouble? Also, is there any solution to receive these channels better.

Also, what would be the best base home antenna and mobile antenna too.

Thanks
 

kearthfan101

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#2
Are you in your vehicle attempting to listen? Low band is terrible on a portable. You need a mobile with an external antenna to get the best reception. By the way.. don't use a rubber duck antenna.
 
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#3
The signal generally doesn't bounce - it's actually the reverse. Things get in the way of the lower frequencies, more so than UHF, for instance. Terrain affects VHF-low more so than others. Line of sight matters a lot!

Low band is terrible on most multiband mobile antennas too - I use a dedicated antenna cut to 42 mHz (and a dedicated scanner for that matter!) for the mobile. Optimally a 1/4 wave whip is great, but a base loaded antenna that's made for the band is good also.

For base monitoring, the more metal in the air the better - the ST-2 by Antennacraft works great for me. I have have the luxury of 2000 feet in elevation and a clear radio view to the south, so I can easily listen to Bay Area CHP offices from 100 miles away with it.
 
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#4
Wouldn't you think that VHF low band would have a strong signal and bounce that signal all over the place?
The signal strength itself isn't really the big issue as long as the signal is reaching you, but, especially with VHF low it's more about the wavelength and antenna length, as the other replies have mentioned.

With CHP's 39.44, for instance, the wavelength is about 299" or 25' (yes, feet) long. A 25-foot long anything isn't going to bounce around all that easily, especially indoors or in a car. 800 MHz signals, on the other hand have a wavelength a bit over a foot long, so you can probably envision them bouncing around all over the inside of your car or kitchen. Since quarter-wave antennas are pretty efficient and practical, VHF low works well with antennas 6' or shorter, usually bottom-loaded. And quarter-wave 800-band antennas do just fine a bit over 3" long.

Someone else can probably express this better than that, but that's my story and I'm stuck with it.
 
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#5
1/4 wave antennas have zero gain( gain=more signal recieved), you want a higher gain antenna if you want distance, most commercial high gains are 3db.. I prefer a dedicated antenna for VHF low like Laird CW-42 , but most do not have a dedicated antenna and radio for CHP. I also have an Austin Spectra antenna roof mounted in a NMO hole. Its works awesome, I highly recommend it if you want the best 4 band antenna on the market. Just my .02....
 

pepsima1

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#6
Thanks for all of the input when it comes to antenna's.

I think I am going to go and buy one of those ST-2 Antenna's. I have been reading a lot of forum posts on RR and everybody loves them. I am going to put a pre-amp on it too or a combo so I can run mutiple radios from one antenna. I want to make sure I do not get any db loss and have the most gain I can.

Looks like this antenna is the winner. I think using a 10 foot pole and put it on my second story chimmy and see what happens. I don't think I can go wrong.
 
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#7
No one has said it quite this way, the longer wave length frequencies bend with terrain, thus bending around and over much of the topography. They also bounce off the ionosphere when conditions are good causing problems such as the Missouri Highway Patrol interfering with the CHP at times. The advantage of using lower frequencies is their ability to cover more terrain with fewer remote base or repeater sites. In cities with tall buildings and inside large buildings low band VHF works poorly. High band VHF still has some ability to bend over terrain, but can also bounce a little bit. Moving up the spectrum results in less bending and more bouncing. Antennas can be shorter and more efficient as frequencies increase and wavelength decreases. That is how a cell phone, with its 800 MHz frequencies and internal antenna works inside buildings and in the concrete valleys of large cities.

Radio Lady: I've always been impressed with your knowledge of dispatching and radio use protocol and now I'm impressed with your knowledge of radio theory as well. I've often noted that radio users, even dispatchers, and most especially police officers don't know the basics of how radio works. Firefighters usually know far more than cops, but not near as much as most ham radio licensees.
 
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#8
No one has said it quite this way... Moving up the spectrum results in less bending and more bouncing.
I like that. And done with Accuracy, Brevity, and Clarity.

Radio Lady: I've always been impressed with your knowledge of dispatching and radio use protocol and now I'm impressed with your knowledge of radio theory as well. I've often noted that radio users, even dispatchers, and most especially police officers don't know the basics of how radio works. Firefighters usually know far more than cops, but not near as much as most ham radio licensees.
Well thank you. :wink: Everything I know about radio I picked up either directly or indirectly from my being an in-the-closet scanner buff. My adequacy in dispatching was helped, I like to think, by my near-obsessive listening to other agencies and their dispatchers both in Southern California and when traveling around the country. I picked up many little turns of phrase and other over-the-air efficiencies by listening to how things were done or said elsewhere. And just as often I heard things that really made me cringe and vow to never take back to work with me!

I agree about the end users usually knowing very little about how radio works, but to some extent I'm of two minds about that. As you doubtless know even better than I, those people are often busy enough with the crises in their faces (or ears) that when they push the button they just want the darn radio to transmit and the person on the other end to respond appropriately. But then, that immediately goes to the other side of it... your HT's gonna work better if the antenna is held vertically (if you're physically in position to do it). Your mention of firefighters reminds me of the fact that the LAFD's library does a better job of explaining radio basics than anything I ever saw at the PD. Fortunately in the last decade or so, LAPD has picked up several PSRs who are serious radio buffs, and supervision and management are recognizing their knowledge and skills and putting them in spots that make good use of them. There's always hope!
 
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KB6KGX

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#9
I know I’m late to the party, here, and I hope I don’t get censured for digging up an old thread, but…

With radio frequencies, the HIGHER in frequency you go, the MORE line-of-sight it becomes.

The primary reason why CHP has, with a few changes as a result of absorbing the old LASO 39 Mhz channels, has stayed on the same 42 Mhz system that they’ve had forever, is because the lower frequencies work better in covering the kind of area that they need to.

It would be nice if CA was like AZ, where the entire DPS (Department of Public Safety), AZ’s equivalent of our CHP, is all 460 Mhz repeater. You can hear the entire state from anywhere in the state. It’s great. Wish we had that.
 

PaulNDaOC

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#10
As a scanner buff I'm sure the AZ system was a wonderful listening option to have.

That being said I can't even imagine the justification for that kind of expenditure for the CHP with relation to necessity or the logistics required to launch it here.
 

KB6KGX

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#11
As a scanner buff I'm sure the AZ system was a wonderful listening option to have.

That being said I can't even imagine the justification for that kind of expenditure for the CHP with relation to necessity or the logistics required to launch it here.
True. The CHP system has been in place long before I started listening to them (started in the late 70s). As for AZ, a friend of mine lived in Phoenix and Prescott for 20+ years and monitored them ALL the time. Said it was a wonderful thing to be able to hear any part of the state from any other part of the state. You could be down in Tucson and hear the units up in Flagstaff. It was great. Everything clear. No static or interference.
 

W6XPA

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With a 1/4 wave antenna you need more of a ground plane where you mount that antenna though. 1/2 wave you can go with almost none. The metal mount it's on will do sometimes.
 
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