Vehicle Antenna Question

[Sccafire]

Right now I just use a standard 2 meter antenna from Larson. Is it possible or would it even be efficient to have 3 antennas for the scanner. I would get a low band for CHP 2m then an 800mghz. would I be able to do this? I've done some research and am new to the hobby. I have not found anything definitive one way or the other.


Thanks in Advance,

 

[mmckenna]

Yes, you can use a device called a diplexer to combine multiple antennas to one radio.

It can work well, especially in your case where you want CHP low band VHF coverage.

You might be better off with a simpler solution, though. There are antennas that will cover everything you want in one whip, but I've never used any of them, so I'll refrain from recommendations on those.

Using a dedicated low band VHF whip and a Larsen NMO-150-450-800 would be a good solution. Although some claim that the short whip works "pretty well" on low band. That would be two antennas connected to a diplexer set up with the right split, connected to your radio.

There are several other options you can do to make this work, but those are the easy ones.
Some other ideas…
A 5/8th's wave VHF High band antenna works as a 1/4 wave on VHF Low band.
Some colinear 800MHz antennas work well on VHF, UHF and 800.

 

[garys]

You would need a signal combiner to do that. You can do it, but it might be more cost effective to buy a good multi band scanner antenna.

 

[kb3isq]

If you can find one a Radio Shack 20-032 tri band works great, I have used one for many years and have not found a better antenna. I tried the Austin Spectra ( which is supposedly a very good antenna) did not work as good as the Radio Shack, plus it is a very ugly antenna.

 

[Sccafire]

If you can find one a Radio Shack 20-032 tri band works great, I have used one for many years and have not found a better antenna. I tried the Austin Spectra ( which is supposedly a very good antenna) did not work as good as the Radio Shack, plus it is a very ugly antenna.

I do have one of those already. I am looking for a permanent mount (NMO) style.


Everybody else, Thanks for the information so far

 

[kb3isq]

What I did was to get a NMO adapter that will accept the bottom rod of the 20-032.

 

[garys]

I did the same thing, although I found that the Hustler MOT worked better than the RS antenna when used in a NMO mount. The other advantage of the Hustler is that it's stainless and will last a long time. The RS antennas had a reputation for falling apart after a couple of years.

What I did was to get a NMO adapter that will accept the bottom rod of the 20-032.

 

[SOFA_KING]

I must have tried about every antenna made by A/S, Larsen, Maxrad, Radio Shack, Austin...etc. And did some real controlled testing on weak distant signals across many parts of each band to judge performance. It was always a compromise when it came to "one antenna for all". Coils may tune to certain parts of the bands you want to listen to, but often narrow parts of the bands with deep nulls in other parts of the bands. I got so frustrated trying to find ONE antenna that did it all, but never would, that I resorted to triplexers and diplexers and used a well tuned antenna on each band to feed one scanner. That works! But do you really have the room on the roof (the unobstructed place to realize all that effort) and the funds to put all that to task? And are signals so weak that you need that kind of "gain"?

I got tired of trying to max everything out, but I also didn't want deep nulls on any part of any band to almost block any reception there (the "coil" problem). Plus I noticed 800 gain antennas picked up more cell site interference and front-end overload than what was "gained". Most 800 systems are pretty strong in the intended coverage area anyway.

So what single antenna works for all in my car? A simple 19" (thick type) whip NMO. It's a wide-band 1/4 wave on VHF, and a 50 Ohm 3/4 wave on UHF...yet hears all my 800 stuff just fine. Want low band too? No problem! Just triple that length to 57" and the harmonic relationships still apply. Maxrad made a no coil NMO mount with a 3" spring and 54" thin whip that works perfect...and can also transmit on the 6 meter ham band with low VSWR. (Larsen and Antenna Specialists also made no-coil NMO mounts with shock prings for that extra legnth...no 54" whip though) Believe it or not, it still picks up my 800 stuff. Depending on if I want low band or not, I switch between those two antennas. In the winter I listen to State road trucks (plowing and salting roads) with the longer whip, and skip on low band in the summer. Any other time I usually use the smaller whip. NO COILS! Wide band! That works!

Phil

 

[KK4JUG]

......plus it is a very ugly antenna.

What makes an antenna "ugly." I mean, if it spelled out a bad word or looked like my ex-wife, I would understand but it's mostly just wire with an occasional coil mounted on it.

I never thought of an antenna as being "ugly."

 

[kb3isq]

Maybe I should have said unsightly! With the i1 inch can on the bottom.

 

[KK4JUG]

I see your point. All other things being equal, I'd probably take the RS, too.

 

[mmckenna]

So what single antenna works for all in my car? A simple 19" (thick type) whip NMO. It's a wide-band 1/4 wave on VHF, and a 50 Ohm 3/4 wave on UHF...yet hears all my 800 stuff just fine.

Yeah, they work pretty well. Putting one on an analyzer shows very broad band (<2:1SWR) from 144 up to 170MHz. 3/4 wave on UHF, as you stated.
I ran one with a dual band amateur radio for years, and never had an issue with performance.

I've tried recommending them to people, but I think most are swayed by good (bad?) advertising. Seems like the more coils, elements, do-dads and antenna has, the "more better" people think they are. Inflate the cost a bit and it seems like some believe the manufacturer has some secret sauce that makes them cheat the laws of physics.

If I was a nefarious type, I think I'd probably go into the magic antenna business. Seems like I could make a fortune off hobbyists. Add a bunch of loading coils, curly-q's, couple of whips sticking off at odd angles, and of course, magnet mount for those that can't get the wife's approval to drill a hole in the mini-van. Jack of the price and use some dubious gain numbers for good measure.

I do suspect the cellular interference you are experiencing is because of the antenna gain on 800. The 1/4 wave VHF would have less gain and less interference. Scanners are not the most selective receivers, too. With a commercial 800MHz radio with a good front end, it's not usually an issue.

 

[SOFA_KING]

Yeah, they work pretty well. Putting one on an analyzer shows very broad band (<2:1SWR) from 144 up to 170MHz. 3/4 wave on UHF, as you stated.
I ran one with a dual band amateur radio for years, and never had an issue with performance.

I've tried recommending them to people, but I think most are swayed by good (bad?) advertising. Seems like the more coils, elements, do-dads and antenna has, the "more better" people think they are. Inflate the cost a bit and it seems like some believe the manufacturer has some secret sauce that makes them cheat the laws of physics.

If I was a nefarious type, I think I'd probably go into the magic antenna business. Seems like I could make a fortune off hobbyists. Add a bunch of loading coils, curly-q's, couple of whips sticking off at odd angles, and of course, magnet mount for those that can't get the wife's approval to drill a hole in the mini-van. Jack of the price and use some dubious gain numbers for good measure.

I do suspect the cellular interference you are experiencing is because of the antenna gain on 800. The 1/4 wave VHF would have less gain and less interference. Scanners are not the most selective receivers, too. With a commercial 800MHz radio with a good front end, it's not usually an issue.

There you go. And don't forget to put 30' of RG-174 on it and call it "low loss" cable...especially on 800 MHz.

Hey, I'll admit it. Back in 73 those Lafayette catalogs had me dreaming of antennas with coils. I thought the coil must give the antenna "more power". And later in life I tried all those coil antennas, Then I started to learn that the coil was usually used to electrically shorten those antennas, which translated to less than unity gain. That's when manufactures used dBi figures to dupe people instead of something more honest like dBd...gain compared to a dipole...an honest reference point. Live and learn...hopefully!

True, coils can also be used to create co-linear antennas for gain, but then you have to learn about Q factors for bandwidth. And coils can also serve as traps for multi-band separation on a single antenna, but Q factors still apply. And let's not even get into radiation angles on those mega-coil gizmo things! (they usually won't disclose that, and you probably don't want to know anyway) After all is said and done, the simple whip works better and is usually cheaper.

Phil

 

[scottyhetzel]

The best is to run the new liard wideband vhf low which is what chp uses....than add 15xt dedicated to vhf low...

Next use the tri-band Antenna that Mckenna described on a 996xt...

No couplers...you can monitor both the same time... with dual radios. I myself run dual radios so I don&#8217;t miss much. It&#8217;s taken me years to figure this set up.

 

[JohnL999]

I've tried a bunch of different antennas over the past 30 years and the best one I've found is the ABSCANCS from Laird. I started using them when the company was Antenex and I've been impressed with the performance on all bands including VHF low. I'm originally from central CA and the performance on the CHP frequencies was very good.