Best Omni Directional Ant. for 800mhz

[teebee]

Besides the directional yagi what would be the best omni directional antenna for 800mhz. With all the systems surrounding me it is impossible to monitor all of them at once with one yagi pointing in one direction. When i want to monitor each system i have to go out and rotate the pole. I have considered purchasing several yagi's and pointing them in each direction with some type of splitter. But if a omni directional will perform just as great i will try that. Any recommendations on an omni directional would be great.

 

[teebee]

Forgot to mention "besides the rs discone, I have one never worked well for me at all."

 

[Grog]

A higher gain base antenna. Either a true base, or a NMO mobile on a "mobile to base converter".

I know antenex makes a dual coil 5db gain 800 NMO antenna.


The worst thing with this system, is that it does not pull in the signals you want. You can always use the nobile antenna as a mobile antenna (what are the odds ) and use the base converter with another mobile antenna, or as a temporary setup.

http://www.antenex.com

The retail price on a 6db gain base antenna is pretty steep. http://www.antenex.com/c_search.asp...amp;txtSubFamily=800/900+MHz+6+dB+GAIN+MODELS


I'd probably use the 5db mobile with the base converter.

Mobile to base converter http://www.antenex.com/c_search.asp...ly=MTB&selMarket=.&selApplication=...

Mobile 800/900 antennas are here http://www.antenex.com/c_search.asp...ily=ABA&txtSubFamily=800/900+MHz+ANTENNAS


Hope this helps.

 

[dwgelle]

If you are just gunning for the 800mHz band, and want the best. You may want to go to a radio dealer and buy a fiberglass 800mHz antenna. http://www.tessco.com/products/getProductInfo.do?sku=19714 or here is a monitor/scanner antenna http://www.tessco.com/products/getProductInfo.do?sku=482429

You may also be able to get by using a mobile 800mhz antenna as well.

just a couple ideas

 

[Grog]

Edit, quoted myself by accident :lol:

 

[JohnWayne]

I sell the Antenex 800MHz base antennas mentioned earlier in this thread. I have never had one complaint from my customers using them for scanning purposes, so it seems that work pretty well for that.

The 6dB version (FG8066) list price is $187.45, and I sell it for $145. You can check it out at http://shop.waltel.com/catalog/product_info.php/products_id/475 . I also have the 3dB and 0dB versions of the antenna as well.

You are really better off going with a real base antenna instead of a mobile used as a base. This is especially true if it is going on any sort of tower or on top of your house. The wind/rain/snow/ice will eventually kill the mobile antenna, and you will have wished you went with the real base antenna.

Besides the antenna, you will need some decent coax, connectors, grounding, etc.

Please feel free to email me at jeff@waltel.com or call me at 1-888-803-5595 and we can talk about what is best for you.

Thanks,
Jeff

 

[Tweekerbob]

You can also make one for about $10-$15.

Try one of these two links, take the money you save and buy yourself some nice coax, N connectors and you should have enough left over for a pitcher of margaritas. (Really good coax and really good connectors mandatory, margaritas optional) These are easy and QUICK to make. It actually takes longer to read the articles than it does to make it. But I would recommend reading it first though.

This is practically the same method they use to make those fancy fiberglass antennas, yet you get the satisfaction of sniffing the PVC glue along the way, and that is something money just can't buy.



First link

Second link

Also, don't get too carried away with the number of elements. This only works to an absolute max of 16 elements and actually the jury is still out as to how well that works. Stick to 4 or 8 elements and you will get solid performance.

Ryan

 

[fivestarr]

800 mhz dedicated antenna

Greetings,
Lots of good expertise posted above. I tend to go for the commercial antennas like the Waltel or something by Decibel -- the best quality turns out to be the best buy because you dont have to replace it every few years. Same goes for the feedline.

Instead of repeating myself, if you care to read my opinion, I have several posts in another thread in this forum: "improving my discone" along with pics.

That being said, I have used a 800 mhz "phantom antenna" mounted on the pole at about 30 feet. It is unity gain and therefore you *must* use good feedline to keep from losing the signal. I use .25 hardline (heliax).

I have 4-5 of these phantom antennas and I can send you one for ten bux postpaid.

 

[jay427]

Hey Tweekerbob

This is perfect timing, I just bought a PRO-96 and it needs a little help. The 800meg rubber duck only works on one side of the house (the side where the tower is) but not the other.

Nice post I did not think of a collinear for VHF, as a HAM I'm cheap so this is right up my alley. My question to you is did you do the 70cm version or did you scale it down for 860-900mhz?

I was looking at building one of the following and I bought most of the stuff but the collinear is so simple I may just build one first to see if works.

http://www.northcountryradio.com/Articles/crfl.htm

http://www.northcountryradio.com/Articles/discone.htm

BTW where is a good place to get some N connectors, everthing I have is PL259's

Jay, n0mdf

 

[Tweekerbob]

I tuned my down to 865 MHz, the math is all there. Two reasons for this, 1) length, a 440 antenna is twice as long. 2) 440 antennas suck on 860 MHz.

AESHAM.COM would be a good place to start for the N connectors, but I'll PM you a link for a co that primarily does RF connectors, once I find the link.

If you are careful with your measurements, you really shouldn't have to worry about tuning it. It has a wide enough band width that it should be close enough.

The discone probably won't give you enough gain to overcome the feedline loss. But the CR and the collinear are good bets.

Ryan

 

[DaveH]

Re: 800 mhz dedicated antenna

That being said, I have used a 800 mhz "phantom antenna" mounted on the pole at about 30 feet. It is unity gain and therefore you *must* use good feedline to keep from losing the signal. I use .25 hardline (heliax).

That is a "blade" antenna under a plastic radome. Actually, it looks like a UHF version. It is unity gain but requires a suitable ground plane, probably about a square foot. If you mount in on a pole with no ground, it would be better than nothing, but not even as good a unity ground-plane.

Dave

 

[Tweekerbob]

Dupe

 

[Tweekerbob]

DUPE

 

[jay427]

Tweekerbob

Thanks for the input, I made the antenna last night and I cut it for 870mhz. It works great. I did the 8 element ver. It brought the decode rate from 80% to 95-99% with the antenna leaning up against the wall.

I want to make this antenna using hard pipe. I found if I use 1/4" soft copper type "K" and 3/4" type "M" I can make 46.2 ohm feed line. The only thing I'm not sure of is the velocity factor, don't know if it would be .66 like coax? If I use 5/8 brass with a 1/4" brass rod that would make it 52 ohms but for the ease of getting the copper I would use that.

For the price of about a dozen faucet washers and (2) 10' pieses of pipe I could make some nice antennas if I can get the the math to work.


Jay, n0mdf

 

[N_Jay]

Tweekerbob

Thanks for the input, I made the antenna last night and I cut it for 870mhz. It works great. I did the 8 element ver. It brought the decode rate from 80% to 95-99% with the antenna leaning up against the wall.

I want to make this antenna using hard pipe. I found if I use 1/4" soft copper type "K" and 3/4" type "M" I can make 46.2 ohm feed line. The only thing I'm not sure of is the velocity factor, don't know if it would be .66 like coax? If I use 5/8 brass with a 1/4" brass rod that would make it 52 ohms but for the ease of getting the copper I would use that.

For the price of about a dozen faucet washers and (2) 10' pieses of pipe I could make some nice antennas if I can get the the math to work.


Jay, n0mdf

The velocity factor is dependant on teh dielectric, so if you are using pipe, I would start with ethe factor used for commercial "AIR DIELECTRIC" coax.

 

[jay427]

some times the answer is so simple if you can find the information. Will see if I can find the velocity factor on the web some place. will post what I find if anything.

Jay, n0mdf

 

[jay427]

looks like a velocity factor of about 85%, will try to build this weekend.

 

[bsavery]

Am I right that an 850Mhz, 8 element antenna would be just over 4 feet tall??

Can you mix element lengths? Say cut half for 850 and half for 450 ?

Hmmm...

Bob

 

[N_Jay]

Can you mix element lengths? Say cut half for 850 and half for 450 ?

Hmmm...

Bob

Ummmmm, . . . NO!

(edited to clean up what I meant)

 

[jay427]

You are correct the the height is a little lees then 4'

Jay