Cell Phone Antenna???

[steved]

Does anyone know of a source for a durable cell phone antenna?? Talking about external antennas...



I've been running a Wilson Trucker for several years, but they are anything but durable... I usually end up replacing them once or twice a year...



Looking for one that will mount to a typical "cb-type" mount (not a through-glass, as they wouldn't work in my application)... hopefully one with an all metal whip.



Anyone have a suggestion?? Or should I continue to replace the Wilsons??



Thanks in advance,

steved

 

[WTBurke]

Steved,

Any external antenna is better than nothing at 800Mhz to 1. 4 Ghz but, loss on the feed line is critical. Also avoid CB type mounting systems. Anything to do with a SO-239 RF connector above 30 Mhz has a pronounced impedance bump when viewed on a Time Domain Reflectometer. In fact PL-259's and SO-239's are real junk at 1 GHz. The losses you incur at these frequencies are phenomenal and technical finesse is a must to avoid these losses. Example: a gain 5/8 wave vertical @ 2 Db fed with 20 feet of cheap RG-58u @ 1 Ghz = minus 6 Db (approx for example only) your feed line loss exceeds the gain of the stick.



Motorola NMO flush mounts are ideal along with proper terminations in the N-connector category.



There are many good commercial antenna manufacturers out there Larsen, Db Inc. ect... . Many will provide some gain if properly mounted and fed with integrity. I mess with antennas all the time and SWR is not the only criteria. Besides that, monitoring RF at those frequencies require quite an investment or knowing the right guys who happen to have such equipment to evaluate your given installation.



If you just want to goof-off and do something on your own obtain a Motorola NMO mount and silver solider a good 38 caliber shell to the anode. It will work well as a near quarter wave and have the length diameter ratio for broad band low-Q response at those octaves. Anything will work... and a near quarter-wave will provide a very close match to 50 Ohms for most exciters.



Antennas are cool... . they are like a good set of exhaust extractors if fed and tuned correctly one can really excite the either on this planet.



William

 

[steved]

Thanks for that... probably more detailed info than I was asking!



I guess I just got to do a search to find one that will work in my location...



steved

 

[steved]

I found Wilson also makes an NMO base cell antenna... it appears short, and should allow the antenna to be removed if/when needed.



They also offer a "stubby" antenna for that mount... I might go that route. I need to get my antennas off my toolbox because I remove it all the time...



steved

 

[WTBurke]

Wilson makes good stuff and their NMO style mount would be a great choice due to the frequencies your dealing with. I'm sure you are operating the newer GSM cell systems and the wider frequency excursions have caused all the antenna manufacturers to pony-up on their designs. The very cool aspect of the NMO feeder mount will allow you to select many different styles of antennas because the NMO has become such a standard.



BTW to cut a hole for an NMO check out:

Audio and Video, Computer Parts, Batteries, Cable and Wiring at MCM Electronics



Search Part Number: 22-1340 (Antenna Hole Saw Kit)



It is a unique little hole-saw with a very short bit and guard ring. It will allow you to make a hole without over-cutting into headliners and it removes paint in a precise fashion for the NMO to make DC ground at the mount point. It does it all in no time and it's clean. All the professional land-mobile radio installers use these little jewels. I think it's around 20+ bux but well worth the investment.



William

 

[steved]

Wilson makes good stuff and their NMO style mount would be a great choice due to the frequencies your dealing with. I'm sure you are operating the newer GSM cell systems and the wider frequency excursions have caused all the antenna manufacturers to pony-up on their designs. The very cool aspect of the NMO feeder mount will allow you to select many different styles of antennas because the NMO has become such a standard.



BTW to cut a hole for an NMO check out:

Audio and Video, Computer Parts, Batteries, Cable and Wiring at MCM Electronics



Search Part Number: 22-1340 (Antenna Hole Saw Kit)



It is a unique little hole-saw with a very short bit and guard ring. It will allow you to make a hole without over-cutting into headliners and it removes paint in a precise fashion for the NMO to make DC ground at the mount point. It does it all in no time and it's clean. All the professional land-mobile radio installers use these little jewels. I think it's around 20+ bux but well worth the investment.



William

I'm looking at this one currently...



301104 - Wilson Cellular Dual-Band NMO (Permanent) Mount Cell Phone Antenna (Whip only) [W-301104] - $16. 95 : Wilson Cellular - Nielsen Communications, Authorized Wilson Electronics Dealer



or the identical, twin that is a 1/4 wave...



301105 - Wilson NMO 1/4 Wave Cellular Antenna [W-301105] - $12. 95 : Wilson Cellular - Nielsen Communications, Authorized Wilson Electronics Dealer



I'm not sure if one is better than the other...



Probably this mount...



901103 - 3/8 NMO w/ 14' RG58U Cable [W-901103] - $14. 95 : Wilson Cellular - Nielsen Communications, Authorized Wilson Electronics Dealer



Any insight??



steved

 

[WTBurke]

Good choices here. The 104 shows gain ratings in both bands and I'm assuming it's a 5/8's wave over a 1/4 wave to claim such gains at those frequencies.

I believe they have an error in the photos and I wasn't able to see the physical height dimensions of the two models. None the less, the 5/8 wave over a 1/4 wave would give the most gain but, it will be taller.



Now, the standard 1/4 wave decoupled into another 1/4 wave for the lower frequency would be shorter in size but don't rule this out.



Operating a "gain" vertical antenna at these frequencies places the majority of the RF radiation at the horizon for the added gain... and this is good. However; in the big city situation many cell sites are close and located on tall buildings. (San Francisco is an example) Hence, a short unity gain 1/4 wave can have an advantage when you are mobile and under or below the cell your working into. Yes, proper engineering at the cell site provides what they call down-tilt in the antenna's radiation foot-print but, this is the funny thing where a guy with a large gain antenna gets out performed by a stubby 1/4 wave unity antenna.



When I'm out in the boonies (Interstate 80, 40 miles out of Battle Mountain Nevada) I would want an antenna with a low angle of radiation at the horizon to hit the distant cell towers but, in the big cities I like the radiation pattern of a stubby to light up like a light bulb close in.



So I guess for DX go for the gain for local go for the stubby. The overall effect is subtle but, for full quieting into a cell site it would depend on where you do most of your driving while operating a cell phone.



William

 

[steved]

Mostly where I need it is out on the road, in weak signal areas... if I start to "lose" the tower, I can always "unplug"! I do a lot of midwest/south west work that has spotty coverage at best.

I have experienced the phenomenon you eluded to, my Wilson trucker would "lose" a tower up close (less than 1/4 mile), but I could talk fine without the antenna. I always wondered what caused that... I figured I might have been over-driving the cell tower (you know, limit the power reception to eliminate amplifiers)...

Looks like the 1/4 wave might be a "left-over" because Wilson no longer lists it anywhere. The other antenna seems to be the only one available... it is approximately 13 inches long.

steved

 

[WTBurke]

Steved,

Yes, your geographical area of driving would point more towards a 5/8's over a 1/4 wave for optimal gain at long distances. Also, the gain will help make up for some of the losses on the coaxial feed line. With a dimension of 13" at these frequencies that antenna should produce excellent gain characteristics.



Yes, close in proximity to certain cells can easily produce what you have experienced. Also, cells actually control the RF output of your transmitter so as you get closer the AGC (automatic gain control) of the receiver at the cell site begins a roll-back of your power into the system to prevent over load of the receiver and prevent multiplex distortion of digital signals within the passband of the receivers. Of course if your signal is below or out of the capture area of the receiver we loose the cell and the call is dropped. It is easy to see that if your relative field strength indicator on the phone shows "full tilt boogie" signal than you are transmitting with the least amount of RF power and your batteries last a long time. The weak-signal situation is where your batteries are being taxed at full level to run your transmitter at full scream. These things are only putting out micro-pharts anyways but, strong signals on receive means you are exposing yourself to less intense RF Giggy-wiggles and for longterm health this could be a good thing too. So... a good antenna promotes a healthy environment for the operator... as long as we a not standing near it.



If you want to get real crazy with this I would be pleased to make some radical suggestions for an extremely advanced antenna system for your mobile installation. Check out my "readers rig"... . I have a CTD wrapped around a competition HF platform. What I don't produce in horse-power from my CTD I make up for in RF hazards.



You know Steved, I know guys who can roll-coal into the windows of these sawed-off little rice rocket cars and it is funny... I can do a bit of smoke too but, I can sometimes really hurt their over-amplified sound systems electronically by bathing them in an extreme RF field... it is really fun to do.



sorry for getting carried away



William

 

[steved]

Steved,



You know Steved, I know guys who can roll-coal into the windows of these sawed-off little rice rocket cars and it is funny... I can do a bit of smoke too but, I can sometimes really hurt their over-amplified sound systems electronically by bathing them in an extreme RF field... it is really fun to do.



sorry for getting carried away



William

I had a 600-watt linear at one point... the look on their faces when *I* started talking through *their* stereo (at full boom mind you) was priceless!



I think this NMO antenna will suit the purpose nicely... removeable and a little more durable (being it will be mounted in the center of the rook and not the side of the bed)!!



Thanks for all the discussion, it really put some things into perspective.



steved