2 Meter Horizonal Diple, suggestions

Status
Not open for further replies.

jon_k

Member
Joined
May 7, 2008
Messages
271
Location
Fort Worth, Republic of Texas
I've never used a dipole. Up until now it's been discones, Jpoles and verticle whips -- all store bought too.

However, I've got a unique situation with my vehicle in which I need to disguise and/or hide a 2 meter horizontally mounted dipole antenna. I am wondering if anyone here has any suggestions.

Is it best to build your own? Are there particularly good plans you suggest?

Is there any commercial solutions? (They make plenty of HF dipoles commercially.)

The real purpose for this is to mount a dipole on a bumper of a vehicle for APRS operation for a DIY lojack system.
 

zz0468

QRT
Banned
Joined
Feb 6, 2007
Messages
6,036
There is a commercially available 2 meter horizontal dipole antenna called a "halo", but you'd have to be pretty creative to disguise it. It's essentially a dipole folded into a circle. A two meter halo is roughly 10-12 inches in diameter. There are also plans out there to build them.

Can you be a bit more specific as to some of the limitations? Why does it need to be horizontal? Why does it need to be a dipole? Why does it need to be hidden?

Off the top of my head, you're best be might be a transit antenna, but with normal mounting, the polarization is predominantly vertical.
 

SAR923

Active Member
Joined
Dec 19, 2002
Messages
1,514
You could always get a license plate frame antenna if you're only trying to hit repeaters a few miles away. You can aslo do what a lot of underover cars do - mount a thin, black 1/4 wave antenna under the rear package shelf and just have the whip section stick out. Does APRS HAVE to be horizontally mounted? Seems like, if you're trying to do a poor man's Lojack, a vertically polarized antenna would transmit just fine for the ranges you'd need to find the car.
 

n4yek

Member
Joined
Apr 20, 2004
Messages
2,489
Location
Newport, Tennessee
If you mount your antenna horizontal, your signal will be attenuated drastically compared to the other radios your
a digipeating through since they are vertically polarized. This will make your APRS signal weak and possibly not heard
unless your were close in to another station running APRS. There can be as much, and possibly more, as 20db signal
difference between vertical and horizontal polarization.
With most thieves, they would not care if they saw an antenna sticking up in the air or not. If they want
your car, they will take it. I would just go ahead and mount a vertical antenna and not worry about stealth.
 
Last edited:

jon_k

Member
Joined
May 7, 2008
Messages
271
Location
Fort Worth, Republic of Texas
The APRS stations are all of versicle polarization so any radiowaves transmitted should best be vertically oriented.

I've heard of dipoles that can emit vertically oriented waves, when they're horizontally built in nature. The reason this caught my attention is the possibility of mounting the antenna under my dash, under the cowl of my hood, or under the plastic of the bumper became feasible.

I currently have a cellular look-alike 2 meter mounted vertically in one of the steak holes of my vehicle bed.

I've already tested several antennas horizontally oriented inside of the bumper, under the cowl of the bed, and several other out of sight locations. In such orientations I get lucky to hit 1 digipeater in the area every 4th location packet transmitted.

I was seeking ideas for very well hidden antennas without sacrificing range which oddly enough don't seem to coincide. I'm unsure what frequencies lojack operates on, but they have invisible antennas and yet in metro areas reception is good.

New to antennas other than verticle whips, so I'm welcome to some education.
 

zz0468

QRT
Banned
Joined
Feb 6, 2007
Messages
6,036
The APRS stations are all of versicle polarization so any radiowaves transmitted should best be vertically oriented.
Then you want a vertically polarized antenna.

I've heard of dipoles that can emit vertically oriented waves, when they're horizontally built in nature. The reason this caught my attention is the possibility of mounting the antenna under my dash, under the cowl of my hood, or under the plastic of the bumper became feasible.
I think there's something being lost in the translation. A horizontally mounted dipole will radiate a horizontally polarized signal. As for mounting under the dash, or under the hood, you're asking for trouble - engine and electrical noise being induced into the radio, and the radio inducing rf into the vehicle wiring (and computers). That's just a bad idea. Not to mention that the hood is a pretty nifty rf shield, being metal and all...

I currently have a cellular look-alike 2 meter mounted vertically in one of the steak holes of my vehicle bed.
So, use it.

I've already tested several antennas horizontally oriented inside of the bumper, under the cowl of the bed, and several other out of sight locations. In such orientations I get lucky to hit 1 digipeater in the area every 4th location packet transmitted.
That's about what I would expect.

I was seeking ideas for very well hidden antennas without sacrificing range which oddly enough don't seem to coincide.
A good observation. There ARE commercial stealth antennas out there. Try STI-CO.

I'm unsure what frequencies lojack operates on, but they have invisible antennas and yet in metro areas reception is good.
Lojack operates on vhf highband. Reception may not be as good as you think. They rely on nearby police vehicles to find them.
 
Status
Not open for further replies.
Top