J-Pole Question

[airwaves3059]

What I am after is possibly increasing receiving distance of non repeater traffic... car to car, mobiles, I'm sure you get the idea. What it is for... I monitor my local city and county public safety frequencies that all operate in mostly VHF-High, for now anyway.

I found a website on how to make your own J-pole as I'd like to keep my cost down.
http://www.hamuniverse.com/jpole.html

My plans are to place it in the attic, and use RG-6 coax for a run of about 6 feet to my scanner. The roof is constructed of 1/2"plywood and asphalt shingles, so that should cut down reception to bad should it?

So my question mainly is will I possibly gain anything significant from this antenna configuration compared to just the standard screw-in-antenna before I waste my time and money.

Thank you.

 

[OceanaRadio]

A J-pole is a tunable antenna, made for a specific (or very narrow) range of frequencies.

Using 1/2" copper pipe for instance, after the material length is selected according to the desired frequency, the antenna can be fine-tuned to an exact 1:1 SWR match on a specific frequency. It is never intended to serve a wide range of frequencies (beyond +/- 2 or 3 MHz). Thus it would be a poor choice for use with a scanner unless all of the frequencies of interest were in one specific band.

I can recommend a J-Pole for the marine-band for instance, where it will serve that fairly narrow range of channels quite well and for much less than the cost of even a cheap (3dbi gain) marine antenna. Which incidentally are mostly junk and can be easily outperformed by a copper-pipe J-Pole. In other cases, a small ground-plane or wide-band (dipole) stick would probably outperform the J-Pole in spades.

Jack

 

[prcguy]

You can build a simple 1/4 wave ground plane and it will probably work as good if not better than a homebrew J-pole unless you have the equipment to tune the J-pole. You can make a ground plane from plans and it will usually not require tuning.
prcguy

A J-pole is a tunable antenna, made for a specific (or very narrow) range of frequencies.

Using 1/2" copper pipe for instance, after the material length is selected according to the desired frequency, the antenna can be fine-tuned to an exact 1:1 SWR match on a specific frequency. It is never intended to serve a wide range of frequencies (beyond +/- 2 or 3 MHz). Thus it would be a poor choice for use with a scanner unless all of the frequencies of interest were in one specific band.

I can recommend a J-Pole for the marine-band for instance, where it will serve that fairly narrow range of channels quite well and for much less than the cost of even a cheap (3dbi gain) marine antenna. Which incidentally are mostly junk and can be easily outperformed by a copper-pipe J-Pole. In other cases, a small ground-plane or wide-band (dipole) stick would probably outperform the J-Pole in spades.

Jack

 

[N1BHH]

What's with all these indoor antennas? Get it outside on the roof. That's the best place for it. Vent pipe mount, chimney straps, tripod or whatever else you can come up with. Indoor installations, no matter the construction of the building are attenuators. A simple mag mount on the air conditioner will work wonders.

 

[blueangel-eric]

What's with all these indoor antennas? Get it outside on the roof. That's the best place for it. Vent pipe mount, chimney straps, tripod or whatever else you can come up with. Indoor installations, no matter the construction of the building are attenuators. A simple mag mount on the air conditioner will work wonders.

I agree. people are too afraid to put stuff up even when they own their own house. people need to man up and put something outside. and then there are people that worry about vanity too much. can't put outside antennas up because the cable won't look good running on the side of the house. what the heck do people do in the old days before cable when there was an antenna on every other house and even now there's satellite dishes everywhere but people make a big deal out of radio antennas.

 

[prcguy]

Yea, put those antennas up outside and go for the "Best Scanner Antenna Farm for 2009" award.
prcguy