RadioBanter - View Single Post - SUPER J-POLE BEATS YAGI BY 1 dB

February 9th 05, 03:56 PM

On 8 Feb 2005 19:05:06 -0800, wrote:

wrote:

2 bays is big and heavy enough! 4 would be
a bit overkill in this situation.

Definitely! You try putting up a VHF
Super J-pole yourself! You are probably
more used to UHF, so 4 bays doesn't scare
you, but at the broadcast band, you will need
some serious help.

I have done both the super J-pole and 4 bays of Dipole
at both UHF and VHF. I've also tested the result with far better
hardware than you have. Beside being a ham I'm also commercial
licensed and have an extensive radio lab.

I would love to see what a 4 bay
would do though, but you need serious
bucks to do that, plus alot of manual
labor...

Your kidding right? I figure using both 1" copper water pipe, 1/2"
copper pipe and the various fittings to be cheap. How cheap?
Likely if you spent 50$us you spent too much for your materials.

He doesn't explicitely say brass in
his website, and looking at the picture, it
looks like a cheapie SO-239 made of pot metal.

Looks aren't everything. Also potmetal is not solderable
and his was. I'm normal so I have to test with a file to know
what material the connector is. I can never tell from picture.

It's a bad idea overall. I would
mount it with 4-40 nuts and bolts on
an aluminum plate, and then attach
that to the antenna.

You can but, you are making work thats not required
and you run into dissimilar metal electrolytic corrosion
and plain old rust. Water intrusion is the death of coax
most often. I've worked in marine environments
(salt is corrsive) so I have seen what works. Buy a
decent waterproof connector. I'd say Type N if your
really fussy.

I've had to take an antenna
down before, just to replace the
broken SO-239 that i used in this
way. Bad idea. You have to make
your antenna very physically strong,
unless you like to spend a lot of time
on your rooftop.

Mine have spend years on a real tower, roofs and other sometimes more
difficult places to reach. I don't like height so if I put it up
it's staying.

Yep, 3:1. Use light metal. Though using 1/2 inch copper is not as
heavy as it may seem as it's also structural. I have built them for
VHF too.

1/2" copper gets heavy with 2 bays, trust me.

Ah yes, you know all. Some day I"ll post a picture of the antenna
farm both UHF and VHF. Never minding the ones I've given away.
I know what type M and type L 1/2inch copper pipe weigh, do you?

Two bays would use approximately:

6 19" lengths of 1/2" copper (less than 5$)
4 1/2 inch pipe caps (usually less than 20 cents each)
1 10ft length (partial) of 3/4 copper water pipe for the mast (Runs
about 8$ last I paid for one)
2 1/2 inch tees ( 79 cents)
2 3/4" to 1/2" tees ( $1.49 expensive ones).

This is under 12 pounds and is self supporting to that height.
Plenty light enough for this girl. You could use Aluminum tube
to build this and really cut the weight.

Especially for something like the Super J.

Since the super-j doesnt offer the same performance your
claim is specious. As to structural, The super-J often fails
badly at the center insulator and the phasing loop as descrbed often
rarely makes the winter here in the east due to ice, wind and
snow. New England winters are harsh on antennas.

I also have a standard copper cactus Jpole for 6m/2m/70cm (it's only
14 ft tall) made with 1", 3/4" and 1/2 inch coppper. A really robust
antenna.

The rules are simple. Want more signal, put up more metal.

Or want more ERP, or a lower angle of radiation, put up more metal.

Same rules. If you understood antennas you'd know you do not get
increased ERP (or the reciprical, more signal) without concentrating
the RF field. Simply said, to do that requires more metal.

Allison