On 9 Feb 2005 09:42:47 -0800, wrote:

What brand and model # field strength
meter do you have? Or did you build a
homemade RF rectifying "sniffer" amplified
with an Op-amp? Not saying the later
couldn't be calibrated correctly...

An older lampkin, and also a tuned RF sniffer
with gain (at RF) so I only need milliwatts.

Doesn't matter much as it can be performed with uncalibrated
instruments and a simple field reference by using a simple dipole
as a reference antenna first and do A:B comparisons. You don't need
absolute levels, only ratios for good accuracy.

Yeah, but you need a serious tower
to put 4 bays on, esp. at VHF, which we don't have
the money for.

The first tower was built for repeater site using EMT stacked one on
another with sleeve joints (poor mans swage) to 30 ft. Then I put the
4 stack dipole on that (its height was also 22ft VHF). It was done
for a commercial site that was to be temporary and cheap. Worked well
for nearly a year before we planted a DB products commercial 4 bay and
a telephone pole at that site when they decided to make it permanent.
Its about 10$ per ten feet to build and guy that arrangement.

Also, solder has VERY little
mechanical strength. Almost none.

It's a bad idea.

If the connector is holding weight then something else is wrong
as you would normally secure the cable to the supports. Strength
is not an issue then. Also most cut a small slot so the corner is
acutally in a grove, adds imensely to strength.

So then use a brass plate, and
stainless-steel 4-40 bolts and nuts.

Don't forget locking hardware as vibration and themal creep are
problems. You still get galvanic effects. Also drilling holes in the
structure to support the plate detracts from the structures strength.

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.


Opps! I meant to say 1" copper. 1/2" copper
is not strong enough for a VHF super J-pole.

But for the multibay dipole the 1/2 insections are only 19 iches and
very robust for that. The dipole portion could also be done with 1/4"
refrigeration tube as the structre is small.

Aluminum is not solderable.

Again your wrong. It's solderable but, you do have to know how and
use a decent heat source. Though bolted connections would work.

The Super J-pole at VHF is big, and
it's worse depending on how high you want
to get it.

Yes it is.

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.


We used a length of Delrin rod for the center
conductor, it's slightly flexible but ultra strong.
Don't use a wooden dowel coated w/epoxy, it will break.

Delrin works, not easily obtained and often not the right size
meaning a machine shop may be needed. Doesnt solve
the problem of the phasing loop sagging and failing.

The phasing loop was something like AWG#4
solid copper wire. Hasn't failed for 3 years,
but Ca. is a bit less harsh, indeed!

CA is timid save maybe for wind and mountain weather. The use of #4
CU is very heavy and adds to the problems. The problem in that case
is #4 has a low strength to weight ratio. Most use hard drawn 1/4"
copper or brass tube which is far more satisfactory.

Allison