Stainless is readily available, it's non rusting, and is also much
siffer than copper so you can use thinner wall. Downside is that it ahs
much higher resitance than copper, tends to mess up both the gain from
the antenna as well as the exact dimensions.
Stainless would work OK for a j pole. You probably couldnt notice the
difference by ear when operating at frequencies below 400 MHz.
It has always been my experience with HAM antennas that I wouldnt invest
much time in any design that wasnt close to *the best* performance. Copper
is really a good performer for antennas. Aluminum, is often a necessary
compromise. Stainless is great for automotive mounted antennas.
I suggest you post your question on Rec RadioAmatuer Antenna. There are
some *very* well informed guys there.
Would making the stainless steel j pole elements slightly larger in
diamter compared with a copper j pole plan over come the higher
I thou8ght about aluminum but dont have the capability to weld it. I
thought with stainless I could fishmouth the tubes and weld them
together. I am just thinking at this point.
What about using EMT tubing? Is this rust resistant? It is cheap and
light and easy to work with.
I love fooling around in my garage with stuff. I was wondering if it
was possible maybe to make a few bucks doing this as a hobby. I have a
seocond child due any day and money will soon start to be hard to come
Think this is a possibility? ANything else out there a guy could do in
his garage in his spare time to make a buck?
This is your project and you can use any material you want. But you have
no reason to *not* use copper because of the degradation of the electrical
characteristics when it gets tarnished. The RF resistance of the
tarnished looking copper wont be degraded.
I havent seen the post where you indicated the frequency this j-pole will
If your pervious post about making money by building j-pole antennas for
HAM use implies that you think there is a profit to be had by building
j-poles, I'd advise you to get the orders first.
I guess I meant I dont like the look of tarnished copper.
I thought maybe there would be some pocket change selling a few on ebay
or something but I dont know how you would ship a j pole. It would be
I am mainly wanting it for the two meter band and maybe 440. I would
like something I could put up and forget about for many years.
If I used 1/2 or 3/4 inch tubing in ss, how could I bend it?
Also, would an antenna made out of emt result in similar
characteristics of and identical one made of stainless? Does emt have
simialar charactieristics as ss?
As far as the money thing, I wlikme to build things with my hands in my
garage and have always wanted to find ways to make some money on the
side doing this but I dont have as many skills as a lot of you out
there. I have a baby coming any day now and with a family of 4 money is
hard to come by! Any of you guys have ideas? I am not wanting to get
rich but do something I enjoy on the weekends or so maybe to sell to
make some extra money. I always get ideas then talk myself out of it
thinking it wont work or someone else talks me out of it.
Since most people fab their own antennas from copper tubing, maybe you
could come up with some type of bracket to sell that would allow them
to easily mount the j-pole to a sidewall, roof, tree or chimney?
I am a HAM & a welder and machinist, most of my HAM friends are more
into electronics than metalworking and always asking me to fab crazy
shit for them for antenna masts and mounting, etc.
Try to think of stuff along those lines?
Stainless will not work very well compared to copper unless you plate
it. Way back when I knew of a guy that plated his 10 meter ss whip
antenna. silver over copper over nickel. ( I think he worked for bell
labs at murray Hill.) That antenna worked much better than the standard
10 meter whip...
Stainless will get hot with rf flowing through it or along the surface.
Ive seen it happen when ss bolts were used on a hi power rf feed
I tried building a stainless QFH antenna to pick up weather satellites but
the resistance is so much higher than copper that it turned out way off the
target 137 Mhz. I ended up with 1/4" hard wall ACR copper and nickle plated
it. If you want to try stainless McMaster has 50' rolls of 304 stainless
tube that bends pretty well.
I'm building a 45' cutter in strip/composite. Watch my progress (or lack
the resisatnce of the stainless is a pure resistance but it is in
parallel with the radiation resistance/ reactance causing a mismatch
with the transmission line with the associated standing waves. This
factor probably caused the off freq tuning since the transmission line
Many designers stay away from steel and nickel as antenna materials
because they generate passive intermodulation distortion. Probably not a
big concern for ham use. Mcmaster-Carr has stainless thinwall tubing.
Any bad metal to metal connection can act like a mixer diode and cause
intermodulation if other sources of rf are getting picked up by the
antenna. Some of the earlier ELT beacons were subject to that type of
problem. The adjacent channel signals would go from the antenna into
the freq. multiplier diode in the output and mix with other signals and
re radiate to cause interference on other channels.
Magnetic materials do not require an additional source of RF to generate
intermod because the material itself is nonlinear. A "rusty bolt" diode
doesn't need two sources of RF for the same reason.
The distortion and nonlinear problems occur when the iron is magneticly
saturated. This results in radiation of harmonics of the fundimental
frequency. When another signal is present you get intermod products.
The sum or difference of the two signals and of any modulation that in
on the signals. IF one signal is modulated by a 10kc. tone there wil be
a intermod product every 10kc. away from the fundimental signal at
Well, no. A look at a hysteresis curve as it passes through zero will
illustrate this. Google "passive intermodulation" and you can read why
you don't use stainless connectors when it matters. But I suspect that
I, along with (pick your favorite antenna textbook author)will not be
able to convince you of this. So we will again have to agree to disagree.
Or read the Trompeter connector catalog.
Most folks who gold-plate connectors use a nickel strike under
the gold. Ni, being ferromagnetic, causes problems with IMD on
extremely low-level signal lines. Trompeter took great pains
to develop a pulse plating process to put down gold on their
contacts *without* the Ni strike, to avoid this problem.
I found this out when I was trying to locate connectors with
very low remanent magnetization.
I also don't thing that plain copper tubing would work well
for an antenna, the skin effect will cause most of the rf
currents to flow along the tanished exterior. Solution might
be to paint the outside.
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