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Hi Everyone!
I really hope to be transmitting on
AM back in the Spring.I have a “Less than 3 Meters” copper
pipe that has served me for a long time.Hi Everyone!
I really hope to be transmitting on
AM back in the Spring.I have a “Less than 3 Meters” copper
pipe that has served me for a long time.But I was thinking about trying something
different – actually – something that weighed
less.I have some plastic pipes from the hardware
store that are about the same diameter.It would be easy to take a #18 wire and just
put it into the pipe and feed it in the usual manner.
But I don’t believe that would work as well as the copper
pipe. I think everybody agrees that thicker is better.Then I thought about putting 10 #18 wires
(for example) into the pipe. They would be soldered
together at the feed point and at the top.(I hope I am making this clear.) Anyway, I wonder
if this would be worth doing. I have had very good
luck with the copper pipe by itself. Is there any way
to know if the approach I mentioned would have
any advantage over just a single wire in the pipe?
And is there any way to know if it would approach
the performance of the copper pipe I have used up
to this point?Also – an unrelated question. If I have time, I would
like to change the name of my station in the spring.
So when I sign on here, I would like to have a different
station name at the top of the text and at the
bottom. So instead of “Micro1700” at the top, and
“Noise and Static Radio” at the bottom – it would be
something else. Is this hard to change?Thanks very much!
Bruce, MICRO1690/1700
Total posts : 45366Hi Bruce:
Your proposed multi-wire antenna in a pipe reminds me of that other thread where I spoke about a “Litz” antenna and a “cage -monopole,” which is just about what you have described.
But first, about the PVC pipe. I have read that some PVC pipe is less conductive, and thus more transparent to your RF signal. Make sure about that aspect.
Not having tested this sort of thing, but planning to do so, my early hunch is that your 10-wire antenna would: A.) Lower the impedance at the point where the transmitter connects, and B.) Improve the bandwidth much like a copper pipe.
It is my guess that you should keep each of the wires independent of the others by NOT soldering them together at the top, but we’ll see what others say.
Total posts : 45366Theoretically the bandwidth of a single wire would be narrower than that of a pipe but I have never noticed a difference. Due to the extra work and expense I would start with a single wire and observe what happens. (The Rangemaster, for example, uses a CB whip which is essentially comparable to a wire.)
The dielectric effect of plastic should not be an issue.
There is no need other than for support to solder the wires together at the top since all will be at equal potential at the ends so there will be no current from one to an other.
I once built a coaxial co-linear vertical for 2 meter work and had mechanical problems with PVC pipe. A ten foot length of sch. 40 3/4″ pipe was not very sturdy when supported only at the base.
Maybe a fiberglass hollow tube such as a fishing pole would work better than a pipe.
Neil
Total posts : 45366I am just looking for an easier way to
plunk a transmitter package into the
back yard, hook it up, and transmit.There is a lot going on here. That approach
might help me get back on AM. (Which is
really where the fun is, as far as I’m concerned.)By the way, I just found out recently that a
guy in Collinsville, CT had a Part 15 AM station
in his truck!!! And – it got out about a third
of a mile into car radios, which I think is really
good!I don’t think he is on the air anymore. But this
is what I have figured out by piecing different
stories together:It seems like he would produce programming at
home during the week. The programming went
onto cassette tape. Then on the weekends he
would drive his truck into a park (?) in town.He would raise the “3 or less meter stick” up on
the truck. Then he would lay down a bunch of
ground radials in the parking lot. Then he would
run the programing from a boombox into the
transmitter for most of the day on Saturday and
Sunday. I am told the transmitter looked
like a RangeMaster. People would listen in their
cars around the park and around town.He did this for a couple of years, but I think it is
over now.But it’s the first time I have ever heard of a
Part 15 AM station that came out of a truck!Best Wishes
Bruce, MICRO1690/1700
Total posts : 45366If you want a “fatter” radiator, try aluminum downspout pipe. It’s convieniently 10 feet long and roughly 3 inches in diameter.
You could stick the PVC in the ground (or on an elevated mast) and slip the downspout over it. A few screws or thru-bolts would secure it to the PVC. If you want to get fancy, use the PVC downspout adapters which would snuggly fit the downspout pipe. Of course that would take a bigger PVC pipe.
I built a 50 footer with downspout to use on 160 meters (1.8-2.0 mHz.) For the base I used a drywall bucket (with a drain hole) full of sand for weight. The plastic bucket insulated the antenna from ground. I put 3 nylon guy ropes at the middle and top and anchored them in pairs about 15 feet from the base. A homebrew tuner in Tupperware at the base tuned it up.
It lasted through the winter but a strong summer wind storm brought it down. Not bad for a temporary experimental antenna.
Total posts : 45366I have a 10-foot fiber rod but it seems to have a spiral of wire embedded all the way up and down which I think made it more of a shield when I put a wire inside of it. It worked alright with the wire held on the outside with painter’s tape.
Total posts : 45366I love antenna experiments, I’m not exactly sure why … some kinda psych thing I guess, similar to my fascination with microphone specs and things that fly in apparent defiance of conventional aeronautical engineering wisdom (just wasting a little internet bandwidth here ;))
My latest idea for a pickup truck involves a telescoping system, which is also length tunable and has a tunable loading coil on PVC form under the bottom section. Uses parachute cord for guys to the tie-downs on the pickup bed. The truck bed and body serve as its ground.
I already have most of the parts … now I just need a pickup truck 😉
The other is the “apartment antenna” which is a 3′ diameter pseudo-loop antenna made from common 3/4″ copper refrigerator tubing.
Total posts : 45366As a winter storm moves through I’m assembling an experiment based on the cage monopole idea discussed earlier. This will be indoors for obvious reasons.
It’s easy to visualize a physical antenna array in the head but never so easy to make it stand in space all by itself, so I’m using bamboo poles to build a tripod growing out of a triangular base made of pressed board, using wood glue and round-tooth-pick-dowels.
The tripod is around 6-feet standing up on top of a 30-inch wooden stool. Maybe a few tiny screws will add security.I’m doing FM with the Whole House 2.0 because of the more convenient lengths, and first will try a three wire cage, branching from a common feed point at the bottom, then try a four wire version. At a later stage I’ll add some ground plane elements pointing out horizontally to see how that changes things.
I can make fast excursions out into the freezing wind with a portable, but also indoor improvements are easy to notice since FM indoors doesn’t do well from room to room.
I’d had this three-leg-bamboo tower put up before, but the glue popped and it fell with a lot of clatter. This time more attention is being spent on securing the construction.
Total posts : 45366Where do I send a five page write up on a experimental antenna?
JO RADIO
Total posts : 45366We would love to see an experimental antenna report. Upload it to here by either scanning it or typing in the text and linking to the illustrations.
Other members may have other suggestions.
Total posts : 45366Hi JO,
Well, one way, especially if it contains graphic/pictorial images, might be to Save as a PDF (available in the Print window of almost any platform) and email it to me. I can upload it to my site and provide a URL here.
I’m thinking about doing this same thing with a bunch of PDFs, including my own forays into various aspects of radio, studio recording, aviation, and Bible research, although they will invariably give credit to sources.
Total posts : 45366P.S. — I guess the other way for here would be “Book Pages” under “Create Content” … haven’t tried it, though. Lemme take a stab at it …
Total posts : 45366Heven’t heard from Jo yet, but I created a multi-page PDF of the Medium Frequency Antenna stuff, and posted it here:
http://fhtinyradio.com/Library/DocLib/MediumFrequencyAntennas.pdfI… not perfect, but it’s functional.
I made a screenshot of each page as that’s how they were put on the site, saving each as a PDF, then I combined them with Apple’s free OS X app “Automator”. Went quickly.
… I’d be happy to do the same with Jo’s antenna write-up pages if I can get them.
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