Part 15 AM Transmitting Antenna Question

Hi 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.

Hi 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.

Theoretically 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

Theoretically 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

I 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

I 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

If 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.

If 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.

I 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.

I 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.

I 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.

As 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.

Where do I send a five page write up on a experimental antenna?
JO RADIO

We 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.