OK, I think I understand ... in order to form a perfect circle, you'd have to have an infinite number of segments/turn to get the same area, and the software doesn't allow that.
So, is a round tube necessarily a better choice than a square tube (efficiency-wise) as a coil form?
As I mentioned, even the recyle yard wants about $10/ft for 12" PVC drain pipe. With that in mind, can I build an adequate form for making reasonably accurate tests with a square form? If not, how can I estimate how many polygon sides would suffice for the area to reach close enough to the model to work as expected?
... It also appears that a helical antenna needs to be frequency-spec-tuned at build time. A helical receiving antenna could be much more broadband than a TX antenna ... correct?
That means each transmitting helical coil antenna would have to be more or less hard-tuned to the frequency of choice. I guess peak resonance could then be achieved with a large (low resistance) limited-range variable air cap.
Am right about any of that, or am I imagining things from outside the park?
For my part, the reason for all of this inquiry into cage monopoles and helical antennas is because it's way past haul-out time for my boat (home and floating transmitter shack). It''l be out for at least a week, but I want very much to stay on the air during that time.
That means I must come up with an efficient transmitter with nowhere near the available RF grounding I have now. It'll have to be at my studio, which has no dirt surface, and, worse, it'll have to be right in front of the building, because the landlord won't allow me to attach anything to the tile roof.
There is a 25' x 100' island with turf (well, it's not been properly cared for and mostly dandelions now) in the middle of the parking area, but I'd have to dig up asphalt (also a no-no) to get wires out to it, or build a totally wireless system ... which I don't want to spend $$ on right now (other priorities, extremely limited funds).
I could drive a couple ground rods between the asphalt and the concrete walk area that butts the building, but that's about it.
Still looking for other solutions ... TIA ...
How about putting a car/boat battery, your transmitter, a digital audio player and a temporary antenna on a hand truck and wheeling it out to the grass island in the morning? Put a temporary ground rod or four into the island and run the station all day. Then, wheel it back in and hook it up to the battery charger at night then wheel it out in the morning again.
That might keep you on the air until you get back on the water...
The idea of wheeling a station outside in the
morning and bringing it in at night is a very
unique and interesting idea. It would permit
RF experimentation without having to worry
about the studio. (Or a link TO the studio,
if you had the programming on an MP3 player.)
Most of my longwave broadcast band DXing on
153 -285 kHz was done with the radio outside.
Sometimes I have left it out all night long. This
was done to get away from RF interference in the
house. One of my favorite stations is from Iceland
on 189 kHz. I transmitted the audio back into the
house on 88.3 MHz. These guys have great folk music and a
really cool language. I bet they have no idea that
sometimes there has been a listener in Connecticut.
Getting back to the idea of bringing the station out
and leaving it there- makes me think of my SS-Tran
AMT-3000. I used to know how much current it
draws, but now I can't remember. I think it will run
on 18 volts AC or 20 volts DC.
Of course the set-up would have to be in a safe place,
and be protected from the elements. This is not too
different from the Part 15 station in Colinsville, CT
that runs completely from a parked truck. He drives
it out in the morning and brings it back at night.
(This is a weekend operation.)
I wonder...
Bruce,
MICRO1690/1700
Many thanks for suggestions ...
The boat will be out of the water for probably a week.
FWIW, my station serves the community with live updates, local news, weather, ferry reports. I'm on the air live quite often, plus the station runs 24/7 with NOAA Weather overnight. Also, I run a few ads, which I'm responsible for, and one requires updates ... so running an MP3 player (or whatever) isn't an option.
I'll have to measure the draw over time to see if I can get a couple utility batteries (one running and one charging) and an inverter to run the iBook, uplink, and TX continuously for a week. I might as well check out building a solar charger too.