Rick (W-A-one-R-K-T) wrote:
You guys have suggested googling for "T2FD" and "TTFD" and I have done
that, but I haven't yet found anything that really lays out how to design
and build one of these things, what the formulas are, etc.

Actually I suggested you look at Heys book, or the second edition.
The original one had several pages complete with measurments, how
to build resistors from cheap low power ones and so on.

Obviously I'd like to do this a cheaply as possible and I do have a W2AU
4:1 balun sitting on the shelf here, so would 50 or 75 ohm coax, 4:1
balun, and anywhere from 300 to 390 ohms for the terminating resistor work
as well as a higher resistance value and a higher ratio, scarce, and more
expensive balun?

You can wind a 9:1 balun pretty easily, I found that for HF, you could
make one from torroids found in PC power supplies. I tested the ones
I made with a dummy load and ran some power into them. If they got
hot, I did not use them. :-)

However Heys does not suggest you use a 9:1 balun, he suggests a 4:1.

I have seen formulas, which I can no longer find, that say what the length
should be for a given minimum frequency, and what the spacing between the
conductors should be. I assume that the spacing of the conductors has a
lot to do with the balun ratio and terminating resistor.

While they are not extremely critical, they need to be pretty close.
If you change the geometry of the antenna, you change how it acts.
Too narrow and it becomes a folded dipole with a center load and
too wide it becomes a rhombic or rectangular loop.

Note that the antenna needs to be mounted at specific angle with a
a specific height from the ground. Changing them changes the way the
antenna works.

Captain G. L. Countryman, USN(W3HH*), who developed it, placed it over
conductive ground (the sea shore), but it seems to work well over
regular ground too.

I guess if I can find the length, conductor spacing, and terminating
resistor value needed for 2 MHz minimum and 4:1 W2AU balun I should be all
set.

That would be an awfully big antenna. However, I think you could
cut one for 3.5mHz and it would still work at 2. They do work
well at lower frequencies than they are cut.

From Heys' book:

For 1.8 mHz top length 182' 2" spacing between top and bottom 5' 5"".
For 3.6 mHz top length 91' 1" spacing 2'8"

He lists the height as being 35' above ground sloping to 5 feet for a
7mHz antenna and says it would be proportional, so a 3.5 mHz antenna
would need to be 70' up. The angle of the antenna is 30 degrees, from
the mast to the center of the spacer.

You probably could get away with a 7mHz version, (half of a 3.5
version).

Note that he also suggests using 75 Ohm coax,a 4:1 balun and a resistor
made of four rows of six 270 ohm 2w resistors for a 100 watt CW or
300 watt SSB transmitter.

I suggest that before you go any further you get a copy of the book.

Geoff.

* He was W3HH, his call has since been reassigned.

--
Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM
IL Voice: (07)-7424-1667 U.S. Voice: 1-215-821-1838
Visit my 'blog at http://geoffstechno.livejournal.com/