In a message to Wayne Sarosi  Rob Dennis wrote:
 RD> I found a small Basic program for LPDA's
 RD> that does most of the math for you if
 RD> you plug the proper values in for freq. spread and 2 constants.
 RD> Working on making a modification to the
 RD> program to save the data to a file and
 RD> print it out later for use.
 RD> My plans for an LPDA for 50.00 to 435.00 are slowly coming along.
 RD> IF I get it all calculated just right I
 RD> should be able to cover SSB\CW on 6m,
 RD> 2m and 70cm and save myself having three beams up the tower for SSB.
That is something I was going to do here except it would be for 50MHz
to 800 MHz. I want to constuct it so it sits on an AZ-EL rotor.
This way I can use it as a TV antenna, SSB antenna for 2m in the
horz plane and 2m & 67cm FM in the vertical plane. Then my entire
setup will be two LPs and a DXA. 
 RD> Now a question... Can LPDA's be
 RD> co-phased or stacked like a Yagi antenna ?
 RD> And if so would the phasing harness be
 RD> similiar in design using 75 ohm stubs
 RD> to set the phasing up ?
Exactly the same except with one problem. The BW on the LPAs and
the phasing harness at different frequencies. Oooo yeah. See, with
a yagi the BW is limited. Even with phased Dipoles the BW is limited.
But with an LPA the BW is great and the phasing harness that would
work at 50 MHz would be way-off at 450 MHz, unless ...
You cut the phaing harness just perfectly so that each band is a 
multiple of the other and it has to take into account the velocity factor
of the 75 ohm cable. That would be 50 MHz at a quarter wave times the Vf.
It would be slightly higher at 3/4 of a wave for 2m and pretty close
for 450 MHz at 1.5 waves. Take a slight cut off 6m and cut the phasing
harness for 49.5 MHz, X 3 is 148.5 MHz and X 3 is 445.5 MHz.
This will give you low end 6m, high end 2m and middle 67cm. It's
the best compromise. 
The LPDA for HF is up and running! 
Here's the SWR:
13.00 - 1.1:1  19.50 - 1.4:1  26.00 - 1.1:1
13.50 - 1.1:1  20.00 - 1.1:1  26.50 - 1.8:1
14.00 - 1.1:1  20.50 - 1.2:1  27.00 - 1.8:1
14.10 - 1.1:1  21.00 - 1.1:1  27.50 - 1.5:1
14.20 - 1.1:1  21.10 - 1.1:1  28.00 - 1.1:1
14.30 - 1.1:1  21.20 - 1.2:1  28.10 - 1.1:1
14.50 - 1.1:1  21.30 - 1.2:1  28.20 - 1.1:1
15.00 - 1.2:1  21.40 - 1.2:1  28.30 - 1.1:1
15.50 - 1.5:1  21.50 - 1.2:1  28.40 - 1.3:1
16.00 - 1.1:1  22.00 - 1.1:1  28.50 - 1.1:1
16.50 - 1.5:1  22.50 - 1.2:1  28.60 - 1.2:1
17.00 - 1.8:1  23.00 - 1.1:1  28.70 - 1.1:1
17.50 - 1.4:1  23.50 - 1.1:1  28.80 - 1.1:1
18.00 - 1.1:1  24.00 - 1.5:1  28.90 - 1.1:1
18.11 - 1.1:1  24.50 - 1.3:1  29.00 - 1.1:1
18.13 - 1.1:1  24.89 - 1.5:1  29.20 - 1.1:1
18.16 - 1.1:1  24.95 - 1.4:1  29.40 - 1.1:1
19.00 - 1.2:1  25.50 - 1.2:1  30.00 - 1.2:1
20m is basically flat, 17m is basically flat, 15m is surprizingly
flat since my roof flashing can run 40m without a tuner, 12m is
OK, 10m is just fine. All this with no tuner! So 17MHz and the low
end of CB are not that good but who cares. 
It took me six hours to put it up along with two problems; The end of
my longest element, which took the dive during the storm, snapped off
when I tried to straighten it out and an element interconnection
bar broke off at the screw hole. A patch here and a new piece there
and we're cruisin' HF again. Twenty-one trips on the 40-ft
tower. My legs feel like rubber tonight. What would that be ...
40 feet X (21 X 2) = 1680 feet of tower climbing today. That's like
climbing up the World Trade Center in NYC and more. 
Also found that my commercial FM 88-108 antenna and discone antenna need 
some work. Another day.
-WS
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