Sorry I can't see if there is a way to reply specifically to the OP's
question on the reflector, so, I just put in the Subject.
Ok, I'm learning as I go, but I had a 250ft bog with variable
termination. I never saw that they are self terminating.
I used it more on the BCB than 160M, or 80M. But it was the quietest
of the three antennas I had up.
Unfortunately we had a hurricane and the owner of the property brought
in bulldozers and backhoes to clean up the property and my BOG is gone.
Here a comparison of the antenna in the BCB. Note: I'm in the panhande
of FLorida and there was a lightning storm out in the gulf. That is a
good test for me because that happens a lot.
I bought a Rig Experts AA-35 to measure my antenna. and built the
transformer accordingly. I don't recall the numbers and don't want to
look for them.
When I build another one, I'm going to compare a transformer to Dallas
Lankfords 2 FET amp. Find it on page 7 here,
There was a change of a resistor, this version has that change, the
820k as 1M, I think IP2 was increased with the 820k resistor.
The advantage of the 2 FET amp is it unloads the antenna, giving you 3
db more signal and it eliminates the impedance transformer as it has a
near 50 ohm output,
so then (not sure about this) you don't have voltage ratio of the
Impedance (stepdown) transformer, giving you another 10db voltage
increase. (correct me if I'm wrong)
Some impedance meters don't do well at 300 or 450 ohms, so you need
to wind a transformer meter, say a 450 to 50 ohm and then measure your
antenna, and crunch the numbers.
Something from reading all of Dallas Lankfords work on very
directional antennas, any feed line ingress destroys the pattern. His
solution was to use twisted speaker wire.
Now Cat5 or Cat6 wire is now being used. I was skeptical and did my own
test, running out 200 ft of RG58 and 200ft of twisted speaker wire. I
did 50 and 100 ohm terminations, opens and shorts.
The coax picked up more AM BCB signals and at much higher levels than
the twisted speaker wire. The speaker wire was pretty dead, from memory,
I think I only heard 3 local stations at very low levels.
So I used the twisted speaker wire and was very happy with my BOG.
I have had people say you had bad coax, you didn't terminate it
properly (I did) and other things. I would like to see a new thread on
just that subject. "Signal ingress, coax vs twisted speaker wire."
I'm in the process of getting data to build a new BOG. I want mine
usable from 500kHZ to 4MHz.
From my limited understanding inductive loading the antenna will help
to make it more directional at the 500 kHz frequency, but that same
loading well cause a poor pattern as the frequency increases.
(I'll start my own thread on this)
I had nine bead/sleeves spaced out along the length of my bog. I have
new info that my beads were far from optimal. I don't model, but would
love to have the information it provides.
Hope you glean a something from that, Mikek
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