I have never modelled an inductively-loaded Beverage, but my intuition
is that it will not perform any better than an unloaded wire of the same
physical length.
I haven't modeled for 10 years and even then I was in the dark.
I started on this quest when I saw this W8JI page about inductively
loaded beverages, I thought why can't that work on a BOG.
http://www.w8ji.com/slinky_and_loaded_beverages.htm
There is discussion about having to much inductance which causes a
reversal of the receive direction. I also have some idea that the BOG
already
has a slowed VF because it is on the ground. So I don't how much more
inductance we could add.
On a forum, someone modeled my first BOG that I used #73 binocular
cores on, using one pass through one hole. This was about 1/2 of the
suggested value
that the model showed at 1MHz. Also the cores had a Q of less than 2!
It was suggested that the losses did more for the pattern than the
inductance.
The modeler also said that you need 70uH at 500kHz. The modeler did say
the inductors altered the pattern to some degree (I don't think he was
impressed),
He said, "At 1 MHz, front to back at 20 degrees elevation improves by
1.5 dB and gain drops by 6.6. dB. Elevation beamwidth drops by 9.6 degrees."
*However, *those numbers were with the values *I* used, they were not
optimized values.
I have no idea how much iteration the modeler did, I'm thinking not a
lot, he didn't concentrate on just my BOG, but I don't know that for sure.
It needs to be modeled. In the model. I don't know if it would best to
optimize the length for 4MHz and then load and terminate
for best 550kHz or, just make it as long as I can, 250ft in my case and
go from there. It may be a compromise in my case.(550kHz to 4MHz)
For you guys wanting 160M and as side benefit 80M, you might be able to
optimize on 80M and then load it for 160M and still get good results.
In the model as frequency goes down the size of the inductors must
increase to optimize, I expect the termination resistance also would change.
I envision two knobs, one adjusts termination value and one alters the
inductance of the nine inductors. Probably some interaction, so just adjust
them until you have the best S/N. Inductance may have a narrow range so
you could mark your adjustment on the scale for the frequency of interest.
I'd love some response to this, but if you don't have any, can you help
me with this.
How do you respond to a specific post?
I'm just clicking topband@contesting.com and then copy and pasting in
what I want. Is that the way it is done here?
I'm used to forums and newsgroups where you can quote at the push of a
button.
Thanks, Mike
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