Lots of questions, maybe a little bit of useful answers from me.
First, I doubt there is any BOG that will cover 8 octaves with a useful
pattern. Unobtanium, IMO.
Second, your question did cause me to investigate improving the RDF of a
240' BOG which is on my to try list. So using EZNEC/Pro4 I found a BOG
with 9x 20uH loads can improve the RDF to a little over 11db. That is a
nice improvement in the RDF value and it also lowered the peak gain to
25 deg (from 40 deg) and has much lower Z gain. I think worth trying.
BOG at +2.4", two 10' orthogonal radials at each end buried 2.4",
termination 1k ohm, two full cycles of current on the 16ga insulated
wire. Gain -26dbi. Having not traversed this modeling territory before,
the termination value does cause concern and it is a sensitive value +/-
10%.
Third, playing with the 240' model for 500KHz, 100uH 9x does yield
directivity and RDF around 8db with a 40 deg peak gain of -42dbi. So
there is no free lunch and it's possibly not a useful antenna at that
gain level. As I said at first, this antenna does not perform at higher
frequencies, e.g. 160m.
What real inductors will do re resistive losses is TBD. I have to
wonder why you chose the double E core with a gap geometry?
Grant KZ1W
On 8/23/2019 11:40 AM, Mikek wrote:
??I want a BOG that will have a proper pattern over 500kHz to 4Mhz.
??As I understand it,
"loaded Beverages show increased directivity because velocity of
propagation along the antenna is /*decreased*/."
I assume that is for antennas that are shorter than what is required for
that frequency.
Info from here, https://www.w8ji.com/slinky_and_loaded_beverages.htm
???? Is there any reason I can't load a BOG to make it directive at 500kHz?
My BOG length limit is 250ft.
Assuming the answer is yes.
If I do add the proper inductances along the length of the antenna
??then at 4MHz the pattern suffers. (previously I used nine inductors)
The inductance must be reduced as frequency goes up.
To that end I'm searching for a specific ferrite core geometry, like this,
https://www.dropbox.com/s/2bwsxrc58g51yu8/E%20Core%20Ferrire%20DB.jpg?dl=0
??Note, I dropped this and chipped the important part in the center, but
before that, it did what I wanted.
??This material was not good at the frequencies I'm interested in.
So I need a material good to at least 4MHs and with an AsubL of 2000 to
3000, or more, with a similar
geometry. Or any geometry that necks down to a smaller cross section.
Where can I buy such a core?
?????????????????????????????? Thanks, Mikek
??PS, if anyone here wants to model a 250ft bogit over that frequency
range, you would have my undying gratitude.
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