Topband: An oddball question about a BOG.

[Grant Saviers]

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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