Re: Antenna that seem to defy common wisdom

Jim
 

I have built the PA0HNC mini whip, home brew version and it is fairly impressive. I didn’t do the SMD version.


On May 3, 2019, at 3:15 PM, Terry Morris <terry.kb8amz@...> wrote:

This is as exciting as bubble memory touted to be a break through in the 80's. That research is sitting on a shelf somewhere collecting dust. The experiment with the result of the 100 foot VLF test is more exciting for the testers. Extend that distance such as East coast to West coast and I would be more impressed.

Terry - KB8AMZ
Brimfield Twp, OH USA EN91hd
Linux User# 412308, Ubuntu User# 34905, PCARS#78, NAQCC#6668, QRP-ARCI#8855, SKCC#14195


On Fri, May 3, 2019 at 5:45 AM iz oos <and2oosiz2@...> wrote:

The last one, the active antenna is the so called mini-whip and makes sense. There are a few different designs with different transistor. It has to be installed very well, not necessarily very high, but needs a good ground. Otherwise you receive lots of noise. About fractional antenna, I don't know although I have heard about them 20y ago. For receive purpose I have been always impressed by the MTA passive antenna by RF-Systems. Maybe because it is installed well high on the roof but I still am amazed how it works for being just a 7 feet high vertical, from LF to 30mhz. So for receive there are good alternatives.

Il 03/mag/2019 10:52, "Tom, wb6b" <wb6b@...> ha scritto:
>
> Hi,
>
> It is common wisdom that the size, or capture area, of an antenna goes hand-in-hand with its efficiency in radiating or receiving radio waves.
>
> This was just mentioned in an ARRL newsletter. A piezoelectric VLF antenna.
>
> https://www6.slac.stanford.edu/news/2019-04-12-slac-develops-novel-compact-antenna-communicating-where-radios-fail.aspx
>
> So does this try to work by generating an extremely high voltage to try to pump energy into the high impedance that a fractional wavelength antenna, of conventional wisdom, would have into free space? Like a mini solid state Tesla coil, without all the wire and corona discharges?
>
> How about this. I read an article about efficient fractional wavelength antennas for a few hundred MHZ and up based on arrays of "Split-ring Resonators". Don't remember where the original article was, but here is the Wikipedia explanation. If you don't mind soldering together hundreds/thousands of loops of wire, maybe it would work at HF :)
>
> https://en.wikipedia.org/wiki/Split-ring_resonator
>
> And finally, more down to earth, here is an antenna I am going to try out as a receive only antenna, that goes counter to the capture area principle.
>
> http://transverters-store.com/whipinbox.htm
>
> I can understand how an active antenna with a high input impedance pre-amplifier with a little 2 inch piece of metal for the antenna element, might work acceptably in spite of the lack of efficiency, as a receive antenna. Although I won't count on this as my primary DX antenna. I'll likely use it a a secondary antenna for USB SDR receiver. 
>
> The first two antennas seem to groundbreaking, assuming the reality matches the perception given by the claims.
>
> Tom, wb6b
>
>
>  

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