Re: uwb antenna question

Rien Eradus PA0JME

Ok Kent thanks, I will forward this to him

Regards Rien

Op 25-5-2021 om 14:41 schreef KENT BRITAIN:

I can beat their prices!

The size of the circles determines the lowest frequency the antenna works at.

How narrow you can construct the slot between the two disks, or disk ground plane, determines the highest frequency the antenna works at.   

At the low it behaves like a fat dipole or 1/4 wave ground plane.

At the upper end it turns into two exponential slot, or Vivaldi antennas looking off to the sides.

So at the low end your have an omni pattern.transitioning to an oval pattern.

Properly done they never null.   I rate them to 26 GHz and that is really the frequency limit of the SMA connector.
With 'K' connectors they are commonly used at 35 GHz.

You can go down to Tesco or Poundland.   Look for some pizza pans about 40 to 50 cm across.  Mount them a millimter or two apart.  Solder your coax across that gap.  You now have a 2 Meter though 23 cm antenna.  13 cm if you are careful.       73  Kent WA5VJB/G8EMY              

PS The basic design goes back to the 1930's

On Tuesday, May 25, 2021, 03:21:29 AM CDT, Rien Eradus PA0JME <pa0jme1952@...> wrote:
Hi Ken, you might be right.
If one imagines some form of delay or phasingline, there are discrepancies.
The circumference of the outer loop should be a wavelength lambda, i.e. lambda = 2 x pi x R, and the opposite end should be fed by an 180 deg shift.
But it actually is 2 x R  (in which R= circle radius).  Using this ratio delay is 360deg/pi = about 115 deg
For the innercircles it is even fuzier.
Also the price is a bit high to my mind

Best regards Rien

Op 24-5-2021 om 21:53 schreef Ken G3YKI:
I suggest that the loops are mainly for decoration rather than function. A solid disc would work as a wideband antenna.

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