### Author Topic: An interesting old antenna (10dBi at 17° TOA)  (Read 931 times)

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#### A.Z.

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##### An interesting old antenna (10dBi at 17° TOA)
« on: January 12, 2022, 11:58:18 am »
Just stumbled upon an antenna design from P.Carr (N4PC) dating back to 1995 and describing a simple, cheap wire antenna offering a gain of about 10dBi with a takeoff angle around 17° from horizon and a feedpoint impedance in the 50 Ohm range; being interested I decided to model the thing using NEC and the results confirmed what reported in the Carr article (see attached PDF) showing that the antenna should be a pretty good "DX gun"

On the "cons" side, given the dimensions, such an antenna isn't really suitable for the "top bands", yet, for the bands from 17m up to 6m and for the VHF it will be viable, the antenna in object is made by stacking two horizontally "squished" quad loop elements one above the other and the performance of such a simple design is quite impressive; for further informations and pointers about this antenna, please see https://sites.google.com/site/wvfisher/hdoublebay

As for the NEC model I used, it's pretty raw, but if someone wants to fiddle a bit and run some simulations, here it is

Code: [Select]
CM --------------------------------------------------------------------CM H-DoubleBay https://sites.google.com/site/wvfisher/hdoublebayCM Note: according to the informations found at the above site, theCM optimal height for this antenna is the one which places the midCM junction at an height of about 1/2 lambda, also notice that theCM characteristic impedance of this antenna is about 50 OhmCM --------------------------------------------------------------------CE' calculated valuesSY freq=29.000                ' calculation frequencySY wire=0.00125               ' wire radiusSY conv=3.281                 ' feet-meters conversion factorSY wave=(300/freq)            ' wavelengthSY spcr=(110/freq)/conv       ' horizontal elementsSY vert=(365/freq)/conv       ' vertical elementsSY hspc=(spcr/2)              ' half horizontalSY hght=(wave*0.75)-vert      ' height of bottom from groundSY base=hght                  ' lower pointSY midp=base+vert             ' mid pointSY uppr=midp+vert             ' upper pointSY segm=51                    ' vertical segmentsSY segs=7                     ' horizontal segments' vertical elementsGW  1 segm -hspc 0 base -hspc 0 midp wireGW  2 segm -hspc 0 midp -hspc 0 uppr wireGW  3 segm  hspc 0 base  hspc 0 midp wireGW  4 segm  hspc 0 midp  hspc 0 uppr wire' horizontal elementsGW  5 segs -hspc 0 uppr  hspc 0 uppr wireGW  6 segs -hspc 0 midp  hspc 0 midp wireGW  7 segs -hspc 0 base  hspc 0 base wire' ground (real, standard)GE -1GN  2  0  0  0  13  0.005' loading (copper=58000000, aluminium=37700000)LD  5 0 0 0 58000000' feedpointEKEX  0  7  (segs/2)  0  1.  0  0' test frequencyFR  0  0  0  0  freq  0' end of modelEN
as a note, an alternate way of building such an antenna (other than the one described in the PDF) is to use a pair of "squidpoles" to support the antenna vertical sections, with such an approach the squidpoles will be almost free to swing in the wind and the antenna should be able to support even strong winds, then, some "T" support at the bottom could allow to rotate the antenna and aim it as desired

« Last Edit: January 12, 2022, 05:29:13 pm by A.Z. »

Smf