The "H-DoubleBay" antenna

Just stumbled upon an antenna design named "H-DoubleBay" (HDB) designed by P.Carr (N4PC) and dating back to 1995, the antenna is described in this article

https://sites.google.com/site/wvfisher/fwhdoublebayarticle.zip

and more infos about it can be found at this web site

https://sites.google.com/site/wvfisher/hdoublebay

basically, the antenna is a quad loop, squished on the horizontal side and with a second loop placed above the first one, the resulting antenna presents a gain around 10 dBi with a takeoff angle of about 17° over the horizon and with a feedpoint impedance of around 50 Ohm, this makes it a very good DX antenna, plus simplifies feeding since one will just need a 1:1 choke/balun (the coax is unbalanced, the antenna is balanced); also, the antenna is built using a bit of wire and some spacers so building it would be really cheap and easy.

On the "cons" side, given the overall size such an antenna won't be suitable for the "top bands", yet it will fit well if built for bands from the 17 meters up to the 6 meters and even for VHF, offering good radiation characteristics, also, the antenna could just be hung with the top tied to a tree branch (hello Harry !); so, in case someone is seeking for a DX antenna for the upper HF bands or for VHF, the HDB may be worth a check

As a note, I've tried simulating the antenna in NEC, and the results confirm the very good characteristic of the antenna, in case someone needs the NEC model here it is, just load it in 4NEC2 and give it a spin, change the "freq" as desired to recalculate the antenna for a different band (the model is for the 10 meters one)

Code:



CM --------------------------------------------------------------------
CM H-DoubleBay https://sites.google.com/site/wvfisher/hdoublebay
CM Note: according to the informations found at the above site, the
CM optimal height for this antenna is the one which places the mid
CM junction at an height of about 1/2 lambda, also notice that the
CM characteristic impedance of this antenna is about 50 Ohm
CM --------------------------------------------------------------------
CE

' symbols and calculated values
SY freq=29.000                ' calculation frequency
SY wire=0.00125              ' wire radius
SY conv=3.281                ' feet-meters conversion factor
SY wave=(300/freq)            ' wavelength
SY spcr=(110/freq)/conv      ' horizontal elements
SY vert=(365/freq)/conv      ' vertical elements
SY hspc=(spcr/2)              ' half horizontal
SY hght=(wave*0.75)-vert      ' height of bottom from ground
SY base=hght                  ' lower point
SY midp=base+vert            ' mid point
SY uppr=midp+vert            ' upper point
SY segm=51                    ' vertical segments
SY segs=7                    ' horizontal segments

' vertical elements
GW  1 segm -hspc 0 base -hspc 0 midp wire
GW  2 segm -hspc 0 midp -hspc 0 uppr wire
GW  3 segm  hspc 0 base  hspc 0 midp wire
GW  4 segm  hspc 0 midp  hspc 0 uppr wire

' horizontal elements
GW  5 segs -hspc 0 uppr  hspc 0 uppr wire
GW  6 segs -hspc 0 midp  hspc 0 midp wire
GW  7 segs -hspc 0 base  hspc 0 base wire

' ground (real, standard)
GE -1
GN  2  0  0  0  13  0.005

' loading (copper=58000000, aluminium=37700000)
LD  5 0 0 0 58000000

' feedpoint
EK
EX  0  7  (segs/2)  0  1.  0  0

' test frequency
FR  0  0  0  0  freq  0

' end of model
EN