Topband: fishbone and comb antennas

[Sam Dellit]

> Where can I see details of fishbone and comb antennas?? These are new
>terms to me.

g'day

i recall some detailed articles i think in an old RSGB handbook
but couldn't find a reference in a more recent edition
the arrl antenna handbook has about one page on the fishbone
my internet searches yield only dictionary entries
the comb is just half a fishbone
i know it is used a lot in microwave circuits, will have to keep digging
fishbone is a long linear array of coplanar dipoles, fed by a travelling
wave from one end and terminated at the far end
i have in mind a comb being a string of 10 insulated monopoles each 10
metres high and separated by 10 metres, fed by a single legth of high
velocity factor coax (to shield out the
surface wave), termination with a vactrol to allow good termination match &
maybe a little reflection to steer rearward nulls, the short electrical
length of each dipole with consequent high base reactance  should reduce
coupling into the feed line (and unwanted slowing of the wave) and also
minimise mutual impedance between elements (upon which this version of the
comb relies). the theory looks ok and should provide similar pickup to a
1000 metre beverage, but can't find any reference to them as yet and i can't
believe that a top antenna would have been overlooked by the topband gang
for so long. someone out there will have played with these for sure.

73s

sam dellit vk4zss







--
FAQ on WWW:               http://www.contesting.com/FAQ/topband
Submissions:              topband@contesting.com
Administrative requests:  topband-REQUEST@contesting.com
Problems:                 owner-topband@contesting.com