A buddy is going to install a M2 40m yagi [4-el] at 180'... and a 2nd
identical 40m yagi... at 89'.
The question is.. whether a upper /lower/BIP/BOP switch should be used... or
just a BIP/BOP ??
I don't have eznec... so bumbled my way through the maths... and it looks to me
that just a BIP /BOP switch is
all that is really required.
When this same array was up b4... it was at 161' for the top 40m yagi.. and 90'
for the lower yagi. At that time,
an AS stackmatch box was used.. and the 3 x available configs were
top/bottom/BIP [ NO BOP] For domestic usa
contacts, the BIP always outdid the lower ant by itself... which baffles me. [
hundreds of tests run]
The BIP always out performed the Upper by itself for all offshore dx
contacts. The BIP mode also was the loudest in W6 land..
a mere 800-1200 miles away !
Later on the AS box was removed... and replaced with a hb LC box. ..[ npo
doorknobs at left side.. and a series tubing coil, 50 ohms in
and 25 ohms out] At that point it was BIP only... and it worked very well.
This time around.. with the new 180'/89' config.... he is thinking of
re-configuring the LC box.. and adding ONE vac relay..and
one 1/2 wave of coax to enable BOP operation. [so it becomes BIP/BOP].
I'm convinced ...[on paper] that BIP will outperform
the top ant alone.. and that BOP will outperform the lower ant alone.
Another thought is to build a u/l/bip/bop box... but to enable
top/bottom/BIP/BOP will require 5 x vac relays,
and although doable... IMO... I think it's a waste of time. Station is located
in the pacific northwest.
If I have it anywhere correct... I believe the angle is slightly lower on the
top ant by itself [11 deg] VS the BIP Mode...[12 deg].. and even then
the BIP mode will have higher peak gain.. and cover a wider range of 'lowish
angles'.
Somebody must have gone through this b4... are we close to reality here ?
Does anybody else [on the west coast] have any experience with this?
Tnx........ Jim VE7RF
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