Yet another alternative is the coax cable bidirectional Beverage
described by ON4UN (see fig 7-118 in the 5th edition). I've built a
couple of them with ok results. Various small (cheap) coax can be used,
mine were ebay surplus Belden RG59. RG6 is also a good choice. With a
copperweld center conductor it is pretty tough for runs amongst the
trees. On 160 or 80 it's hard to fault the performance of all of the
small coax's. Another advantage is no relays in the weather but a
downside is two feedlines although that is much to my taste rather than
building open wire line spacers, etc and the problems that come with
insulators, debris, and wet weather. A couple of Beverages currently
being planned are through a forest which is an impassible swamp in winter.
For a DHDL (ala TX3A) receive loop coax choke I found that miniature TFE
coax (RG303 of RG316) wound on two type 31 cores 1.125L x 1.0D x .5ID
Fair-Rite 2631102002 taped together in a binocular configuration has
several K ohms of choking Z with 9 to 11 turns and fits in the same
weather-tight box as the matching transformer. So I plan that as the
choke for any future Beverages. A couple of DHDL's were very useful for
our recent E51MQT/E51MKW DXpedition and are on their way right now with
the improved chokes to Willis, VK9WA for a serious effort on 160. see
vk9wa.com
Grant KZ1W
Redmond, WA
On 11/7/2015 8:01 AM, Jon Zaimes wrote:
An alternative to Bill's "stacked" wires is to use a single wire, with
feedlines to both ends, and a SPDT relay at each end to either connect the
Beverage wire to the feedline transformer or to ground it through a
terminating resistor. The relay voltage may be piggy-backed on the feedline,
with appropriate capacitor and resistor at each end to isolate the DC from
RF. Switching to one or the other feedline in the shack then switches
directions.
I used that system on several wires in the '80s and '90s and it worked well.
K1VR also wrote about a variation without the relays, bringing both
feedlines to the shack and switching there, with the unused one terminated
through a 72-ohm resistor (he was using 72-ohm feedline).
73/Jon AA1K
Felton, Delaware
www.aa1k.us
snip...
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