Hi, All
In the past couple of years I have put up two different two-wire
reversible-direction Beverage antennas, and have experience good results
with both of them. I constructed the reflection transformers according to
details found in John, ON4UN's, book (3rd edition) and I use the binocular
cores that Tom, W8JI, is so fond of. These antennas have afforded me the
opportunity to work stations from direction (N and W) that, had I had to
rely on simple unidirectional single-wire Beverages, I would not have been
able to hear due to my inability to run wires in those directions.
However, last month I picked up a copy of the 4th edition of ON4UN's book,
and while thumbing through Chapter 7 (Receiving Antennas) last night, I
came upon the diagram for the two-wire, two-direction Beverage (page 7-70,
fig. 7-98). This diagram shows one of the two antenna/transmission line
wires grounded at the reflection transformer end where one side of the
reflection transformer is attached. This has got to be a misprint, doesn't it?
I know that (only) when the Beverage antenna impedance matches the
impedance of the transmission line used to construct the two-wire Beverage,
then grounding one of the wires at the "far" end will achieve the desired
reflection, and no transformer is used. In my case, however, I use 300-ohm
TV twin-lead for the antenna wire, and I figure the resulting Beverage
impedance is about 450 ohms, therefore I use a 5:4 turns ratio transformer
to match the Beverage impedance to the transmission line's impedance before
sending the signal back towards the feedpoint end. Neither of the antenna
wires is grounded at the "reflection" end; the only ground connection is to
one side of the 450-ohm (Beverage impedance) winding.
Isn't this correct?
Charles - K5ZK
_______________________________________________
Topband mailing list
Topband@contesting.com
http://lists.contesting.com/mailman/listinfo/topband
|