Aren't there several issues being discussed simultaneously here?
1. The question asked was about the "basic" two-wire Beverage using, in
lieu of a reflection transformer, one wire grounded and the other open,
to effect a reflection/conversion from balanced to unbalanced to convey
the far-end signal back to the feed-end. Devoldere points out that,
while this "works". there is a 2:1 impedance mismatch, which is avoided
by use of a proper reflection transformer.
An interesting aspect of using two ports is that a mismatch of either
mostly degrades F/B ratio. This is seen by tracing the path and phase
reversals of the reflected components due to mismatch. But the same
effect can be had with a single feed, since the Beverage is, in either
case a two-port network.
2. Misek pointed out that if separate feedlines were employed for each
direction (supposedly for either the one-end feed or both-end feed), and
brought back to the shack, they could be combined with a tunable circuit
to create a steerable rearward null. I believe RCA and others built
Beverage arrays that utilized this and other types of combining back in
the early days of the Wave Antenna.
On 11/20/2010 6:01 PM, Milt, N5IA wrote:
> I have been constructing 2-wire Beverages for the past 15 years using
> separate feeds for each direction. In fact, I have never constructed them
> any other way. My reasoning for doing this is as follows.
> Besides 4 different fields of Bevs at home and other close to home
> locations, I also was instrumental in constructing the Bev RX antennas at
> VP6DX in 2008. All have been done with separate coax feeds from each 2-wire
> antenna feed point.
> In contesting environments and DXpedition environments each feedline is
> signal split for feeding independent switching from each operating position
> for 160, 80, 75 and at times 40 meters. All antenna azimuths are
> simultaneously available for any operating position.
> This is not possible with the single feedline application with switche
> directions. The 2 feedline app is also advantageous in SO2R low band
> contesting so that both the main RX and the sub RX or separate RX can each
> independently select any azimuth available.
> I trust this will help your decision making.
> Milt, N5IA
> ----- Original Message -----
> From: "Kenneth Grimm"<email@example.com>
> Sent: Saturday, November 20, 2010 12:23 PM
> Subject: Topband: 2 wire beverage question
>> Has anyone built a two wire beverage simply fed with two lengths of RG-6
>> instead of the usual switching arrangement in the feed end box? The
>> arrangement appears in most of the literature since the earliest days, but
>> don't think I've ever heard of anyone doing it that way. At this stage
>> however, I've got more RG-6 than I have inclination to build a switch box,
>> bias T, etc, plus the fact that I already have a switch box in the shack
>> take the two coaxes. Advice appreciated.
>> Ken - K4XL
>> UR RST IS ... ... ..9 QSB QSB - hw? BK
> UR RST IS ... ... ..9 QSB QSB - hw? BK
UR RST IS ... ... ..9 QSB QSB - hw? BK