I barely managed to get my new Unified
Microsystems (W9XT) BevFlex-4X Beverage installed and operating
for the CQ CW contest last weekend. I installed it Friday but
encountered problems with one of the feedlines; that problem
wasn't corrected until Saturday morning. It appeared to be a bad
arc capsule in the lightning protector for that antenna. I
replaced the capsule and all was well. It took a lot longer to
find than it did to fix, of course. The antenna isn't really fully
installed yet, just "roughed in". I still need to go back in the
woods and secure the terminator and feed boxes to their supporting
trees and waterproof all the connectors.
I chose the BevFlex antenna because it allows for bidirectional
patterns, and the feedpoint can be located anywhere along the
antenna. It's constructed using RG-6 coax, and all connections to
termination boxes and the feedpoint box are F connectors. The
design requires separate feedlines for the Forward and Reverse
feeds. I used a 100' length of "siamese" dual RG-6 Quad shielded
coax to run the feeds to the station. It's necessary to terminate
the unused direction's feedline with a 75Ω load to make the
reflection transformers work properly. A small switch box that
does this is included as part of the kit. Since all my switching
is remotely controlled, I built a new relay box to handle the
reversal function under software control. My property can support
a length of about 350 feet in the NE-SW direction I ran the
antenna, so that's the length I used. I just mounted the coax by
running it through a series of screw-in insulators installed
about head high in the trees. The feedpoint is located about 240'
from the NE end.
Initial checks with AM broadcast band stations looked encouraging.
Even with daytime propagation, there was obviously a real signal
strength change when the two directions were selected. The rather
short 350' length made the antenna pretty much omnidirectional
below 1200 kHz, but at 1400 kHz and higher there was a noticeable
change in signal strength on many BC stations when the direction
was changed. In a couple of cases, one station was actually
replaced with another.
Returning to the contest, I first tried the Beverage on 20 meters.
By the time I got back on the air, around 2000Z, 20 meter
propagation to Europe was essentially gone for me. I wasn't
hearing many signals other than strong US and VE stations. It
wasn't clear whether or not the Beverage would be useful on 20.
When I changed to 40 meters it became obvious that the Beverage
was going to be very useful. I was immediately hearing lots of
weak EU signals on the Beverage that were difficult or impossible
to hear on the inverted vee transmit antenna. Using a combination
of the transmit antenna and the Beverage in Diversity mode made
copy of weak DX stations dramatically better. I was literally
hearing a whole new layer of DX signals that were extremely
marginal copy on just the transmit antenna alone. Sometimes when
QSB would take the signal out on one antenna and it would be Q5
copy on the other. Most of the time I used the Beverage in the NE
direction since most of the DX was from Europe. Switching the
Beverage to the SW direction would usually make the EU signals
completely disappear. Unfortunately, this vastly improved receive
capability proved to be a double-edged sword. I found I was
clearly hearing a bunch of DX that couldn't hear my 500W to an
inverted vee at all. Repeated calls to many Q5 EU stations went
unheard on their end.
Around sunset, I went to 80 meters and had similar results. The
superiority of the Beverage to the inverted vee transmit antenna
was even more dramatic. In Diversity mode, many times I could
easily copy EU stations on the Beverage that I couldn't hear at
all on the transmit antenna. In some cases, I could hear them
working other EU stations and both sides of the QSO were inaudible
on the transmit antenna. Of course, the disparity between receive
and transmit capability was even more apparent on 80 than on 40.
It quickly became evident that if I want to work DX on 80 I'll
need to come up with a significantly better transmit antenna.
I have no 160 meter antenna so far, so I just spent a few minutes
listening on 160 meters. I was able to hear some EU stations on
the Beverage quite well. Unfortunately, I also found that there
was some kind of ugly local electrical noise on 160 that I'll need
to track down and get fixed before I can expect to do anything on
that band.
After the contest, I've been listening around on the bands to get
a better idea of what the Beverage can do. I've found that it does
work pretty well on 20 meters and definitely improves copy on
marginal signals in Diversity receive mode. It's also extremely
effective on 40 meters, especially at night. In the Wednesday
morning CWT session it didn't really seem to do much on 40, but
signals for the most part were short skip and quite strong. On 80
meters I found that it is definitely useful on stateside signals.
In the Wednesday CWT it helped a lot in improving copy on many
domestic signals, even in the morning. I also hooked just the
Beverage up to my Airspy HF+ Discovery SDR and tuned up and down
the AM broadcast band. Above about 1300 kHz the Beverage starts to
develop very good directivity and on many frequencies switching
directions would replace one station with another. This effect was
especially noticeable at night.
In summary, This Thing Works! I'm very happy with the station
receive capability improvement it gives. As a matter of facti, I'm
now looking at installing a second BevFlex-4X in a SE/NW
orientation. It's somewhat uncommon for an antenna project that
involves a modest amount of effort and expense to make a dramatic
difference in station performance. This one did.
73...
Randy, W8FN