Topband: DX-Enginneering Active Antenna System

[Bill Tippett]

WB2NMI wrote:

 > I am constructing a DXE style receive 4 square using shortened 
verticals with ICE 135B preamps for each active antenna. I will use a 
small choke and resistor is series at each preamp to impedance match 
the short vertical to the preamp input at 1.8 Mhz. I will also need 
to modify the ICE amps for power input thru their RF output 
connectors. I bought the DXE RFS-2 switching/phase delay box and I am 
homebrewing everything else. I have everything I need  cable, control 
wire, etc purchased now and I figure I reduced the cost by 50% from 
what the off the shelf DXE receive 4 square solution would cost. I 
have to now assemble and test to see how well it works. I can report 
progress later this year.

         I've done the same but using 4 of K7TJR's Hi-Z preamps 
(Option 003 for $28 each in kit form):

http://www.hizantennas.com/hiz_amplifiers.htm

Option 003 includes the power over coax circuitry and an input 
protection relay.  The only anomaly I saw in using the DXE controller 
was a ~1V drop from the controller box to the preamps.  I'm using 18V 
in the shack to deliver 13.8V measured at the preamps with the + lead 
to ~800' of shorted WD-1A and - lead (ground) to the coax shield of RG6.

         I'll repeat the advantages I see of using small non-resonant 
20' verticals:

1.  Total area required is <1/6 that of using using 8 each 60' 
radials per vertical (80' X 80' = 6.4k total square feet versus 200' 
X 200' = 40k).

2.  No top hat loading required (versus 16 for a short resonated 
vertical).  In my case this was a major issue considering we have 
many deer which might have caused maintenance issues with the top hat 
guy lines.

3.  Much less work!  Less land to prepare, no radials to lay, no 
top-hat wires to construct and guy, and the total cost of the 4 
preamp kits was just over $100.

4.  The only minor downside is supplying power to the preamps.  I'm 
doing array switching via coax using DXE's FVC-1 and supplying preamp 
power (positive side only) with one run of WD-1A (both sides 
shorted).  Since I had to bury 800' of RG6, it was no more work to 
bury the same length of WD-1A at the same time.

5.  My total equipment cost was <$500 including a DXE RFS-2 (second 
hand), DXE FVC-1 and 4 Hi-Z preamps.  I already had enough RG6, 
WD-1A, aluminum tubing and assorted PVC pipe and fiberglass 
stiffeners for my mounting system.

6.  Support from both Lee K7TJR and DXE is excellent!

         I must say the quality of the DXE components is 
phenomenal.  It actually may be overkill in my case.  The RFS-2 case 
is polished stainless steel with an etched DXE logo on the top!  The 
internal PC board is absolutely first class.  I mounted a $9 Wal-Mart 
tub over my RFS-2 and the big coils of delay lines (to prevent 
critters from chewing them) so there was little need for stainless 
steel in my system.  Next I've got to protect the feed lines where 
they exit the ground with something to discourage chewing (maybe a 
small length of hose).

         In the two days I've used the system I've been very pleased 
with it.  I optimized my array spacing and delay lines for maximum 
F/R performance (...not RDF) per K7TJR's analysis.  I'm running the 
4SQ to one RX in my K3 (in diversity) with my Beverages going to the 
other RX.  Although a 1200' Beverage is a little better than the 4SQ, 
the latter is not bad especially considering it's all contained 
within an 80' X 80' area and covers all directions.  If I was space 
constrained, I would definitely have one of these as my primary RX antenna.

                                         73,  Bill  W4ZV

P.S.  K7TJR's controller is only $150 but it does not have the 
capability of switching over coax.  If I had known about it before I 
got a used DXE controller, I would probably have gone with it instead.

http://www.hizantennas.com/controller_4_elements.htm