Stacked Blake Aerials for Digital Television
Shown at right are 2 Blake Aerials, Model JBX14WB high gain, UHF only antennas and a horizontal stacking kit.

The Blake antennas are well made and were easy to assemble. The director elements are made of solid rods, rather than easily bent hollow tubing, and the boom comes in two sections. The driven element comes with a printed circuit board type balun that you attach your coax to without a connector. Each antenna has an 8 bay reflector.

The stacking parts, purchased from A Tech Fabrication, consisted of a 48 inch fiberglass pipe with dual universal mounting brackets and a center boom bracket. Fiberglass is used so as not to disturb the antenna field patterns.

Also purchased from A Tech Fabrication was a pair of custom 6.5 inch coaxial baluns with 30 inch pigtails to replace the Blake PCB baluns, a Winegard SP-1002 splitter/combiner and 40 feet of RG-11 coax for the main downlead.
Blake Aerials JBX14WB
Blake Aerials JBX14WB UHF Antennas
The completely assembled and mounted antennas are at right. Together both Blake Aerials are smaller and lighter than the single Radio Shack VU-160 antenna that they replace.

The Blakes are mounted with a stacking distance of 44 inches on the centerline of each boom. The stack is heavy to the backside, so the boom to horizontal mast mounting was made to balance the center of gravity as best as possible.

The phased antennas are fed into a Channel Master CM-7777 VHF/UHF amplifier. The coax below the amplifier is RG-11 down to the grounding block where it transitions to RG-6 quadshield into the house. The telescopic mast and coax shields are connected to an 8ft earth ground at the base of the mast.

The antennas are currently mounted below the roofline of the house! Surprising, or maybe not, the signal strengths were higher at a lower elevation than when I started pushing them up above the roofline! Perhaps higher heights were overdriving the receiver with too much signal.
Horizontally Stacked Antennas for DTV

Original Setup Observations 8/4/2002 at 1:15pm:
Hughes E86 Signal Strength with Radio Shack VU160 antenna, Radio Shack Amp and RG6 downlead

DTV Channel
Signal Variations
Most Stable Signal
Remarks
10
65-72
65-72
watchable 50-60% of the time
19
30-72
51-58
in guide, but completely unwatchable.
20
0-100
72-79
watchable 60-70% of the time
25
0-79
65-72
watchable 50-60% of the time
27
93-100
100
39
0-93
65-72
frequent dropouts
43
0-100
na
in guide, but completely unwatchable.
51
0-6
na
in guide, but completely unwatchable.

Overhead aircraft on approach to Hartsville always causes dropouts.

NOTE: Ch 19 WGCL repaired their station on 7/31/02 and with the antenna aimed at the tower, the signal would be stable at 72. But for these tests, I'm keeping the antennas pointed in the direction of the other channels.

New Setup Observations 8/10/2002 at 5:00pm:
Hughes E86 Signal Strength with stacked Blake Aerials, CM-7777 Amp and RG11 downlead

DTV Channel
Signal Variations
Most Stable Signal
Remarks
10
0-21
na
antenna is UHF only.
19
93-100
100
rock solid
20
station down
na
25
station down
na
27
100
100
dead on 100!
39
100
100
dead on 100!
43
93-100
100
rock solid
51
0-6
na
in guide, but completely unwatchable.

Overhead aircraft on approach to Hartsville causes NO DROPOUTS! only a little pixelation!

New Setup Observations 8/12/2002 at 5:00am:
Hughes E86 Signal Strength with stacked Blake Aerials, CM-7777 Amp and RG11 downlead

DTV Channel
Signal Variations
Most Stable Signal
Remarks
10
0-12
na
antenna is UHF only.
19
100
100
dead on 100!
20
93-100
100
rock solid
25
100
100
test pattern, dead on 100!
27
100
100
dead on 100!
39
100
100
dead on 100!
43
65-72
72
test pattern, no dropouts, solid.
51
0-3
na
in guide, but completely unwatchable.

Links:
Robert D. Merritt - KA4BYP