My current 70cm antenna here @ M0BEW
Performance, details, construction and comments.
Performance.
Gain: 18.81dBi @ 432.200MHz
F/B: 40.75dB @ 432.200MHz
Peak Gain: 18.97dBi
Gain 10m above Ground: 24.77dBi
Peak F/B: 42.32dB
Power Rating: 3kw
SWR: Below 1.1.1 from 432.00MHz to 433.00MHz
Boom Length: 5.210m
Stacking Distance Vertically: 1.36-1.7m (best trade-off 1.622m)
Stacking Distance Horizontally: 1.37-1.8m (best trade-off 1.710m)
Following figures calculated at 432.200MHz
2 Stacked Vertically 10m up @ 1.622m spacing - Gain: 27.47dBi
2 Stacked Vertically 10m up @ 1.622m spacing - F/B: 37.83dBi
2 Stacked Horizontally 10m up @ 1.710m spacing - Gain: 27.65dBi
2 Stacked Horizontally 10m up @ 1.710m spacing - F/B: 37.95dB
4 Antennas 1.622m V x 1.710m H Gain (corrected): 24.41dBi, F/B: 36.24dB (free space)
Sky Temperature (corrected): 25.45 Kelvin @ 432.200MHz
G/T Figure (corrected): 10.35dB @ 432.200MHz
Comments:
Well built antenna. Very solid.
One or two little issues but were sorted very quickly.
I first tested the antenna in a RSGB 70cm activity contest and it appeared to perform as expected.
I gather the overall conditions were not very good so it'll be intresting to test it again next month.
Seemed good towards the north and poor towards the south east.
Fed the driven from around the rear and back around the boom underneath.
Needed some very exact measuring while assembling as the elements weren't marked and within 0.5mm of each other. ie. 272.5mm, 273mm, 273.5mm and 274mm.
Testing with a 10 year old piece of Ecoflex on a flat band I'm hearing GB3FNY, GB3UHF, GB3MCB and PI7CIS consistantly. There are others that come in/out of the noise during an evening if I monitor long enough.
The pattern is as sharp as a torchlight. Quite an eye opener compared to some VHF yagi patterns im used to. Checking performance, pattern and swr in heavy rain appears to have no effect. Good news.
All in all very pleased so far. Be nice to set up a box or a 4 stack for contesting. But be rather an expensive luxury for my current uses.... we will see.
Tim M0BEW.
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