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DIY Field Test G-H gen1 split screen - Cent-2 - M4's Click images below for a larger view
The antennas tested were a G-H gen1 with a split screen reflector, a Cent-2 and (3) sizes of M4's The centipede shown in the center had #6 copper elements which measure 23 1/2" wide and 27" tall and uses a 36" wide x 40" tall reflector with additional upper and lower shelf reflectors making a total reflector area of 36" x 56" of 2"x 4" wire screen. The G-H shown on the left uses elements that measure a max of 23" wide x 30 1/2" tall it uses a split screen reflector that measures 29" wide x 36" tall with a 1" gap running vertically up the middle it's made of 1" x 1" wire mesh. The feed gap is 1 5/8" and the diamond parts of the elements measure 7". The (3) M4's shown on the right were sized with 10" whiskers x 9 1/2" bay spacing, 9 1/2" whiskers x 9" bay spacing and 9" whiskers x 8 1/2" bay spacing. The average size is 19" wide x 31 1/2" tall, the reflector used for all sizes was a 40" wide x 40" tall curved reflector made from 2" x 4" wire screen.
All readings were taken on the same afternoon back to back, all antennas except the G-H were tested twice in different order to verify the readings. I broke a screw on the G-H feed point which didn't allow me to test it twice but the readings were pretty consistent with other tests I've done in the past as compared to the M4's.The conditions were down a little from usual but they were steady all afternoon which made for good testing conditions. A Channel Master CM0064 amp was used on all antennas while testing to allow me to get the maximum amount of stations. Some antennas may respond slightly different if not using an amp. The amp can help mask some high SWR conditions by limiting the high SWR to a short piece of antenna lead between the antenna and amp. All antennas were about 20ft above ground in the exact same location in an open field with no obstructions and were carefully rotated on all channels to find the best reception. Antenna height and surrounding terrain can affect antenna performance so your mileage may vary. The DT250a starts to lock on a station at 15 on the meter and achieves a steady lock at 20 on the meter. All antennas are pretty close on UHF, the fringe stations that one antenna could get over another may not even be receivable on certain days. On VHF-hi the M4's were clearly better, I'm not able to test VHF-HI NARODS on my G-H due to the mesh screen reflector. The DT250a meter readings are not a true measure of signal strength but a blend of signal strength and quality you will see some channels where the spectrum analyzer show higher signal strength but the DT250a shows less on the meter. |
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