On 6/21/2014 3:23 PM, Dan Hearn wrote:
It is interesting to note that the Mosley claimed gain is about 2db
greater than other tri band beams. They use dbd reference instead of dbi
while I think their claims would be about right if they used dbi reference.
Exactly the opposite. The peak gain of a dipole is 2.2 dBi. So a gain
specification of 4 dBd is equivalent to 6.2 dBi.
I suspect if you used a good line choke at the coax feed point and subtract
2.1db from their claimed gain you would have a typical triband beam.
I don't agree with that logic or that statement. A simple common mode
choke simply reduces common mode current, which mostly prevents RF
received on the feedline from filling in the nulls in the pattern.
In his book, "Array of Light," N6BT shows optimized designs of
2-element, 3-element, and 4-element MONOBAND Yagis. He put these IDEAL
gain figures in a table with the CLAIMED gains of a dozen or so
competing products. In nearly all cases, the advertised gains were 2-3
dB better than the best monoband beam. In other words, they claimed
impossible gains. After the first edition of "Array of Light" was
published, nearly all of those manufacturers revised their gain claimed
downward by several dB.
73, Jim K9YC
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