[TowerTalk] Optibeam Log Yagi

[Jim Brown]

On 12/29/2025 10:01 PM, Tony wrote:
> Anyone using one of Optibeam's "Log Yagi" antennas? The documentation states that they have several advantages over standard log-periodic designs — it also mentions enhanced performance above the calculated gain, which is attributed to the large radiation area of the antenna.
> 
> One of the models has a F/B of 35db which is pretty impressive for an HF antenna.

One of the messages of N6BT's "Array Of Light" is that the advertised 
performance specs must be taken with a not a grain, but a mountain of salt.

If that F/B spec is real, it is undoubtedly in anechoic conditions. 
You'll never see tight sidelobes and high F/B if you don't have a 
spectacularly good common mode choke at the feedpoint, and the antenna 
very high above anything that can affect it's pattern. Including things 
like conductive guys, other antennas, buildings, vegetation, and so on.

And, of course, every element of the pattern, including gain, is 
affected by those reflections, including the earth.

Several years ago, I replaced a 7-el M2 Yagi for 6M with G0KSC's 7-el, 
for which he claimed a tighter vertical pattern. Both were/are at 120 
ft, looking into the vegetation of a dense redwood forest. Listening 
carefully, I found improved S/N of a dB or two in my noisiest 
directions. When noise is a limiting factor on a band that you take 
seriously, this can be a very big deal.

73, Jim K9YC