'
应该是2单元折合式yagi，至于高增益我认为是在吹牛。
'
how does it compare to other triband yagis?
compare the diagrams and tables in the technical data section. you will find that the spider beam is always equivalent or better than a big conventional tribander with about 7m (20ft) boom length. especially the operating bandwidth is much better than with trap designs:
- forward gain is about 5dbd (7dbi) in free space (= 12dbi in 10m height above ground) and stays nearly constant over the whole band(s)
- f/b ratio is about 20db or better on all bands
- swr stays below 1:2 on all bands
on-the-air comparisons and measurements confirm these results.
only a true 3 element monobander will still be a little bit better: it has the same f/b ratio and pattern and 6dbd (free space) gain.
unfortunately some manufacturers still claim much higher gain numbers, even for their multiband antennas, which simply is not true.
an interesting feature is the flexibility to quickly optimize the spider beam for the cw or ssb band section.
the basic spider beam dimensions are designed to cover the whole band. if you want to operate cw or ssb only, simply change the wire lengths slightly to shift the optimum pattern into your desired frequency range.
