IIRC, the maximum frequency is limited by the diameter of the coax. At some frequency, it begins to act more like a circular waveguide than coax, and the attenuation increases dramatically. A Google search for "coax moding" or something similar should turn up more information. 73, Jim KQ6EA
--- Jim Sanford wb4gcs@amsat.org wrote:
Gents: I happened upon a chance, at a very small (but fun!) hamfest on Sunday to get my hands on some LMR 600 coax, which I'd hoped to use at 2m/70cm. Turns out it was too short for my 110' tower (building at base). In followup, I have a chance of some 1 1/4 Andrew heliax, or some 7/8 andrew heliax.
I'd hoped to run one line for 2m (dedicated) an another to be switched among 220, 432, 900, 1296, 2304, and 3456.
I'm seeking <1db loss at 2m and < 3db on the other bands.
The Andrew datasheet says 3.3GHz is the max frequency for the 1 1/8, which I'm really tempted to buy based on price and the expensive acccessories that come with it. BUT, if I take the mfr data literally, it won't work on 3456.
Question: Does anybody have any idea whether or not the 1 1/8 can be "pushed" to 3456? Or does the loss really start screaming up above 3300?
Thanks & 73, Jim wb4gcs@amsat.org
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