The early charts had gross errors in attenuation for these line types, I
have no idea if the later ones do. The error was in the direction of much
to little loss.
> I have been eyeballing the line loss charts in the ARRL antenna book and
> keep thinking that open wire line or twinlead would also be a super
> low-loss feedline for VHF/UHF into 50 ohm antennas as long as I could
> care of the matching.
Remember MOST 450 ohm ladder lines are not 450 ohm at all. Some 450 lines
are as far off as the upper 300 ohm range. TV twinlead is pretty good for
dry weather impedance, but ALL of these unshielded lines have high wet
weather loss at VHF and above. Mounting is also critical, as is current
balance and physical balance to surrounding conductors.
Myself, I'd use CATV trunk line as a cheap and better alternative.
FAQ on WWW: http://www.contesting.com/towertalkfaq.html
Administrative requests: towertalk-REQUEST@contesting.com