Hi All, as a result of the donation of some old mags I came across the
following table in an article in 73 mag (April 1972 ), which may be of
interest to those without a tower contemplating a BIG vertical. The table
relates to lift generated by a helium filled balloon at different gas
temperatures.
Balloon Gas vol lift (lb) lift (lb)
diam. ft cu.ft. @0degC @20degC
2 4 0.25 0.25
3 14 1 0.75
4 33 2 2
5 65 4 4
6 113 7 7
7 180 12 11
8 268 18 17
9 381 26 24
10 523 36 33
11 696 48 44
12 904 62 58
Sorry to our metric friends (1ft=0.3m and 1lb=0.45kgm or there abouts) I
think metres are unknown the other side of the pond. They even measure the
size of the engine bay in cubic inches (It IS the engine bay isn't it?)
It goes on up to 16 feet diameter but I reckon if you have got a big enough
garden to blow up a 16 foot diameter ballon you have enough room for tower!
He mentions flying a 160foot vertical with an 8foot weather balloon inflated
to 3.5 feet diameter. (He ran out of gas). He also relates burning out a
30AWG aerial wire with about 180 watts on 80m. Though I must admit I have no
idea how he derives an impedance of feed 50ohms for the end of a halfwave!
That shouldn't bother us as, at least I, will be quite happy with a quarter
wave on 136!
Cheers de Alan G3NYK
[email protected]
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