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Showing posts from August 25, 2019

5/8 10m vertical and K3 with TR-2018 HD 144MHz

The impedance of a 5/8 wave vertical is given as (75 -425j) Ω
   needed is XL  +425j to balance out the capacitive -425
Rothammel  say  2.3uH for D/d=4000  the ratio of lenght and conductor diameter does have influence on the inductance the thinner the conductor the higher the inductance
The original coil in the base for 11m is  8 wdg 32mm = 2.8uH The CD 11m vertical matching uses a grounded coil with tap at 3 wdg to the center pin PL259.
This 0.64 wave has uses a series inductance to match not grounded
I could not find a match with a grounded tap that would protect against static discharges. 
The best matching found was a 3 wdg 50mm diameter coil of 2.5mm2
Way less then the calculated 2.3uH
according to this calculator only 0.3uH ...  more coil gave worse result....
https://m0ukd.com/calculators/air-cored-inductor-calculator/

   source  https://ham.stackexchange.com/questions/9780/calculating-all-specifics-for-a-5-8-antenna

interesting sources : https://ham.stackexchange.com/que…