From Dave G3YMC
No radio reports on the eclipse, but just to say that the visual eclipse in
Salzburg was superb (2mins 6secs of totality in (surprisingly) an
absolutely cloudless sky). No pictures I have seen on TV or elsewhere do
justice to the sight.
Last Tuesday I had a pleasant evening with Heinz OE5EEP and he showed me
his 136 transmitter (with replaced FETs!). It is encouraging that there is
growing interest in 136 in Austria and it appears there will be soon other
stations active. Good luck with your transmit loop Heinz!
I note with interest the mails from Dave ZL3FJ on loop resistances. His
estimated resistance of several ohms does not tie in with the experience
with my loop. I have not measured the true RF resistance, but a good feel
of how it compares to the DC resistance can be found by the values of
matching components required in my capacitive match. The loop has a DC
resistance of 0.1ohms - however the capacitor values indicate an RF
resistance of possibly 0.3ohms, no more. If it had the RF resistance Dave
suggests the Q and hence the bandwidth of the loop would be much poorer -
bandwidth is around 200Hz.
I will try to do some more measurements and calculations to quantify the
resistance better, but it is my feeling that at 136 skin effect is an
insignificant effect. Possibly it is more significant at 180kHz.
73s Dave G3YMC
[email protected]
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