Hello Christer,
Thanks for your signal report via E-mail and the later comments re antenna
efficiency/ ERP etc. during the Decca antenna tests.
Sorry we didn't make a QSO the other night but now that we hopefully have
sorted out the matching constants on both 73 and 136Khz we should be able
to concentrate on making as many QSO as possible whilst we have this
limited access
window which came at short notice. We plan to return tomorrow to site and
also Saturday. We will post more info shortly on times etc. We have also
looked at the close range key click question and will take some appropriate
components to increase the slugging of the rise and fall times of the
keying envelope and fit them to our TX which we had left on site.
As far as the ERP is concerned , we used the reported Decca figures for
efficiency of the mast and tuning system of 15% close to 136 Khz (which we
believe are derived from measurement) and then applied some correction to
allow for the losses of our much smaller loading coil and base matching
auto transformer arriving at an overall figure of 10%effy. hence our use of
an RF power of 10W to the antenna. There is a relatively small platform at
the top of the mast with,
I think , 8 wires sloping down almost to the ground and terminating on
large insulators a few feet outside the base area of the mast but not
connected to the bottom of the tower - almost like a folded umbrella. There
is of course an extesive buried earth mat.
Look forward to working you over the weekend again.
73, de Derek, G3GRO/G3WSC/G3KAU
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