[AMRadio] Loading antenna with BC 610 E


ne1s at neandertech.com ne1s at neandertech.com
Thu Jan 17 12:48:54 EST 2008


----- Original Message -----
Subject: [AMRadio] Loading antenna with BC 610 E
Date: Thu, January 17, 2008 11:32
From: "John King" <k5pgw at yahoo.com>

> I would appreciate recommendations regarding a
> "loading" device to help transfer RF from the tank
> coil to the antenna. Will installing a C2 from output
> to ground tune the reactance out of the feed line and
> facilitate loading the dummy load better or loading
> the Coax feedline to the antenna??
>

Hi John,

I believe what you want to do is put a variable capacitance in series with
the output link to resonate it. This should be connected such that the
rotor of the capacitor is grounded/connected to the coax braid, and the
stator connects to one end of the link. The coax center conductor gets
connected to the opposite end of the link. About 1200pF maximum should be
adequate for all bands except 160M. If you operate 160M you can put a
large 1000pF transmitting mica in parallel with the variable capacitor
when you operate there.

I don't have experience with an actual BC-610, but know folks that do, and
use the above method (W1CKI, for one). Also, I have a homebrew rig that
operates up to 300W output and uses BC-610 coils with the above method. I
use the three-section ganged air variable from a late 1920s-era TRF
broadcast radio. The spacing between rotor & stator seems adequate for
this power level with this vintage capacitor. More modern broadcast air
variables may not be. All three stators, ~400pF each, are connected in
parallel.

GL,
-Larry/NE1S


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