[TowerTalk] Link Coupled Tuner Question
k2xx at swva.net
Sun Mar 19 11:33:35 EST 2006
Peter, thanks for the input. And Cebik also suggested 1700 pF or so as
a starting point for the 160M link. I am currently using a 3" coil with
five turns cut out of the center as the link. It's not as effective as
a concentric link, but the SWR is very responsive to the output
capacitor and I do see 50 ohms and about zero reactance at the tuner
input. It occurred to me that the link capacitor was added to the early
link tuner designs as a refinement, and I'm wondering if, with my
particular combination of component values, a link capacitor is
necessary at all.
Nevertheless, thanks for confirming that it tunes fairly flat. That
gives me the confidence to go forward.
Peter Chadwick wrote:
>K2XX asks: Is this relative insensitivity for the series link typical?
>The usual 'rule of thumb' is that the link should be the same reactance as the transmission line, or about 50 ohms. This will tune with about 1800pF on 160, and will have a Q of around 1, so you can expect it to tune fairly flat. You do want a fairly tight coupling between link and tuned circuit, though.
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