Date: Fri, 6 Dec 2013 10:21:59 -0500
From: "Carl" <km1h@jeremy.mv.com>
To: "Jim Thomson" <jim.thom@telus.net>, <amps@contesting.com>
Subject: Re: [Amps] PARALLEL CAPS IN OUTPUT
>
> ## For folks with a PI net, make sure you use a piece of 50 ohm coax
> between the load cap and the TR relay.
> And with shield bonded to chassis at BOTH ends. If wire or cu strap is
> used instead...then u end up with a huge Z bump.
** The coax isnt long enough to act as a transmission line at HF....in most
amps anyway.
#### OK, do it ur way. Use a chunk of bare wire, strap etc..and watch the
PI net load cap values change asap. Ditto with coax...and only 1 end of
shield bonded to
chassis.
### strap, wire, etc is NOT 50 ohms, not even close. Try it urself.
> That alone will put the load cap at something higher than a 50 ohm
> point... increasing the peak V. On 10m band, the
> stray L of a piece of wire instead of coax will make the PI now appear
> as a PI-L.... putting the load cap at a much
> higher Z point. same deal peak V increases. Now with a wide open on
> the ant, coax cable etc, the load cap
> will weld shut.
** All the coax does is act as a shielded cable with some value of C.
At 10M even 1/10 wave of cable is 1.6' so it is invisible as coax.
##### I don’t believe it for a second. Of course, I have tried it both ways.
Replacing the junk typ used from load cap to TR relay will solve..and has
solved all sorts of issues.
Later....... Jim VE7RF
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