[Amps] CB amp directly coupled via cap to antenna

[Bill, W6WRT]

ORIGINAL MESSAGE:

On Thu, 8 Apr 2010 21:58:55 -0700, "Hardy Landskov" <n7rt at cox.net>
wrote:

>Actually a match is dertermined by the ratio of the antenna Z to the 
>tranzmission line Z. The generater Z has nothing to do with it. At least 
>that is what I remember. So all these amp specs are irrelvelent.

REPLY:

In this case, there is no transmission line and no matching network
(pi-net), so the generator Z is important. In a normal amp, the pi-net
transforms the tube's plate load resistance down to 50 ohms while
adding Q to provide the flywheel effect.  In this case, there is no
pi-net, but one is not really needed for matching purposes since an
end-fed half wave antenna presents a load resistance of several
thousand ohms. When connected directly to the tube's plate load
resistance,  which is also several thousand ohms, you have a close
match and a circuit Q of about one. No doubt there is some mismatch,
but it will be in that ballpark.

With a Q that low, there is very little flywheel effect and thus you
need a separate parallel LC tank coil, not for matching purposes, but
to provide the flywheel effect needed by any class of amp other than
class A.

This whole thing is a little bizarre, but that's my understanding.

73, Bill W6WRT