[Elecraft] amp and coupler questions

[Pete Goudreau]

Vic Rosenthal wrote:

> Pete Goudreau wrote:

>> If anyone has any comments on the use of the Motorola AN-762 amp 
with
>> the K2 while using an LDG AT-11MP as the antenna coupler and low 
pass
>> filter, I'd certainly appreciate any. I figure running at or below
>> 100W, the 3rd harmonic should easily be down better than 40dBc
>> regardless of the coupler setting. Could be wrong about that 
though.

> The LDG tuner uses an L network. Depending on the impedance of the
> antenna that you are feeding, it might act as a low or highpass
> filter. Even in a lowpass configuration, a single-section L network 
is
> not going to provide adequate harmonic suppression. You are going to
> have to bite the bullet and build or buy a set of lowpass filters.

I think it just switches the cap from the output to the input for 
increased impedance matching range so it's still technically a low 
pass at all settings, just not a very good one at some.

I found the AN762 app note at rfglobalnet late last night and 
discovered that it isn't as clean as I'd thought it was so the LPFs 
are indeed an absolute necessity.  Dang.

Thanks and 73,
Pete, AD5HD