Thanks to all who responded to my initial question, very interesting to read
the comments !. Much appreciated.
Seems (as most of the time..) there isn't a free lunch served...Will just
continue with some moderate Q (10 or so).
Marv, if you could scan the article ? I suppose a 50 year old legacy one
will infringe copyright much...
Thanks in advance,
73's Carel, pc5m.
-----Original Message-----
From: Radio WC6W [mailto:wc6w_amps@yahoo.com]
Sent: dinsdag 13 november 2012 17:58
To: pc5mCarel; amps@contesting.com
Subject: Re: [Amps] low Q output matching
Hi Carel,
There's an ancient article in the February 1962 issue of 73 Magazine, pp
12-19, that covers this topic in depth.
If you can't run down an on line copy, I can have it scanned for you.
73 & Good morning,
Marv WC6W
http://qsl.net/wc6w/
--- On Sat, 11/10/12, Carel, pc5m <pc5m@xs4all.nl> wrote:
> From: Carel, pc5m <pc5m@xs4all.nl>
> Subject: [Amps] low Q output matching
> To: "'AMPS'" <amps@contesting.com>
> Date: Saturday, November 10, 2012, 7:26 AM Hi, I was wondering what
> else, besides bad harmonic suppression, will happen when I design my
> (single band) output matching network
> (PI-L) with low Q
> (lowest Q needed to get the match done) ?
>
> When using low Q design I will get
> - much smaller (variable) capacitors, especially for the bigger load
> C, so easier to get components
> - broader no-tune range
> -smaller RF stress on the components
>
> As an example for a 160mtrs amp, with Rload of 1700Ohm and
> intermediate impedance around 330Ohm:
> With Q of 10:
> CLoad =1200pF
> L-l=10uH
> Ctune=293pF
> Lpi=33uH
>
>
>
> With lowest Q:
>
> CLoad=400pF
> L-l=10uH
> Ctune=132pF
> Lpi=33uH
>
>
>
> When you plot both matching networks in a Smith diagram you see
> immediate the difference. Low Q is much more straightforward.
> To get the needed harmonic suppression a lowpass filter with fixed
> components is easy to construct (first harmonic at 3,8MHz needs 25dB
> and second one 20dB to get the same values as higher Q design).
> But maybe I have
> overlooked something . Thanks for your ideas 73's Carel, pc5m
>
>
>
>
>
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