You're right, Peter. I misspoke. It's the large required L1 & L2 that make a
pi-L impractical for an 8877 on 160m. For example, for Q=12 and a plate
impedance of 2600 ohms (roughly correct for an 8877 with 4KV plate voltage),
L1=43uH and L2=11uH. L1 would truly be a monster inductor! For a pi-network,
L1=23 uH, or roughly half as great as for a pi-L. The values of C1 and C2
aren't really of practical significance, since one can always use fixed
capacitors as needed. Thanks for correcting me.
73,
Jim W8ZR
> -----Original Message-----
> From: Peter Voelpel [mailto:df3kv@t-online.de]
> Sent: Monday, June 18, 2012 11:03 AM
> To: 4CX250B; amps@contesting.com
> Subject: RE: [Amps] Pi-L Network Question
>
> It´s the opposite.
> The required capacitance of the load-C of a simple Pi network is much
larger
> then that of a Pi-L, a big advantage beside the much besser harmonic
> supression and easier tuning.
> The two coils should not couple to keep the harmonics as low as
calculated.
> However, the required inductance is larger with the Pi-L.
>
> 73
> Peter, DJ7WW
>
>
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of Jim Garland
> Sent: Montag, 18. Juni 2012 17:57
> To: amps@contesting.com
> Subject: [Amps] Pi-L Network Question
>
> I've been noodling around various tank circuit possibilities for a 160m
> monoband amplifier. A pi-L network isn't very practical for an 8877
because
> the relatively high plate impedance mandates very large values of C1 and
C2.
> For an 8877, a simple pi-network is preferred. On the other hand, a Pi-L
> makes a lot of sense for, e.g., three 3CX800a7s or GU-74Bs, because the
> combined plate impedance is under 1000 ohms and the required capacitance
and
> inductance values are quite reasonable.
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