At the same time, Rich Measures has a nice Excel spreadsheet available on
his website that does a good job of defining the values for L1, C1, C2 and
L2 values for a Pi-L network for HF. In moving transmitters from the BC
band to the 160 M and 75 M bands, I've used his application on several
transmitters with excellent results.
73
Bob, K4TAX
----- Original Message -----
From: "Bob McGraw - K4TAX" <RMcGraw@Blomand.net>
To: <geraldj@storm.weather.net>; "Discussion of Ten-Tec Equipment"
<tentec@contesting.com>
Sent: Sunday, February 08, 2009 10:16 PM
Subject: Re: [TenTec] Ig drift on amps
> Sorry, I didn't read it that way. And in a Pi-L network the output C
> components are by design at the midpoint of the network.
>
> Yes, without knowing the values of L, it is a challenge {best guess} to
> figure the correct values for C and the network center is unknown as well.
>
> 73
> Bob, K4TAX
>
>
> ----- Original Message -----
> From: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
> To: <tentec@contesting.com>
> Sent: Sunday, February 08, 2009 10:14 PM
> Subject: Re: [TenTec] Ig drift on amps
>
>
>> On Sun, 2009-02-08 at 21:36 -0600, Bob McGraw - K4TAX wrote:
>>> The output of the amp is indeed a Pi-L network. These work great and
>>> have
>>> been in BC transmitters very successfully for years. I wish more
>>> companies
>>> would use Pi-L networks in their amps. Better attenuation of harmonics,
>>> lower currents in the coils and components and a better match. All at
>>> the
>>> cost of increased costs.
>>>
>>> I can't imagine any amp today being able to handle a 300 ohm load on its
>>> output at rated power. That's an SWR of 6:1.
>>
>> He was talking about the design impedance at the junction of the Pi and
>> the L. Higher than the load Z, lower than the plate Z. 300 to 600 ohms
>> are common values for that mid point in the output network. Higher takes
>> more L section coil and a higher loaded Q but allows smaller load
>> capacitors.
>>>
>>>
>>> 73
>>> Bob, K4TAX
>>>
>>>
>>
>>
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>>
>
>
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