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The Pi Network Upgrade for my 160 Meter AM Transmitter




 
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Author Topic: The Pi Network Upgrade for my 160 Meter AM Transmitter  (Read 1166 times)
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AE2EA
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« on: March 24, 2022, 08:50:25 AM »

Two years ago I posted here asking for advice on converting my RCA-BTA250M to the ham bands. A couple of members suggested scrapping the RCA output network and putting in a Pi network. It took me a year to get around to that, but it was the way to go. Thanks for the advice!

Here's a short video about the project:
   https://youtu.be/3o6MokfWLHk

73, Mark ~ AE2EA

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DMOD
AC0OB - A Place where Thermionic Emitters Rule!
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« Reply #1 on: March 24, 2022, 12:58:23 PM »

Two years ago I posted here asking for advice on converting my RCA-BTA250M to the ham bands. A couple of members suggested scrapping the RCA output network and putting in a Pi network. It took me a year to get around to that, but it was the way to go. Thanks for the advice!

Here's a short video about the project:
   https://youtu.be/3o6MokfWLHk

73, Mark ~ AE2EA

Can you give the values of the Pi-net components as they may help other's doing a conversion.

thanks,

Phil - AC0Ob
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AE2EA
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« Reply #2 on: March 25, 2022, 09:33:42 AM »

No Problem Phil.

For a 2900 ohm plate load:
Tank capacitance : 250pf variable in parallel with 150pf fixed.
Tank inductor: 23 uH
Loading capacitance: 2000pf variable in parallel with 2000pf fixed.

FYI, RCA Ham Tips volume 14, number 2, dated July-August 1954 is devoted to Pi-networks, and has a chart for impedances of common tubes at various voltages, and a chart for component values to match various operating impedances. A very handy tool to have. Itís available here: http://n4trb.com/AmateurRadio/RCA_Ham_Tips/issues/rcahamtips1402.pdf

73, Mark ~ AE2EA
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W3GMS
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« Reply #3 on: March 25, 2022, 03:36:33 PM »

Very nice job Mark.

Joe-GMS
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DMOD
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« Reply #4 on: March 26, 2022, 02:07:02 PM »

No Problem Phil.

For a 2900 ohm plate load:
Tank capacitance : 250pf variable in parallel with 150pf fixed.
Tank inductor: 23 uH
Loading capacitance: 2000pf variable in parallel with 2000pf fixed.

FYI, RCA Ham Tips volume 14, number 2, dated July-August 1954 is devoted to Pi-networks, and has a chart for impedances of common tubes at various voltages, and a chart for component values to match various operating impedances. A very handy tool to have. Itís available here: http://n4trb.com/AmateurRadio/RCA_Ham_Tips/issues/rcahamtips1402.pdf

73, Mark ~ AE2EA

Thanks Mark for the cookbook article.

In my case I use the Wingfield (W5FD) equations programmed in MatLab with the Terman correction.

"New and Improved Formula's for the Design of Pi and Pi-L Networks," QST, aug. 1983.

Phil - AC0OB
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F6BGV
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« Reply #5 on: April 26, 2022, 06:44:51 PM »

Hello !

The Pi-Network Tank Design in QST 09/1958, is more convenient !

Best 73
John

P.S: 500 for Class C  /  600 for Class B   /  700 for Class A
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