The AM Forum

Assuming 600 VDC and plate current around 80 mA, would one calculate the input Z of the Pi network simply by doing the Delta V plate voltage/Delta V plate current, or is it more involved?

Thanks!

Read this. It explains it pretty well.

http://rfcec.com/RFCEC/Section-3%20-%20Fundamentals%20of%20RF%20Communication-Electronics/04%20-%20AMPLIFIERS%20-%20RF%20POWER%20AMPLIFIER%20BASICS/RFPA%20-%20Design%20Formulas%20(By%20Larry%20E.%20Gugle%20K4RFE).pdf

This is more simple with examples from RCA Ham News in July1954.
They assume that you are designing a class C amplifier.

https://worldradiohistory.com/ARCHIVE-RCA/RCA-Ham-TIps/RCA-Ham-Tips-54-07-08.pdf


So, if you assume that it will be a class C stage and have 600 volts on the plate, the load resistance is estimated at
600/(2x 0.08)= 3750 ohms

The rest of the design is easy if you get Jim Tonne’s software called PI-EL.
It is free at Tonne Software.
http://tonnesoftware.com/piel.html

What frequency or frequencies? 50 ohm Load?

Pi Net values vary with frequency.

Phil - AC0OB

Thank you all!

To answer Phil, an 809 with 600 VDC and about 80 mA plate current.

Planned frequency range 400 Khz to around 1500 KHz.

BTW, nominal load 150 to 200 ohms.

Q of 6 or 7 OK.

Here are some numbers from PIEL as a starting place. I did not set the plate swing, so it will be off a little, but the impedances are correct and the operating Q.
I ran it at 400kHz and 1500kHz
I only get three images, so no plot for the second one.

Inductors for a operating Q of 7 will be very large compared to a Q of 10-20

281uH can be had for about 80-85 turns on a 4 inch pvc sewer pipe or you could stack several T300-2D toroids and load them up for greater expense ans smaller package.
400-1500kHz is a very wide tuning range- about like 80-20 meters

Would you be kind enough to run the following:

Q of 10.

400 KHz, 700 KHz, and 1100 KHz.

That would not be so great a span.

Thanks!

See later listing


If these emissions are to go beyond the Lab then I suggest you obtain an FCC Experimental Radio Station Construction Permit and License.  

Phil

😂😂 Yes, this is definitely above Part 15 and unintentional radiator levels, though a license for 470 is not that difficult, I think.
Or you could go the traditional route and put it in Mexico.😉

I hadn't thought about Mexico. ;D ;D ;D ;D

I have to apply for these occasionally and with supporting documentation, it's not that much of a deal:

Applicants in all services, except market-based services (i.e., services where licenses are issued through an auction), are strongly encouraged to file electronically via the Universal Licensing System (ULS). Applicants for Special Temporary Authority should apply on FCC Form 601 accompanied with the appropriate schedules. All applications for STA must also include an attachment justifying the need for an STA.

https://www.fcc.gov/applying-special-temporary-authority

The last time I applied it cost $70.00 and the authorization came out of the FCC field office in St. Louis.

Let me tell the OP why it is a good idea to file a 601. If a complainer hears you testing and reports it to the FCC, the FCC can check the database and tell the complainer that you are legal (not a pirate) and to go pound sand.  :o

You will be issued a special call sign such as WY2XEZ, so you use that assigned call if you have to identify by voice or CW.

BTW, this information is for experimentation purposes only and is not to be used for any commercial venture.

Phil



  

Corrected for Rload = 170 ohms. Previous listing was for Rload = 50 ohms:

0.4e6 Hz for Q = 10 for 70% Efficiency Class C
Cptune = 950pf
L = 192uH
Catune = 3700pF


0.7e6 Hz for Q = 10
Cptune = 540pf
L = 110uH
Catune = 2,100pF


1.1e6 Hz for Q = 10
Cptune = 340pf
L = 70uH
Catune = 1,350pF

BTW, this information is for experimentation purposes only and is not to be used for any commercial venture.

Phil

XERF near Del Rio Texas in Mexico.
They could kick out 500,000 watts at 1570AM

Now that is real power!

https://www.theculturecrush.com/feature/conmen-at-the-border

The X stations inspired the song Texas Radio and the Big Beat by the Doors.

:-)