’29 MOPA Progress


'29 MOPA Plan
I have completed manufacture of the three RF chokes required for my new MOPA project. Two of the chokes (the ones in the amplifier) are broken into three sections, presumably to reduce stray capacitance or unwanted resonances while the choke for the Hartley oscillator section is one single winding.


The choke forms were first turned on the wood lathe, using Mahogany hardwood scrap, to a diameter of 3/4", and then stepped down slightly, for the space occupied by the windings. The windings, using single silk enamel #31, were then done, still on the lathe, while rotating the spindle manually.





I've always been surprised at how little inductance is really needed for effective choking on HF and it would seem that the 'standard' 2.5mH is much more than is actually required. The single-ended version is just 190uH, while the three-section chokes measure just 240uH, about 10% of what normally might be specified today.
Steve McDonald, VE7SL, is a regular contributor to AmateurRadio.com and writes from British Columbia, Canada. Contact him at [email protected].

Leave a Comment

Subscribe FREE to AmateurRadio.com's
Amateur Radio Newsletter
News, Opinion, Giveaways & More!

E-mail 
Join over 7,000 subscribers!
We never share your e-mail address.



Also available via RSS feed, Twitter, and Facebook.


Subscribe FREE to AmateurRadio.com's
Amateur Radio Newsletter

 
We never share your e-mail address.

Please support our generous sponsors who make AmateurRadio.com possible:

KB3IFH QSL Cards

Hip Ham Shirts

Georgia Copper

Ham-Cram
Expert Linears

morseDX

Ni4L Antennas

N3ZN Keys

West Mountain
R&L Electronics


Do you like to write?
Interesting project to share?
Helpful tips and ideas for other hams?

Submit an article and we will review it for publication on AmateurRadio.com!

Have a ham radio product or service?
Consider advertising on our site.

Are you a reporter covering ham radio?
Find ham radio experts for your story.

How to Set Up a Ham Radio Blog
Get started in less than 15 minutes!


  • Matt W1MST, Managing Editor




Sign up for our free
Amateur Radio Newsletter

Enter your e-mail address: