Post #4188216

2026-07-11 05:20 UTC

Can we for concreteness discuss this DIY arrangement from https://homebrewcorner.blogspot.com/p/pa-150-hf-linear-200w-amplifier.html just as an example for the kind of design I am talking about. This apparently uses such a push pull configuration with two separate core halves. The OM says they get appropriate power levels out of this and there is no reason to doubt the measurements shown. But how? Is this due to high quiescent current settings making the "off" transistor still do some work on the other half wave, or do the parallel caps work some magic here? #hamradio #electronics

Replies (2)

@fullywoolly@mastodon.social 2026-07-11 05:38

@Quantensalat@scicomm.xyz first off these aren't FETs they are BJTs. I don't know if it will help but what I'm seeing in the schematic is a winding with a center tap with the top transistor energizing part of the top winding to ground in one half wave, and then the bottom transistor doing the bottom winding to ground during the other half. The energy is transferred to the other winding on both portions of the wave. I've never made a linear amp and never done power electronics with BJTs so could be wrong.

Open ##4188217
@vk3kri@mastodon.radio 2026-07-11 06:13

@Quantensalat@scicomm.xyz IN "Linear Amplifiers for Mobile Operations" https://www.communication-concepts.com/content/AN762/AN762_Application_Note.pdf Granberg says that if the DC feed is done through the center tap of the '1 turn' transformer, rather than the bifilar feed , the IMD and power output is unaffected , but 2nd harmonic suppression may be reduced by 10 dB. Given he was doing this in the Motorola lab I figure he knew what he was doing , but I still don't see how it works.

Open ##4188220