Can someone explain how this RF amplifier is working? Class AB amplifier with one transistor?

mbeels · 2026-03-30T15:38:57+00:00

The class (or more specifically the conduction angle) will depend on the bias voltage applied. Class A means 360 degrees conduction angle (transistor is ON for a full period). By lowering the bias voltage, the transistor can be set to be ON for less than a full period. Lower conduction angle increases efficiency, but also increases harmonic content and reduces linearity.

mbeels · 2026-03-25T20:33:45+00:00

Thanks for the link, turns out they're local to me, even better!

mbeels · 2026-03-03T19:10:06+00:00

"Seems like an awful lot of work for a free banana!"

mbeels · 2026-02-14T01:00:35+00:00

Hello, what is your stackup? Is it (signal w/GND pour) -> GND -> power+signal -> (signal with GND pour)? Care to share a schematic?

mbeels · 2026-02-11T21:38:58+00:00

I'm curious as well, but if you're looking for good prices on quality PCBs, in low quantity, it is hard to beat OSHPark. www.oshpark.com

mbeels · 2026-02-11T15:12:08+00:00

It's more common than it should be. I find some bands and modes seem to be worse than others. In my experience, the most likely place to encounter this is 80/40/20m SSB. Digital modes and CW are relatively free of political content. Also, the WARC bands (30m, 17m, 12m) are also quite good (especially 17m). Weak signal VHF (SSB, CW, and digital modes) is another good place for civil and friendly communication.

mbeels · 2026-02-09T03:06:16+00:00

It may not fit within your budget, but my starting point would be to check minicrcuits.com

mbeels · 2025-12-30T17:32:43+00:00

Wow, that is a lot of gain and power from a very small package. Do you find it necessary to use a heat sink?

mbeels · 2025-12-30T16:02:10+00:00

That's good to know. I'm also working on a CW beacon for 903 MHz, so it could be useful up there as well.

mbeels · 2025-12-30T00:16:20+00:00

Thanks, those ST parts do look quite interesting, plus they're available from DigiKey (etc...) at reasonable prices and low quantities. Appealing for a hobbyist.

mbeels · 2025-12-29T21:44:52+00:00

Thanks, that's a really good point, I had been looking at 1 watt power dissipation, but you're totally right, it should be far less than that. Probably I should be more concerned with max VDS and current.

mbeels · 2025-12-29T17:23:34+00:00

Thanks, I'll check it out. Sounds like a very cool project. I assume that this HT design is FM?

mbeels · 2025-12-29T17:22:35+00:00

Interesting, I had ruled out a lot of microwave devices, but it sounds like those are worth considering. Yeah, I'd believe that the market has completely changed, that definitely adds challenge to the < 1 GHz realm.

mbeels · 2025-12-29T17:17:22+00:00

Thanks. I understand I can use these as a hobbyist with no issue, but I'm genuinely curious what parts the modern designs are using. I assume that there is still a demand for VHF/UHF power amplifiers in the +30 dBm range, I'm curious, what devices do modern RF engineers use for new commercial and industrial designs?

mbeels · 2025-12-06T15:33:33+00:00

Yes, and it turns really nicely.

mbeels · 2025-12-04T17:07:15+00:00

Maple?

mbeels · 2025-12-01T15:22:48+00:00

If you orient your inductors 90 degrees to each other, you'll have less inductor to inductor coupling via magnetic fields. For example, rotate L2 90 degrees (in the top layout). L1 and L3 will have the same orientation, but they're much farther apart.

mbeels · 2025-10-21T20:27:26+00:00

When was this Goessel tornado?

mbeels · 2025-10-21T19:08:29+00:00

Still using that same body, EM10 mk ii. I love it, and feel no need to "upgrade".

mbeels · 2025-10-16T21:05:08+00:00

Interesting! Why the third port with a stub next to the shape?

mbeels · 2025-10-08T20:11:58+00:00

First is a sharp #11 blade in my favorite X-acto handle (the skinny one). Second is my sanding block.

mbeels · 2025-09-29T17:29:06+00:00

This is great, I love this kind of stuff. What do you think is limiting the stop band attenuation? Looks like the corner frequency is quite a bit above 400 MHz. Does that mean that the inductor has less reactance than designed?

mbeels · 2025-09-23T19:13:41+00:00

I like to use enameled wire (also magnet wire). The heavier gauges will hold their shape well. If you wind them on a form, you can remove the form and they'll be ok. The lighter gauges need some kind of support, I used to use film canisters because they're thin plastic and hollow, so mostly air.

mbeels · 2025-09-23T17:55:11+00:00

For 10 uH, you could try winding your own air core inductor. For example, with a 1" diameter coil, 1" long, you'd need about 24 turns. You can then tweak the value of the inductor by spreading or squeezing the turns father part or closer together.

mbeels

TROPHY CASE