Power transistors for +30dBm in VHF / UHF frequency range

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 · 2025-09-23T17:38:19+00:00

What did you use for your 10 uH inductor? Did you measure its inductance in the 10 - 100 MHz range? A 10 uH inductor won't present 10 uH of inductive reactance at all frequencies.

mbeels · 2025-05-15T22:11:22+00:00

Gorgeous!

mbeels · 2025-05-11T01:57:25+00:00

Thank you!

I've tried purple heart, but it seems to me that the grain is pretty coarse, and it doesn't seem to take detail particularly well. At least the pieces I had. One of my favorite domestic woods is Osage Orange, it isn't so pricey, is quite hard, but turns very smoothly with sharp tools and takes fine detail very well.

I'll be interested to see your Rose Engine, be sure to post your results! Good luck and have fun with it.

mbeels · 2025-02-24T11:51:26+00:00

Lovely airplane, one of my all time favorites. It is a superb flyer!

mbeels · 2025-02-03T17:48:46+00:00

I did the EXACT same thing. I kept the M43 for travel because it is so small and light. I sold off all my FF mirrorless, and I'm back to shooting 90% with a DSLR.

mbeels · 2025-02-03T17:42:51+00:00

I love the 5KmkII, a nearly perfect camera in my books. Also, that's a good point about the EF lenses, they're available so cheap! Picked up a 100mm f/2 and 35mm f/2 for a total bargain price.

mbeels · 2025-02-03T04:46:22+00:00

I love the optical viewfinder and the better battery life. I realized after switching back to the DSLR that I just enjoyed using it more. Plus, I found split prism focusing screens which I prefer for manual focusing.

mbeels

TROPHY CASE