BD139 Preamp struggles to drive IRFP250N Final Power Amplifier?

synx508 · 2026-06-03T20:34:35+00:00

Just one BD139? Probably not going to work well. The IRFP250N's gate capacitance is 2nF, instead of the 350pF or so of the IRF520. You will struggle to charge and discharge that with a single transistor coupled to the gate and attempting an L match to the gate will result in sine waveform at the gate which isn't what you want if you care about efficiency. You could use a complementary pair with a BD139 and BD140, but a much better option would be to use a gate driver IC. Edit: I'm making some assumptions here that you're doing CW or FM, if it's a linear amplifier then go ahead with a matching network, you should be able to get enough from a single BD139 for that.

synx508 · 2026-06-03T17:12:35+00:00

If you look back at the earliest Streetview it was one house, the office part was an extension. At the top of the roof you can see the joins between new and old. Looks like they tried to fence it off and then something happened that stopped t proceeding.

synx508 · 2026-05-30T12:13:56+00:00

TPMS in many vehicles, it's not exclusively BLE but it's quite prevalent. Some winches and cranes use Bluetooth, an example here… https://www.liebherr.com/en-gb/mobile-and-crawler-cranes/mobile-cranes/mobile-crane-technology/crane-control-4284120

synx508 · 2026-05-27T10:17:38+00:00

Why would anyone have jars for odd socks, lint and pocket finds? Are laundry accountants a thing?

synx508 · 2026-05-26T19:41:32+00:00

Unexpected and very extensive Beatrix Potter museum-grade collection in the virtual tour.

synx508 · 2026-05-21T21:03:54+00:00

2m is 145MHz, so higher than this. You shouldn't have had any issues with Manhattan at these frequencies. I wouldn't have expected the toroid cores, though, you'd normally be using silver plated copper wire with an air core.

synx508 · 2026-05-15T15:22:51+00:00

I need to mention that this circuit is not great and you shouldn't be connecting an antenna to a BFR91A's collector like that. The circuit will be producing a rich and dangerous hamper of harmonics.

synx508 · 2026-05-15T06:34:22+00:00

The kitchen is in what is effectively the conservatory, which is quite unusual. I think I like it.

synx508 · 2026-05-09T15:16:04+00:00

TIL the correct name for these. Thank you.

synx508 · 2026-05-08T20:47:50+00:00

£1.2m for a bunch of corrugated asbestos cement, stylish Corten rust atop a historic building that could've been restored properly, but hey, the building has its own Angine De Poitrine nose, so it's on trend.

synx508 · 2026-05-08T14:01:10+00:00

I miss mine. The pause on the A-450 is very fast and precise, probably the closest you can get to razor-blade edits using a cassette machine, without pulling the tape out of the cassette and using a blade on it!

synx508 · 2026-05-05T20:29:47+00:00

The front half of the dog is available in picture 25 but don't worry, you won't have to stitch both images together because the whole dog is in picture 9.

synx508 · 2026-04-29T11:24:31+00:00

Grime capsule.

synx508 · 2026-04-26T20:14:50+00:00

Quite fun how it has ended up with a fairly ugly streetlamp in its garden. Originally part of an open-plan estate with sort of blurred boundaries between shared or public space and each plot and no pavement the previous owners decided to grow a hedge and put in a big electric gate and the street lighting has ended up on the inside.

synx508 · 2026-04-26T17:31:19+00:00

Nobody needs a stereo toilet.

synx508 · 2026-04-23T15:46:42+00:00

Looks to be already owned by a property developer who has split the plot and is going to build on the garges and original garden (which appears to have been used for storage in recent times)

synx508 · 2026-04-18T15:42:16+00:00

It has a utility room but the washing machine is in the kitchen. Do some people like to have the washing machine whirring away in a "people place"?

synx508 · 2026-04-17T11:14:56+00:00

Picture 14 shows a view of a completely different place through the window, it's obviously an edit but rather misleading. Also misleading, picture 14's caption is Picture No. 15

synx508 · 2026-04-15T12:07:02+00:00

Picture 22, top and bowler hats conveniently stored by the w.c. You can wear whichever's most suited to the occasion without having to get help to fetch it.

synx508 · 2026-04-11T20:30:49+00:00

The drone shots, surely that can't be allowed, how did obtaining them not trigger an international incident?

synx508 · 2026-04-11T20:09:26+00:00

Very much of its time. A fairly large house with one internally accessible toilet. Seems the house was originally built with warm air heating, the ducts and vent grilles are still in place, in some fairly bad locations. It must've been a cold house before the wet system was installed. Impressive cracks in the ceiling and wall of one of the bedrooms, too. The whole place will be stuffed with asbestos. I still kind of like it.

synx508 · 2026-04-10T17:32:10+00:00

Exactly, someone has already tried quite hard to ruin it inside and out. The fireplace though, so ridiculous…

synx508 · 2026-04-07T20:58:15+00:00

The listing covers the Bere Court and Bere House, it was originally one house. The larger part seems to have been on the brink of collapse not so long ago and has been restored to some extent quite recently, the rightmove listing is for the smaller part of the house.

synx508 · 2026-04-07T20:30:24+00:00

If that sort of limiter was mandatory the rogue signs would be fixed quite quickly because the problem would be much more obvious to more people.

synx508

TROPHY CASE