0.2MHz - 2MHz step up transformer

Careful. That can quickly ruin an engineer's marriage. There are things that are better left non-calculated :-)

--
Regards, Joerg

http://www.analogconsultants.com/

And if you bias it in the middle you better had liquid cooling for that transistor :-)

It was possible with the old BF types that you could screw onto a heat sink but AFAICT they don't make those no more.

--
Regards, Joerg

http://www.analogconsultants.com/

Piece of cake. #43 ferrite works just fine for that, it's not even expensive. End of last year I designed something similar but for north of 50 watts.

Core loss != power to be transferred :-)

It takes a lot more to heat up a core. Although I must confess that I have accidentally detonated a two-incher at about 1200W of transferred power but that was as a kid. Should have used a stack of two but that wasn't in the budget back then ...

Actually, at 2MHz it does.

That depends on the number of turns. You can get to 200kHz with the right material. Then I'd probably opt for something like #77 material but many times the core shape I want only comes in #43. Such as the BN block-style cores. Got to live with what's on the menu. Just don't ever let things saturate with ferrite.

With pot cores you can get almost any material but I do not like pot cores too much.

Then Tim and I must live in the same universe :-)

--
Regards, Joerg

http://www.analogconsultants.com/

On a sunny day (Mon, 23 Jan 2012 10:51:53 -0800) it happened Joerg wrote in :

Yes, heat sink needed. I once bought a transistor replacement for the PL802 I think it was (IIRC) TV video out tube. It had a FET and a power transistor on a heat sink, and a large wirewound resistor so it would not interrupt the 300 mA heater chain.

Anyways, finally managed to get dvb-terrestrial, plus DVB-satellite HD (DVB-S2) working on this laptop, it is recording now, testing if I can screw it up by doing lots of other things at the same time. This will replace my media PC, still have to test HD. A hundred patches and compiles and recompiles were needed. And it runs smooth in Linux, unlike in redmond7 virus,

I am intending to drive electrodes with a variable 200Khz to 2MHz sinewave, at around 100Vpp, in an experiment to inhibit soil bacteria.

Hence the specified 1K Ohm inductance at the output.

If it matters, 50V output would possibly be adequate to get me started

Of course this can easily be done at audio with an off-the-shelf amp and PA mathcing transformer. I had hoped to extrapolate this to IF.

If I just used a HV amp, a load matching netweork might still be needed anyway.

Any further suggestions, or transformer fabrication details, would be most appreciated.

Thank you for the replies so far.

Paul

Ah, that reminds me of the old days. Somewhere I still have that article "Torrenbuizen" from the Dutch ham radio magazine of the VERON. No, it was not in the Vonkenboer :-)

Years ago there was an issue in the test set of a client. We were eating lunch and I said "Oh, that's easy, we'll just use a video transistor". Shouldn't have said that. Back in the engineer's cubicle we quickly found out that those had gone the way of the dinosaurs, extinct.

You guys must watch a lot of TV. My wife would not want a PC in the living room and I don't either. We watch the evening news and maybe one old movie. That's it.

--
Regards, Joerg

http://www.analogconsultants.com/

Ok, so no big capacitive load. That helps.

Nah, why not go all out and do 100V? :-)

BTW, if neither electrode has to be grounded you can drive push-pull. One goes to +50V while the other goes to -50V and vice versa.

Just add a few Versa-Pac transformers to your next order, maybe VPH4-860:

100-200uH per winding would be good. They aren't truly bifilar, just a little, but then again 2MHz ain't that high. Maybe it works. Drive one winding, stack the five others. Hang a 2nd one parallel on the primary and stack its five remaining secondaries in series with the five of transformer #1. Buy a few lower inductance variants as well, in case the 680 won't get you to 2MHz.

If they don't perform well enough then an order at Amidon-Corp is required. Some big fat #43 ferrite toroid or double-hole core, some wire, and wind your own. Rule of thumb: The Z (2*Pi*f*L) should be about four times whatever the transformer load impedance is. At the lowest frequency you want to use. For example, if you made a 1x plus 9x transformer where the 9x gets stacked on top of the 1x primary then with a 1k load the source gets loaded with about 10ohms. So about 35uH per winding would be ok. Way to wind them is you take a bundle of ten wires, twist that slightly, then would that "long sausage" around the core as many times as it takes to get to

The Amidon BN-43-7051 core is pretty good if you can get the wires through the holes. Should be possible because 200mA is not a lot and that goes only for the primary. All the secondaries can be much skinnier wire. Two turns is kinda skimpy but could be enough here and I don't think you can squeeze three through there.

Now drive this hard with 10V. The really good buffers from my youthful days are extinct but you could try these:

Use the TO220 version and a heat sink because they'll get hot.

--
Regards, Joerg

http://www.analogconsultants.com/

One suggestion - limit the frequencies you emit, to those which are FCC-categorized as being in one of the ISM bands.

Although it may seem counter-intuitive, soil driven in this way can make a fairly good antenna. Certainly, RF currents flowing through the soil structure do play a very important role as part of the "ground plane" of many ground-mounted vertical antennas, both for receiving and for transmitting.

If you simply frequency-sweep through the 200 kHz - 2 MHz range willy-nilly at the power levels you are mentioning, you will almost certainly radiate enough RF signal to create Cthulhu's own amount of RF interference through several different bands, including AM broadcast and the amateur 160-meter band. You may generate enough harmonics to interfere with the 75- and 80-meter bands as well. You're likely to have people (hams, AM-radio listeners, and the FCC itself), showing up on your doorstep and asking you more or less politely to Cut It Out Right Now.

--
Dave Platt                                    AE6EO
Friends of Jade Warrior home page:  http://www.radagast.org/jade-warrior
  I do _not_ wish to receive unsolicited commercial email, and I will
     boycott any company which has the gall to send me such ads!

My wife is a speech pathologist, and has phenomenal language and people skills. SPs tend to marry engineers, to do the grunt work for them. Maybe they feel sorry for us, too.

I do the cooking that involves any serious time:temperature profiles.

John

I think that would be obvious with a use of an amp, you simply use a series R in the load or current limit the amp to equate to the same.

Jamie

So do nurses (my wife's original background before she went into industry). She said she vowed not to marry an engineer and then ...

One thing I learned lately: Do not question the price of a hand bag :-)

I used to cook my own elaborate meals every day while at university, didn't like any of the cantina foods there. Since my wife is much better in that department my cooking duties is now reduced to Sat/Sun, barbecue. But then everything is cooked outside, meat, vegetables, pizza, bread, potatoes, whatever she hands me.

--
Regards, Joerg

http://www.analogconsultants.com/

IFYPFY

My wife is the epitome of feminine grace and elegance. Just a few minutes ago, she delicately remarked to me that "The great thing about beer is that the burps are so satisfying."

John

(full of Dungeness crab, sourdough, Purple Haze.)

My wife has a nursing degree, though she got it after we were married. She's never used it, since the kid came along a couple of months after she graduated.

Oh, I always do. I don't care but I always question it. She pays me back when I buy tools. ;-)

I can't stand cooking. Since I'm by myself four nights a week, meals are pretty monotonous.

supply

Guys just eat ribs and Scoops over the sink. It just takes a minute.

John

*******

A little fraud here - and the last time I was in full-time work was May 2003, which isn't even one decade ago yet.

I Fraudulently altered Your Post for You. And got it wrong - as you'd expect from AlwaysWrong.

-- Bill Sloman, Nijmegen

On a sunny day (Mon, 23 Jan 2012 12:59:21 -0800) it happened Joerg wrote in :

I still have one...

(DVB-S2)

Not that much. Did you know there are a lot of religious channels on satellite here?

Actually the notebook in the living room is not so bad, you do not even notice it next to the 46 inch LCD, the 300 W RMS amp, speakers, the DVD player, the mp3 player, the DVD collection, and now that cigarette sized HD USB receiver, lotsa cellphones, other laptops, gadgets, what not. DVB-t antenna. I got a new insurance against burglars. In Amsterdam I was robbed 12 times.... Up here does not seem to happen.

It doesn't qualify as "a few years" either, asshole. After three, the term is "several".

supply

Nah, they eat buffalo hot wings at the local beer joint while watching football re-runs on the big screen TV there and making caveman noises :-)

--
Regards, Joerg

http://www.analogconsultants.com/