I spend weeks deciding...

[Amphiprion]

...if I want to shell out the cash for a 300MHz oscilloscope, or if I should just get the 100MHz version. I decided to go with the 300MHz one for digital audio and PWM purposes (24.576MHz bit rates on 24/192 and cleaning up PWM amp signal edges to prevent messing up the FM band).

It turns out that, as soon as I power up the 300MHz scope, I discover that the big tower two blocks up the road is the local Channel 12 broadcast tower. Kilowatts, just two blocks away. Kilowatts. Two blocks away.

Frequency? 204MHz.

Any chance February 2009 will change this? I can't exactly sell the house to get away from the tower, and short of kicking in the 20MHz BW limit it puts a nice small little sinusoid right on top of everything I do.

[NEO Dan]

That sux big time :M , I think the signal will remain at 204MHz, but will be QAM on top of that carrier instead of just sinusoid. Actually i'd call the engineers of the station and ask for advice on how much aluminum foil it takes to shield the nads. 8O

[Amphiprion]

Would lead paint help? I can always repaint the room...

Besides, the tower is only two blocks up the road and a hundred or two meters high. Maybe a range finder and dad's deer rifle? That's probably a bad idea

QAM will only make things worse. I can see a sinusoid and mentally ignore it...

ETA: I wonder how badly it would hose up something like a benchtop multimeter.

[Hdale85]

Get some copper mesh and built a cage around your desk

[Amphiprion]

Maybe there's something to those tinfoil hats...

[NEO Dan]

Maybe you could build a testing hut from that aluminum faced foam-board insulation and some aluminum foil tape for ductwork. %100 foil shield

[Amphiprion]

That's a far cry from the 10 meter EMI shielded test chamber I used to have access to :/

That's what happens when you quit your job though. Meh.

[1Michael]

"Maybe there's something to those tinfoil hats..." Absolutely, but it must be in the shape of a large speaker like the one I'm building. http://www.htguide.com/forum/showthread.php4?t=11873 8)

[Dennis H]

You know, I suspect stuff like this is why some people hear big differences with fancy wire and some don't. Megawatts of RF bombarding your gear and trying to get in any way it can just can't be a good thing, Martha. Fortunately, I live in a small town now, not like when I lived 1/4 mile from a TV tower. Man was that a pain.

[Amphiprion]

With the ground clip attached to the probe lead (shorted) I get a real nice ~200MHz sinusoid at between 20 and 60mV pk-pk. Blech.

[Hank]

Yep, quitting your job led you to the path of the radio waves. We have two faraday cage test rooms at the plant here - that's the ticket - yeah, build a faraday cage around your workbench area :T Also, you can have my leftover leaded paint.

See you at my house Friday for Texas Hold-'em poker. I want your money :twisted:

[Amphiprion]

You think I should tell these guys what job I had? They would probably think me crazy for quitting. I mean, with what I could tell them about Tripath alone....

Anyway, you can have my money. Just make me some of those fajitas Is the buy-in $5 or $10 this time?

[---k---]

Yuuummmm..... Fajitasssssssssssssssssss.

[Amphiprion]

Take a trip down to Austin --k--, we'd love to have you!

[Scottg]

..build a faraday cage around your workbench area :T

..or simply test it in your car - thats a faraday cage. :W

[Brian Bunge]

Yep, quitting your job led you to the path of the radio waves. We have two faraday cage test rooms at the plant here - that's the ticket - yeah, build a faraday cage around your workbench area :T Also, you can have my leftover leaded paint.

See you at my house Friday for Texas Hold-'em poker. I want your money :twisted:

Damn, can I come too? Oh wait, I don't play cards....

[Amphiprion]

Neither do any of us. It's mostly drinking and throwing chips around. The cards you are holding matter little

[JJones]

Aluminum foil is not all that expensive, eh? Seriously, can't you build some kind of shielded work area inexpensively?

[Amphiprion]

Trust me.... no I've already tried foil.

Most of my work at my last job revolved around reducing EMI emissions (for example, preventing a PWM audio amp from interfering with the FM band). Using a certified EMI chamber to test our designs cost thousands per day. With tens of kilowatts just two blocks up the street, a home brew version just isn't feasible.

[Hank]

Come on over, Brian, and bring your unmarried sister-in-law :W Some of the guys are very good poker players: Stogels, Tubes, Big Dog and Barrister.

Mark, I dare you to tell these guys where you worked in Austin 'til recently. :P Since you're unemployed, I'll make the buy-in $5. Burgers this time, not fajitas - less work for me.

[Amphiprion]

LOL. Yes, 'KK' Tubes and Five-Deuce Stogel are forces to be reckoned with at the table, but they do ease up at our games (well, maybe not Tubes ). As far as your dare...

I worked at Cirrus Logic in Austin as a factory applications engineer. I was supporting pulse width modulation amplification products, hence my access to all manner of cool stuff - unfettered access to the latest Audio Precision gear, $25-50K 1GHz+ oscilloscopes, 10 meter certified EMI test chambers, and of course the knowledge of what the Tripath intellectual property Cirrus bought will be turning into, product-wise.

Of course, I can't repeat any of it. So don't even bother asking - not worth me getting sued over.

As far as the buy-in, it's moot. I'm taking home money anyway

And crap, while typing this my brand new monitor just went on the fritz. I've got vertical rows of pixels that are out. Bummer, it's going back...

[Hank]

All right! Let the questions begin!

I'm taking home money anyway

Yeah, right.


Vertical rows of pixels: are you sure someone didn't sneak up behind you and plug the Matrix control cable into the base of your skull? :twisted:

[Amphiprion]

No, this is definitely a flaw. It's going back.

[Saurav]

$25-50K 1GHz+ oscilloscopes

2nd year electronics class, lab test/viva/interview thingy, the professor asks me what the bandwidth of the scope was that I'd just used in my experiment. I said, I think it's a couple of gigahertz. He says, are you sure. I say, yes, I think so. He says, OK, makes a note, continues with his questions. I think, sweet, passed that one, I have no idea what the bandwidth is.

On the way out of the lab, I check the scope. 20M. Hmm. Go online and look up what a GHz scope costs. Shit.

[Amphiprion]

Thinking back to the junk equipment we had access to in college, 20MHz analog sounds about right...

[Dennis H]

Hey, at least you can buy a GHz (or as Doc Brown would say, jiggahertz ) scope now. Back in my youth, I had a summer job at Tektronix working with the design team trying to beat HP to be the first to reach 1 GHz. Pretty exotic stuff for a dumb kid.

[Amphiprion]

I was at AMD working on K8 (aka their current processors) back in 2001 as a college student I never had any passion for it though. Electronics is way more fun but doesn't want to pay as much. I would have had a heckuva fun time working on a GHz scope.

Were those analog or digital scopes? The last analog scopes I know that Tek made went to 400MHz I think (2465B)?

As an aside, we had a guy from Romania who got his PhD in robotics and was an awesome electronics engineer at my first job out of college. He always called it "jigga" whatever. I don't know if it was a language thing or if he just liked to mess with people's heads. This guy was a veritable deity when it came to electronics, so I always thought it funny.

[Dennis H]

Yeah, this was waaaaay back so it was basic analog stuff. No problem getting the electronics to sweep that fast but, with a conventional CRT, the density of the electrons hitting the phosphor wasn't enough to light it up at those speeds. So we were trying to build an amplifier screen behind the phosphor layer that would send out many electrons for every one that hit it. It sorta worked but they never got it good enough to market as far as I know.

[sokoban]

Maybe there's something to those tinfoil hats...

Unless you're working at about 1.5 GHz, not so much apparently.

http://people.csail.mit.edu/rahimi/helmet/

[Amphiprion]

LOL. You gotta love grad students.

In other news, here's an output pin of a microcontroller transitioning from low to high (and my awesome dog, that Hank won't let come to poker parties):