AoE x-Chapters, High-Speed op-amps section, DRAFT

That was just the edge of downtown. Our new business place is much better. Where we live is a nice clean little village with a canyon full of critters.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

True. That transmitter is somewhere in the Ukraine. I'm 6,000 miles away in California.

Also in the Ukraine and a different problem. That's a 150 kW short wave broadcast tower. The cut cables are the tower grounds across the concrete tower leg supports. They're for lightning protection by providing a bypass route around the concrete. Without such ground wires, lightning would go through the concrete which would then explode in a rather messy steam explosion. Concrete is about 15 - 20% water. Such ground cables are usually made from copper and are a prime target for copper thieves.

--
Jeff Liebermann     jeffl@cruzio.com 
150 Felker St #D    http://www.LearnByDestroying.com 
Santa Cruz CA 95060 http://802.11junk.com 
Skype: JeffLiebermann     AE6KS    831-336-2558

I probably mis-remembered the actual values. But good points about placing the vias for them.

Definitely not in

A pair of dipoles fed in quadrature gives a turnstile antenna. A reasonable solution if nulls are a problem.

That's what used to be on most apartment buildings in Germany for AM reception, combined with FM/VHF/UHF, amplified and then fed into the radio and TV lines to each apartment. I never saw it for a transmitter though.

This has fallen by the wayside a long time ago and now I think they discontinued AM band transmissions. Not a smart move IMHO.

--
Regards, Joerg 

http://www.analogconsultants.com/

Not trying to be difficult, just to understand. (I have profound respect for your RF chops, as you know.) Do you have any data about "cannot handle the transients at the onset?" ISTM that it's mostly a well-grounded impression that RFI crap can show up anywhere at seriously inconvenient amplitudes if one is't knowledgeable as well as careful. Amirite?

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

On a sunny day (Tue, 16 Jul 2019 13:27:09 -0700 (PDT)) it happened Lasse Langwadt Christensen wrote in :

Would not like to stand there. OTOH his camera has no problems it seems, is just RF HV being rectified, AM station?

You know as little about broadcasting as you do about CATV.

FM is circular polarized, not vertical. Vertical would favor car radios and portables with a whip. Home receivers with an outdoor antenna are Horizontal, which was originally used for FM broadcasting. They switched to circular to serve both markets.

Here for main TV transmitters, yagis are placed horizontal. To get the smaller repeater sites used to fill in the gaps, end user's yagi needs to have its elements vertical.

NT

I don't know of any datasheet information that's useful. Not 100% sure about the mechanism either, just that it's really bad with BJT opamps. What I think happens is this:

The first stage in an opamp is a diff pair with a wimpy current source in the common emitter leg. A few microamps in slow opamps. This does not allow the first stage to react really fast upon a regular input signal. At the same time this current source has capacitance. The capacitance does not matter in normal operation.

When RF sneaks in and rectifies at the BE junctions of that first stage it often gets into only one of the BJT, or into both and then with opposite polarity because PCB traces form a small dipole antenna. Rectification is instant and hard because at a GHz the tiny capacitance of the current source does matter. IOW lots of 1st stage non-diff gain

-> wham-bam. The feedback loop can only react to that after this unwanted pulse has reached the output which is too late to muffle the onset of this rectified signal.

IOW, it's the usual voodoo :-)

--
Regards, Joerg 

http://www.analogconsultants.com/

You could have said that more politely. I do (or did) know CATV quite well. FM and stuff is back from Europe.

You are correct. I mixed that up with AM. FM is or at least was horizontal, that's what the turnstyles were for and AM used the vertical whip.

--
Regards, Joerg 

http://www.analogconsultants.com/

Polite haa gone out of style here in the U.S.

--
 Thanks, 
    - Win

One way to avoid front-end RF rectification is to use a chip that just amplifies anything that shows up. Specifically, one can sometime use multi-GHz MMICS for AC or pulse gain.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

I find most people to be polite and cheerful in person [1]. And lately I see a lot of very considerate driving, with people waving or something to acknowledge courtesy. Of course, there are still a lot of rude jerks who cheat to gain small advantages.

Without physical proximity to another's face and body, it's easy to abstract a car or a usenet post as not representing a person.

A few of the posters here are basically 100% personal insult generators. I wonder what they are like in real life. I'd guess that they are very self-centered, which explains why they are bad with objective things, like electronics.

[1] Not to change the subject, but we went to lunch on Saturday at The Old Clam House and afterwards Mo put her backpack into the rear seat of the Audi and slammed the door. As we were about to drive away, we heard a tinkling sound in the back. The rear side window was slowly, progressively shattering itself into a thousand pieces, still stuck together. When we got home, there was a mobile car-window truck working just across the street. The guy hand-wrote their phone number on a dirty scrap of paper. So I called and they were super nice, and another guy showed up at 6:30 PM with the replacement glass. He did a wonderful job, even swept and vacuumed the sidewalk of little glass bits. He didn't speak any English but we got along great. I gave him $40 extra.

America is great. So way are so many people rude and angry?

Well, a few of them are Australian. Are Australians especially rude?

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

I read the 22MW number in some article about the tower. It may be ERP in some plane.

In my office, a pair of 3' banana leads from my Fluke to a schottky diode makes about 80 mV. Some may be 60 Hz, but a lot seems to be rectified RF.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com

On a sunny day (Wed, 17 Jul 2019 10:10:54 -0700) it happened John Larkin wrote in :

80 mV is enough (if some current) to start a JFET oscillator with step up transformer to light a LED, here from a thermocouple heated with a lighter

Depends bit on the Zi of your ciruit.

That wouldn't be very palatable in most of my situations. Mostly the replacement part can't cost more than 10c and it can't draw more than half a milliamp.

--
Regards, Joerg 

http://www.analogconsultants.com/

You weren't the least bit polite when you claimed that FIOS was CATV. You've also claimed that you don't read anything posted from Google Groups.

That was years ago when Google spammed groups was and thus necessary. What's that got to do with politeness?

--
Regards, Joerg 

http://www.analogconsultants.com/