Small EMC antenna

Fred Abse snipped-for-privacy@cerebrumconfus.it posted to sci.electronics.design:

Maybe not, considering the crime

Joerg snipped-for-privacy@removethispacbell.net posted to sci.electronics.design:

Mucho thanks. i have barely started reading the manual and can see why it was one of HP's last masterpieces. Reminds me of when i had an opportunity to fiddle around trying to play a B3.

I can't play it (my wife can play some songs though) but I had the "pleasure" to repair a M100. It had been totally neglected, played for almost 10 years without oiling, shafts completely seized and gummed up. After 20+ hours of hard work it's purring again but does on occasion need three generator start attempts so it doesn't squeal. The sad thing is that this organ came with half a can of Hammond oil. But nobody had bothered to put it in there :-(

As for the analyzer, yes, that was IMHO one of the last masterpieces by the old crew. Same for the 3577 which, of course, is the network analyzer du jour here in the lab. Later they outsourced R&D to Yokogawa and I wasn't too much of a fan anymore. Then the topper: A fairly new Agilent spectrum analyzer, EMC pre-compliance at a client. Had a hard time figuring where some serious peaks were coming from. Thoughts crept up that the Porter I had the night before may have impaired my thinking. Then I found it: The noise originated at the flat panel display of that analyzer itself (!). Had to go to the HW store to buy spark screen for shielding. Pathetic. I believe companies like Tek or Agilent need to pucker up WRT engineering or the Asian competitors will eat their lunch. I've already fallen for it, bought a Taiwanese DSO. Not because it cost less, it simply is better.

I sometimes wonder where my Hammond organ is (T3? It was the home edition of the B3...) My parents got it for me back in the early 70's, but when I went to college, had no place to put it. Had it for a while again in the 80's, but when I went back to get my Master's, let my sister have it, and haven't spoken to her for almost 15 years. It kept breaking keys, and it was a major hassle to replace them...

Charlie

Maybe visit her?

AFAIK ours never broke any keys. It was bought by the original owner in

Yeah, could be truly amazing when you started modulating the Leslie, and started playing counter-tunes on the footboard!

But don't even know where my sister lives (and, since we moved to the desert, we are now probably withing 10 miles of her!) We had a falling out after our mom's death, and have barely spoken since.

Charlie

Someone, has already posted the design. I built a copy of the HP11966P broadband antenna,(check out the HP1995 catalog) from one I borrowed for a few weeks. But it is hardly aircraft portable. It will however do a full compliance test if I could ever be motivated to get a certificate for it. BTW It covers 30Mhz to 1Ghz with its wings attached. or 200Mhz to 1Ghz without.The LISN spec and designs are buried in the EMC specs somewhere. I haven't reproduced them but IIRC they are fairly simple. I also did the accompanying preamp and made a cable out of LMR400 30 metres long.

regards Andrew

Yep, that's the usual discone/logper combo. It's also in the 1999 catalog. Those things will raise some hackles at the checkpoint.

I'd rather get a used one if needed. By the time you bought all the aluminum and treated the bleeding knuckles it might not pay to build one.

The LISN isn't a big deal. What is a big deal is educating people to never, ever, power cycle the DUT while the analyzer is connected. Beep ... bzzzt ... $2000 repair and calibration.

Have you a website, or something like plans for your shop-built copy? I can't find an HP 1995 catalog. The 1991 catalogue has several antennas in the 11966 series, but no "P" and no pics.

Thanks and regards,

Barry

It was scribbled out on a sheet of paper which is long since misplaced, One of the things I found interesting was that the elements weren't placed in a straight line but in a log curve as they attached to the 2 beams. The original design was not HP but an English company Chase EMC Ltd.The spacing between elements was also logarithmic. I wen't looking on the Web and found,

which is a more compact design with bent elements.

Also

Which was basically the one I copied.

These ones which fit in a suitcase

This general explanation which is really quite good.

Also you could try and this idea is OT, to take a standard UHF/VHF Antenna and measure it and then apply some modification by chopping it's elements. The result may not be quite as good but I would expect it may not be much different from the real thing which when I costed it many years ago was about $AU10k. A TV Antenna maybe 1-200$. The obvious problem is it will probably have a dip at 200 to 400Mhz and >860Mhz or 520Mhz. Also its bottom range would cut out at 50Mhz. A bit of judicious trimming should be able to flatten the response out. Also they are normally designed to fold up for transport.

Hope this helps,

Andrew

Hope this helps.

Andrew

Thanks for the links.

As it happens, I picked up a few nice UHF/VHF TV antennas in a box at a yard sale recently for a few $. The plan is to use the major parts as the guts for a small EMC pre-compliance antenna.

These won't be transported so they can be fairly solid. I'm a reasonable hacker with a TIG welder, so they can be permament and robust. A hopeful side-effect of this is that their characteristics and hence long-term stability are "welded-in".

If the prototype looks promising, I may build 2 or 3 and try the old

Barry

Go to

make contact and they will get you a small wideband antenna with a known em to voltage transfer so that you can get a good emc pre-compliance measure!

marc

Thanks, Marc. I'll do that. Their products page is "under construction" but maybe their products aren't.

Called a few rental places because I need it next week but they don't seem to be too hungry these days, takes forever. Maybe I fire up the old DOS antenna field simulator and whip one up. Mise en bouteille dans notre garage ;-)

IIRC that simulator has a Swedish user interface. Oh man, it's been eons since I used it.