RF: Working a smith chart without a compass?

Hello Folks,

Since safety regs are now much stricter you cannot really take a compass on board an aircraft anymore. Chances are they consider it a weapon and take it away. Any tricks to share on how one can work on smith charts with that kind of handicap?

I have tried using a comb with a hole drilled into the end and stuff like that but it's really clumsy. It kind of puts a crimp into transmission line calcs.

Regards, Joerg

How about a laptop and software?

John

I read in sci.electronics.design that Joerg wrote (in ) about 'RF: Working a smith chart without a compass?', on Sat, 17 Sep 2005:

You mean 'a pair of compasses' - the drawing instrument, not the direction-finding aid.

Sharp point!

Assuming you are using a proper draftsman's instrument, not a school kid's one, remove the sharp steel point and carry among your spare pencil leads a 6H or harder (if possible) one, and sharpen it to a point with fine abrasive paper when you want to use it. Keep the unsupported length as short as possible, and adjust the length of the other (softer) lead to suit.

--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

But if we can just feed it alcohol ;-)

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

| 1962 | I love to cook with wine. Sometimes I even put it in the food.

That depends on the laptop.

This doesn't make your comments (re: slipsticks et al) any less true.

[snip]

Come on, Joerg, that's a bit of a stretch, the Citroen wasn't a CAR, it was a tin can. I used to drive a tin can until I realized they crash, or is it "crush", like a tin can ;-)

Yep, I used to drive the other fathers in Indian Guides nuts. I'd start dinner right after lunch... the buried charcoal trick, then we'd do our hike. At dinner time the others were burning hot dogs over the bonfire, while I and my two sons, were having roast beef, baked potatoes and green beans, and apple pie for desert.

But you do have to show wives how to pull the emergency track release ;-)

Now I agree with that ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Probably not, which is why our family car is a Q45. Got rear-ended once by a pickup truck... totaled the truck ;-)

I actually got the buried dinner trick out of a Girl Scout handbook ;-)

Which is why I expect to have some fun with my "contest"... 100% transistor-level... which, of course, I've been doing for some 45+ years ;-)

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
|       http://www.analog-innovations.com           |    1962     |
             
I love to cook with wine.      Sometimes I even put it in the food.

Hello John,

Yeah, but it ain't the same. Some things are easier done on paper. Also, the "modern" laptops run out of juice after 1.5 hours or so because they need to run the CPU at a Gigahertz just to write "hello world".

Regards, Joerg

Hello John,

Yes, I did. Most folks here just say compass but that, of course, doesn't make it right.

Well, it's grampa's old set. A very fine set so I don't want to run the risk of parts of it being taken away. The lead is a great idea. As long as it doesn't go "ka-crunch" on the first turbulence during the flight.

Regards, Joerg

Hello Jeff,

Thanks! I am going to look for one of these. Still sharp points but if they do take it away at least I wouldn't lose a fine instrument that has sentimental value.

Regards, Joerg

In article , John - KD5YI wrote: [...]

A high end TI graphing calculator would be better.

Go to the local 5 and dime and see if you can find a plastic compass. It would likely go past the screeners without trouble.

--
--
kensmith@rahul.net   forging knowledge

In article , John Woodgate wrote: [...]

I think McMaster-Carr carries thin G10 rods. If you sharpen one of these to a point, it would be reasonable strong.

--
--
kensmith@rahul.net   forging knowledge

Hello Jim,

Not on Jetblue. I guess you could get beer there if you really wanted to but IIRC no real booze.

Regards, Joerg

Hello Ken,

It won't have the resolution of ye olde smith chart.

That's what Jeff also suggested and I am going to find one of these.

Regards, Joerg

Smith Charts, as useful as they were, have been out of date ever since somebody invented the personal computer. Get yourselves out of the Smith Chart user/operating manuals and into the 21st century.

There are inumerable, small, easy-to-use software programs available which more than cover Smith Chart applications, with greater speed and accuracy, and without loss of educational value which the Smith Chart used to have. Anyway, the Smith Chart has its limitations and inaccuracies which are all too frequently ignored or users are often not aware of.

--
Reg.

I read in sci.electronics.design that Joerg wrote (in ) about 'RF: Working a smith chart without a compass?', on Sat, 17 Sep 2005:

They are extremely strong in compression, but don't bend without breaking. Hence the 'keep it short' advice.

--
Regards, John Woodgate, OOO - Own Opinions Only.
If everything has been designed, a god designed evolution by natural selection.
http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk

Hello Reg,

The same would then go for the slide rule calculator which I still use at times. It is indispensable for jobs like calculating filters and resonant circuits while trying to stick to catalog parts. And it weighs a lot less when you are trying to cram clothes and everything else into a pilots suitcase that doesn't exceed airline standars. I am trying not to be a space hog for overhead bin space.

A smith chart can be quite accurate. At frequencies above 100MHz it is tough to cut a cable to the precision that the chart calculates to. And caps below 5% are usually not in the cards either for cost reasons.

I use the laptop a lot but sometimes low-tech is just more practical. Also, I do not have to wait minutes while the puter sloshes through the Windows start-up and blows the first few percent of battery life on that.

Regards, Joerg

Hello Jeff,

Yes, laptops in the luxury price range can do what my trusty old Compaq Contura could do 15 years ago. I did use that one for RF calcs because if you throttled it way down it could yield 5-6 hours on a rather old technology NiCd. Enough for a 10 hour flight. Then came Windows and it was all over ...

My rule is a hard limit of $1500 for a laptop. They age fast, get banged up on flights, IOW they don't last long and are also a theft risk. In that price category technology has gone backwards, less battery life despite LiIon technology.

With cars it's a similar "backwards" trend. My 1969 Citroen could do

50mpg. Now even a hybrid has a hard time matching that and fuel-only powered cars are far away from this kind of performance. Except for some Diesel models from Europe.

It's like cooking on a Weber. Everybody can do a steak or ribs but rice, gravy and vegetables? Some people can't even get their cars out of the garage when the power goes. But the topper are some newly minted engineers. They can't even solder.

Regards, Joerg

Hello Jim,

True, its crash worthiness was a bit iffy. But I am not sure one of the new small hybrids would fare much better if they get hit by a Ford F150 or something like that.

Maybe you know this: 20 some years ago we pitched our tent and then a huge delegation of bikers rolled it. Harleys, tattoos and all. They invited us over for a beer. Actually, lots of beers. Before going to sleep they kneeded some dough and buried it inside their fire pit after throwing sand on it for the night. It was certainly not a precision gourmet chef job since everyone was quite snookered by then.

In the morning they invited us again to the scent of freshly baked bread. It looked a little like the Greek pita bread. Delicious. Then, vrooom .. brap .. brapa .. brap .. vroooooom .. off they went. Rolling thunder, as they say.

I looked up and down the web and couldn't find it. This must be the trick to bake bread overnight on mild winter days when you can let the wood stove go out before bed time.

Oh, she knows. But neighbors didn't. They also hadn't kept any non-cordless phones (we still have a fully functional Western Electric from the 20's, with crank).

And even less of them can design on the transistor level. If it doesn't come in a TSSOP or SO package they can't do anything with it. I guess it's like all those people nowadays who can't cook.

Regards, Joerg