Prototyping?

ways

expect

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The trick is automation. Much of that comes down to a brain crunching exercise. Tuning with PINs, FETs, varicaps is easy. But what mechanism is there to auto-check the response with the least in functional interruptions? Then toss the napkin over to the programmers. Ok, it ain't quite that simple but almost.

the

You'd be amazed how versatile some ham radio guys are. The railroad tech I mentioned built himself all kinds of complete systems. Transmitters, converters, automatic morse code readers (before uCs became affordable), strung his own core memory fields and so on.

T'is the right way to do it.

OK... but is there such a thing is a UHF dip meter? One of the few that I'm aware of that's still being produced -- MFJ's at

---Joel

Pointer to a post in ABSE with pictures--topic is "Prototyping--first try at antenna-coupled waveguide modulator and detector".

This is one case where prototyping has demonstrated at least 1000:1 better productivity than simulation!

Re dip meters:

Joerg, you're so right. Filters are much more sensitive to errors in the section resonances than to the impedance levels, so dip meters are the greatest for this. I have one I got of ebay for $20, and it works great.

Cheers,

Phil Hobbs

Ok, assuming precision parts you are right, then all the parasitics need to be taken into account. However, after a few years on the beat people (hopefully) have a pretty good grasp and can plug those into Spice as discretes. Just like we add the otherwise undesired input capacitance of a follower in as a cap.

I've built a few of those and they all worked right away. Never for myself though because I considered the actual ham radio usage of anything above 30MHz boring.

Sure is. It's still used in specialty designs but not much. One problem is that there are less and less guys who are familiar with debugging such a laser station. You have to deal with a lot of spurious EMI from the laser, it's supplies and so on. They usually weren't made for that purpose. Then there is EPA and all that. The fumes are miniscule but when you have to submit an enviro study for every speck on the back of a fly that gets old.

Man, he died young. But there is not much you can do against leukemia. A good friend lost his wife that way, around 50 years old.

You should link to that when advertising a job. BTW, did you guys fill the RF and FPGA/DSP positions? There should be anough folks longing for such serene living conditions, no traffic jams, no noise, no crime. Me and my wife, we'd be perfectly happy living on a remote island. As long as Digikey ships there.

Nice post, Phil.

I guess all of us just "know" what we can design, build, and expect to work "right off the bat" vs. what we need to build a prototype of first because we're not 100% certain of our understanding of exactly how (or if) it works, how sensitive to component values it is, just what the "correct" component values are given the parasitics involved, etc.

I know I *can* sit down and just design, lay out and build what should be production-level PCBs for large digital designs, whereas I also know that I

---Joel

With that experience you can probably get pretty close.

Were they only 10MHz wide though?

If you want to read an incredibly sad -- but well-written and still somewhat inspiring -- memorial you can read about Tom Gootee's wife here:

Cancer and similar dieases are awful; my wife's mother died from it and my own mother had it but luckily recovered. I do, however, have faith that man is smart enough to figure out how to cure it... maybe not for another hundred years, but I think we'll manage eventually.

RF, no. FPGA, yes. :-)

---Joel

Yep, got to build your own. Young grads have no clue about dip meters -> no market -> no off-the-shelf products.

This is how it was done in the good old days, scroll way down:

Come to think of it, the good old days are now. When I was a kid we had to scrap AF239 transistors out of TV tuners (very tricky to extricate) and then we could build dippers to 800MHz or so. Buying such transistors was out of the question, would have cost weeks of allowance. Now we can buy 20-45GHz hotrods for under a buck, with a few mouse clicks.

Some were much narrower. We had two challenges. Or rather others, not me, because I never did anything on that band. One was to provide a really narrow filter for situations where there was a contest and another crew was operating a MHz away. The other is repeaters where there must be a huge attentuation at the transmitter frequency. Those were tuned cavity resonators. We polished this stuff until the wrists hurt.

Maybe we aren't supposed to figure it out. Personally, I am not too afraid of death and neither is my wife. But this has religious reasons and would seriously go OT here.

Well, at least one :-)

There should be RF folks willing to move there. But you guys need a property tax cap like Prop 13 here in California. I'd have a hard time moving into a state where that's not in place. Seen too many folks being taxed out of their homes.

Nice!

Prototyping certainly helps a lot the instant you move into serious 3D territory like here. However, even there people have written programs. A long time ago I bought a Swedish antenna simulator for such purposes. Unfortunately that's one of the disks I missed when replacing the only PC that had a 5-1/4" drive and now it's stuck on that lone disk. Oh well, I'll fire up the old machine on a rainy day and copy it over. Thing is, AFAIR that disk might have some kind of laser hole pattern in it to prevent copying.

Put an occasional reminder in your daytimer to check the battery. I've had years where I only designed ultrasound stuff and didn't need my dip meter. Then I needed it, nada. Ah, an empty battery. The result was me sitting there in the garage with vinegar and scrubbing off all that nasty white stuff, at 40F.

Mmm... I've yet to see a cavity resonator where the tuning wasn't variable!

I don't think most people -- secular or religious -- are particularly afraid of death itself, since everyone realizes that life is finite. However, cancer inflicts plenty of horrible suffering before it kills, in most cases (physical, emotional, financial, etc.), and hence I think one could even make a religious argument that man should alleviate his fellow man's suffering by finding a cure.

Suffering always tests peoples' faith anyway... I've read that a large number of formerly religious people became agnostics or even atheists after either suffering through or having witnessed the Holocaust, being unable to comprehend why any benevolent God would "allow" such an event to transpire.

You're right this is getting rapidly OT...

There are some caps -- measure 5,

---Joel

I hate it when that happens--software improves with age. I've recently replaced WordPerfect 5.1+ (1990) with LaTeX (1984), which is therefore a clear advance. ;)

Free space antenna simulators (e.g. the Numerical Electromagnetics Code (NEC)) usually use the method of moments, which is a cute technique that's sort of an automated Galerkin method--you use an eigenfunction expansion for the fields in the simulation region, and just combine them so as to force the total field to satisfy the boundary conditions on the metal surfaces. That way the computation isn't a 3D problem, and you can build fancy antennas using tube computers.

You can put in finite conductivity effects using first-order perturbation, the way it's done for metal waveguides. That way you only need the zero-order field solution to get the first order loss.

When you get into a more general situation like mine, you more or less have to do a full 3D electromagnetic simulation like FDTD (finite difference, time domain). What I'd like to be able to do and can't is to simulate with 5-angstrom resolution in a 10 x 5 x 2 micron box. The problem is that for a typical complete design, which needs 100 or so optimizer iterations, I might need 10**17 floating point operations to do that. So I make do with 250 angstrom resolution, and try to make intelligent guesses as to what's happening down in the 25-angstrom-thick tunnel junction region, by using an imaginary material with 10 times the dielectric constant to represent the junction.

Mine's so old it plugs in--it uses a 6CW4 Nuvistor. No worries about batteries.

Cheers,

Phil Hobbs

It was, via a threaded rod. But only CF could be adjusted. The slope came out just as predicted. If you machine all the parts to a higher precision you could build them non-tuned.

When you look through the bible, God has allowed a lot more suffering in the past. We won't understand that during our life on earth. But yes, this would go OT if I'd start now. And our pastor would be much better at that anyhow ;-)

Last I heard it's effectively around 2% in OR. I mean, if the school tax part alone used to be 1.5% something must have been seriously wrong. Usually lots of squandering, some of which I have seen live here in CA. Made me sick.

A law like this must be pretty water tight for me to believe in it over the longhaul. Else politicians from a certain side and unions will keep trying to shoot holes into it, as evidenced numerous times here in CA. Luckily voters smelled a rat when they tried to lower the tax increase threshold from 2/3rd to 55%. That would have been like giving them our ATM cards.

I don't remember how mine works, some of the innards were in Swedish which I hardly understand. We did use the trick to scale 10:1 when calculating SHF antennas.

It used to be fairly slow on an 8MHz XT. On the 25MHz 386 'puter it began to be fun. Then on a Pentium Pro is was like stepping into a Lamborghini. Wish I could try it here in the dual-core now.

Yep, got one of those as well. A Boonton "Megacycle Meter". The mini-tube pod is connected to the main unit in style, with cloth cable. The other dipper for daily use is ye olde Heathkit.

Apparently this is somewhat difficult, based on how most of the commercial filters you see out there still use tuning screws. Perhaps it's more indicative of a small market, though -- wanting one machined design for a handful of different resonators.

You certainly have a lot of faith, Joerg. :-)

Here in Oregon, passing new taxes in the regular legislature requires a 60% supermajority vote, so right now there's a ballot measure for tobacco taxes that's been written to "simply" *change the state constitution!* instead -- since doing so requires a regular (50%) majority. I'm confident it's not going to pass, but seriously... a group that tries that sort of an end-run deserves not just to be defeated, but to be tarred and feathered as well. Sheesh. Talk about actively working against the will of the people...

---Joel

It's a cost calculation issue. Tuning these things requires less than five minutes, given a proper written procedure. If the extra precision in machining costs $20 more they'll stick with manual tuning.

Trying to spread that :-)

Shows how far some folks go. Here the voters have clearly spoken against same-sex marriage yet some politicos and city "leaders" took it upon themselves to decide that the voters must have been incompetent and blessed such marriages. Blew my mind. Now I have my opinion here but that doesn't count, what counts is what the voters decided on. It's the American way. Luckily we now have a governor who vetoes pretty much anything that violates the will of the voters. Else we wouldn't be in CA anymore, along with a whole lot of other business people who were on the verge of packing it up.

You have to be careful sometimes with orchard wood...

Friend of mine a while ago was out driving, when he saw a bunch of orange trees piled up by the side of the road. He stopped, and the owner said he could have all that he could carry, so he ran back home, got his chainsaw, and cut himself about half a cord.

He got home that night, with visions of sweet, orange scented wood burning in the fireplace, so he put a log of it in the fire...

Moments later, he was out the door. He would run in every once in a while to open another door or window, but then it was back outside to breathe again.

He had forgotten the twenty years of pesticide sprays that had soaked into that wood, that all came out when he started to burn it. He was afraid he was going to die before it finally burned down enough for him to go in and douse the fire...

Charlie

This almond doesn't smell at all. However, we have a modern stove with several combustion stages in series and it does not let any fumes inside. Even outside it's all odorless and smokeless. All you can see at the chimney is a little flicker like over a hot car roof in summer. Once I actually stood two feet away from the operating wood stove chimney outlet while cleaning the pellet stove flue. No smell.

But yeah, some wood can be toxic even if you don't see smoke. For example, we just cut lots of oleander. It's sad that we can't use the big stems for firewood but supposedly it would be toxic. So we don't.

Joerg, are you a citizen? You don't seem to understand a very important element of the American Way, which is that democracy should not be abused to deny the civil rights of a minority.

For example, we no longer allow the voters to ban mixed-race marriage. Do you agree that that is a good thing?

Anyway, here in SF, we voters overwhelmingly favor same-sex marriage. I believe this is true of the rest of the greater Silicon Valley also. Maybe we should secede.

Then how come that Prop 22 was on the ballot in 2000? Its essence was: "Only marriage between a man and a woman is valid or recognized in California." Passed with well over 60%, IMHO a pretty clear message.

Segregation has IMHO never been a good idea.

And don't get me wrong, I do not believe that a gay person is a bigger sinner than I am. Even our pastor told us that this is not so. But marriage is a different matter. I happen to live by the bible or at least try to. It says marriage is between man and woman. But it also says we shall not judge others (such as gay people).

Ok, I live in El Dorado County, maybe that explains our difference of opinion here ;-)