Bob’s Mailbox: PLL Circuits, Hiking Experiences, And More Reader Reactions

Hello Bob,

It has been quite a long time since we communicated. I was reminded of this as I was cleaning out old e-mails. Mostly it has been my fault, as I have been quite intensely busy searching for a job and attempting to get my dad’s house ready to sell. He passed away last April 15, at 90 years old and still living by himself, and mostly taking care of himself. But now it is some big task to get the house into a condition in which some younger person would want to buy it. After all, I don’t think that there are many really old people looking to purchase a larger house.

Aside from that, I have been sort of interested in the new LF band frequency that may be given to radio amateurs. It is in the 162-kHz range, I think, although there may also be an allotment in the 462-kHz area. My thinking has run toward direct conversion, image-cancelling receivers using the “Tayloe” circuit, which seems to be the CMOS equivalent of the diode-ring mixer, but using an analog switch IC and running into both inputs of an op amp.

These frequencies should be much less dependent on circuit layout than the VHF circuits, and possibly less demanding on IC high frequency performance as well. I don’t know if you have investigated the Tayloe detector, but there has been a fair amount of stuff about it written. (Of which I have seen or read nothing. Where’d you get the idea I know anything about radio? I’m dumber than three boards. /rap)

The nice part is that getting the required 90° phase shift is quite simple using cheap digital logic, at these lower frequencies. Relative to that, I wonder if you have done much experimenting or developing with phase-locked-loop (PLL) circuits. A PLL system is mostly analog. Even the digital part is really analog, after all.

William Ketel

Hello Bill Ketel,

Yeah, old people and old big houses do cause interesting problems.

I was on the distribution list for a PLL study group 28 years ago. One day, a guy asked me if I could help him a little on a low frequency PLL. I said, “I can take a look at it.

What’s your frequency?” He said, “20 MHz.” I stopped and thought. I told him, “Where

I come from, a low-frequency PLL is 20 Hz. No kidding.”

See at AN-210, which I wrote 32 years ago (www.national.com/an/AN/AN-210.pdf). Yes, I did once make a good PLL at 200 MHz, but that was a stretch for me! I was using a couple 1N914s for varactors!

Best regrds.

/rap

Bob,

I, for one, enjoy reading about your exploits—everything from Philbrick to Nepal. Please keep up the flow of information from one who is a wise soul to us many neophytes (and some say Neanderthals). (I do plan to keep writing. /rap)

Reading in the latest Electronic Design about hiking with the wee ones made me reflect back on an incident my wife and I had while on a short day hike in Australia back in 2003 (see “What’s All This Small Hiker Stuff, Anyhow? http://electronicdesign.com/article/analog-and-mixed-signal/What-s-All-This-Small-Hiker-Stuff-Anyhow-.aspx). It was early March and we were in the New South Wales village of Tenterfield, which is a fantastic town with a marvelous past. Bald Rock National Park is located a few kilometers outside of town. Bald Rock is the largest piece of granite in the Southern Hemisphere and we were assured by many that it was a very easy hike to the top.

Indeed it was, after parking our hire car (as “they” call rentals) we began the very pleasant 2.5-km hike to the summit. Most of the journey was through savannahs and mossy forest. The path was well worn and well marked. (Oh, and something you should know—I left my handheld Garmin in the car, and this was the days before smart phones. I had a Motorola Flip with me.)

As we began the ascent to the summit, which was not all that difficult, the trail markings became fewer and fewer. (Oh, that’s a caution! /rap)

I guess the park service reasoned that up is up, so why bother marking which way is up?! We did notice that at places we were to turn, someone had placed small drops of white paint, usually three at a time to show the way. (How charming! /rap) In a short while, there we were enjoying the summit and the commanding view of the valleys below. There was a survey marker as well as a guest book to sign. We were about the eighth party to visit that day.

As quickly as you can say “down under,” the weather turned from slightly cloudy to insanely intense thunder and rain. It wasn’t a matter of “Oh, a storm’s coming,” it was “Oh my God! Let’s get out of here!” (We had no rain gear). (Nobody has any lightning-proofing! Nobody volunteered to act as a lightning rod for the group? /rap)

Hurriedly we dropped down from the summit only to realize that everywhere we looked, it looked the same: a sloping granite block leading to the forest. The white paint drops weren’t visible anymore as the glare from the sky coupled with the rain made them have little to no contrast. (Check. So you should complain to the rangers! Even now! Insist that they add small, tasteful but noticeable arrows... /rap)

We dropped from one ledge to another, only to make it into a forest patch ending in a 40-foot drop. A retreat led us to an escarpment and a very precarious situation. (Uh, yeah. And there were no landmarks or markers of any sort to guide you to the trail. Trouble! /rap) We looked left, right, and even to the other end of the rock and could not find the path back to the trailhead.

I was just about to dial “000” on the cell, which is Australia’s equivalent of 911—the signal reception was phenomenal—when we heard someone yell up “Hello!” It was a party of Americans much better equipped than we, as they had rain garments and warm clothing. They were on the way up when the rain hit and decided to hunker down. As the rain let up (it lasted for, say, 10 minutes) they resumed their hike. We were still in a panic to get out of there because we were soaking wet and very cold. (Exposure to cold rain can be very serious. You recognized that. /rap)

We explained what happened to us and asked if they knew the way back. They pointed out the trail to us: “Look towards the right of those two trees down there,” and sure enough, it was a short sprint back to the car. (Yeah, but it was still not obvious! /rap) Yes, we were ill-equipped but this was a short hike in a public park on a marked trail. (No, on an almost marked trail. Man, what a difference. /rap) The weather was sunny when we started. (I don’t know the weather “down south.” But I know there are a lot of places where the weather can change fast. I guess that’s a good reminder to always bring a parka or poncho. /rap)

What would you have done to ensure that you never got in this mess?

I’m kicking myself to this day for not bringing my GPS to mark the trail, but would it have been all that helpful? (Oh, yes, a GPS might have been useful, but you’d have to remember to mark a few waypoints on the way up. /rap)

Karl Strauss

Valencia California

Dear Karl,

A lobster goes out for a walk on a fine day. He finds an appealing entrance to a nice lunch, but can’t find the exit. Soon he is somebody else’s lunch. You have to plan your exit strategy! If you can’t plan your way back, it may not be safe.

I don’t ever recall being caught in (or near) such a fine lobster trap as yours. But you have to get suspicious when there are no proper landmarks or permanent signs. In some Japanese cities, where you want to be is not obvious, not to mention Sao Paulo or Los Angeles. But I’m careful to buy a good map.

I’m with you: there are some places that are inherently dangerous in the wrong conditions. You have to recognize them before you get too far in.

Comments invited.

/ rap

Bob (if I may),

I have just read your column in the 3/10/11 issue of Electronic Design and I want to add my voice in strong support of the diverse nature of your subjects, including the current piece on hiking (see “What’s All This Small Hiker Stuff, Anyhow? http://electronicdesign.com/article/analog-and-mixed-signal/What-s-All-This-Small-Hiker-Stuff-Anyhow-.aspx.) I fully share your belief that it takes much more than an engineering focus and background to make a strong, creative, and worthwhile contribution to the development of modern electronic technology and systems. (Fair enough. /rap)

Personally, I have experienced this path throughout my own career. I am trained as a physicist (teaches one “how to think”) ( I was in Course VIII Physics at MIT for three-and-a-half years before transferring into EE (Course VI). /rap), and I obtained my “engineering” expertise and background beginning from age 13 in 1955 with my experiences as a ham and continuing to this day (I never took a single engineering course), and I have used these skills to manage large, sophisticated engineering teams and companies, especially in satellite telecommunications.

(Wow. Without going to an accredited engineering school, you seem to have figured out a lot of good engineering. I guess the UNH (College of Hard Knocks) still works well. Some of the best engineers I know didn’t go a full year at good engineering schools. /rap) 

Of course, I appreciate and benefit from the common sense technical advice offered by your column, but I find your columns on non-engineering matters to be equally valuable as they illustrate successful and diverse living, a trait I believe necessary for success in the engineering business.

So here’s a vote for more columns like the one on 3/10/11. Keep it up. Your column is the first thing I read in every issue of the magazine.

Best regards,

James “Buzz” Beitchman

PS: Of course, I’ve been a Trains Magazine subscriber since 1961.

Dear James,

Thank you.

It takes quite a bit of planning and engineering to plan good hiking and camping for kids. It’s very educational for parents to do this planning.

Thanks for the kind words.

Beast regrds.

/ rap

Hi Bob,

We’ve communicated and met several times through the years. I’ve always enjoyed your responses, tutorials, and columns. This time you really outdid yourself. I am sitting here at my screen, literally laughing out loud. Not just because of the humor and your colorful expressions (“Fornicate that!” indeed!), but some of the things you say are exactly what I have said in the past. (I’m happy to see that Electronic Design was brave enough to publish your words.) (Thanks for your words of support! Better that we should fornicate bad cars before they fornicate us! /rap)

I thoroughly enjoyed your response to the young analog designer wannabe from India (see “Bob’s Mailbox: Advice To A Young Engineer, Julie Resistors, Key-Less Acceleration, And Hiking with Kids”http://electronicdesign.com/article/analog-and-mixed-signal/Bob-s-Mailbox-Advice-To-A-Young-Engineer-Julie-Resistors-Key-Less-Acceleration-And-Hiking-with-Kids.aspx). I somehow doubt he will ever make the grade and will end up staying in the software world. If he didn’t already have analog design in his blood, or just by tinkering in it since he was a young pup, then I doubt he ever will.

(I told him the best way for him to become a real analog man was to go back on a time machine and buy 10 Heathkits (and I told him what types), build them, and get them running right, and to meet all the people you meet when you build radios, tuners, amplifiers, voltmeters, etc. Since Heathkits and time machines are almost equally hard to find, obviously I was just saying he had taken the wrong fork in the road, and was also born too late, and maybe in the wrong neighborhood.

Can you imagine a farmer’s kid in India 30 or 40 years ago trying to save up enough rupees to buy a kit for a Heathkit tuner? My first Knightkit cost me $26 in 1957, and I still use parts of it. (And my father was a farmer, and not a rich one. But he did have a car, an old pick-up truck, and a tractor...) /rap)

Perhaps even as much, I loved your comments on the unintended acceleration (UA). I too am of the old school of automotive control. As I now have hit Social Security (if it still exists anymore) age, I can proudly admit I have never owned a car with an automatic transmission or one of those silly push start/stop buttons. I want to have control over the machine that can readily mean life or death for myself and others around me. Even my brand new Subaru Outback has a real key and a manual transmission. I had to wait months for this to come in, as perhaps only a few percent have the manual! From the beginning of the push-button “ignition key” design, I thought it to be a bad idea. Why a push-button? Is it so difficult for a user to operate a key or perhaps even a simple toggle switch?