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Wednesday, October 19, 2011

Oh No! Short Circuit Danger with Anodized Heat Sinks?

Our friend Brent out in Minneapolis sent me some pre-Halloween HB frights yesterday. I'm still concerned. Am I living dangerously with my anodized but collector-connected heat sinks glued to the ground plane?
What say the HB gurus?

--- On Tue, 10/18/11, KD0GLS wrote:

From: KD0GLS Subject: Re: JBOT Amp
To: "Bill Meara"
Date: Tuesday, October 18, 2011, 9:38 PM

Bill,

Well, it is nearly Halloween, but it wasn't my intention to frighten you!

I think it's hard to argue with the fact that it works as-is. The heatsinks you bought look like common anodized aluminum to me. Out of curiosity I dug a couple of similar ones out of my parts bins and measured them. I found exactly what you did - wide open on the surface, and, not surprisingly, a dead short just underneath. I've always assumed that anodize finish was metallic and conductive, but now I know otherwise. I like to learn at least one new thing each day, so thanks for providing today's opportunity!

The clearances are no doubt small, but I think with the low voltages present in your circuit you'll probably be fine. The only potential problem might be if movement or vibration might someday break through that coating. I'd certainly recommend a fuse in the power supply line if you don't already have one.

Anyway, it looks great sitting there in the middle of your old rig. It's inspiring.

Brent


On Oct 18, 2011, at 19:42, Bill Meara wrote:

Brent: You scared me with your question but I think what I did is OK. Maybe. I looked more carefully at the clip on heat sinks I bought. They are covered with a non-conductive coating, but f I scratch them up a bit I can reach the conducting part. So i guess you just have to treat them gently if you intend (as I did) to super-glue them to the PC board. I notice that Farhan did the same thing (see his JBOT page) so I guess I'm OK. I put some heat sink compound in there too. And then there is the super glue. I have no short circuits from the collectors. I guess I could have used a Dremmel to isolate the copper just below the transistors. Or I could have put some mica between the heat sinks and the boards.

The sinks are deeper than the transistors, so there is no direct contact between the top of the transistor and the PC board.

What do you think?
--- On Tue, 10/18/11, KD0GLS wrote:

From: KD0GLS >
Subject: JBOT Amp
To: "Meara Bill" >
Date: Tuesday, October 18, 2011, 5:27 PM

Bill,

The amp looks mighty FB, and maybe I should try it as well. But I'm curious how you've insulated the collectors of all those transistors from the ground plane. From the picture, it looks like all of the metal heat sinks are sitting right on the ground plane copper.

.73,
Brent, KD0GLS, Minneapolis

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Tuesday, October 18, 2011

My JBOT 5 Watt Linear (Farhan's Design)

There it is -- my version of Farhan's JBOT 5 watt linear amplifier. JBOT stands for "Just a Bunch of Transistors." But I think Farhan is being modest. I really like the design, especially the effort to make this something that hams around the world can reproduce from readily available parts. For example, Farhan's original version used TV balun cores for the transformers. I didn't have any of those around, but I found three "mystery spec" binocular cores in my junk box. They seem to be working just fine. (I tested them a bit: Farhan had written that FT 37-43 cores would work. T1 has seven turns trifilar. Seven turns on my mystery cores yielded 13uH. On an FT 37-43 core 7 turns yields around 20 uH. Close enough -- these are, after all, broadband transformers.)

Note how closely my build follows Farhan's schematic (which you can see in the background). When building this circuit, I just kept Farhan's web page on my computer screen, and scrolled up and down from his schematic to the photo of his version.

This is the first linear amplifier that worked the first time I powered it up. It didn't release any smoke, or leave transistor burn tattoos on fingers, or try to be a 14MHz oscillator.

This version is going into my Azores-built 17 meter DSB transceiver. See how nice it fits:

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics"http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20

Monday, October 17, 2011

My JBOT passes the Smoke Test

Over the weekend I built my first version of Farhan's JBOT. I really enjoyed building it. I soldered in the last connections this morning and I am happy to report that it passed the smoke test. More info (and a picture) tomorrow. Thanks Farhan!

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics"http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20

Sunday, October 16, 2011

Bringing some Knack into Astro-Photography

I've been meaning to do this for a long time. It is a neat little project that allows for a quick and satisfying mixture of electronics and astronomy. It has been described on the web many times: Take an old web cam (preferably one of the old eyeball-looking devices) and remove the lens (I found it very cool to expose the charge coupled device).
Take a plastic 35 mm film container (hurry, while supplies last!) and chop off the bottom. Tape the container to the sans-lens webcam. Here's the fun part: Insert 35 mm container and webcam into the focuser of your telescope. Bring laptop out to the telescope and take digital pictures with your telescope.
I used Billy's old Asus eeepc and a very simple program called Cheese. (There has got to be something better for this kind of work.) But my results were very good. Last night I got images of Jupter and two of its moons. This morning I got some great shots of our moon.
Our book: "SolderSmoke -- Global Adventures in Wireless Electronics"http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20

Friday, October 14, 2011

SolderSmoke: Engineering Site of the Day on EE Web!

Dilbert would be so proud! In spite of my Bachelor of Arts Degree, yesterday the SolderSmoke blog was named Engineering Site of the Day by EE Web. I'm especially pleased that the Sputnik rig of the G3XBM team was the featured photo. Check it out:

http://www.eeweb.com/websites/solder-smoke-daily-news

http://www.eeweb.com/

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics"http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20

Thursday, October 13, 2011

Can we put a Sputnik signal back in space for $300?

This article from Hack-a-Day caught my eye:
http://hackaday.com/2011/10/11/send-a-satellite-into-space-for-300/
We just make the antenna a bit longer and put it on 20 MHz. Or for a shorter antenna, 40 MHz.
Bert and the fellows out at UVA are going to take care of the whole SETI thing (Jerry, NR5A, was in the lead on this -- he started the SolderSmoke SETI-AT-HOME group). But we'll need some additional volunteers to cover the Low Earth Orbit portion of the SolderSmoke Space Program. And of course we have to come up with the 300 bucks.

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics"http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20

Wednesday, October 12, 2011

An HW-7 that Glows in the Dark

Hi Bill,

You are right, there is a lot of disdain for the HW7 out there.

While looking for a reasonable selection of do-able modifications to the HW7, I observed a sentiment that when all boiled down would sound like this: “Yea, rip out the innards and build a new transceiver in the carcass that is left.”

On the flip side, I have experienced relatively good results from my virgin HW7. Oh yea, I did add dial and meter lighting along with A nice set of Radio Shack Knobs but that is about the extent of the changes.

So Bill, I was wondering if any listeners to Solder Smoke know of a good source of reasonable modifications to the HW7 without inducing an implant? Second, is there a way of adding an S-meter to a direct conversion receiver? Are there any mods that can be lifted from the HW8 or HW9 and applied to the Old Senior HW7?

Thanks & 73’s

Harv WA3EIB Albuquerque, NM


Our book: "SolderSmoke -- Global Adventures in Wireless Electronics"http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20

Tuesday, October 11, 2011

Comet Hits Sun, SFI up, Report from San Vito



The SOHO spacecraft caught some great images of a comet crashing into the sun. The YouTube clip above is from July. Here is NASA video of one that took place just last week:

http://www.nasa.gov/mission_pages/sunearth/news/comet-cme.html

Coincidentally I'm sure, the solar flux has increased significantly and the upper HF bands are working again. My 17 meter rigs still need final amps -- I am ordering parts for Farhan's JBOT circuit. (I plan to build three or four.) But because I had the 2B on 15 meters for the Sputnik event (still no Sputniks heard here) I noticed that DX was coming on that band. Using my HT-37 and a 40 meter dipole I easily worked several Europeans on 15 meter SSB. Especially nice was a long rag chew (using my rusty Italian) with Gianfranco, IZ4NPE, in beautiful Ferrara, Italy (a bicycle city).

Somehow tying this all together, I got an e-mail from Walter in San Vito, Puglia (the heel on Italy's boot). Walter has one of those "dream jobs" for a radio amateur: He tracks sunspots!

Hi Bill,

Walter here from San Vito, Italy. Just wanted to drop a note to say hi and let you know that I'm enjoying your book. Thanks for making it available as a Kindle version. While reading, it brought back similar experiences with me as a youngster. I too was fascinated by airplanes and would ride my bike to the local airport and watch for hours as the planes would take off and land. My mom gave me my first airplane ride as a birthday present when I was 11. I have to admit that I was scared when we made our first airborne turn. I didn't realize that a plane banks in the turns. I was also fascinated with shortwave radios and my best Christmas gift was a Radio Shack Globe Patrol (regenerative... hi hi) receiver kit. The gift from by grandparents was a Weller soldering gun (140 watts) to put it together with. Again, great job on the book.

The Sun has been keeping us busy at the Solar Observatory. I'm monitoring anywhere from 4 to 12 flares a day, 2 regions popped out of nowhere yesterday. The radio bands have been favorable with all the activity. I've got several projects in the works, a Genesis G3020 SDR rig is about 1/3 completed on the workbench now. It's probably me when you see Puglia show up on the website spinning globe. Take care and keep the podcast's coming. Ciao for now.
- Walter
I7/AC4IM

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics"http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20

Monday, October 10, 2011

Amateur Rocketeers Reach 121,000 feet (36,880 meters)! AMAZING VIDEO!



Our book: "SolderSmoke -- Global Adventures in Wireless Electronics"http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20

Sunday, October 9, 2011

Carl Sagan on the META (SETI) Results

Project META's Control Room

I mentioned this in Ppodcast #138 and wanted to provide more info. Here are the relevant paragraphs from Sagan's book, "The Pale Blue Dot."

"Of course, there's a background level of radio noise from Earth-radio
and television stations, aircraft, portable telephones, nearby and more
distant spacecraft. Also, as with all radio receivers, the longer you
wait, the more likely it is that there'll be some random fluctuation in
the electronics so strong that it generates a spurious signal. So we
ignore anything that isn't much louder than the background.
Any strong narrow-band signal that remains in a single channel we take
very seriously. As it logs in the data, META automatically tells the human
operators to pay attention to certain signals. Over five years we made
some 60 trillion observations at various frequencies, while examining the
entire accessible sky. A few dozen signals survive the culling. These are
subjected to further scrutiny, and almost all of them are rejected-for
example, because an error has been found by fault-detection
microprocessors that examine the signal-detection microprocessors.
What's left-the strongest candidate signals after three surveys of the
sky-are 11 "events." They satisfy all but one of our criteria for a
genuine alien signal. But the one failed criterion is supremely important:
Verifiability. We've never been able to find any of them again. We look
back at that part of the sky three minutes later and there's nothing
there. We look again the following day: nothing. Examine it a year later,
or seven years later, and still there's nothing.
It seems unlikely that every signal we get from alien civilizations
would turn itself off a couple of minutes after we begin listening, and
never repeat. (How would they know we're paying attention?) But, just
possibly, this is the effect of twinkling. Stars twinkle because parcels
of turbulent air are moving across the line of sight between the star and
us. Sometimes these air parcels act as a lens and cause the light rays
from a given star to converge a little, making it momentarily brighter.
Similarly, astronomical radio sources may also twinkle-owing to clouds of
electrically charged (or "ionized") gas in the great near-vacuum between
the stars. We observe this routinely with pulsars.
Imagine a radio signal that's a little below the strength that we
could otherwise detect on Earth. Occasionally the signal will by chance be
temporarily focused, amplified, and brought within the detectability range
of our radio telescopes. The interesting thing is that the lifetimes of
such brightening, predicted from the physics of the interstellar gas, are
a few minutes-and the chance of reacquiring the signal is small. We should
really be pointing steadily at these coordinates in the sky, watching them
for months.
Despite the fact that none of these signals repeats, there's an
additional fact about them that, every time I think about it, sends a
chill down my spine: 8 of the 11 best candidate signals lie in or near the
plane of the Milky Way Galaxy. The five strongest are in the
constellations Cassiopeia, Monoceros, Hydra, and two in Sagittarius-in the
approximate direction of the center of the Galaxy. The Milky Way is a
flat, wheel-like collection of gas and dust and stars. Its flatness is why
we see it as a band of diffuse light across the night sky. That's where
almost all the stars in our galaxy are. If our candidate signals really
were radio interference from Earth or some undetected glitch in the
detection electronics, we shouldn't see them preferentially when we're
pointing at the Milky Way.
But maybe we had an especially unlucky and misleading run of
statistics. The probability that this correlation with the galactic plane
is due merely to chance is less than half a percent. Imagine a wall-size
map of the sky, ranging from the North Star at the top to the fainter
stars toward which the Earth's south pole points at the bottom. Snaking
across this wall map are the irregular boundaries of the Milky Way. Now
suppose that you were blindfolded and asked to throw five darts at random
at the map (with much of the southern sky, inaccessible from
Massachusetts, declared off limits). You'd have to throw the set of five
darts more than 200 times before, by accident, you got them to fall as
closely within the precincts of the Milky Way as the five strongest META
signals did. Without repeatable signals, though, there's no way we can
conclude that we've actually found extraterrestrial intelligence.
Or maybe the events we've found are caused by some new kind of
astrophysical phenomenon, something that nobody has thought of yet, by
which not civilizations, but stars or gas clouds (or something) that do
lie in the plane of the Milky Way emit strong signals in bafflingly narrow
frequency bands.
Let's permit ourselves, though, a moment of extravagant speculation.
Let's imagine that all our surviving events are in fact due to radio
beacons of other civilizations. Then we can estimate-from how little time
we've spent watching each piece of sky-how many such transmitters there
are in the entire Milky Way. The answer is something approaching a
million. If randomly strewn through space, the nearest of them would be a
few hundred light years away, too far for them to have picked up our own
TV or radar signals yet. They would not know for another few centuries
that a technical civilization has emerged on Earth. The Galaxy would be
pulsing with life and intelligence, but-unless they're busily exploring
huge numbers of obscure star systems-wholly oblivious of what has been
happening down here lately. A few centuries from now, after they do hear
from us, things might get very interesting. Fortunately, we'd have many
generations to prepare."

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics"http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20

Meet the Author (of SolderSmoke) Event TODAY

For those in the Washington D.C. area: Today from 2-4 pm I'll be at "One More Page Books" in Arlington, Virginia at a "meet the author" event. The store will have on sale ten copies of "SolderSmoke -- Global Adventures in Wireless Electronics." Please pass the word to local hams who might be interested. Thanks.

One More Page Books
2200 N. Westmoreland Street #101
Arlington, VA 22213
703-300-9746

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics"http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20

Saturday, October 8, 2011

Happy 50th Birthday to the Parkes Radio Telescope



http://www.cio.com.au/article/402613/australia_celebrates_50_years_dish_/?fp=16#closeme


This is my favorite antenna. And it is the subject of the BEST movie ever made about an antenna.

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics"http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20
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