Reverse Polarity Protection -- Words of Wisdom from K7QO

Words of wisdom from Chuck Adams, K7QO:

Wednesday, February 24, 2010 12:11 AM

From:

"chuck adams"

Add sender to Contacts

To:

qrp-l@mailman.qth.net

This posting due to the traffic on the SST reverse
voltage application.

Here is what I do. There is a diode, the 1N5817,
a Schottky Diode. Will take 20V peak reverse voltage,
will handle 1A continuous with 25A surge and has only
a 0.45V forward drop and the reverse current is 500uA.

I put one of this in series with the 12V line input of
every electronic device I build. If the designer used
a 1N4001-7 in series, I replace it.

I am not a fan of the diode across the voltage input
line and having it short out when reverse voltage is
applied. What if the applied voltage is a gel-cell
without a fuse? You blow the diode and you blow the
rig. IMHO is this not an ideal way to do it. Should
be using fuses too, but I don't. Haven't found a way
to use the flat auto fuses with gel-cells in a handy
low-profile way and inexpensive parts. I'd appreciate
the education, if someone has film and photos of great
arrangements.

I buy the diodes from Mouser.Com for about $26 per 250.
For a dime a rig it is a real cheap way to protect your
equipment from yourself and others.

With the limit of 1A at 13.8V, it is well within the
QRP operating limits. And why do you need more than
1A anyway?????? :-) And the low forward voltage
drop means that the finals (which are usually fed
direct from the B+ line anyway) don't lose much
in applied voltage and you get pretty much the
same output as without the diode. And you protect
those expensive parts for a dime. A quarter if you
buy just one diode from Mouser.

Hope this helps. Just the way I do it, and I'm
not always right. But I've only lost a few parts
and that was before I started using 1N5817's on
everything.

The 1N4001 through 1N4007's are fine if you are
feeding 9-12V to a 78L08 regulator.
FYI
chuck
--
chuck adams, k7qo
http://www.k7qo.net/
chuck.adams.k7qo@gmail.com

F8CKH: The Knack, 747s, and Homebrew QRP

Here is some further evidence that The Knack is a global phenomenon. I'm sure our readers will find Antoine's story quite familiar. Looking at his QSL (below) we can see that he has a special reason to be interested in QRP: After a full workday of operating a very high-powered rig (!), a simple little QRP rig must represent an appealing contrast. And even if that 747 is very QRO, I think we will all agree that Antoine has the kind of job that most knack victims dreamed about when they were kids.

Hi Bill,

I have been listening to your podcasts for a while now after I heard about them in one of the Amateur Logic TV shows. I picked up one podcast randomly and I got to say that I really enjoyed the tone and content of your talks. Very informative and interesting. I like also the fact that your amateur radio experience is based on homebrewing and experimenting. Back in 1997, I earned my French amateur radio license at the age of 16 (extra and big CW lover). I have been always amazed by what we could do with very little and go very far. My family is Hamradio friendly: my grandfather was F8KE back in 1930s and he has been around the hobby for most of his life. At 7 or 8 I remember times where we were at his place and I would ask for permission to leave the table early to go upstairs and visit my grandfathers shack. Everything there was homebrew and I was really pleased to see that the magic of Radio was achievable with only few components, homebrew antennas and a bit of luck. He encouraged me to learn the Code and at 12 I was already up to 20 wpm! My dad used to be 6W8FC while he was in the service and he gave me the passion for weak signal and DXing. Technically speaking, I HAD to become a Ham Radio operator.

I am really fascinated by your level of dedication to homebrewing and also that you share that we us, fellow operators addicted to -soldersmoke-. Just like you, I have been all over the place since I am an Airline Pilot qualified on the Airbus and Boeings... UK, New Zealand, US, I got a chance to operate from couple of places and something got the pleasure to be behind the scene and become the reason of a pile up. Operating from down under from Kiwi lands was a wild and exciting experience, indeed!

Finally I am about to move permanently to the US, in Pennsylvania. I applied for a Vanity Callsign (NY3G) and hopefully I will hear from the FCC soon.

I wanted to mention also that I got rid of almost all my regular Yaesu, Kenwood rigs to start from scratch. My project? To design, build, operate an HF station from scratch. No more commercial rigs for me! Well I will try! I am really happy to finally make use of a workbench that I just cleaned at home. I will set up a blogspot account to illustrate my projects... I think that would be great to make QSO with you Bill, sometime!

Thanks again for bringing some much enthusiasm into this fascinating side of Ham Radio, Homebrewing.

Best Regards,

73

Antoine Pierre GAMET F8CKH

Homebrew QRP Contest... With DSB!

Walford Electronics Brendon 80m DSB kit

Hi Bill

I trust all is well and that the roadkill PCs are not fighting back. Thought you might like to hear about a new contest we are trying here in the UK. Having assisted lots of new knack victims to build their first rigs at the 3 Bath Buildathons we thought we should encourage them to get on the air - 30 QRP DSB rigs on 80m all at once - now that's what I call a contest.

We have opened it up to any QRP voice radio to cover the QRP appliance operators but homebrewers get extra points. Not sure how much support we are going to get but there is a £50 voucher for Walford Electronics kits up for grabs.

Hopefully this will be a fun contest with freindly extended exhanges rather than the all too common '599 1002 73 QRZ'. Picture is the Walford Electronics Brendon 80m DSB kit in all its glory.

73, Steve, G0FUW

Big Filament -- On the Sun

The WSPR system has become something of a personal solar activity detector for me. I know, there are lots of ways to detect solar activity: there's the internet, of course. WWV is also there. You could even set up a small telescope and (with the appropriate eye-saving screen or projection systems) watch for spots yourself. But I like using my 20 mW DSB WSPR signal. If I get up in the morning and see that my little signal has been received during the night in Norway by LA3JJ (1950 km) I know that something different is going on with Old Sol.

LA3JJ was detecting my signals all night long last night. And other stations in Europe were picking up U.S. and Israeli stations throughout the night. So, what was happening on the sun? It may have had something to do with the filament pictured above. For more info on this kind of solar event, take a look here:
http://www.ips.gov.au/Educational/2/4/1

QRP Quarterly -- Winter 2010

Lots of great stuff in the latest edition of QQ from QRP ARCI:

Mike Czuhajewski's "Idea Exchange" column has been sending out great ideas for many years now. In this edition he opens with a piece from Wes, W7ZOI, that originally appeared on the EMRFD mailing list. It deals with diode ring mixers, specifically the power requirements for the local oscillator. What do they really mean when they specify 7 dBm? Wes explains: "If we say that the LO power is +7 dBm, what this really means is that a signal generator is attached to a power meter or spectrum analyzer and adjusted to deliver +7 dBm at the desired frequency to the 50 ohm instrument. Once the power is set, the cable is disconnected and reattached to the mixer." I'd always wondered about how to measure that. Thanks Mike! Thanks Wes!

Preston Douglas, WJ2V, has a nice article on our latest craze: WSPR. Preston also discusses SDR radios -- his encouraging comments may help me get out of my current luddite curmudgeon rut. Preston mentions recent efforts to use a BITX-20 for WSPR and concludes that this would be "a tall order for any analog rig." This comment lessened my feelings of inadequacy about my SDR SMT problems, because I recently used my ancient Drake 2-B to receive WSPR sigs (see earlier blog entry). Luddites Rule! But Preston is right -- it's not easy! But -- at least for a little while, before drift takes you out of the band -- it can be done.

Ward Harriman, AE6TY, writes of a "homebrew" SDR project. In his opening paragraph, he tells us what the term "homebrew" means to him: "homebrew design, homebrew assembly, homebrew programming, homebrew in a wide range of disciplines both familiar and untried." That's pretty hardcore! FB Ward!

Jim Osburn, WD9EYB, has a nice article on "circuit stickers" and how they can be used to simplify project construction using a variety of circuit boards and breadboards. I really liked Jim's description of old Electronics Illustrated projects in which they pasted a diagram to a wood base and then put finishing nails at specified points. Components were then soldered to the finishing nails. When the thing works, you can say you "really nailed it!" (Sorry!) Cool technique.

Thanks to the folks at QRP ARCI for another inspiring edition of their wonderful magazine. If you are not a member, you are missing a lot. Sign up for the club and the magazine here:
http://www.qrparci.org/

Solar Rocket Destroys a Sun-dog

Continuing with our solar theme, here is a neat little video taken on Feb 18 by a thirteen year-old kid. It shows the Atlas rocket carrying NASA's new Solar Dynamic Observatory crashing through a "sun-dog" and obliterating it with the rocket's shock wave. Obviously an auspicious beginning for this mission.

Sunspot 1046 Explains Mysterious Rome-Norway Propagation

I've been trying to understand the propagation conditions that caused my little 20 mW DSB signal to be received ALL-NIGHT-LONG at a distance of 1900 km by station LA3JJ on the night of 12/13 Feb 2010 (click here for more details).

A visit to spaceweather.com provided the answer. At around 1126 UTC on 12 Feb we had the brightest solar flare in more than two years: Sunspot 1046 produced an M8.3 Flare. Helge Mortensen in Norway reported that on 15 Feb in Norway there was "a fantastic blast of aurora." He took a beautiful picture of it (above). Could it be that we see in this picture particles from the same flare, or a coronal mass ejection associated with it?

One of the really cool things about the spaceweather.com site is that it includes lots of input from amateur astronomers and photographers like Helge. Emiel Veldhuis in the Netherlands happened to be observing 1046 when the M flare occurred and he took this series of shots:

Terje Isberg in Switzerland was listening to a DRM station on sortwave. He observed and recorded the radio blackout (SID) caused by the flare:
Rogiero Marconi in Brazil took this shot of the sunspot:
Amazing stuff. This is a good example of how WSPR really puts you in touch with solar conditions and space weather.

HOMEBREW HERO: Arnie Coro, CO2KK

I was getting ready to write a quick blog entry on Arnie Coro's latest contribution to ham radio (his idea to revive the old 40 meter novice band) when it occurred to me that Arnie's long track record of providing good ideas, technical advice, and inspiration definitely puts him in the HOMEBREW HERO category. Thanks Arnie!

Below you can find the transcript of Arnie's latest edition of Radio Habana Cuba's "DXers Unlimited." There is a good discussion of current solar conditions (improving!) and of Arnie's 40 meter CW initiative.

Arnie's work at RHC is archived and available on the net. It is a real Caribbean treasure trove for us: http://www.dxers-unlimited.dxer.info/

Here is Arnie's blog: http://dxersunlimited.blogspot.com/

From "DXers Unlimited" 16-17 Feb 2010:
Hi amigos radioaficionados around the world now enjoying the ongoing
upsurge in solar activity that has brought to us DX signals as
strong as we had not heard them since 2005 !!! Yes my friends,
finally, after waiting, and waiting, and waiting, we are seeing a
nice comeback of the sunspots... As a matter of fact, only two days
of 2010 had gone by with a totally blank Sun. The all important R
number from the very much respected Catania, Sicily reference solar
observatory was 39 yesterday... and two other sunspot groups are
just about to turn into view...
As a result of the sustained increase in sunspot count, we are
seeing the 15 meters or 21 megaHertz amateur band opening up every
day... I will tell you more about amateur radio Dxing later , here
at th emid week edition of Dxers Unlimited... The daily solar flux
is very near 90, and forecasters were looking at a lower flux during
the next three days, but this may change dramatically and in just a
few hours, if the new solar sunspots regions that are rotating into
Earth's view show high activity.
Item two: The amateur radio hobby is alive and in good health... ham
radio operators are enjoying the hobby and finding new ways of
improving their communications skills... Here is a recent example,
by carefully studying the behavior of activity on the 40 meters
band, I was able to find out that the band
segment from 7105 to 7125 kiloHertz was seeing very little use here
in ITU Region II, that is the Americas. So I launched the idea to
start using that segment by low power stations, on several of the
popular ham radio Internet mailing lists. In just a couple days , CW
activity , mostly by low power or qRP stations on that segment
roughly 20 kiloHertz segment has increased dramatically... For many
operators, finding such a nice and clear , interference free
segment, has meant having the opportunity of making many more two
way contacts.... and not only exchanging reports, but also , thanks
to less interference, we have carried out some really nice ragchews,
and just notice that I have just said WE, because I am , of course,
one of the happy radio amateurs operating on CW between 7105 and
7125 kiloHertz.
There are no digital stations using that segment... as they are now
present between 7030 and 7040 kiloHertz, the two frequencies were
QRP , or low power operators, are used to gather, and where for the
past year or so, it has become extremely difficult at times to make
even a single two way CW contact.
I am not saying that QRP operators should abandon the two favorite
watering holes, 7030 and 7040, what I have told the QRP , GLOWBUGS
and Regenerative receivers Internet list members, is that the
segment between 7105 and 7125 is in a much better shape regarding
QRM... yes there is a let less interference from other
communications modes...so chances to make nice contacts increase in
a very significant way.
Si amigos , Yes my friends , Oui mes amis...amateur radio operators
around the world are now enjoying the upsurge in solar activity, and
with it, we all must look around the bands and find ways to make
better use of them... After all, many other users of the radio
spectrum are always monitoring the ham bands, just to have data
available to substantiate their requests for more spectrum space....
In other words, if we, amateur radio operators are able to be more
time on the air, and the bands sound like a beehive of activity,
chances that those spectrum hungry users will just go elsewhere !!!

The complete script of the program , devoted to the promotion and
development of our radio hobby in general and amateur radio in
particular, can be read at:
http://dxersunlimited.blogspot.com
later this Tuesday, after the program goes on the air

Comments , suggestions and ideas on how to help promote
amateur radio are welcome at my e-mail address
inforhc at enet dot cu

72 and DX
Arnie Coro
CO2KK

Embedded Systems Video

Frank, VK2AKG, sent us this interesting video about the development of what we today call embedded systems.
http://www.ganssle.com/misc/esc2008.mov

More Workbench Eye Candy

I blame Rogier for the title of this post. He saw yesterday's workshop pictures and declared them to be porn-like. We all know what he means. Gil sent me this link with more workshop shots: http://www.crystalradio.net/bench/index.shtml
I really like the one above. It is from Catalonia in Spain. It belongs to Josep Busquets Vinas.
One question about yesterday's slide show: Where's the WD-40?

An AMAZING Workshop

You guys have to take a look at this slide show:
http://www.flickr.com/photos/mtneer_man/sets/72157594474602738/show/

About the owner:

I'm a geo-physicist by degree, a design development engineer by trade and a mountaineer by choice...
I live in very, very rural Oklahoma and worked for a Norwegian company. And a Chicago company... and a Salt Lake company... And now... well, I just do work for whowever I feel like dealing with.
and I climb mountains, mainly in the western hemisphere. Occasionally, I go to Patagonia in South America to climb.
I like my ATV rides out in the country to photograph things... all over western Oklahoma roads. Dirt roads only., thanks...
I do "projects"; around our place, building things and creating mechanical devices. So a lot of my photos revolve around my workshops (I have 4) and the things I build... + our cats.
Whatever..... I'm having fun.

http://www.flickr.com/photos/mtneer_man/sets/72157594474602738/show/

Weekend Sale 15% off on SolderSmoke --The Book

Lulu is running a sale through Monday. 15% off on all books.
Just use the code word WASHINGTON when asked for a coupon.
Click here: SolderSmoke - A Global Adventure in Radio Electronics