Another JBOT Amplifier

Over the weekend I built another JBOT 5 watt linear amplifier (design by Farhan). I used a nice piece of copper-clad board that Dave, W8NF, sent me (thanks again Dave).

This time I chickened out regarding the possible conductivity of the anodized heat sinks. I didn't have any trouble with this on my first JBOT, but I worried that if the anodized layer gets flaked away, a heat sink might short one of those collectors to ground. To be on the safe side, I put small squares of Gorilla Tape on under the heat sinks. (PLEASE don't tell me that Gorilla Tape is conductive!)

For T1 and T2 I used FT50-43 toroids instead of the TV baluns used by Farhan. He had recommended FT37-43's as an alternative to the TV baluns, but I went with the slightly larger toroids. For T3 I rolled my own binocular core using four FT37-43 toroids stacked 2X2.

The amplifier has passed the smoke test. Next I have to put in the low pass filter (Steve Smith: Please note that I have left space on the board for the filter.) Then this version will face its real test when it goes into the 17 meter Azores SINGLE sideband rig.

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Sunspots: As Good As It's Going to Get

The good news is that conditions are not a lot better than they have been. The bad news is that they won't be getting much better. But take heart guys: the next few years should be pretty good. Now is the time to get those rigs and antennas for the upper HF bands in shape. Construction of a second 17 meter JBOT amplifier begins today (this one for the Azores SSB transmitter).

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Warning! QRPers May Find This Disturbing!

Greg, KC2DWF, sent me this link to a really great web site about the AM broadcast station WLW (aka "The Nation's Station"). Brace yourselves guys, for we are now moving out of QRP land: The exciter on this baby is 50 kilowatts! The modulator could produce 400 kilowatts of AUDIO! The article is very well written, obviously done by an aficionado of high power RF. There are some great lines in there. Here is a sample:

This brings up the real fun part of 1934 AM broadcasting - NO LIMITERS! WLW, like any big-time station at the time, gave the Full Monty: 100 per cent modulation. Now, radio textbooks always have cute little pictures of sine waves at 100%, but people don't talk in sine waves. They don't beat drums, play hillbilly music, or yodel in sine waves. If the studio asked the big rig for some outrageously asymmetrical upward modulation barely crossing zero at all, the DC-sucking beast said FEED ME and obliged - briefly. Voltmeters dipped at the power company, antenna current went haywire, cows felt funny tingles in odd places, and various shotgun-loud bangs and sparks filled the transmitter building.

Have fun, but don't get any QRO ideas...

Here's the link to the article:
http://www.ominous-valve.com/wlw.html

More info and pictures here:
http://www.oldradio.com/archives/stations/cinc/wlwpix.htm

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SolderSmoke Podcast #140

Universal VXO

A new episode of the SolderSmoke podcast is now available:

http://soldersmoke.com/soldersmoke140.mp3

January 9, 2012

-- Santa Claus: Ice Skates, Brownie Box Cameras, and Piper Cubs
-- On the air with 17 Meter Azores DSB rig
-- Seeking balance (with antennas)

-- 23/24 recycling of Azores SSB Rig: Adding Soul to the Old Machine!
-- Attacked by my own soldering iron!

-- RG-174, swarf, and other insidious threats to the homebrewer
-- Inspiration from QRP Quarterly
-- G3RJV validates the D-104
-- T/R admonition from the 1973 Handbook (words to live by)
-- The Woz on electronics and teenage social isolation
-- BANDSWEEP: Straight Key Night at WA6ARA
-- MAILBAG
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Helliwell and the Whistlers

Paul, W2IOG, alerted me to the passing of Robert Helliwell, one of the discoverers of the "whistlers" and an expert on VLF phenomena and the magnetosphere. Paul met him and tells me that he was a real gentleman. His obit is fascinating:

http://news.stanford.edu/news/2011/may/robert-helliwell-obit-052011.html

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Homebrew SSB Portable from Australia

Peter Parker, VK3YE, is one of the true gurus of QRP phone. When I first started building DSB and later SSB rigs, I frequently found inspiration and ideas in Peter's articles and web sites. This morning I came across this amazing video, produced just days ago, showing Peter and his new SSB transceiver in operation from a beautiful Australian beach. The rig is a 40 meter version of Farhan's BITX-20. (I really like the frequency dial.)

Peter describes his rig this way:

It's made from scratch, ugly style, with 99% being from the original design.
It covers 7 to 7.2 MHz, using a 9.05 MHz IF and a 2 MHz VFO.
I used a different microphone amplifier (I got more and clearer output than
the original with my electret mic) and a BD139 driver transistor.
The PA circuitry is also slightly different.
It's been about my easiest and most trouble-free transceiver project to
date. Performance is excellent and a tribute to Ashhar. The furthest distance so
far was a 5/6 report from ZL (about 2000 - 3000km away).

The grand finale of the video is a four-way contact with homebrew rigs in use at all four stations. Excellent. Thanks a lot Peter.

Here is Peter's web site: http://home.alphalink.com.au/~parkerp/

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Las Cruces QRSS Mafia Attacks Pensacola!

OM Dave, WA5DJJ, writes to us about a different kind of SKN -- I guess this would be SLOWWWWWW Key Night!
-----------
Dear Bill,

Hope you and yours have a very Happy New Year.

I agree that Ashhar Farhan is one of the guys that I also admire
mainly because he is trying a valid approach to get amateurs on
the air. His designs are easy to construct, use simple common
parts and work well. I got really tickled when he said that he
kept his parts in two plastic tool boxes. I have so much I have
a hard time keeping mine in a garage with some spillage over to
the storage shed. But alas, I need to downsize.

Keep up the good work with SolderSmoke podcast. You are reaching
a lot of folks and also making a difference.

Our Las Cruces QRSS Mafia had a New Years 2012 on the air celebration
on 30 meter this New Years. We got 14 transmitters on the air and
managed to jam the Pensacola Snapper with so many signals that Bill
couldn't count them all. I attached the sheet I sent W4HBK to
mark the event. There wasn't much room left but others still got
in the holes. We did have a lot of fun plotting the event and getting
the 15 guys installing antennas, building transmitters, and programming
keyers. So, there was a lot of activity here to do the deed.

Anyway, Keep the soldering hot and the projects going. I like your
rebuild of your 17M transmitter. Nice project.

Take care and have fun in 2012.

73 Dave
David R. Hassall WA5DJJ
WEBSITE: http://www.zianet.com/dhassall/


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2012 Off to a Good Start: Balanced ATU Success!

2012 is off to a good start here at SolderSmoke HQ. I'm planning on putting up an 80-10 dipole fed with open wire (window) line. So I need a balanced ATU. A very simple link coupled design appears in lots of the antenna books and handbooks (1980 ARRL Handbook page 19-8, RSGB's "Practical Wire Antennas" by John Heys, page 86): Just a series LC circuit in the primary and another tuned circuit with a split stator variable cap in the secondary. The junk box was VERY cooperative: I found a big tuning coil (or might it have been two coils?) probably from an old Heathkit DX-40 or DX-60) -- that would work for the secondary coil. Then for the primary I found a smaller coil that would fit perfectly (with one layer of Gorilla tape) inside the secondary. I also found two really pristine 1000 pF air variables (I know, they can't handle much voltage, but, hey, that's one of the benefits of being a QRP guy, right?) I used the HW-7 as a signal generator and this morning did some experiments with different loads. You have to play around a bit with the taps on the secondary, but the ATU seems quite capable of matching loads from about 50 ohms up to at least 10K, and it works from at least 40 meters to 15 meters.

I found it very pleasing to see that SWR meter go down to 1:1. I'll now -- in the finest traditions of ham radio -- wait until the snow starts falling and the wind starts howling before I try to put an antenna in the trees.

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

Homebrew Hero: Ashhar Farhan, VU2ESE

I wanted to start off 2012 with something inspirational, and here it is: Ashhar Farhan's work bench. I was visiting his site yesterday and found lots of good info, good humor and, indeed, inspiration. Be sure to check out his RF generator project. And the page that gives his thought on tools and test gear. All of it is wonderful -- you'll find lots of evidence of Farhan's long-term case of The Knack, his efforts to put "soul into his new machines" (his kids are mentioned frequently in his descriptions of his projects), and his obvious qualification for membership in the International Brotherhood of Electronic Wizards. I really like Farhan's efforts to design rigs that can be built with parts available all around the world -- a JBOT amp of his design is percolating nicely in my 17 meter DSB rig, and has been crossing the Atlantic almost every day.

As we were throwing a football around yesterday, I told Billy about Farhan. I mentioned that he lives in Hyderabad -- Billy thinks that's one of coolest city names on the planet and plans to work it into the plot of a novel he is working on.

Here is the site: http://www.phonestack.com/farhan/

Three cheers for Farhan! Happy New Year to all!

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Back to the Barebones (Receiver)

My rehabilitation of homebrew 17 meter gear from the last solar cycle continues. Following the same path that I followed in 2001-2002, I will now move from DSB to SSB. I pulled out the little receiver that I put together way back when. It is a version of Doug DeMaw's "Barebones Superhet" (aka "Barbados Superhet"). I bought it on the net. It had been put together by a skilled builder on a FAR Circuits board. The fellow who built it had changed the IF from Doug's original color burst freq (3.579 MHz) to 5 MHz. He had also put in a varactor controlled VFO using a DC voltage multiplier to get more voltage variation across the varactor. I also think he had it built for 20 meters.

I converted it to a 17 meter receiver. I put in a VXO, using two crystals controlled by a panel switch. I also changed the caps in the filter so as to broaden the response for SSB.

As I was going through all these modifications, I turned to the USENET for help and advice. Dale, W4OP, came to my assistance. Little did we know how DETAILED his familiarity with my RX was:

"Bill N2CQR MOHBR" ...@virgin.net> wrote in message

news:22f6e3ee.0503292244.1b9a1481@posting.google.com...

> Dale: Wow, another Barbados RX builder. That was my first successful
> superhet project. I now have the one I built (still on 20), and this
> morning
> I got another one (the one built by someone else on a factory-made
> board)going on 17 with a VXO. I have a THIRD partially built Barbados
> RX board. If this
> keeps up, I'll soon have a BBRX museum.
>Hi Bill,

Did I sell you mine years ago? I seem to recall using a temp stabilized
varicap in a shielded enclosure for main tuning. It was done on a factory
board. Or was that a 6M xverter I sold?

Dale

Newsgroups: rec.radio.amateur.homebrew From: meara.lon...@virgin.net (Bill N2CQR MOHBR) Date: 30 Mar 2005 22:33:57 -0800 Local: Thurs, Mar 31 2005 1:33 am Subject: Re: Homebrew projects Dale: Wow, small world! Yea I think that is the one I'm working on. I think you also had a DC-DC converter to bring the voltage to the varicaps up. Very nice enclosure for the oscillator. I now have it percolating nicely as a VXO around 23 Mhz (for the 17 meter band). Bill - Hide quoted text -

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

Arduino and the Techno-Hippies

Phillip Torrone over on Maker blog has a good article about the Arduino, and what you can do with it. I especially liked his comments on the "techno-hippie" aspect of the Arduino project (“Arduino: baby-talk programming for the pothead”), and how it might be "Italy's Google."

Check it out:
http://blog.makezine.com/archive/2011/02/why-the-arduino-won-and-why-its-here-to-stay.html

Will we soon see Arduino's working alongside Raspberry Pi computers?

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Homebrew Hero: Kazuhiro Sunamura, JF1OZL

In case anyone in the SolderSmoke community has not yet visited the site of Kazuhiro Sunamura... Be sure to check out his site. He has a really amazing range of projects:

http://www.intio.or.jp/jf10zl/

Here is the bio of OM OZL. As you can see, he definitely has the Knack, and clearly has the sharing attitude of a true member of the International Brotherhood of Electronic Wizards:

My name is Kazuhiro Sunamura. I am a 50 year old mechanical engineer, born in 1956. I am not an engineer in electronics. I have been interested in electricity and radio from the age of ten. For the last ten years, I have been active on my ham radio station JF10ZL. I have also written articles about my some of my radio projects in Japanese for the Japanese CQ Magazine. Now I have decided to get onto the internet and will take the opportunity of showing you my equipment and ideas. Please have a look at my schematics. I will be very happy if this material helps you with your own radio projects. I am a member of the J.A.R.L. affiliated Tsuchiura Club, the local ham club in my home town.

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