Links Fixed, Podcast Version of Hamfest Presentation

Armand, WA1UQO, with BITX 17

 

Using Dropbox to post the video of my BITX presentation at the hamfest didn't work out too well, so I put it on Vimeo:

 https://vimeo.com/87725154

The slideshow is here: http://soldersmoke.com/winterfest.pptx

I stripped out the audio for those who would like to dispense with the video.

Audio only is here: 

http://soldersmoke.com/soldersmokewinterfest.mp3

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Hamfest Presentation on SolderSmoke and BITX (Video)

The Vienna Wireless Society of Northern Virginia asked me to give a talk at their 23 Feb 2014 hamfest.  I spoke about homebrewing and the BITX transceivers.  Click on the link below to watch the video.  (Special thanks to Elisa for doing the video.)

https://vimeo.com/87725154

The Powerpoint slides are here:

http://soldersmoke.com/winterfest.pptx

For those who just want to listen podcast style,  I will try to turn the audio into a podcast and will post it via the normal channels. 


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

HB Chips! Discrete Component Version of 555 Timer

The world would be a better place if we could do more of this...  Thanks to David Cowhig for alerting me to this wonderful development. Details here:

http://spectrum.ieee.org/geek-life/hands-on/build-your-own-giant-555-timer-chip


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

Tuna Tin Mojo Transferred to BITX17!!!!!!

It happened at the Vienna Wireless Society's Winterfest Hamfest today in Northern Virginia.
That is Doug DeMaw's original Tuna Tin. 
This may be the first time TT Mojo has been given to a phone rig. 
Doug DeMaw would, I'm sure, approve.

Thanks Rex!


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

Brilliant! New "TX Factor" Ham Radio TV Show from the UK

I really enjoyed this.  It is the first episode of what I hope will be a long-running series.
These guys did a great job.  Excellent quality video production and very interesting subject matter. A LOT of work went into this.  I liked the PSK from a smart phone on a foggy hillside (with Moroccan soup!).  The Marconi stuff was wonderful.  Beer barrels as 2 meter cavity resonators! Excellent Knackish-ness!  And a two meter repeater in an astronomical observatory.  Well done! 

Thanks to Nigel and Dino for alerting me to the TX Factor.

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

Taking the Knack a Bit Too Far

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BITX 17 Build Update: More Filter Maintenance

 

 

 

Having had great success in straightening out the 11 MHz filter in my BITX 2040 (scroll down for details),  today I decided to see what I could do with the filter in my 17 meter BITX (four 5 MHz crystals in Cohn MIN LOSS configuration, with 40 pf caps all around).  The key to my success in all this has been the filter programs that came with EMRFD.  After characterizing my crystals with the G3UUR method, I plugged the values into LADBUILD 8, then took a look at the expected results.  As you can see from the image above the predictions were not pretty.  Yuck.  Lots of ripple and lots of insertion loss.

I went into the rig and using my DDS sig generator and my RIGOL 'scope, measured actual performance.  It looked worse than the prediction (part of the worsening is a difference in vertical scale):

LADBUILD lets you play around with the values of the components in the filters.  I know that ripple is usually related to an impedance mismatch.  So in LADBUILD I experimented (virtually) with different impedance values at the end.   I noticed that at about 1000 ohms, the ripple and insertion loss got better:

So I went and built two broadband toroidal transformers.   4 turns primary with 12 turns secondary (1:9 Z).  I'm assuming that the BITX has around 150 ohms at either end of the filter.  That would put about 1350 ohms at the ends of the filter.

Here are the results:

Much better.



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ISEE-3 Spacecraft Returns after Being Forgotten

Hack-A-Day has issued a challenge to hams and hackers:

http://hackaday.com/2014/02/14/call-for-hams-and-hackers-welcome-iceisee-3-home/#more-114769

If a BITX 20/40 would help, I stand ready to assist!  


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

Homebrew Junkbox Machine Tools

In the book "The Ugly American"  the hero (the ugly guy!) come up with a way to use old engine blocks to build water pumps to help farmers in South East Asia. Now, Mr. Delany is putting them to similar good use.  Homebrew junkbox machine tools!  Yea!

http://makezine.com/magazine/make-37/patdelany/

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

BITX 2040 Build Update #10 : Fixing my Filter

That dip on the high side of the passband was bothering me.  The GPLA crystal design program predicted it, and indeed, when I measured the performance of the actual filter, there it was.   The rig was working fine -- the receiver sounded fine and everyone tells me that it sounds great on transmit.  But still, it bothered me.

So I started working out with the various crystal filter software packages.  

This filter was -- sort of -- a Cohn Min-loss filter, but I had built it with four crystals and three shunt caps (80 pf each) and no series caps at the input/output.  This morning I decided to see what would happen if I put the series caps in there.  Here is what Wes's GPLA predicted:

Wow, that looked a lot nicer.  And the 150 ohm terminations seemed to be just about perfect for the BITX design -- no need for impedance transformation.  I heated up the soldering iron and searched the junkbox for suitable caps (I found 2 82 pf caps -- close enough).

Here is what the results looked like (I didn't measure insertion loss so the top of the curve is just the peak of the response curve).

Exactly as predicted!  Thanks Wes! And thanks to Farhan for encouraging me to characterize my crystals and to use the available software

Now I have to go back and de-ripple the 5 MHz filter in my BITX 17.

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Back to the W7ZOI/W7PUA Power Meter

Recent e-mails and Facebook postings from Jim (W8NSA) and Michael (AA1TJ) got me thinking about my old W7ZOI/W7PUA power meter.  The 15 inches (38 centimeters) of snow that fell last night gave me the day off -- and time to play with this very useful and interesting piece of gear. 

The last time I used it I remember thinking that a digital readout would be nice.  But I didn't feel like going back into the world of Arduinos and LCD screens.  So I came up with a real Kludge solution:  I had cheap little DVM that I wasn't using, so I just velcroed it to the side of the power meter.  That little connector above the BNC is the output for a DVM.  I might work on calibration later today.

Wes has some very interesting info follow-up info on the meter on his site: http://w7zoi.net/qststuff.html
I really like the part about how the meter is so sensitive that you can see the thermal noise in the input circuit and can actually measure the strength of signals from your antenna. 

I think I might need a low pass filter at the input of the meter.  There are strong FM broadcast transmitters in this area (some of you may have listened to them in the background of early episode of the SolderSmoke podcast!). I notice that just bringing my fingers close to the input causes the meter and the DVM readout to swing up.  That's not good.

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A Very Simple SSB Transmitter

 

 

I found this in the files section of the BITX20 Yahoo Group.  There is no information on the source.  I see two balanced modulators and two very simple phase shift networks. 

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