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.

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

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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Mars Star Party from La Palma (video)

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BITX 2040 Build Update #9: On-the-air Observations

The BITX 2040 has moved from the bench to the operating position and is producing a steady stream of contacts on 20 and 40 meters.  In the picture above it is the rig with the copper-clad front panel (the BITX 17 is below it).  It has already crossed the pond on both bands.

Some observations:

I get significantly more power out on 40 than on 20:  about 7.2 watts PEP on 40 and about 4.4 watts PEP on 20.  I saw a QST article that showed similar frequency/power out variations from IRF510 amps.   But I notice I get more power out from my 17 meter rig.  On that rig I am using trifilar (9:1 Z) transformer instead of the standard BITX bifilars. 

My 40 meter receiver is LOUD.   Too much AF out.  I am not used to having this problem!  On this rig I am using the same discrete component 2n3904 2n3906 transformer-less circuit that I used in the BITX 17.  But AF out on 40 was so loud that I had to go back and add 20 k ohms to the top of the volume control pot.   I didn't have this problem with the 17 meter rig, and I didn't have it on 20 with this rig.  Any ideas why this rig would be so loud on 40?

I still want to go in and fine tune the crystal filters in both rigs.  I am studying the various software packages out there (especially Wes's LADPAC).  I hope to get rid of the ripple.   

In most of my contacts with these rigs, I end up describing the circuit and its Indian origins.  Most people are really fascinated.  Yesterday W1IDL in Michigan suggested that I contact my Indian friends and get some assistance in making some Hindi or Urdu labels for the rig and the controls.   I think that is a very cool idea. 

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