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Saturday, March 1, 2014
38 Year HB Mystery Solved? Was it the phasing dots?
During the summer of 1976, at the age of 18, I made an audacious attempt to join the ranks of the true homebrewers. I tried to build a receiver. It was the Herring Aid 5 from the July 1976 issue of QST, a 40 meter Direct Conversion receiver intended for use with the famed Tuna Tin 2. As I have recounted (perhaps ad nauseum), I never got it to work. My recent encounter with the ORIGINAL Tuna Tin 2 (Mojo was transferred to my BITX17, and it definitely works better now) got me thinking about this painful experience. I decided to try again.
There is an updated NORCAL schematic for this rig. I found it (and some good articles) on the NJQRP club page. In the original, designer Jay Rusgrove, WA1LNQ, used only parts that could be found at Radio Shack stores. In the days before the internet and Mouser, this was a good idea. Instead of toroidal ferrite and iron powder coils, Jay built his coils around Radio Shack solonoidal 10 uH chokes.
The NORCAL version dispensed with the Radio Shack chokes, and used toroids. But I wanted to try to find out what went wrong 38 years ago. So I dug up some 10uH chokes.
I know that my problem was that I never got the oscillator working. I remember being able to hear signals with my "almost" receiver when I put my HT-37 in "CAL" mode and tuned through 40. I was so close! The Herring Aid was picking up RF from the HT-37 and using that in lieu of the LO energy that obviously wasn't coming from my Herring Aid VFO. But WHY didn't that oscillator work?
Today I started with the VFO. Again, it didn't work! But now I have decades of troubleshooting experience under my belt. So I poked around a bit. Then I decided to look closely at the phasing.
Take a look at the schematic(above) and the picture (below). L7 is the 10uH choke. L6 is 4 turns wound over it (or adjacent to it). Now, here is the key question: Look at the phasing dots. How would you guys connect those coils? For me, the schematic indicates that the TOP of L6 should go to the Zener and the BOTTOM of L6 should go to the drain of the JFET. The TOP of the choke should go over to C5, and BOTTOM of L6 should go to ground. Right? Or am I reading the phasing dots wrong?
Well, the oscillator was not oscillating in this configuration. Then I did something that I might not have known to try back in 1976: I reversed the phase of L6: I put the top of the coil to the Drain of the JFET and the bottom of the coil to the Zener. Bingo. The joy of oscillation. Now it works. (The picture below shows it as it is when the oscillator is working well.)
So, is there an error in that diagram? Was this not all my fault?
Aha! I just looked at the schematic of the NORCAL version. Check out the dots! I think that was the problem!
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
Thursday, February 27, 2014
Links Fixed, Podcast Version of Hamfest Presentation
Armand, WA1UQO, with BITX 17
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
73
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
Labels:
BITX20,
Hamfests and Flea Markets,
SolderSmoke Podcast,
video
Wednesday, February 26, 2014
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
Labels:
BITX20,
Clubs,
Hamfests and Flea Markets,
Jean Shepherd,
Knack Stories,
video
Tuesday, February 25, 2014
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
Labels:
ICs
Sunday, February 23, 2014
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
Labels:
BITX20,
DeMaw--Doug,
Hamfests and Flea Markets,
QRP,
radio history,
Tuna Tin 2
Saturday, February 22, 2014
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
Labels:
astronomy,
Marconi-Guglielmo,
radio history,
UK,
video
Wednesday, February 19, 2014
Taking the Knack a Bit Too Far
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
Labels:
Physics,
space program,
video
Monday, February 17, 2014
BITX 17 Build Update: More Filter Maintenance
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.
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
Labels:
BITX20,
Hayward--Wes,
SSB
Sunday, February 16, 2014
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
Labels:
satellites,
space program
Saturday, February 15, 2014
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
Labels:
workbench
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