Bill N0YUD built this really nice Michigan Mighty Mite. I like the wood base (with little feet!). And the classic black 35 mm film container. And the Vero board. Fancy connectors too! Nicely done Bill.
Bill has also wisely left space for a low pass filter. As you can see in his 'scope picture below, the MMM produces a lot of harmonics. With a low pass filter, that mess will turn into a beautiful sine wave. We'll be talking about harmonics and low pass filters in the next podcast.
Hi Bill and Pete,
I just completed my Michigan Mighty Mite and am proud to announce it seems to be generating about 1 watt of what appears to be extremely harmonically challenged RF. I was worried about the ugly signal on my scope until I saw another screen shot on the blog page that looked almost exactly the same as mine.
What a fun project and lots to learn with just 7, or in my case 8, parts (I had to stack a couple of 56ohm resistors). I utilized those small pc board sockets for the coil and crystal so I can easily change bands and also left room for a low pass filter....
I am still struggling with the tank coil theory and impedance... Impedance matching is a very murky area for me!
I am looking forward to building the low pass filter. By the way, I checked for third and fifth harmonics and could not hear anything on my receiver. There's another question, why does this circuit generate odd harmonics? Fun stuff, this learning game!
I love the Podcast! Thank you for your efforts and keep them coming.
'73
Bill McMillan
N0YUD
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
Pete and Ben's LBS Receiver
SolderSmoke Podcast #172 is available
http://soldersmoke.com/soldersmoke172.mp3
16 February 2015
Bench Reports:
Pete under the gun to finish SSB transceiver project. NEW VIDEO:
http://youtu.be/hbLXW0sHTFo
Bill fixes his BITX 2040 Oscillator (Bandsweep!)
Next: LP filter for 120 watt amp.
Bill's 13 dollar Chinese freq counter (Blue! With anti-wobble tape!)
Bill's next rig: Chipped to the Max, DDS, SBL-1s, plug in filters!
Radio Shack going under and JAN no longer making crystals.
Mighty Mite Project: Let's get them DONE!
An easy way to get Q or ESR measurements on crystals?
SI5351 as a crystal substitute.
DuWayne's Scalar Network Analyzer lights up the internet!
The Portable SDR rig -- Pete almost goes to the dumpster!
Report from the cutting edge: Pete's new Elecraft KX3.
MAILBAG: Meeting W7ZOI and WA7MLH at a hamfest.
Instant Messaging with Farhan
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
Crystal Filters built by WA7MLH
SolderSmoke Podcast #163 is available:
http://soldersmoke.com/soldersmoke163.mp3
Saturday July 26, 2014
Part III with Pete Juliano: Tribal Knowledge -- Sideband Sidecars
-- Moxon Update "A Thing of Beauty"
-- Pete is Building Peter Parker's Knobless Wonder
-- Ladder Filters
--Construction Practices for SSB rigs
-- Essential Test Gear
-- Junk Box development and parts storage
Next time: Tubes, Valves, Termatrons, Firebottles.
Thanks to Bob Crane and the FDIM musicians for this episode's musical opening.
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
As reported yesterday I have the 20 meter receiver portion of my BITX 20/40 rig up and running. I decided to take a closer look at the crystal filter I built.
Here is my method:
1) Using an Arduino/DDS sig generator, I put 11 Mhz energy into the base of Q2 (the stage immediately prior to the crystal filter).
2) Using my Rigol 1052E oscilloscope, I measured RMS voltage at the output of Q3/Q3A (the stage immediately following the filter).
3) I looked at Vrms as I MANUALLY varied the input frequency in 100 Hz increments.
4) I took the results and plugged them into a spreadsheet. I then used the spreadsheet to calculate the db drop from the peak Vrms value (So I wasn't looking at insertion loss, just the filter shape).
I used 20*LOG(Vrms/276)
5) I ended up with the chart displayed above.
I have a few questions:
1) What do you folks think about my methodology for evaluating the filter?
2) Where would you guys put the BFO frequency?
3) I know the ripple looks ugly, but the receiver sounds great. Should I attempt to get rid of the ripple?
Here is the filter I used (as prescribed by the AADE software): I estimated Q at 10000 and used LM and CM values derived by the G3UUR method, and made no effort to match impedances going into the filter:
Here is what GPLA predicted. I estimated Rin and Rout values. That probably accounts for the difference between the GPLA prediction and what I measured.
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
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