Winterfest Hamfest with Armand WA1UQO

 I had a great time at the Vienna Wireless Society's  Winterfest Hamfest.  As I have done for several years now, I joined forces with Armand, WA1UQO. A prediction of cold rain caused many of the tailgaters to stay home, but there was still a lot of good stuff to be found at the 'fest.  I came home with a large stock of potentiometers, a 130 foot doublet with open wire line, TWO copies of SSDRA (one given to me by Armand) and various other bits and bobs (including some Cadmium Sulphide light sensitive resistors....)   I successfully resisted the siren calls of several old Hallicrafters receivers.  After the 'fest Armand came with me for a visit to SolderSmoke HQ.   Armand always brings along some part to be used to help members of the International Brotherhood in their radio endeavors.  This year, that included several 80 meter crystals suitable for Michigan Mighty Mites and the ColorBurst Liberation Army.  Thanks Armand!  And thanks to the Vienna Wireless Society.  

Great Video on Mixers

You know that you are sinking deep into The Knack when you watch a video like this one and find yourself thinking: "FANTASTIC!  WOW!  Now I know why square waves are better!" I really liked this one.  In the beginning I was kind of concerned about his refusal to explain how non-linear, non-switching mixers work.  He actually used the dismissive non-explanation that I've always found so disappointing:  "Blah, blah, blah... it's in the trig."   And he actually said, "Blah, blah, blah." But he more than made up for it when he got into the switching mixers.   Note that his drawing (at the start) of "Mixing by Switching"  attempts to show the waveform that results from an LO "chopping up" an incoming RF signal.  I always find that picture worth a thousand trig equations.

I also really liked his explanation of the benefits of rapid rise time in switching mixers, and how slow switching causes the diodes to spend some time in the non-linear part of their curves, giving rise (!) to IMD products (I'm paraphrasing).  You can really see why they say it is better to drive diode rings with square waves.  So stop trying to put low pass filters between your LO and the diode ring.  Square waves are your friends here. 

Mr. Marki seems to be one very cool EE.   And I'd like to hear more about his dad.  Here is some more about the Marki engineers:

http://mwexpert.typepad.com/markimicrowave/

GREAT Video on Mixers

You know that you are sinking deep into The Knack when you watch a video like this one and find yourself thinking: "FANTASTIC!  WOW!  Now I know why square waves are better!"

I really liked this one.  In the beginning I was kind of concerned about his refusal to explain how non-linear, non-switching mixers work.  He actually used the dismissive non-explanation that I've always found so disappointing:  "Blah, blah, blah... it's in the trig."   And he actually said, "Blah, blah, blah." But he more than made up for it when he got into the switching mixers.   Note that his drawing (at the start) of "Mixing by Switching"  attempts to show the waveform that results from an LO "chopping up" an incoming RF signal.  I always find that picture worth a thousand trig equations.

I also really liked his explanation of the benefits of rapid rise time in switching mixers, and how slow switching causes the diodes to spend some time in the non-linear part of their curves, giving rise (!) to IMD products (I'm paraphrasing).  You can really see why they say it is better to drive diode rings with square waves.  So stop trying to put low pass filters between your LO and the diode ring.  Square waves are your friends here. 

Mr. Marki seems to be one very cool EE.   And I'd like to hear more about his dad.  Here is some more about the Marki engineers:

http://mwexpert.typepad.com/markimicrowave/

KiwiSDR

https://www.kickstarter.com/projects/1575992013/kiwisdr-beaglebone-software-defined-radio-sdr-with?ref=video

QRPi WSPR with a Raspberry Pi Shield from Hungary via Tuscon

VA2NM's Michigan Mighty Mite (with Tuna Tin LPF!) (video)

Bill,

  Here is my contribution... After managing to somehow get my hand wound transformer to melt a pill container, I used my Dad's hand made, circa 1950 transformer and got it working on a 1.4 MHz xtal and also on 3.58 MHz with a colour burst xtal.  A re wound coil on the remaining unmelted pill container worked on 40 meters. I succeeded in getting my Mighty Mite working on three bands.  My father would have been pleased, as this was kept aside all this time and now has been put to use. He had built the coil while working part time in post World War II England at the GEC labs in U.K.

Thanks for the motivation! I'm going to move forward and clean up the 80 meter signal and see how far it goes on the reverse beacon website.

The coil form was about 80 turns on a 1 inch diameter with a 20 turn secondary that I used for the center tap portion by joining both bottom ends.  Then I wound an 10 trim secondary, loaded up with a 50 ohm resistor to tune up (capacitor fully opened up) on 3.58 MHz in the video, and the audio coming from my receiver tuned to the 3.58 MHz signal.

Regards,
Nigel Maund

A Great Knack Story: Peter Parker Interviewed on "QSO TODAY" by 4Z1UG

I really liked Eric's interview with the Peter "The Wizard of Melbourne Beach" Parker aka VK3YE. What a great Knack story!  There he was, trolling the garbage dumps of Western Australia, looking for discarded electronics.  Using the LO of one broadcast receiver to demodulate SSB signals coming in on another... Great stuff!  Check it out:

http://www.qsotoday.com/podcasts/vk3ye