Be afraid! Be VERY afraid! Digital Audio on 20 Meters (video)

Here is a very interesting comparison between digital audio, and plain old SSB audio (from a Collins rig!).

I don't know.  I may be prejudiced here, but that digi audio just doesn't sound too good to me.  And I ask myself: "How could it?"  They are restricting the transmit bandwidth to 1.2 kHz.  Can the error correcting elements of the software help them get around the bandwidth limits of Shannon's communications theory?  

The digi audio sounds quite robotic to me. Even Siri sounds better.  Is this because -- as the receiving station noted -- they were only getting "80 percent decode"?   Would the digi audio have sounded better if signal strength had been better? 

Again, I don't know.  But remember. I am a Ludite (with a single d -- the ORIGINAL spelling!).

W6JL's Amazing Phasing Station

Eric 4Z1UG interviewed Don Huff W6JL a few months back.   I really like Don's approach to homebrewing.   I recently came across his QRZ.com page -- I was lured in by the phasing receiver with the Tayloe detector.  And of course I like the modules spread out in the desk.  FB Don.  

Here are the details on Don's rig:

https://drive.google.com/file/d/0B7YOOrbLoXkvbHkwWDRnV1JFVHc/view

Here is Eric's interview on QSO Today:

http://www.qsotoday.com/podcasts/w6jl

Could Grayson's Arduino Thermatron Shield Protect Us From Digi Domination?

Something old, something new, eh Grayson?   The author of "Hollow State Design" is engaged in an (I suppose) admirable effort to bridge the gap between our beloved Thermatrons and those new-fangled Arduinos.  Here Grayson tries to explain and justify his flirtation with the dark side:

I want to do some experimenting with Thermatrons and Arduino.  Sound weird?  Maybe not.

I really like playing around with the Arduino even though it violates my ban on digital technology in my shop. (My excuse is I am trying to use it teach my son something he can use to get a job someday.)

Sure Grayson.  That's what they all say.  "I was doing it for the kid..." 

Kidding aside, that tube shield looks pretty cool.  And I like the MeTubes base for the Thermatron.

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

HEAVY METAL! How to Handle HEAVY Boatanchors -- And Which is Heavier: R390 or DX-100?

Grayson: 

I was on 40 AM today and I mentioned to the guys your thoughts about the possible need for a block and tackle and a metal beam in your shack roof to help you deal with your R-390A.  They sympathized completely.  One fellow claimed he knows hams who are working out with weights just so they can handle their boatanchors.  Another guy said he is thinking of building a small crane, perhaps powered by his chain saw (yikes!).  A third fellow said he actually bought a thing called a "lifting table" from Harbor Freight.  

This got me to thinking:  How much do those R-390s really weigh? 

A MERE 85 pounds!  That's it?  Holy cow, the DX-100 has a listed shipping weight of 120 pounds!

73  Bill  

Bill:

Nice thing about a “regular” boat anchor (DX100, HT37, SX101, etc.) is that you can put it on its side and get fairly easy access to both sides, and all the components at once.  The problem with the R390 (and a lot of Collins military gear) is Collins worked hard to cram so much in a “small” space that you have to take whole sections apart to get at anything.  So you have to “flip” the chassis over, side, over, on its back, etc.  UGH.  To get at the RF front end components, you gotta take the front panel off before you can remove the RF chassis.  UGH

I know about the lifting table from harbor freight.  A really nice shack accessory.  Puts the rig at a better height to work on.  With a “lazy susan” thing on top, a nice arrangement!   Maybe next Christmas.

73, TA2ZGE

Grayson

TA2ZGE - Ankara, Turkey

KJ7UM

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Another Lightwave Communication Knack Story from the UK

Hi Bill,

I've been following your podcast since you started and enjoy every episode. I've been licensed here in Scotland since 1970 as GM8EUG.

I thought you/others might be interested in how I got into radio/electronics and how I feel I may have the 'Knack'. 

The above reference reminded me of some experiments I carried out in 1967 as a schoolboy. There were no ready sources of parts locally for me.. I lived  in a rural area so the nearest electronics parts shop was 50 miles away so it was all done by letter and mail order.

My first audio link was driven by a tube broadcast receiver with a 3 volt torch bulb connected instead of the loudspeaker. (I hadn't heard of impedance matching!)  This flickered nicely on speech/music peaks. The bulb was positioned at the focal point of a parabolic car headlamp reflector from a scrap car.  I now had a beam of light with audio on it.
Next step was the receive side...I didnt have access to a photo cell but had a Cadmium Sulphide photo resistor. Connecting a pair of low impedance headphone in series with this cell and a 1.5 volt battery gave me recognisable audio when the cell was in the beam...no amplifier needed!

Next step was greater range...this was achieved with a 6 inch shaving mirror to focus the beam onto the photo resistor. This gave me the length of the street (100 yards when it was dark outside )with the flickering beam shone out of my schoolboy bedroom window resulting in puzzled  looks from passers by.

Next problem was the frequency response.. all bass and no treble. Some research indicated that the photo resistor had a slow response so that was part of the problem but I had a hunch... How fast does a filament bulb react to audio? Biasing the bulb with a 1.5 volt cell so that it glowed  dimly with no audio improved the audio response greatly.

So what got me into radio...my father was a Chief Radio Officer in the Merchant Navy during WWII and my schoolboy bedtime reading (the only technical stuff I could find ) was his textbook ...the 1939 edition of the Admiralty Handbook of Wireless Telegraphy. Capacitors  were called condensers and they were measured in 'jars'!

That was the start of a career. I've now moved through testing international telephone exchanges, installing 2 way radio for the whole of Scotland for British Rail (paid for my hobby!) and finally 32 years in IBM writing manufacturing test software from the original IBM PC to Thinkpads.
Now retired I am active on WSPR and am writing Android apps to keep my brain in gear.

I just can't leave this stuff alone!

Hope this of interest/amusement.

73s

Neil Roberson GM8EUG