The Southern Appalachian Radio Museum

Chris, KD4PBJ, of SMT Solutions, sent us a thumb drive with pictures and videos of his visit to the Southern Appalachian Radio Museum.   What a great collection of radios!   I saw many old friends on those shelves.

There is a lot of radio history in that museum, and much of it is conveyed by the photos and videos that Chris took.   Here they are, all 111 files:

https://picasaweb.google.com/116927941005026017464/SARM#

The museum is in Asheville, N.C.  http://www.saradiomuseum.org 

Thanks Chris.  And thanks to the curators of this fine museum.

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A Beautiful Receiver by W1DN

I wish my prototypes (or final products!) looked this good.    I like the way Lee puts the switches onto the prototype board.  Very nice.

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

Wow! Raspberry Pi as an RF Transmitter

https://github.com/threeme3/WsprryPi

This site shows you how to use a $35 Raspberry Pi Computer as an RF transmitter for the WSPR (Weak Signal Propagation Reporting) System.  All you need is a simple low pass filter and an antenna. (Oh yea, and a ham radio license.)  The site says you can get 10 milliwatts out.  That's enough for WSPR!   Very cool. 

This looks like a real international effort:

Credits goes to Oliver Mattos and Oskar Weigl who implemented PiFM [1]  based on the idea of exploiting RPi DPLL as FM transmitter. Dan MD1CLV combined this effort with WSPR encoding algorithm from F8CHK, resulting  in WsprryPi a WSPR beacon for LF and MF bands. Guido PE1NNZ extended this effort with DMA based PWM modulation of fractional divider that was  part of PiFM, allowing to operate the WSPR beacon also on HF and VHF bands.

For more info on WSPR:  http://soldersmoke.blogspot.com/search/label/WSPR

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

Podcast Noise Explained; Mic advice from Germany

Hello Bill,

This might be down the drain for you, but I only listen to your podcast very few months:

The background hiss you mentioned in Soldersmoke 148 definitely was a crosstalk from the switching voltage converters for the CPU in your laptop. The CPUs these days are operated with voltages in the .7 V to  2 V range,with currents from several Amperes up. A high-performance CPU may dissipate150 W which can easily mean supply currents of 100 A an more. The CPU operating voltage, especially in a laptop, might change several 100 times a second. I think you can imagine the rest.

Why is that voltage adaption so important? This is within your domain: The biggest heat source in digital electronics these days is charging and discharging capacitors. Unless you use a resonant circuit (which you cannot do on a chip) you dissipate P = 1/2 C U^2 with every discharge. Yes: Power depends on the square of the supply voltage. And at a clock frequency in the 2 GHz range you charge and discharge all those capacitors quite often. Each of these has a capacity in the fF (.001 pF) range, but you have billions of these...

Over the time you had quite some complaints about your whistling s. In former times this was definitely made worse by some technical problems. But this is a problem long gone. An Soldersmoke 149 I believe the remaining problem simply was the tooth gap you described a few years back.

BTW: You could easily reduce the file sizes of your podcasts by at least 50% with a few simple measures:

- You should record the podcast as you do now, with a 44 or 48 kHz sampling rate, that's fine. I would even record in wave format.

- Afterwards downsample your recording to a sampling rate of 12 or 16 kHz. This provides ample audio bandwidth for this purpose. See e.g.http://forum.audacityteam.org/viewtopic.php?f=28&t=19705

- Then create the MP3 file with a signal rate of 48 or 64 kbit/s.


BTW: Last weekend at a ham flea market I got a variable transformer. Now I can try to revitalize my Drake TR4C that has not seen any electricity for some 30 years. I bought it when I got my shortwave license in 1975. At that time I lived with my parents. Then I could operate it during my military service. But after that I got an electronics engineer and lost all possibilities to erect any kind of SW antenna. Only three years ago I got my own house near Munich. But I'm hardly at home and I nearly exclusively operate from my car. I will not try this with any kind of boatanchor :-)

vy 73
Alexander
DL4NO

------------------------------------
Von: solder smoke [mailto:soldersmoke@yahoo.com]
Gesendet: Dienstag, 19. März 2013 09:49
An: DL4NOAlexander
Betreff: Re: Soldersmoke 148: Background Hiss

Thank you Alexander.  That is very useful information.   I have switched to a new computer and I think the hiss  problem is gone.   The gap in my teeth remains however!    I am thinking about getting a better microphone.  Any advice on this?   I am glad to  hear that you are back into ham radio.  My Elmer (the guy who helped me get started as a novice) was an immigrant from Germany (Hilmar,  WN2NEC).  He was an excellent technician.   I still use some of the things he made for me.   73  Bill ------------------------------------------------ Hello Bill,   about a microphone: Think about a headset, possibly a wireless one. I would search forums about dictation software for advice.   A headset fixes the position of the microphone relative to your mouth. At the same time the microphone is near your mouth so any ambient noise is suppressed. A wireless [Bluetooth] headset would allow you to move around freely. Unless you come near a larger hard or soft surface or leave the room the sound should not change much. You could arrange the materials for your next podcast around the room and move from "chapter" to "chapter". And as the digitizing happens in the headset all weak analog signals are safe away from any voltage converters and digital electronics.   I had never left ham radio, I just reduced and modified my activities. 2m or 70cm FM were always possible. Here in Germany we have more than 1,000 repeaters. Many of these repeaters have Echolink capabilities. For the last 15 years I have more or less exclusively worked from my car while driving. In my car I have a FT-857D. For shortwave I use monoband antennas on a PL mount at on the roof of my car. For pictures see http://www.dl4no.de/thema/amateur1.htm. The schematic in http://www.dl4no.de/thema/mobil-st.htm shows how I ensure that my TRX gets its 22 A peak from the 12V outlet in the trunk of my car: I buffer it with a 1 F capacitor - really 1,000,000 µF! The mean supply current during SSB transmit is less than 5 A.   A quite important role in my ham life play the local chapters of our German ham radio society DARC. There are more than 1,000 of them, each with its own DOK. So wherever my customers are, at least one local ham meeting a month is not far away. I participate in their activities, give a lecture from time to time. This is a big help as I mostly work at my customers and these are scattered all over southern Germany.   Just a short story with some local connection for you: Peter, DL5NC, spent quite a few years in the Washington, DC area. He has a US call, but please don't ask. He was born some 50 km from my home town. Formally this area, Franconia, has been part of Bavaria since 1806. Nevertheless we believe that the Bavarians have no clue how to brew beer.   One Friday morning (your time) he was on his way into Washington, DC. Through Echolink he connected to a Munich repeater while I was in the afternoon rush hour on my way to a beer garden. I told him that this was one of the few places in Munich where you could get a decent beer. And otherwise I had my own beer at home imported from Franconia. He threatened to never again talk to me because of mental cruelty. In the meantime he returned to Germany and got a neighbor. We drank a few Franconican beers together in the meantime :-) vy 73 Alexander DL4NO

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DeMaw's Barebones Superhet

A recent e-mail got me thinking about Doug DeMaw's Barebones Superhet.  June 1982 QST.  Mostly 40673 Dual Gate MOSFETS (this one's for you Dino!).  Barebones indeed.  Check out the schematic.

I literally blew the dust off my version and fired it up on Sunday.  It sounds really great.   I had lowered the values of the caps in the ladder filter to widen it out for phone.   Also, I see that I used LM386 instead of the op amp AF Amp prescribed by W1FB.   I notice that my version has much better audio than another version of this RX (with the op amp) that I'm using on 17 meters.  Could the difference be the LM386 vs. op amp?  There is a lot more audio with the 386, and the AF response seems wider.  

I feel the urge to put this receiver to use.  I am rehabilitating the W1VD CW transmitter that used with it during the late nineties, but I'm a phone guy now, and I feel compelled to use this RX as part of an SSB rig.  Of course, I could build a standalone SSB TX, but how about a diode switching scheme to make use of the Barebones' filter, the VXO and the BFO in a transceiver?

Here is my article on the original build of this receiver: http://www.gadgeteer.us/HBHOME.HTM

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

A Beautiful Workshop in Scotland

A nasty Coronal Mass Ejection hit our magnetic field at around 0600 UTC today.  The HF bands are now in poor shape.  What better time to visit a really impressive workshop in Scotland? 

Ian has an interesting site: http://www.ianjohnston.com/

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

Vanguard!

Wow, Vanguard even looks like a QRPp satellite. 

I suspected that something was up:  I noticed that Mike Rainey, AA1TJ has recently been crossing pond with a QRPp Germanium rig...  Then Steve "Snort Rosin" Smith clued me in: The next period of  Vanguard QRPp Activity Days begins tomorrow.  "Club 72" has a nice write up, and a nice collection of pictures of the Vanguard rigs that have been built around the world:

http://www.club72.su/vanguard.html

Go Germanium!  Go Vanguard!

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