Nightmare Turns Real: "Rig Here is a Raspberry Pi OM, and I'm listening to you with my Dongle..."

As with many other nightmarish things, this one was launched at the world on Halloween. It all seems a bit flaky, but we knew this was coming.  Don't complain to me about the lack of low-pass filters, SSB testing on 7.000 MHz,  or the rather nebulous identity of the creator.... I'm just the messenger here.  And remember that I am a HARDWARE Defined Radio,  Discrete Component,  "Menus are for Restaurants" and (now) "Pi's are for eating" kind of ham. 

Here it is:

http://www.rtl-sdr.com/transmitting-fm-am-ssb-sstv-and-fsq-with-just-a-raspberry-pi/

 

CB to 10 Conversion? The Radio Gods Seem Ambivilent

A lot of trouble can begin with a 5 dollar purchase, as I found out after I bought a nickel bag of CB at a hamfest. 

The embarrassing little Good Buddy appliance has been hidden away in my junkbox for a while.  I pulled it out after watching Pete's videos about the conversion of his Ten-Tec Model 150A commercial rig.  I thought perhaps I could use a little DDS or PLL board to bring that CB rig onto 10 or maybe even 12 meters.  

The first thing I noticed when I opened it up was the smell -- there was a very strong chemical electronic smell.  It was as if components and wires and adhesives and PC boards had been venting inside that case for several decades.  This wasn't that pleasant electronics smell that you get from a Drake 2B or a DX-100.  No, this was different.  It gave me a bit of headache.  That's a bad sign.   I began to wonder if the Radio Gods might be sending me a message. 

But then I found this very cool conversion site:
http://www.jcoffman.net/WB5RUA/10_meter_AM_conversion_w_Photos.html

Wow, a few snips, a few jumper wires on the PLL board, and a few coil tweaks and that thing would be on 10 meter AM.  I also learned that the "Cybernet" board that was stinking up my shack was VERY common in CB rigs, so there is a lot of info about it on the internet.  This thing seemed to be crying out for a quick and easy conversion to ham-dom.  

So I don't know which way to go with this one.  I'm getting contradictory signals from the Radio Gods.  What do you guys think?  Garbage can or workbench? 

Rocket Knack in the Congo

This guy clearly has a rocketry version of The Knack.  Busted by the police for a match-stick rocket at age 17,  Jean Patrice stuck with his dreams of a Congolese space program.  Years later, when the rat flying in one of his rockets crashed and burned, he declared that the varmint had "died for science."  Indeed he did.  That is what I said about the lizards and mice killed in the payload chamber of my Astron X-Ray Estes rocket during the late 1960's.  A moment of silence please...

Imagine how difficult it would be to make any progress on something like this in the Democratic Republic of the Congo.  Godspeed Jean-Patrice! 

http://www.wsj.com/articles/one-africans-personal-space-race-turns-vermin-into-astronauts-1446239060

De-mystifying a chip -- Looking inside the 741 Op-Amp

Inside a 741 op amp, showing the die. This is a TO-99 metal can package, with the top sawed off

This is really cool and potentially life-changing for radical fundamentalist ludite homebrewers.  As our readers will know, my big objection to the use of integrated circuit chips is the fact that these little black boxes are in fact often, well,  little black boxes.  We don't know what is going on in there.  It seems to me pointless to shy away from the use of large black boxes (the extremely complex "radios" that dominate the amateur airwaves today) only to fill our homebrew rigs with smaller black boxes. 

But when we crack one of these boxes open and take a look at the transistors, resistors, and capacitors formed on the substrate, then diagram it all out,  I think the fog of mystery is blown away by a refreshing wind of insight and understanding.  We saw this happen on a much smaller scale when someone cut open an SBL1 mixer, but that wasn't an IC.  Ken Shirriff has now done this with the venerable 741 Op Amp.  And he did it with a hack saw.  Bravo Ken.  I can now in good conscience uses 741 op amps in my rigs.    

http://www.righto.com/2015/10/inside-ubiquitous-741-op-amp-circuits.html

Listen to my BITX17 Signal as Heard in France

I was talking to Alan F5LIW on 17 meters yesterday and he was kind enough to record a bit of my transmission and then e-mail it to me.  So here is what my BITX 17 sounded like in Dijon, France. I had the BITX17 going into the CCI EB63A amplifier running at about 100 watts into my Moxon antenna.  Thanks Alan! 

http://soldersmoke.com/N2CQRF5LIW.mp3
 

Real DX: The Mysterious Flicker of KIC 846

Artist conception of a Dyson Sphere Alien Mega-structure

This story somehow seemed appropriate for Halloween.  But it is for real (this is Halloween, not April 1!). The role of amateur scientists in this matter is especially interesting, as is the radio-astronomy follow-up.  Stay tuned!

 

http://www.theatlantic.com/science/archive/2015/10/the-most-interesting-star-in-our-galaxy/410023/

http://www.sciencefriday.com/segments/the-mysterious-flicker-behind-star-kic-8462852/

http://www.seti.org/seti-institute/news/alien-engineering-around-strange-star

http://www.cnet.com/news/the-full-story-behind-the-alien-megastructures-scientists-may-have-found-but-probably-didnt/

Si5351 -- G4GXO says "Give it a go!"

Hi All,

 

Many of you will know of the low cost Si5351A programmable clock generator which can serve as a VFO with a remarkable range of 2.5kHz to 200MHz. This device is available from the larger industrial component suppliers such as RS for as little as £0.68 +VAT and is offered as a small PCB module with regulator and level converters from many amateur component suppliers for around £7.00. I bought a couple of the Adafruit modules to evaluate as the second conversion oscillator in a DSP IF system I’m developing and once I’d overcome the hurdle of writing the dsPIC33 software to drive the device I decided to test the unit as an HF VFO. My reason for doing this was to assess the phase noise of the si5351A; a quick Google will turn up many blogs and forum listings on this subject with mixed opinions of the suitability of this device for VFO service. With no direct method of measuring phase noise I decided to examine instead the impact of phase noise on receiver performance, after all it is this effect that will determine the suitability of the Si5351A as a VFO. My strategy was simple, I used the receiver section of my 60m SSB transceiver which is based upon the Eden IF (SPRAT 144) and uses one of the club 9MHz SSB filters. The front end mixer is a discrete diode ring made from two trifilar wound FT37-43 toroids and four 1N4148 silicon diodes. Unlike a schottky diode mixer this silicon switching diode version requires more drive to keep conversion loss down. The VFO is a low phase noise 7ppm Si570 running on the high side of the IF at 14MHz, a MMIC output stage delivers +10dBm of drive to the mixer. The Si5351A was compared directly to the Si570 – which is a known “very good” performer.

 

The test strategy was to measure the receiver Minimum Discernable Signal (MDS) at 5MHz with the Si570 and the Si5351A as the VFO. With no buffer stage to raise the 5dBm output of the Si5351A to match the +10dBm output of the Si570 VFO module, I accepted that this compromise would have some bearing on the results through increased mixer loss.

 

Results (14MHz oscillator drive, 2.2kHz IF bandwidth)

 

Si570  +10dBm output, MDS –122dBm  (Well below noise from the antenna, perfectly acceptable for 60m!)

 

Si5351A +5dBm output, MDS –118dBm (Note, mixer drive 5dBm down!)

 

Some if not most of the 4dB difference in MDS is without doubt attributable to the lower drive power of the Si5351A in my test configuration, this is borne out by the AGC threshold which moved up by 4dB suggesting increased mixer loss. I’m confident that had I been able to match the +10dBm output of the Si570 then it would have been a close match. My conclusion is that for HF at least the Si5351A is a very useful oscillator which is easily applied and can deliver good performance. If you had doubts about using this device at HF I hope that these results encourage you to give it a go!

 

73 Ron G4GXO