These are some of the drawings that I made during the Mars 2020 opposition. I would go out to my back porch with my 6 inch Dobsonian Newtonian telescope. I would look closely at Mars, making mental note of what I was seeing. Then I would go to the shack and immediately draw what I'd seen. I would then look for relatively recent images of Mars made by people with more experience and better equipment, and I'd compare my drawings with their images -- this enabled me to understand what I was seeing. Also useful was the Mars Profiler of Sky and Telescope magazine -- you just plug in the date and time and it displays the part of Mars that is facing us.
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Monday, December 21, 2020
Observations from the Mars 2020 Opposition
Sunday, December 20, 2020
The Parkes Radio Telescope Picks Up a Possible "Wow" Signal from Proxima Centauri (maybe)
An article about SETI and our favorite dish. From Scientific American:
Saturday, December 19, 2020
A Very Clever Way to Build a Moxon for 17 and 20 meters
Jim AB9CN sent us Dan Zimmerman N3OX's page in response to my plea for help in SolderSmoke #227. I think this is a very clever and attractive way to cover both bands with a single Moxon.
http://www.n3ox.net/projects/2017moxon/
Of course there are other ways to do this -- other listeners wrote in with confirmation that it is indeed possible to nest a 17 meter element inside a 20 meter Moxon (as is done routinely with Hex beams), but this requires a lot of cut-and-try tuning of both antennas. More in this in future posts. Thanks Jim, and thanks to all who wrote in.
I kind of like the N3OX approach. I think his design makes it more of a workbench electronic project, as opposed to a mere wire and coax antenna project. But hey, that's just me.
Friday, December 18, 2020
Grayson Evans KJ7UM's New Blog -- Lots of Great Technical Info
Tuesday, December 15, 2020
SolderSmoke Podcast #227: Solar System, SDR, Simple SSB, HA-600A, BITX17, Nesting Moxons? Mailbag
Mars is moving away. Jupiter and Saturn close in the sky. And the Sun is back in action – Cycle 25 is underway. Also, the earliest sunset is behind us. Brighter days are ahead.
Book Review: “Conquering the Electron” With a quote from Nikola Tesla.
No real travel for us: Hunkered down. Lots of COVID cases around us. Friends, relatives, neighbors. Be careful. You don’t want to be make it through 10 months of pandemic only to get sick at the very end. SITS: Stay In The Shack.
Pete's Bench and Tech Adventures:
Backpack SDR keithsdr@groups.io
Hermes Lite 2
Coaching SSB builders
G-QRP talk
A new source for 9 MHz crystal filters
Bill's Bench:
Fixing the HA-600A Product Detector. Sherwood article advice. Diode Ring wins the day. Fixing a scratchy variable capacitor. Studying simple two diode singly balanced detectors. Polyakov. Getting San Jian frequency counter for it.
Fixing up the 17 meter BITX. Expanding the VXO coverage. Using it with NA5B's KiwiSDR.
Resurrecting the 17 meter Moxon. But WHY can't I nest the 17 meter Moxon inside a 20 meter Moxon? They do it with Hex beams. Why so hard with Moxons? DK7ZB has a design, but I've often heard that this combo is problematic. Any thoughts? I could just buy a 20/17 Hex-beam but this seems kind of heretical for a HB station.
Suddenly getting RFI on 40 meters. Every 50-60 Hz. Please tell me what you think this is (I played a recording).
MAILBAG:
Dean KK4DAS’s Furlough 40/20
Adam N0ZIB HB DC
TCVR
Tony G4WIF G-QRP
Vids. Video of George Dobbs.
Grayson KJ7UM
Collecting Radioactive OA2s. Why?
Pete found W6BLZ
Articles
Rogier KJ6ETL PA1ZZ
lost his dog. And we lost ours.
Steve Silverman KB3SII
-- a nice old variable capacitor from Chelsea Radio Company.
Dave K8WPE thinks we
already have a cult following.
Dan W4ERF paralleling
amps to improve SNR.
Jim W8NSA -- An old friend.
Pete Eaton
WB9FLW The Arecibo collapse
John WB4GTW old
friend... friend of:
Taylor N4TD
HB2HB
And finally, we got lots of mail about our editorial. No surprise: Half supportive, half opposed. Obviously everyone is entitled to their opinion. And we are free to express ours. It’s a free country, and we want it to stay that way. That is why we spoke out.
Yesterday the Electoral College voted, finalizing the results. All Americans should be proud that the U.S. was able to carry out a free and fair national election with record turn out under difficult circumstances. And all loyal Americans should accept the results. That’s just the way it works in a democracy.
We are glad we said what we said. It would have been easier and more pleasant to just bury our heads in the sand and say nothing. But this was a critically important election and we felt obligated as Americans to speak out. We'd do it again. And in fact we reserve the right to speak out again if a similarly important issue arises.
Thursday, December 10, 2020
Pete Juliano's Presentation to the 2020 G-QRP Club Convention -- Building SSB Transceivers
Saturday, December 5, 2020
Adding 10 kHz of Coverage to My BITX 17
"Radio, Radio" By Elvis Costello and The Attractions
Friday, December 4, 2020
The Terrible Collapse of the Arecibo Dish: Climate Change, Hurricane Maria, and Funding Cuts. Also: China's New Dish
From https://www.thewrap.com/watch-crazy-footage-of-the-arecibo-observatory-collapse-goldeneye-video/ :
"Alas, over the 2010s it was battered by a series of severe, climate change-linked tropical storms and hurricanes, culminating in terrible damage inflicted by Hurricane Maria in 2017. Unfortunately the 2016 election led to a government unwilling to fund repairs. Though new sources of funding were cobbled together late in 2018, in late Nov. 2020 it was determined there was no way to safely repair the telescope and the National Science Foundation announced it would be decommissioned.
The decommissioning was supposed to proceed after NSF determined the safest possible method, but physics had other plans. So it is that on Dec. 4, the whole thing up and collapsed with almost no warning."
More info (from NSF):
https://www.nsf.gov/news/special_reports/arecibo/index.jsp
Here is a good 2017 article that discusses the electronic and mechanical arrangements at Arecibo, and the budget cuts it was facing. The article seems to almost predict the collapse:
Here is a comment from someone who worked there and heard the collapse:
Jonathan Friedman, who worked for 26 years as a senior research associate at the observatory and still lives near it, told the Associated Press news agency of the moment the telescope collapsed on Tuesday.
"It sounded like a rumble. I knew exactly what it was," he said. "I was screaming. Personally, I was out of control... I don't have words to express it. It's a very deep, terrible feeling." https://www.bbc.com/news/world-us-canada-55147973?fbclid=IwAR3RuwzTfJmqInrOOFB-nctknDzyB_VSr_qdNrjg9LbbxUnAbynKBv9stPQ
Here is an interesting WIKIpedia article on China's FAST dish, with comparisons to Arecibo:
Thursday, December 3, 2020
Receiving Signals from China's Chang'e-5 Lunar Sample-Return Mission
Background info:
A great report from Daniel Estevez EA4GPZ on radio amateurs receiving telemetry from Chang'e-5:
Wednesday, December 2, 2020
Radioactive Regulator Tubes -- OA2s! Who knew?
Monday, November 30, 2020
Adam N0ZIB's Direct Conversion Transceiver
This is obviously very cool, but looking ahead I think Adam should think about adding one more mixer, changing the bias on the TX amps, and adding a mic amp. Boom: A Double Sideband Transceiver.
Pete wrote: When I was in the US Navy and a particular unit did something outstanding – the Command ship would raise the Bravo Zulu Flag for a job well. Don’t know if you can see it there in MO but I have raised the BZ flag to you. Outstanding and congratulations.
Bill and Pete:
Just finished a DC transceiver using Arduino nano, SI5351 (my sincerest apologies, Bill), diode ring mixer and lm386 audio amp. The transmit portion is a two-stage class AB pre-amp (from EMRFD page 2.32), which is driving an IRF510 final (biased at 2.08 volts) from Pete’s design. Output is about 5watts into a CWAZ low pass filter, based on the design from here: https://www.arrl.org/files/file/Technology/tis/info/pdf/9902044.pdf
I’m using a manual TX/RX switch which is doing multiple things. It brings the Nano A1 LOW, offsetting the transmit frequency 600 Hz for CW, grounds the audio input to prevent deafness (learned that one the hard way), and it engages a relay that switches the antenna from the receiver to the transmit, and also turns on the transmitter stages. Keying is through the first stage of the pre-amp.
I still have some tidying up to do, and I’m not sure the LPF works so well using two component inductors instead of all toroids, but I finished it today and made my first QSO into Ontario almost 1000 miles away. It’s been great fun!
73,
Adam
N0ZIB
Missouri
Sunday, November 29, 2020
Rocket Knack
Friday, November 27, 2020
6EQUJ5 -- SNR, the Big Ear Radio Telescope, and the "Wow" Signal
This Hack-A-Day article explains the significance of 6EQUJ5 on the paper readout of the Big Ear radio telescope. It is a signal-to-noise readout.
The article also has interesting information about the radio telescope that was used.
I have on my shelf John Kraus W8JK's wonderful book "Big Ear Two -- Listening for Other Worlds." John Kraus is the guy who built the Big Ear. In a reminder of how new radio technology really is, Kraus got his start in radio as a ten year-old boy in 1920. He ripped the wire out of the ignition coil of a Model T Ford to make a tuning coil for a crystal radio. He took the earpiece out of the family telephone. His father gave him a chunk of Galena. He used the crystal radio to listen to the early broadcasts of WWJ in Detroit.
Thursday, November 26, 2020
VK3YE's Super Simple Phasing Receiver
Sunday, November 22, 2020
Wrapping up the HA-600A Product Detector Project -- Let's Call Them "Crossed Diode Mixers" NOT "Diode Rings"
This has been a lot of fun and very educational. The problem I discovered in the Lafayette HA-600A product detector caused me to take a new look at how diode detectors really work. It also spurred me to make more use of LTSpice.
In the end, I went with a diode ring mixer. Part of this decision was just my amazement at how four diodes and a couple of transformers can manage to multiply an incoming signal by 1 and -1, and how this multiplication allows us to pull audio out of the mess.
But another part of the decision was port isolation: the diode ring mixer with four diodes and two transformers does keep the BFO signal from making its way back to into the IF chain. This helps prevent the BFO signal from activating the AGC circuitry, and from messing up the S-meter readings. LTSpice helped me confirm that this improvement was happening: in LTSpice I could look at how much BFO energy was making its way back to the IF input port on the diode ring mixer. LTSpice predicted very little, and this was confirmed in the real world circuit. (I will do another post on port isolation in simpler, singly balanced diode mixers.)
At first I did have to overcome some problems with the diode ring circuit. Mine seemed to perform poorly with strong signals: I'd hear some of the "simultaneous envelope and product detection" that started me down this path. I also noticed that with the diode ring, in the AM mode the receiver seemed to be less sensitive -- it was as if the product detector circuit was loading down the AM detector.
One of the commenters -- Christian -- suggested putting some resistance into the input of the diode ring circuit. I put a 150 ohm pot across the input, after the blocking capacitor. The top of the pot goes to the capacitor, the bottom to ground and the wiper to the input of L1 in the diode ring circuit (you can see the circuit in the diagram above). With this pot I could set the input level such that even the strongest input signals did not cause the envelope detection that I'd heard earlier. Watching these input signals on the 'scope, I think these problems arose when the IF signals rose above .7 volts and started turning on the diodes. Only the BFO signal should have been doing that. The pot eliminated this problem. The pot also seemed to solve the problem of the loading down of the AM detector.
With the pot, signals sounded much better, but I thought there was still room for improvement. I thought I could hear a bit of RF in the audio output. Perhaps some of the 455 kHz signal was making it into the AF amplifiers. I looked at the circuit that Wes Hayward had used after the SBL-1 that he used as product detector in his Progressive Receiver. It was very simple: a .01 uF cap and 50 ohm resistor to ground followed by an RF choke. I can't be sure, but this seemed to help, and the SSB now sounds great.
A BETTER NAME?
One suggestion: We should stop calling the diode ring a diode ring. I think "crossed diode mixer" or something like that is more descriptive. This circuit works not because the diodes are in a ring, but because two of them are "crossed." From now on I intend to BUILD this circuit with this crossed parts placement -- this makes it easier to see how the circuit works, how it manages to multiply by -1, and to avoid putting any of the diodes in backwards.
The Wizard of Horseshoe Bend: VK2FC's Wonderful Projects
http://www.vk2fc.com/progressive_receiver.php
Glen's site has many other projects. Check them out:
http://www.vk2fc.com/index.php
And here he is, the Wizard of Horseshoe Bend:
Thursday, November 19, 2020
Diode Ring Magic
Tuesday, November 17, 2020
A Diode Ring Product Detector for the HA-600A? Problems.
I got the two diode, one transformer product detector working well, but with it a new problem arose: 455 kHz energy from the BFO was leaking past the product detector back into the S-meter/AGC circuitry. This showed up in the form of a constant S-3 reading when I switched to SSB/CW. This was annoying.
I figured the problem was that the only signal really being balanced out was the IF signal going into L1 of the product detector. I took another shot at putting the BFO signal into this port, with the IF signal going into the unbalanced potentiometer port. This did indeed take care of the BFO leakage S-meter problem, but once again the SSB did not sound great -- I think the old problem of simultaneous envelope and product detection returned.
This was obviously a port isolation problem. I remembered that the diode ring "doubly balanced" configuration has much better port isolation. So on Sunday morning I built one, first in LTSpice and then on the bench.
For the bench model I used some PC board pads out of Pete Juliano's $250,000 CNC machine. For the toroids I used two trifilar coils wound by Farhan's dedicated staff in Hyderabad. The diodes were sent to me by Jim W8NSA. So there was lots of soul in this new machine.
The circuit worked in LT Spice and at worked well when tested on my bench with my FeelTech (for the BFO) and HP8640B (for the IF signal) sig gens with my Rigol 'scope watching for the audio out.
But I ran into some problems when I popped the new board in there in place of the old product detector: The 455 kc BFO leakage problem is gone and the S-meter is where it should be, but...
-- I'm seeing a return of the old simultaneous envelope and product detection problem. SSB was sounding scratchy again and indeed, when I removed the BFO signal from the diode ring circuit I could hear SSB signals making it into the audio amplifiers. These signals sounded just like AM signals as heard through an envelope detector without a BFO.
-- The diode ring circuit also had a very bad effect on how the HA-600A worked in AM mode. It seemed like the new circuit was loading down the diode AM demodulator. SW broadcast signals sounded awful in the AM mode until I disconnected the IF input to the diode ring circuit (this input is NOT switched -- it is always connected, even in the AM mode).
So, for now, am back to using the two-diode, single transformer, singly balanced product detector with IF signal going to the balanced (L1) port and the BFO going in through the wiper of the 100 ohm pot.
Any suggestions on how to overcome the problems with the diode ring circuit?
Monday, November 16, 2020
Shortwave Listening
I was listening to Glenn Hauser's excellent shortwave listening show on WRMI this week, and he mentioned a technique that I had not been aware of: listening for the harmonics of distant stations. This is apparently being done for medium wave broadcast stations, but also for stations in the lower frequency range of the shortwave bands. If propagation makes it highly unlikely for you to hear the main frequency, perhaps propagation would be better for the the second or third harmonic. This method is discussed here:
http://www.pateplumaradio.com/genbroad/harmonics.htm
Here is some more background information on Glenn Hauser:
https://en.wikipedia.org/wiki/Glenn_Hauser
Here is a real treasure trove of articles and recordings about the history of shortwave radio:
http://www.ontheshortwaves.com/history.html