Just go to http://soldersmoke.com. On that archive page, just click on the blue hyperlinks and your audio player should play that episode.
http://soldersmoke.com
That's the Russian radio-telescope that picked up what was thought to be a possible signal from an extraterrestrial civilization. This article from the SETI Institute has some interesting tech info on antennas and power levels. Definitely not QRP!
Note the establishment of a new acronym (M4MMRX) for Lew McCoy's Mate for the Mighty Midget receiver. We have needed this acronym for a long time, and SolderSmoke HQ is proud to have come up with it. We do our part my friends. Jan has made more progress on his amazing Dutch M4MMRX and has produced a short video showing the receiver in action with SSB and CW signals. Here is a bit of intriguing homebrew mystery: Jan has gone to a LOT of trouble to create that semi-circular opening in the center of the front panel. He even cut a corresponding semi-circular hole in the sewer pipe cap that serves as the large wheel in his amazing homebrew reduction drive. But he won't tell us what he plans to do with that space. So I ask you, dear SolderSmoke readers: What is that space for? Why the see-through panel and sewer-pipe cap? What is Jan's plan?
From Jan:
Hi Bill,
The rattle is gone, so I made a little video of the MMMRX in ssb and cw mode.
Brad WA8WDQ wrote to us about a VLF (24 kHz) his receiver project (see below). This led to some Googling about the VLF station NAA. Wow, there is some important radio history associated with that call sign. The station's original location was just a few miles from I where I live now. From Wikipedia (https://en.wikipedia.org/wiki/VLF_Transmitter_Cutler):
The station began operations in 1913 as a radio telegraphy station call sign NAA in Arlington, Virginia, at a facility next to Fort Myer. Although its broadcasts occasionally included band concerts and speeches, it was most famous for its nightly time signals. The three towers known then as "The Three Sisters" stood 600 feet, 450 feet and 200 feet (183, 137, and 61 m) above the ground. The site was referred to as "Radio", Virginia. The towers were the second largest man-made structure in the world behind only the Eiffel Tower. The word "Radio" was first used instead of "Wireless," in the name of this Naval Communications facility. The First Trans-Atlantic voice communication was made between this station and the Eiffel Tower in 1915. The Nation set its clocks by the signal and listened for its broadcast weather reports. The Towers were dismantled in 1941 as a menace to aircraft approaching the new Washington National Airport. The towers stand today at United States Naval Academy in Maryland, on the edge of the Chesapeake Bay.
Be sure to read about the de-icing system for the antenna. It uses more power than the actual transmitter!
From Brad:
Bill, Pete,
Here's the current status of the 24 KHz NAA SID receiver. All the major sub-assemblies are mounted in the chassis and power is hooked up. For convenience, I've been using the PowerWerx USBbuddy switching DC-DC converter to supply +5V power to the Raspberry Pi from the +12V input. I've found them extremely RF quiet, clean and stable; capable of supplying 3A though this project will only need about 1.5A @ +5V. At this point, I'm just waiting for Adafruit to send the A/D chip I'll wire up to the Pi on that empty protoboard just under the meter. Speaking of the meter, it's not really needed as the Pi records and broadcasts over Wi-Fi the received signal level. However, I like my projects to have some sort of physical human interface so I added the signal level meter and an LED for SID event alarms :).
As previously mentioned, my bench test of the receiver using my signal generator was successful. Once everything is wired, I'll do an actual on-air signal test receiving NAA.
The day is off to a good start here at SolderSmoke HQ, with Radio New Zealand booming in on my homebrew Mate for the Mighty Midget receiver. I was listening from around 0900 to 1030 UTC on 7245 kHz. Once again we see that The Radio Gods favor homebrew receivers. Gray line propagation also played a role.
Obviously the Radio Gods (Spirits in the Sky) approve of Jan's work. How could they not? I can now see why he took the trouble to cut that hole in the sewer pipe cap that forms the large wheel on his homebrew reduction drive. But what are we going to see through that center hole Jan? What will the frequency readout be like? ---------------------- Hi Bill,
Just finished the last stage of the Mighty Midget MK2.
There are first signals!
The first one I heard was a broadcast station, believe it or not, the song that was on was “Spirit in the Sky” ..
All stages were built, tested and as far as possible, adjusted separately.
It was built from back to front, so the RF amplifier was last.
I added an ECL82 for more audio, the first thought of only using an EL84 didn’t bring enough.
The triode of the ECL82 as a pre-amp, the pentode as final.
Furthermore ECF82’s were used instead of the 6U8, they’re more widely available over here.
The Miller coils are hard to come by, so the 300 uH coils are homebrew.
Also used a grid detector instead of the two germanium diodes.
The triode of V1 originally intended for audio was used for this.
Made the BFO adjustable as well, still remember the screwdriver sticking out of the coil on your side...
Happily there was not much troubleshooting needed.
The 80m coil was only 5 kHz off, the 40m coil 300 kHz (to low in frequency), still have to fix that.
Initially the receiver worked reasonably well without adjusting, but C1 quit at some point.
After some investigation, the problem was a dirty wiper contact on the rotor.
An ultrasonic bath fixed the problem, so no looking out for a replacement there. (hope it stays that way)
After adjusting, sensitivity is around -114dBm (0,4 uV) / 10 dB S/N! (with the FT241 crystals in place, and careful tuning of the controls)
Really not bad for this small receiver, Lew McCoy was right, it really is a Mighty Midget.
I wanted to make some video’s, but over here there’s a terrible S9 rattle from 160 to 15 meters.
Every now and then it appears out of nowhere, and disappears the same way.
As soon as it is gone, I’ll make some video’s.
I made one video though, just after completing the receiver.
Bob Crane, our intrepid correspondent at the Dayton Hamvention talked to Guy N7UN (pictured above) about taking ham radio up to the mountaintops. It was nice to hear Guy mention Wayne Burdick and Wes Hayward and WG0AT. Thanks Bob! Thanks Guy! Listen here: http://soldersmoke.com/N7UN.mp3 More on N7UN here: http://www.n7un.com/
Could it be that Bob Marley's son Ky-Mani has The Knack? Probably not (no mention of it in Wikipedia) but he certainly has some nice old receivers on his 2007 album cover.
I'm a younger ham, just 26, and I've just experienced what I think you call Joy Of Oscillation as I completed my first L-C VFO. What fun!
I'm working on Peter Parker VK3YE's Beach 40 Double-Sideband transceiver, and while my natural proclivity is toward the SI5351 and it's brethren, I figured it would be character-building to actually put together an analog VFO for once.
After much tweaking of the feedback capacitor in the oscillator, and massaging the tank inductors, and conking out an additional buffer stage to drive the diode-ring mixer at the appropriate level, and gluing Manhattan pads on top of Island pads.... I say, without reservation, that this was great radio fun! And isn't that what it's all about?
(Now it only it didn't drift so much... so I guess it's not quite complete yet)
Just wanted to share, love the podcast and the blog, I learn something new each episode.
All the Best,
Jeff, KK9JEF
---------------------------
Great stuff Jeff. Character building indeed! As for the drift, try this:
-- Replace the toroid in the oscillator circuit with a coil wound on a non-metallic core. I use a cardboard tube from a coat hanger.
-- Make sure the capacitors in the oscillator and even in the buffer are NP0 caps (they don't change in value as they heat).
-- Try to run the oscillator stage at reduced voltage. Six volts is better than nine.
-- After you solder, always let the device cool down for several hours (or even overnight) before you evaluate it. Heat from the soldering iron will be dissipating and changing the freq for a LONG time.
Above all, IGNORE the inevitable recommendation from Pete Juliano that you forget about all this nonsense and just go with an Si5351.
I think Tryg should get that Ladybird receiver working again.
-------------
Hi Bill,
Thanks for the great podcasts and also to Pete for his unique contributions. I have been interested in radio since I was a kid but only really got back into the hobby in 2009. Back when I started playing with electronics in the 1970's I hankered after a soldering iron of my own. I bought the one in the picture in 1977. A "modest" 60 watt job, it was the cheapest one in the shop but I used it to harvest parts from all manner of abandoned old iron. I was really surprised to find it clearing up recently. The snips in the picture was a tool that my late Uncle had surplus and passed on to me, it too played a role in my scavenging for parts. In Ireland in the 1970's it was hard to get parts. I remember my Grandmother taking me from Galway to Dublin - 3 hours each way!!!) to buy parts for my first project, Rev. G.C. Dobbs venerable transistor radio from the "Making a Transistor Radio" book by Ladybird. I still have the book and the dusty remnants of the radio, long since plundered for parts. When I returned to the world of radio it wasn't long before I discovered QRP and the GQRP club. It was a real surprise to find the good Reverend was at the helm there. I just thought that the picture and story might raise a smile amongst followers of the blog. Thanks to yourself and Pete for the podcast. Keep up the great work! QRP Forever!
Doug KB8M did a beautiful job with his Michigan Mighty Mite. But, as often happens, it still didn't work. He turned to us for advice. I gave him a long list of things to check, but Pete brought the power of superior tribal knowledge to the problem and spotted the defect immediately: The transistor was in backwards. It is a P2N2222. That means the pin out it C-B-E not the usual E-B-C. I had fallen into this trap with one of my BITX rigs and had to pull out and reverse many of those transistors. Fortunately for Doug he had used a socket for the transistor. TRGHS!!!!!!!!!!!!! JOO!!!!!!!!!!!
I met W1VLF on 40 meters last week. "VLF" was a hint. And indeed, Paul has been experimenting in the 10 kHz range. His antenna loading coil is seen above. More info here: http://rescueelectronics.com/9-Kilohertz.html Very cool that Mike was working with Jay Rusgrove, W1VD, on this project. Jay designed the 6 watt VXO rig that was my first homebrew transmitter.
SolderSmoke Podcast #189 is available: http://soldersmoke.com/soldersmoke189.mp3 Billy in Europe. Bill in Virtual Reality. Great News: Little Gonzalo is "all clear." Thanks for the help. BENCH REPORTS: Pete paints the rigs blue. Pete's FET amplifier project with FET switching and key pad Using an Si5351 for CW offset and QSK. Bill working on VFO for a rig built around HRO dial and gear box. HRO gears seem a bit loose. What should I do? The search for an Imperial Whitworth. For variable caps, brass is better, but two bearings beats brass. QSO REPORTS Pete having fun with homebrew rigs. Bill works K3MRK, WA3O, W4OP, W1VLF and N6ORS MAILBAG: Dallas CBLA Conventional Current Flow Controversy "I regret ever listening to your podcast!" LCR recommendations
I sent you an email a few weeks ago to let you know that I joined the Colorburst Crystal Army and that I was preparing to teach a couple of classes at the Dallas Makerspace on constructing the MMM. We had our first class last night,
https://talk.dallasmakerspace.org/t/build-a-radio-transmitter-class/11010/8 It was a great success, every student had a working transmitter at the end of the class! So there are six new enrollees in the CCA! For all but two of the students this was the first piece of radio electronics they had ever built, including one who had been a HAM for 15 years.
Just wanted to thank you for preaching the MMM, it was just the simple circuit needed to get folks started! We have another class on the 20th, and requests have been made to schedule additional classes!
The free-range rig is coming along! I'm receiving with decent sensitivity (my generator's only calibrated to -100 dB/m, and I hear a CW note there just fine) and I'm getting about -2 dB/m out of the mixer. Yippee!
I ended up using an IF of 20 MHz, mainly because I had a bunch of crystals left over from my Minima. The architecture (left to right) is: Diode ring mixer using 1N4148s, 20dB W7ZOI bilateral TIA, 6 pole crystal filter (BW ~= 2.3 KHz), Another 20dB bilateral TIA, 1N4148 product detector (cribbed from the Minima), 2N3904 audio driver, LM380 PA. Microphone amp is two FET stages (J310). Oscillators are courtesy of an Si5351, controlled by an Arduino Uno. T/R switching is done using a couple of counterfeit 2SC1969 RF transistors that, ironically, don't amplify at RF, but work fine as power supply "pass" transistors.
Yet to do is the PA, which I've noodled in LTSPICE (shooting for 20W PEP using a bunch of BD139s, just because...) and cleaning up my Arduino sketch. Right now, I just modified the start-up values of the sketch from my all-band rig for testing. Since that code is pretty full featured (dual VFOs, RIT, filter switching, LCD Display, etc.) using multi-function pushbuttons to select all sorts of crap, I'm betting that 80% won't be used in this rig. Adding simplicity is always good.
So, nearing the end, I'm already thinking about my next rig (that and building a 60m antenna...) I think this one will be similar to my "all band" rig, but limited to the WARC bands (I have a WARC tribander that's screaming for a rig of it's own.) That's kind of boring, so, to challenge myself, I'm going to try using a touch screen in lieu of the usual pushbuttons. What would really be cool, though, is an interactive slide-rule dial - don't think anyone's done that before! One of the things that has always drawn me to the SX-101 is that large slide-rule dial. To me, that allows each station to occupy a physical place on the dial, so after scanning the band, you know were everyone is. It's really a joy to operate those rigs!
I happened to come across this fellow's signal on 40 a week or so ago. His warm up routine really had me scratching my head. I've been on the air for a long time, much of it on CW, and I never heard anything like this. Listen to the video (!) and you will see what I mean. Harmless fun I guess, and there does seem to be a connection to radio history.
On the G-QRP list guys have been talking about the Peregrino. This is a nice little homebrew rig out of Spain. Peregrino = Pilgrim and usually refers to people who are hiking along the Trail of Santiago that runs through the North of Spain to Santiago de Compostela. I'm normally averse to chips, but this little rig uses two very understandable NE602s and an equally understandable LM386. It has a homebrew crystal filter. I like it. GM4WZG came up with a really wonderful enclosure for his rig. This reminded me of the time I put a QRSS transmitter inside a copy of "The DaVinci Code." The Spanish guys have a nice site that describes the rig. Google Translate should help, but even without it you can get most of the info you need from the schematic, chart, and foto gallery. Check it out: http://ea3ghs.qrp.cat/peregrino.html
We are adding Sherwin Williams "Juliano Blue" paint to our investment mutual fund: Drake 2Bs, copies of SSDRA, QF-1 Q Multipliers and now, Juliano Blue! We'll all be RICH!
I've talked on the podcast about launching a worldwide campaign to require the reversal of ALL those little arrows on the symbols for transistors and diodes. You see, they are saying that electricity flows from the positive to the negative. Engineers apparently got that idea from Ben Franklin, and they are sticking with it. It is time for a change! Reverse the arrows! Down with CCF! Viva Electron Flow! Let's tell the truth! This morning Bob Crane W8SX sent me this very interesting article on this topic from Nuts and Volts: http://www.nutsvolts.com/magazine/article/which-way-does-current-really-flow?utm_source=Newsletter+%2332&utm_campaign=Newsletter+%2332&utm_medium=email The article describes very well the origins of this controversy. (There were one or two scary moments in which I thought the author was getting ready to tell us that positive ions can move through wires and transistors (NO!) but he pulled back from the brink and clarified that he was talking about ion flow in electro-chemical batteries. Whew, that was scary!) But here's a question for the philosophers and historians of electronics: When physicists decided to label the electron as "negative" this was an arbitrary choice, right? They could have just as easily decided to call it "positive" with the protons being called "negative" right? In this case all the arrows in our diagrams would not be in need of reversal, right?
Yesterday I came across this very nice video -- I thought you guys would like it. 2E0VIR obviously has The Knack! I'm building a very simple LC VFO today. This is for the HRO Dial Receiver that I've been slowly working on. Mine is a Hartley, from Chapter 3 Figure 7 of SSDRA. Stay tuned!
Bill: Just thought you would like to know that I am a new member of the color burst army. I am also a member of the Dallas Makerspace and our Amateur Radio Special Interest Group is planning on offering classes (open to HAMS and non-HAMS) where we build these Mighty Mites for the colorburst frequency.
The class version will have a resistive dummy load instead of antenna, to allow the project to be built by non-HAMS. The idea is to get our HAMS who just use commercial radios interested in building radios. It is also to get our general members (who like making things) into HAM radio. Walter
This beautiful old variable capacitor came out of a 1930's British regen receiver that I picked up years ago at the Kempton Park rally near London. When I rebuilt that receiver, I found that the cap was thoroughly stuck. No amount of solvents could loosen it. I put it in the junk box and used a more modern cap in its place.
When planning for my current BIG VFO project (see yesterday's post) I re-read Frank Harris's chapter on VFOs. Frank recommended a non-linear cap -- actually a cap that maintains a constant percentage change in capacitance as it goes through its tuning range. My old British cap seemed to fill the bill. Also, it appears to be brass or bronze which is said to have better temperature stability. So I pulled the Brit cap out of the junk box. It was still stuck, but as I tugged on it a bit, it suddenly loosened up. Wow! TRGHS.
When I tried to mount the capacitor in the QF-1 box, I discovered another problem: the nut for the main mounting screw was missing. And guess what: None of the nuts in my "big box of screws and nuts" (I know you guys all have one of these boxes) was the right size. Or, as Pete put it, all were of two sizes: a bit too big, or a bit too small.
Dex ZL2DEX informed me that the needed nut was likely an "Imperial Whitworth" (Don't you love British names?). I started to think about how to get such an elusive part....I thought about walking into Home Depot and asking them where they keep their Imperial Whitworths. This wouldn't have been productive.
Then I started to wonder where the original nut went. It would have stood out in my junk box because it is brass-colored. I looked again in the junkbox. No luck. Then I realized that I might have used it to mount that replacement cap in my rebuild of the old British regen. I pulled that old beast (wooden chassis!) off the shelf. There it was, the needed brass nut. Cap and nut were reunited, problem solved.
It is kind of fun to include an old part like this in the new project.
Thanks Dex. And thanks again to Frank Harris for the great book.
Once again, The Radio Gods have Spoken (TRGHS). An off-hand comment at the Manassas Hamfest, a bit of encouragement from Pete Juliano, and the next thing you know Armand WA1UQO has sent me this beautiful National HRO dial and reduction drive. This thing is so nice... Well, put it this way: this is the first time I'm building a rig around the dial!
Further evidence that TRGHS: I needed something on which to base the HRO dial and a box for the VFO. Wouldn't you know it: That Whole Foods "grilling plank" that I bought a few weeks ago was PERFECTLY sized for this task. Eerie, don't you think? As for the VFO box, well TRGHS again: pictured above you see a side view of the box from one of the Heath QF-1 Q multipliers that I cannibalized for the variable caps. Finally, for the main tuning cap, I took another look at that old brass variable cap that I took out of a 1930's era British regen (pictured above). It had been hopelessly stuck for a long time. I twisted it a bit and was amazed to see that it is stuck no more. TRGHS! (I just need to find a suitable nut so that I can mount the old cap in the QF-1 box.)
I'm thinking that this VFO will be the heart of a general coverage shortwave superhet receiver. I want filters for AM and SSB and I'd like it to cover 5 MHz to 10 MHz. I've been noodling various IF possibilities, but concerns about birdies and spurs keep driving me back to 455 kHz. I have a crystal-mechanical filter for that freq. And a big box of 455 kc transformers. What do you guys think of this option?
I was on twenty today with my BITX, finishing up a rather disheartening contact with a fellow who told me that he is a "checkbook operator." I was trying to encourage this fellow to build something simple -- perhaps a Michigan Mighty Mite? He told me that he might give it a try, but only 16 years from now, after he retires. It was like a case of the Anti-Knack! Then Keith N6ORS saved the day by calling in with his beautiful MIN-X HOMEBREW transceiver. We had a nice talk -- Keith mentioned the beauty of Pete's "Blue Rig." That's HB2HB (phone) QSO #5 for me. Thanks Keith!
Bill, That was great fun! I was just tuning around and heard you mentioned the Michigan Mighty Mite so I stopped to listen and realized it was you! Well here was my chance for a homebrew to homebrew with 'the man' himself. I wanted to record it but missed the chance. Here is the Min-x boxed up. the case is made from thrown away computer cases. It runs about 70watts on 160,80 and 40 meters and about 35watts on 20 meters. I promise to write it up, maybe even draw a schematic. hihi. 73, Keith N6ORS
Ira Flatow of "Science Friday" was recently talking about how best to preserve important bits of the history of mankind's exploration of space. Our old friend Vanguard 1 was mentioned several times. It is now the oldest satellite still in space. You can listen to the Science Friday show here: http://www.sciencefriday.com/segments/protecting-the-historic-human-record-in-space/ They also have a transcript of the show on the same page. SolderSmoke fans will remember the Vanguard adventures of Mike Rainey AA1TJ: http://soldersmoke.blogspot.com/search?q=Vanguard This seems to be the month for Vanguard: just a couple of weeks ago, on 40 meters I spoke to Dale Parfitt W4OP. Dale was one of the first people to pick up Mike Rainey's Vanguard replica signals (see link above). AND... The Vanguard reproduction project came up during Eric Guth 4Z1UG's "QSO Today" interview with Graham Firth G3MFJ of the G-QRP Club: http://www.qsotoday.com/podcasts/g3mfj
(Graham has such a great voice. He definitely SHOULD build a phone rig!) VIVA VANGUARD!
Jan sent me an amazing update on his Mate for the Mighty Midget Mk 2 receiver project. I'm really blown away by the skill that he brings to the mechanical phase of this project. This is a homebrew dial-string reduction drive using the end cap from a sewer pipe as the big wheel. Think about that. Amazing. Jan reports that with the mechanical work almost done, he is almost ready to start melting solder. FB Jan! Check out the video above and the photos below.
At the recent Manassas Virginia hamfest Armand WA1UQO and I came across an old HRO receiver. Armand mentioned in passing that he had an HRO dial and drive for me if I wanted one. When Pete heard this he said I definitely NEEDED one. Armand heard Pete's comment and very kindly put an HRO dial and reduction drive in the mail for me. Wow, it is a magnificent thing! After years of struggling with small Jackson Brother reduction drives and with reduction drives brutally cannibalized out of innocent Heathkit Q multipliers, I now realize that I have been playing in the minor leagues. This, my friends, is the reduction drive that helped win WWII! I will have to build something worthy of its inclusion. The designation HRO has a wonderful story behind it: This is from: http://www.cryptomuseum.com/df/hro/ The new radio was also designed by James Millen at the National Radio Company, but this time with two RF amplifiers and two IF amplifiers at 455 kHz with a 20Hz crystal filter. He kept the pluggable coil packs as part of the design and added the now famous epicyclic dial, which allows the operator to tune the frequency scale in 1/500th units (with the aid of a calibration chart).
The design was finished in 1934 and National pushed hard to get the receiver out by the end of that year. When creating the tools for the first production run, the tool makers had to work overtime and used HOR (Hell Of a Rush) as a job number on their overtime slips. As National's marketing department didn't want their radios to become known as HORs (whores), the name was changed to HRO (Hell of a Rush Order). Despite the best engneering efforts, technical problems delayed the release of the the radio until March 1935. The price at the introduction was US$ 233. Another site provides tech details and history on the drive itself: https://www.prismnet.com/~nielw/PW_NPW_Dial/hro_dial.htm The HRO dial introduced by the National Radio Company in late 1934 was the hallmark of top-of-the-line National receivers from the mid 30s through the 60s. By late 1936 the "HRO dial" was appearing on the NC-100 series of receivers and even the 1-10, National's VHF receiver. Throughout WWII many of the NC-100 variants that National provided to the military used this same dial. By 1950 National had added built-in direct frequency readout to the HRO-50 but still kept the same 0-500 reading dial. Through the mid-50s and into the 60s National mimiced the HRO dial look on their mid-priced receivers such as the NC300, 303 and 270. Even the solid state HRO-500 introduced in the early 60s used a version of this dial. When combined with the required 20 to 1 venier gear drive, the HRO dial provided an effective scale length of 12 feet and was direct reading to 1 part in 500. Ten turns of the dial drives the tuning capacitor stop to stop. Published HRO calibration curves showed each ham band spread over eight turns (or 400 divisions). In addition, dial divisions were about 1/4 inch apart. On all bands below 10 meters the HRO dial is easily resettable to within a KC (or KHz).
Our ace correspondent in Dayton, Bob Crane W8SX, caught up with Paul Darlington M0XPD (above, the guy with the rifle) and interviewed him about his presentation at Four Days in May 2016. You can listen to the interview here by clicking on the link below. I especially liked the comments on the joys of fixing things and the advantages of SIMPLE analog circuitry. Listen to the end and you will learn about Paul Darlington's connection to the famous Darlington Pair. http://soldersmoke.com/M0XPDFDIM.mp3 Paul provided more info (including his slide show and presentation notes) on his BRILLIANT Dayton talk here: https://sites.google.com/site/shacknasties/presentations/fdim-2016 You can buy Paul's book here: https://www.amazon.com/getting-there-Paul-Darlington/dp/1523452196
Thanks Paul! Thanks Bob! And thanks to George Dobbs and William of Occam!
On the G-QRP mailing list our British cousins are discussing the use of Narrow Band FM on Top Band. 160 meters has long been used for day-time local "chin wags" in the UK. Noise, of course, is a factor to consider on 160. FM would take care of the noise problem.
I was wondering if this would be legal in the USA. This is the kind of question that seems to provoke passionate, sometimes angry reactions. I think the answer depends on the resulting bandwidth of the signal.
Especially intriguing to me was Tom's comment about the link between Narrow Band FM and the early SSB phasing rigs. I hadn't heard about that:
Title: RE: Narrow Band FM is it legal below 30 MHZ. Post by: N5EG on January 22, 2010, 11:10:43 AM
Hi Tim,
Yes - NBFM is legal. This is actually a hold over from long ago equipment. Back in the olden days phasing SSB exciters could also be adjusted to produce NBFM.
It's a little different than modern FM, in that the signal looks just like an AM signal, except the phase of one of the sidebands is 180 degrees reversed compared to the AM equivalent (doesn't matter which sideband). This gives an angle-modulated signal with +/- 45 degrees phase variation, but also 3 dB of amplitude variation.
While we don't normally like amplitude variation on an FM signal, it has the effect of preventing the generation of the higher order sidebands that true FM produces. A receiver than has a limiter stage doesn't care that much.
The result is that the old phasing exciters could produce this different kind of Narrow Band FM (probably the true meaning of NBFM long ago) that had the same channel width as AM, and a modulation index that's well below 1. Such a signal is compliant with current FCC regulations on HF bands.
"SolderSmoke -- Global Adventures in Wireless Electronics" is now available as an e-book for Amazon's Kindle.
Here's the site:
http://www.amazon.com/dp/B004V9FIVW
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Over the last few weeks I had been thinking to build a small AF speech
processor to add to...
A New Look for your uBitx!
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Adding a "Cool Blue" Display to your uBitx!
The standard "green background" with black lettering frequently reminds me
that I suffer from Chronic seasickn...