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MS5351M as a substitute for Si5351A
Hi all QRP Labs kits are heavily dependent on the Si5351A from SiLabs. Sadly this chip is a victim of the ongoing global semiconductor shortage, and perhaps also the acquisition by SkyLabs, of parts of Si5351A business including the clock generator ICs. At the same time there is a new substitute chip MS5351M which has good availability, and has been recommended by several correspondents; I am also aware of some kit vendors already using the MS5351M in their products. Clearly it "works". However, the MS5351M documentation is very sparse and I have not seen any actual performance measurements or comparisons documented. To gain enough confidence to be able to start using this chip I undertook as many detailed measurements as I could, including phase noise measurements and use in QCX-mini CW transceivers, and documented them here: http://qrp-labs.com/synth/ms5351m.html The conclusion is that the MS5351M is a 100% direct substitution for Si5351A and has slightly improved performance in some areas. In my opinion, MS5351M can be used in place of Si5351A in any hobby project or commercial product. Due to my substantial former purchases as the global semiconductor shortage was getting underway, I still have a stock of around 1,000 Si5351A ICs but it is inevitable that going forward, in order to continue production of QRP Labs kits, we will start to use the MS5351M in some manufacturing batches. Much as I dislike cross-posting normally, I am cross-posting this one to other QRP discussion groups in the hope that the measurements may be of interest to some. Many of us use the Si5351A in our hobby projects and some of us in our commercial products too. This is previously unpublished information that I have not seen anywhere else. http://qrp-labs.com/synth/ms5351m.html 73 Hans G0UPL http://qrp-labs.com
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OT IEEE Spectrum article cipher machine spy case
4
Hello all: My IEEE Spectrum article about a 1963 cipher machine and a huge espionage case Rubicon just went online https://spectrum.ieee.org/the-scandalous-history-of-the-last-rotor-cipher-machine about a yers work. Last photo has some HP and TEK equipment. Your thoughts appreciated! Jon
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Low cost/Field Day HF test bench concept
3
I'm assembling the following suite of test kit just to see what it can do for radio design work. After evaluating the performance relative to my mid 90's HP & Tek kit, I plan to use this kit to do various exercises such as design an amplifier, oscillator, filter, etc and measure the performance. For most of my life my RF ambitions were stymied by the lack of access to test gear. So for me, the nanoVNA and tinySA are huge. I have decided to make a project of building out the most complete, lowest cost Field Day portable HF test bench I can come up with. The objective is coverage up to 222 MHz with sufficient accuracy and resolution to make experimental design more tractable. Hantek 2D42 (DSO-DMM-AWG) 3x tinySA (SA and 2x RF synthesizers) nanoVNA RFzero (GPSDO) LCR/transistor tester (need USB unit) DMMCheck Plus (DMM cal) Bodnar's pulser w/ 1 MHz repetition rate (TDR) diode noise source 2x step attenuators 2x RF bridges 2x wide range matching networks dedicated netbook to control above cables, adapters, cal kits, etc battery powered lab PSU The Hantek is a compromise chosen because it provided 3 functions, was small, cheap and with a claim of 40 MHz BW appears good enough to me. There are possibly better options at the same price point, but they are much larger which is not meet the Field Day portability constraint.. With some care in shopping, the above should be available for under $1000. Despite my grad student slave wages 30 years ago, I'd have bought all that for $1000 in a heartbeat. And $1000 then would be much more today. All I can say is "Wow!" Don't just sit there, say something! I did *not* start this to hear myself. The wall already serves that function ;-) Have Fun! Reg
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Control feed thru connector suggestions?
5
I have a bunch of RF eval boards from China which I want to connectorize in shielded enclosures. I don't want to spend $20 packaging a $8-15 board. I make the enclosures from scrap 28 gauge galvanized steel scrap from a local HVAC shop. Quarter inch copper foil tape on the seams soldered to the zinc plating provides an RF tight seal. For power connectors I've standardized on 2.1 mm coaxial power sockets. All Electronics has them for under $0.20 so I bought 100. For prototyping I epoxy them to SS FR4and use copper foil on the epoxy side for pads and microstrip. This works great for Manhattan style construction. Even a small amount of epxoy goes a long way, so I make them up in batches of various size boards that use up all the epoxy I've mixed. For obvious reasons I don't want to use the same connector for control lines. I'd like to find a cheap option for feed thrus. Ideal would be the connectors HP used in the 8601A, but I've never seen those for sale anywhere. Does anyone have suggestions? Have Fun! Reg
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July/August lead article in QEX
16
I'm curious what others think of this article. I have read it a few times and find it completely incomprehensible to the point I question the correctness. In particular, figures 9 and 13 are very hard to square with the central notion of a class C amplifier that it is in cutoff for more than 180 degrees. If the BE junction is in cutoff, then I'd expect the input current to be a periodic impulse, not the visually perfect sinusoids of figure 9A. Most troubling of all is figure 13A which purports to show the input current swinging between -58 mA and 89 mA. Where's the cutoff? I'm a retired geophysicist, not an EE. I started playing with RF over 50 years ago, but couldn't afford the T&M kit to do serious work. I'm playing RF hardball for the first time using "RF Circuit Design" by Chris Bowick among numerous other books. Bowick has the clearest design procedures I've found. So far I've designed and built CC and CE small signal amplifier examples with CB next in the queue before moving on to power amplifiers. The Spice implementations I've tried have resisted my efforts. Thus I have relied on the methods Bowik describes and measurements. But my goal is to compare design specification, simulation and measured data for each amplifier example. Have Fun! Reg
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"Systemizing RF Power Amplifier Design" by Roy Hejhall
Here's the app note referenced in the QEX article. It is much better written and gives a clear explanation of the design considerations. More importantly it describes how to measure the large signal parameters with a VNA using a very simple test fixture. Now that we have the nanoVNA, the technique becomes vastly more useful for the hobbyist. So no need to find a transistor with a datasheet with specs or guess based on small signal parameters. "Measure twice and cut once." While the app note only treats class C, the measurement technique extrapolates to other amplifier classes very easily in an obvious fashion. By modularizing the matching networks separately from the transistor biasing network one can cover a broad range of use cases with very few fixture modules. The main take away is to use a broad tuning range test fixture and tune it for minimum S11 reflection using a directional bridge. Then remove the transistor and measure the BE and CE port complex impedances. The input and output impedances of the transistor are the complex conjugates of the measured values. From there it's pretty much pencil and paper work, though it also provides the input for a Spice program. Have Fun! Reg
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RF amplifier design book recommendations wanted
2
The QEX article has highlighted the age of my references on the topic. I'd like to get some more recent monographs. Does anyone have books they think are particularly good? I am looking for things on a par with "Planar Microwave engineering" by Thomas H. Lee which I consider the best general treatment of RF I've ever read. Lee's enthusiasm for RF is quite infectious. Have Fun! Reg
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Optimal Crystal Filter Design
8
There is quite a lot of literature and software for designing filters using idealized xtals, but so far as I can find, no one has presented selecting which N xtals from a set of P xtals will best match a specified N pole response. All the treatments I've found use the N xtals which most closely match the idealized design values. A VNA makes measuring the phase and amplitude response of xtals very simple. And the nanoVNA has made it cheap. This suggests simply multiplying the transfer functions of each possible section and using linear programming to solve for the set of N of P xtals which most closely give the desired response. The general term for this is "basis pursuit". Though NP hard on the surface, in fact, the optimal (L0) choice can be computed in L1 time using linear programming. David Donoho of Stanford proved this in 2004. L0 is combinatorially intractable. L1 is more easily handled, even very large problems which would be combinatorially impossible. Does anyone know of prior work on selecting which of a set of measured xtals will most closely match the required amplitude and phase response? Have Fun! Reg
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"Projector of the Sharpest Beam of Electric Waves"
43
My copy of QEX came today and I was immediately drawn to the famous paper by Yagi & Uda. Though not meant in any way as a criticism, I had hoped for more mathematical rigor. I don't know if that was presented in another paper as mention is made that more was forthcoming. Does anyone know? I don't recall ever seeing a Fourier analysis of the Yagi-Uda design. Ronald Bracewell discusses many interesting arrays, but at least to my recollection, only covered slotted RF arrays in the 2nd edition. Seismic style point receivers are well treated, but point receivers are trivially simple. At least to me. But that may simply reflect a career spent on elastic waves instead of electromagnetic waves. It's the same wave equation, but the devil is in the details so I get very nervous when I switch the physical domain. The title of the paper should be mathematically provable. I'm interested, but a bit too busy and too lazy to do the analysis required for a proof. Which completely neglects whether I still have the skills for such an undertaking. Math was never my strong suite and it has been far too many years. If anyone knows of a rigorous proof that the Yagi-Uda is the "sharpest beam" I am *very* interested in reading it. On inspection it seems plausible, but mathematics at that level is rather a black art to mere applied math people like me. Thanks and.. Have Fun! Reg
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EM slow waves
In a PM Kai mentioned "EM slow wave structures", something I'd never heard of. I started this as a reply to him, but decided it might be of more general interest to the list. A perusal of 2 ft of EM monographs produced no more than a few hundred words in total on slow waves. The most illuminating was Weeks IIRC who noted that the phase and amplitude peaks of a plane wave do not coincide. Unfortunately Pozar does not have an index, so not very helpful and I don't have access to his papers on the subject. Thomas Lee said nothing which was a great surprise as he takes such delight in the subject and the associated arcana. Google scholar did turn up a few things, but in a very different situation where there was a continuous conductor and they were inducing scattering by altering the dielecric constant of the substrate. The other examples were simply serpentine conductors. Before I strayed from the strait and narrow path of petrology into the debauchery of reflection seismic research I spent a year with a polarizing light microscope and 54 thin sections for 6-8 hours a day. Anisotropic crystals have different propagation velocities in 2 or 3 directions. Accurately measuring those with the microscope is an art and skill of considerable merit in my view, but it has been completely displaced by other methods. The wonderful thing about the PLM is you can carry one in a car or truck and do an analysis in the middle of nowhere on the hood and get an immediate answer. This is of great value in exploration where it is very expensive and arduous to return to the location after taking samples and sending them to a lab for analysis. It had been my goal to go into minerals exploration, but at the time I graduated that field was completely dead. PhDs with 20 years of exploration experience were pounding the pavement looking for work. Not a lot of hope for a newly minted MS. Later when I was in grad school at Austin studying reflection seismology I took considerable exception to the term "transverse anisotropy" as it was used in connection with isotropic layers with varying velocities in each layer of a series of thin layers (shales). I should describe the "EM slow wave" as an example of a scattering matrix very similar to the "transverse anisotropy" of shales. The most detailed discussion I found in my library was in the context of electronically steered radar arrays. In that context I'd describe it as the inevitable consequence of a discrete array of emitters of finite dimensions. In a layered system it is a function of the layer thicknesses. I have a Tek 11801 and SD-24 sampling head so I am well equipped for measuring femtosecond delays. As the step from the SD-24 is very broadband, constructing my hypothetical line of conductors with a dipole feed point in an asymmetric position relative to the ends is quite tractable. The biggest obstacle seems at present to be the relationship between the length ofand spacing of the conductors. However, if I use elastic yarn from the sewing supplies section at Walmart to support the conductors I should be able to simply make a line of some 40-50 elements and then vary the spacing by stretching the line. I have additional 20 GHz SD-26 heads, which are SD-24s minus the 2x 19 ps rise time step generators, so I should be able to probe very well so long as I don't make some botch of the setup. So if anyone else is crazy enough to be interested in this stuff I'd love to hear what you think would be a good experiment. Have Fun! Reg
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How do we build advertising revenue for QEX?
2
Including covers, the current issue is 30 pages. There are 5 ads, one of which is ARRL and doesn't count. Confronted by the removal of technical articles from QST, I requested that QEX be an available choice for member print publications. I am happy to say that was approved, though it has not appeared in any of the renewal forms yet. I care far more about the technology of radio than I do about operating. "Wall paper" just never appealed to me. QEX is important to me. So how do we make it thrive? The only way I can think of is to have more content over a diverse range of levels from the uber techno wonk of my Yagi-Uda post to simple stuff suited to, "I just bought a kit on ebay." I must put myself first in line for the dock in the latter case. Most of the older QRP designs have output filters which do not meet the currently mandated standards. Despite that, they are being sold on ebay to novices who have neither the knowledge nor the test kit to determine that they are illegal. I did a bunch of work on the Chinese kits for the Pixie 2 designed by WA6BOY and posted it to EEVblog. https://www.eevblog.com/forum/rf-microwave/oshw-redesign-of-the-pixie-2/msg3161588/#msg3161588 I contacted Kaz to see if that level of topic would be acceptable, but never got around to writing an article. I shall correct that omission shortly. The sad fact of the matter is if the current readers of QEX do not help generate new readers and revenue, QEX will fade away and ham radio will drift even farther in the appliance direction. Almost everything important to modern radio was developed by amateurs. Admittedly, many were professional electronics engineers, but it was what they did on their own time with their own money that made the technology we enjoy today. They cared enough to try what management would not fund. What won't be developed because amateurs don't try it? Reg
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TDS784C 4ch Color 1 GHz Oscilloscope For Sale - Fully Working
I need to make some space on my bench, and for measurements as high as this will go, I usually move to a spectrum analyzer anyway. 4 channels, 1 GHz, color display. GPIB and floppy work; I didn't test serial or Centronics but those rarely fail. All four channels work. Likely out of "official" calibration, but everything looks good by comparing to my other equipment. Includes the deep memory 8 meg option. A bit of sticker residue where someone before me peeled off a sticker or two, top left corner of the face and along the top edge of the front bezel. Seal "calibration void if broken" sticker still intact. Power cord included but no probes or other cables. Missing left rear foot. I'm asking $500 here (and on other fora that you may be subscribed to) plus shipping, if you can't do local pickup. I'm in northeast Ohio, USA, more specifically about halfway between Cleveland and Akron. I'd prefer local pickup, will even drive a reasonable distance to meet you. Shipping weight will be about 35# (16 KG). Steve Hendrix
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File /ReducingImdInHigh-levelMixers_QEX_2001_05,06.pdf uploaded
#file-notice
The following files have been uploaded to the Files area of the [email protected] group. /ReducingImdInHigh-levelMixers_QEX_2001_05,06.pdf By: Daniel Ricardo Perez
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Frequencies to be terminated at DBM output
2
Hello group! Happy new year to all! In PA3CJD's site there's a good compilation of articles from QEX and QST: www.robkalmeijer.nl -> Technic -> Electronics -> Radio Tech -> Radio Amateur Magazines I am specially interested in this: www.robkalmeijer.nl/techniek/electronica/radiotechniek/hambladen/qex/2001/05_06/page45/index.html Here he makes several IMD tests on a DBM, with matched and mismatched impedances both at the IF and RF ports. I was surprised that RF port matching has an important impact. After reading this and other similar articles, there's a point that remains unclear for me: what are the specific frequencies that really demand having proper termination? RF+LO if I use RF-LO (or vice versa)? The LO feedthrough? Whatever? Suppose I want to receive 7.00MHz, and there are strong undesired signals at 7.01 and 7.02. 3rd order IMD within the DBM will fabricate a fake 7.00 IF even with a resistive 50 ohm load. Now, I place a diplexer after the DBM, and a xtal filter after the diplexer. The diplexer is much wider than the filter, so the DBM will still see a capricious Z at frequencies so close as 10 and 20kHz away from the desired IF, so I thought these ones would reflect back into the DBM, mix again, and worsen the overall IMD. But I must be wrong because if this was true then a diplexer would be useless. Can anybody explain the IMD worsening mechanism? Thank you! Daniel Perez LW1ECP
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Crystal notch filter
2
Hello Group, There is a good deal of crystal knowledge here so I thought to ask this group. I am working on a crystal notch filter at 14 MHz for NPR measurements. Notch would be ideally about 1-2 kHz wide and 100 dB deep. I have seen designs by OE3HKL and W7ZOI, which is, as far as I can see, just about all that is published in amateur literature. Others refer to these publications. Basically the design comes down to an LC low pass filter with crystals at the nodes to ground. I follow that approach as well. I have transformers (1:9) at the input and calculated a Chebyshev LPF at 22 MHz with 400 ohm impedance. A series L as input and output, 4 L's in total. Each node has a crystal to ground, actually 5, so also directly at the transformers. These crystals merely make a short to ground. The LPF works as expected with a little more insertion loss, likely caused by the not ideal RF transformers. Construction is "Manhattan" style, the input and output connectors are separated by about 10 cm. My first results were less than satisfactory so then I tried pulling the crystals with a series trimcap. I have not seen this before but now I am able to control the notch much better. This of course lowers the Q somewhat. On my vna (HP8753C) I can trim a notch of about 1 kHz wide and 60 dB deep. I am wondering if this has been done before and if a better construction with screening would effectively give me about 100 dB isolation. I guess yes but I am curious to learn from others. Or would I need more sections? In the end, if I have a fair chance of success, I will built a better screened version, of course. Any advise welcome. Best 73 de Harke, PA0HRK
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Hi all I inherited an old function generator (Tristat Electronics FGC001) from another ham (W7OSP SK). I know enough to be able to use it, but I have no idea what some of the knobs on here do. I can't find a manual (or any specs) for this particular model online. Does anyone know what these knobs do or can someone direct me to a manual? The controls I'm wondering about are: Sweep: Lin/Log and Ext/Int (1st and 2nd knobs from the left) Pulse: TTL -> CMOS (4th knob from the left) Also I don't know how to work the frequency counter, which would be nice to have. Thanks Cory KG7BBV
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Intriguing PCB holder
5
Hi all, I was doing some window shopping at Amazon and came across this: https://www.amazon.com/Toolour-Pieces-Circuit-Board-Holder/dp/B07TDGT21L/ref=pd_di_sccai_1/141-0245591-8116743?_encoding=UTF8&pd_rd_i=B07TDGT21L&pd_rd_r=7b0da477-6da5-44bc-a310-0cadc5342c46&pd_rd_w=sxl4t&pd_rd_wg=BWTHC&pf_rd_p=c9443270-b914-4430-a90b-72e3e7e784e0&pf_rd_r=60J8V780JFKXTPYVWZYK&psc=1&refRID=60J8V780JFKXTPYVWZYK Has anyone tried these? They look cool and you can get flexible arms to hold your PCB up higher and change the orientation of the board. Any feedback god, bad or indifferent would be appreciate any info. Hope you all had a wonderful Thanksgiving! -- Bob de k2ki k2ki@... k2ki.bb@... (Goes to my cell) 4SQRP #2292 FP #4214 SKCC #12195 NAQCC #2337
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This is a somewhat long missive on my experience of buying crystals for amateur radio projects. It represents my experience, your experience might be different but I hope this may be of use to some of you. As many of you probably know, International Crystal Manufacturing went out of business in May of 2017. While not cheap (about $35 a crystal), they were one of the few (last?) in the US to make a single crystal to your order. Over the years I purchased a number of crystals from International for land mobile radio, amateur radio, student projects and consulting. When they closed, I felt like I lost an old friend but I have managed to find some potential replacements. What I needed were some 3rd overtone crystals in the 40-80 MHz range for microwave LO¡¯s and some new crystals for my GE MASTR PE radio. The PE is a 2 watt 2m FM hand held radio made by General Electric in 1970¡¯s. The first company I found is in England: Quartslab: www.quartslab.com Their website clearly states that they cater to the amateur radio market and they will make a single crystal, no order too large or too small. However, I found their website limited technically. It suggested that Quartslab would only calibrate fundamental crystals with 32 pf load capacitance or overtone crystals to series resonance. It was also missing some technical information on available calibration and temperature tolerances. However, I corresponded via email with Dave Hayes GW4AKY at Quartslab. Dave was very responsive, answered my questions, and helped me understand where their cost trade offs are. They had options that didn¡¯t appear on their website. I purchased two 39.625 MHz 3rd overtone crystals in a HC49u package. They were calibrated to +/-10 ppm at 25C with a 24 pf load capacitance and a +/-10 ppm -10C to +60C temperature tolerance (yes, you can specify a load capacitance for an overtone crystal. I needed to pull the crystal +/-500 Hz around its specified frequency for a PLL). The crystals cost 27.63 pounds Sterling each (~$36) with shipping. Payment was made through PayPal. Many crystal companies have manufacturer¡¯s data for land mobile gear but Quartslab did not have data for the GE PE. They said they would measure the PE crystals and make a new set. I sent them a set of crystals from the PE radio. Their website does say they have data for the crystals in a lot of vintage ham radio gear so, if you need something, ask. Don¡¯t expect fast turn around. They quoted me approximately 20 working days (~month). My order was placed 2/19/2020. The crystals were shipped 4/11/2020 via Royal Mail. Unfortunately, they took 2 months to get here. That was not Quartslab¡¯s fault. The pandemic had significantly slowed international mail. You could probably get them to ship via DHL or Fedex but you would have to pay for it. However, it took them a fairly long time to measure the test crystals for the GE PE. While I sent them with the 2/19/2020 order, the PE crystals couldn¡¯t be ordered until 5/27/2020. They were shipped on 7/13/2020. The Royal Mail was faster this time and they arrived 7/23/2020. Quartzlab made the PE crystals in the same package as the originals. The originals were solder sealed but the new ones have a resistance weld seal. The seal crease around the bottom of the crystal was just a little too big to fit in the very small PE oscillator module so I never got to check their calibration. My mistake. As a footnote, good crystals are a little like fine wine. They need to age. The stresses caused by the cutting and polishing operation need to age out. Crystal frequency drift is logarithmic with time so crystals are often baked after initial cutting to reduce the drift to a reasonable level before final calibration. This operation can take a couple of weeks. I would be skeptical of anyone who offers you a custom crystal in less than a week. If my memory serves, International used to offer a 1 week expedited service (for a price!). While waiting for Quartslab to measure the GE crystals, I contacted Bomar Crystals. http://bomarcrystal.com/ Bomar is located in the US and is pro
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Direct Sequence Spread spectrum modulation
12
This is a simplified outline of a digital mode I have wanted to test for almost 40 years. It's a direct application of the basic theory of probability and random processes. I later learned it had been done in the 1950's. I'll skip the math for now. Generate a pair of Pseudo Random Number (PRN) sequences using the station call sign forward and backwards as seeds. Clock the PRNs using a GPSDO time base and fixed set of frame epochs. Spread the signal out over most of the band allocation and use a set of binary window lengths so each step in frame length is 3 dB of power gain. One of the two station PRNs is used for MARK and the other for SPACE. So at the receiver the signal is digitized and crosscorrelated with the 2 PRNs. The one with the largest peak energy at the expected arrival times is the symbol. This simplifies additively including multipath as useful signal. This also permits easily listening to other stations on a selective basis. CQ is done with the same PRN generator system using "CQ" and "QC". Once contact is established shift to the communicating stations unique PRNs. For net operation, use the net name as the seed value when joining or leaving the net. This allows stations in the net to track what stations to listen for. Identification is by sending the station call using a standard PRN pair (e.g. "FCC"). The effective signal power at the receiver is the time-bandwidth-power product. So the power level and data rate can be adjusted as conditions permit. Mathematically, the system should get as much power gain relative to the noise level as desired at the price of reducing the data rate. There should not be significant mutual interference despite stations occupying the same BW. For a 30 second/bit data rate one should get around 55 dB of gain. Technically there is nothing new in the concept outlined above. It simply was too expensive and complex to implement in the past. The economics have changed. A Raspberry Pi 400 and an RFzero should be able to implement this with ease and drive a 4K display. Have Fun! Reg
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MilliWatt asynchronous antipodal communication
9
While my intent is for this to be a forum for discussing QEX articles, I hope that more will come of it. So I thought I'd make a post about my personal major interest. An almost 40 year obsession of mine dating from when I started work in the oil industry and first learned DSP is the idea of creating a reliable communication system capable of achieving antipodal range at mW ERP. FT8 provides similar real time capability, but requires higher power levels to keep the QSO time tractable. My goal is reliable asynchronous transmission of ~ 2 kB text in 24 hours to another station at <100 mW ERP. Email by ham radio. There are a slew of ways to implement the concept. At the moment I am trying to master basic RF amplifier and oscillator design, so it will be a while before I get back into familiar territory doing DSP. My present goal is to be able to take a small signal transistor and based on either the data sheet or if needed measurements consistently design a circuit that does precisely what I want it to do. I *think* I've finally deciphered Chris Boswick's and Thomas Lee's books and know how but have not yet built an amplifier to test my calculations against a VNA. I should note that I am severely ADD and am prone to wander off and do something completely different such as play jazz guitar for weeks or months or do precision metal work. No matter what I do, I feel guilty about all the things I'm not doing. A few too many interests. Have Fun! Reg
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Sat 8:39am
Sat 8:39am