Saturday, May 23, 2020

A Question for You

A question for you, dear readers. 

My article on interpreting the FCC's RF radiation limits drew several thanks.  It makes me wonder what else you're interested in reading about in the general topic of radio.  Since I made my living in high-performance, high-reliability radio design and I've been a ham for 44 years, that's naturally what I gravitate toward. 

I was thinking about a poll, but I don't even know enough to ask the right questions.

So, comments, please!


 


32 comments:

  1. The RF safety posts you've done have wide appeal.

    Maybe something about basic antennas? Shortwave listening? Scanner radios?

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  2. Propagation and ground wave.

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  3. How about a short series on RF design secrets, sharing stuff a radio designer has learned over the years that isn’t in the books. Techniques that are handed down from greybeard to no beards. Stuff learned via the school of hard knocks. Perhaps short stories on how a tough problem were solved. Maybe in the manner the late Bob Pease had published in Electronic Design magazine. RF design should be listed as an “art” as much it is a science, saying so from my experience as Radio Amateur, and self educated designer. As such you might have enough material for a book should you desire to self publish.

    All of us greybeards in our particular career field have these secrets or techniques and have taken them with us upon retirement.

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  4. Go for the dangers of 5G and its relationship with satellite frequencies tieing it in with a demo on what a microwave oven does to a chocolate bar.

    Retired USAF Ground Radio/SatCom tech.

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    Replies
    1. Robin Williams as Mr. Rogers: "now let's put Mr. Hamster in the Microwave Oven. Ooo! Pop goes the weasel!!"

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    2. That brings back memories.

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  5. Propagation, E and Es-layer, sunspot cycle; references also, for further study, please.

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  6. One question nagging at me for quite some time now is "Is there a good short wave/emergency band radio that is American made? Seems like all I find, Amazon, etc. are products that have Chinese names. Surely, not all in this field has been shipped off to the land of the Wuhan.

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    1. Yes, there are American companies making excellent radios that would be suitable, but they cost dearly.

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    2. Do you want a portable, or a desk-top receiver? This limits your choices.

      What's your budget? $100? $500?

      I have no problems with buying a Japanese or Korean made radio, but I'm doing my best these days to avoid CHICOM made products.

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    3. Here's a good place to start, and my apologies to SiG for hijacking his thread!

      https://swling.com/db/category/made-in-usa/

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    4. Nothing to apologize for. The problem with saying "tell me what you'd like to know" is the implication I know something about anything someone would ask. In this case, I just haven't looked for a shortwave receiver in years. I have a house full of them.

      Like you, if the field is enlarged to European, Taiwanese, Japanese or pretty much anyplace other than the Chicoms, I'm more comfortable with sending bucks there. You know the Airspy guys, right drjim? Is their HF+ Discovery made in the US? It's expensive compared to shirt pocket shortwave receivers but I hear it's good.

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    5. I think AirSpy is made in China as one of their distributors says "Ships direct from factory in ShenZhen, China. I have one of the "R2" models and it's an excellent receiver, but it doesn't cover HF, as it starts at ~24MHz. It's a FAR better radio than the SDRPlay, BUT you need a computer (laptop, desktop, or tablet) to use it.

      They also sell an HF converter which allows reception down to 1kHz. Not much down there, but it's useful for some people.

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    6. Thanks Guys! Appreciate the inputs.

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  7. I was in High School and a year or after Sputnik the Feds gave money to foster Stem education which permitted me to take Circuits ! under the guise of a prominent technical university--Tech was in its name. We took the course at night and numbered 180 at the start and fifteen of us finished. It seemed to be, looking back, mainly about how radios worked: superheterodyne receivers and single side band propagation to cheat the power output limitations. Also, we learned about Kirchhoff's circuit laws. But I don't want to revisit that aspect of radio.

    What I urge you to do is give a primer on SOFTWARE DEFINED RADIO.

    Dan Kurt

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    Replies
    1. ... give a primer on SOFTWARE DEFINED RADIO.

      That's pretty much a primer on radio. The term SDR goes from the $25/30 RTL-SDR up to a Flex 6700 that starts priced at its model number ($6700) and higher end. There's nothing that can be done with an SDR that can't be done in an analog radio - it's just cheaper to add options (like more filters) in software than hardware. Doing lots in software can drive the price down.

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  8. I'd LOVE to read a series of articles about two way communications from the standpoint of "I can turn on a radio and tune to a frequency. I can install & use a CB radio but I don't know 10- codes. I know a few basic definitions. I want to learn more"
    Maybe basic RF communications 101?
    Enough knowledge so that in a pinch I can run the radio room in an emergency?

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    1. That begs the question of what kind of radio: CB? Family Radio Service (FRS) - which is just like CB only different? Ham Radio? VHF FM or HF?

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  9. This comment has been removed by a blog administrator.

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  10. Guitar OT:
    https://1.bp.blogspot.com/-IOHHBt0uca4/XsvRi8gtCtI/AAAAAAAAj0E/OAsaMyiY-Y4k0RcG5cZXgGqv-jlo3uryACLcBGAsYHQ/s400/daily_gifdump_3327_12.gif via
    https://ogdaa.blogspot.com/2020/05/tuesday-gifdump_26.html

    Now to the matter at hand: digital protocols, such as AX.25, DSTAR, FUSION, DMR, APCO/P25 their slicing (frequency, time) techniques, bandwidths, data rates, whatever catches your fancy.

    Filtering would be interesting too. This morning I just realized why I had only 3 duplexer cans. The guy that previously had them did packet radio, so only simplex not repeater operation. Doing a project for the local ARES guys and the club repeater site is a RF-intense location so I may need cans on the packet gear. But maybe not. The ARES-provided radio is a 100w Motorola SYNTOR-X.

    Thanks for the FCC RF exposure stuff, much appreciate!

    73, Jim

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    Replies
    1. "Friend to you and me..."

      Those are funny acronyms to me. I've heard of a couple of them, but I'm trainable.

      Filters, OTOH, are my wheelhouse. I wrote a filter design program in the late 90s that I always spread around where I worked, and it always caught on.

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  11. Part 1 (4096 char limit):
    Yeah, it's an earworm. I was making fun of a friend of mine at work once, also named Jim, with the George, George bit except using Jim, Jim ... and then I realized .... oops, that's me too. Everybody got a good chuckle out of it. Apparently the tech support headset made me stupid(er).

    Way too long response....

    AX.25 - X.25 protocol modified for amateur radio.
    Usually called "packet radio" way back in the 1980s & 1990s; recent mild to large resurgence for HF/VHF/UHF EmComm usage. Winlink & BPQ software has helped re-popularize the mode. Substantial digital modulation work being done for the mode (PACTOR, ARDOP, VARA, WINMOR...), including a FCC showdown on bandwidth/data rate on HF, ability to decode the [encoded/not encoded] data, and whether or not sailboat private emails are a legit use of ham radio.
    https://en.wikipedia.org/wiki/AX.25
    .
    https://www.winlink.org/
    https://winlink.org/content/winlink_book_knowledge
    https://en.wikipedia.org/wiki/PACTOR
    .
    http://www.cantab.net/users/john.wiseman/Documents/
    BPQ, John G8BPQ; same guy who wrote TNC2 (packet radio controller hardware) BPQ ROMs back in day. Now it's almost all software altho some hardware TNCs are still available. Most computers not having a serial port really makes hardware TNCs more challenging. There are some RasPi TNC "hats" (daughterboards) available.
    https://groups.io/g/bpq32/topics
    and sometimes BPQ stuff in
    https://groups.io/g/RaspberryPi-4-HamRadio
    Throwing an audio board on the RasPi makes producing various digital modes very flexible these days (see also Direwolf). BTW, the RasPi4 now has a beta USB boot offering, something I consider mandatory for a packet installation on an intermittently accessible hilltop (SD cards eventually die).
    https://packet-radio.net/direwolf/

    I'm sure you know several of these:
    https://en.wikipedia.org/wiki/List_of_amateur_radio_modes#Digital_voice

    D*STAR - initially ICOM-only protocol, later adapted by Kenwood & FlexRadio.
    I bought a D*STAR board for my Kenwood 2m mobile, cost about as much as the radio. Unfortunately most of the local D*STAR repeaters were on 70cm. Goes into "Robot audio" mode when it breaks. Early digital voice offering, was/is quite popular locally.
    https://en.wikipedia.org/wiki/D-STAR

    73, Jim

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  12. Part 2:

    Yaesu FUSION - competing protocol against D*STAR
    Yaesu put out a 50w DX-1R repeater for $500 to promote the mode, but it wouldn't do 100% duty cycle and they neglected to say so. Generated a lot of ill will. Lots of the (numerous) local Motorola guys thought that was just plain silly. Optional internet connectivity. Repeater can run in analog, analog/FUSION, or FUSION mode. Largely decent dual-band (2m/70cm) radio for dirt cheap, but inside it resembles two Yaesu mobile rigs in a box & some glue (or at least the DR-1X was). Readily programmable from the front panel. I sorta suspect it has programming software. Our club dropped it because only one member had a FUSION radio, and he won it at a hamfest. First digital voice mode we dipped our toe into, replacing our (heavily modified) 1970s era Motorola Micor repeater. Our club has more Motorola talent than you can shake a stick at.
    http://systemfusion.yaesu.com/

    DMR - Recent Motorola offering, with a weird station addressing scheme (DMR ID) that looks to be way too small to me (7 digits iirc), at least the way I've seen it implemented. Naturally pricey from Motorola but available used and generally rock solid once you get the firmware squared away (we had a wide/narrow audio bandwidth issue at first). Alternate vendors have arisen, some outright stealing Motorola's IP property. Also internet connectable. Requires the Motorola software to program the repeater.
    https://en.wikipedia.org/wiki/Digital_mobile_radio
    https://dmrassociation.org/
    https://dmr-marc.net/FAQ.html
    https://chicagoland-cc.org/index.html Massive local network
    http://www.arrl.org/news/motorola-wins-multimillion-dollar-theft-of-trade-secrets-case-against-hytera
    I can't find the packet frame doc that shows the addressing scheme, maybe later.
    Our club currently supports this mode on 70cm only; includes internet connectivity (widely used locally).

    P25/APCO - adopted into ham use from public service
    Also internet connectable. Our local club runs our 2m repeater in analog/P25 mode, and dedicated APCO/P25 mode on 70cm with internet connectivity; no internet connectivity on 2m. Our analog mode puts out a PL code on transmit, so you don't have to hear the P25 hiss if you don't want to.
    https://en.wikipedia.org/wiki/APCO-25

    Our local club has, or had, all of 'em except D*STAR. Locally, D*STAR is/was pretty popular but one of the largest local clubs is switching from D*STAR to FUSION.

    Filters: cool. My current interest is figuring out how to tune the cavities, but theory & practical knowledge is always a plus.

    All right, now it's time for me to train the self-driving cars' AI with the Captcha business.

    73, Jim

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    1. Good presentation. I played with Packet radio (AX.25) in the early days, I'd guess '85/'86. I bet the TNC is still in the closet. I know a little bit about DMR and P25 from reading monitoring sites occasionally, and have watched a few demos on FreeDV, but most of that is new to me.


      Tuning those cavities. My experience is limited to lab use and I found nothing better than a network analyzer. I suspect old guys who tuned up repeaters have some tricks I don't know about. The trick on cavities is that if you're tuning band rejection, you need very good dynamic range to see how much rejection you're getting.

      Nowadays, I suspect the little NanoVNAs that are popping up everywhere would be used, at least for bandpass tuning if not rejection, but that market space is undergoing a surprisingly fast growth. The NanoVNAs go from well under $100 to not much more than that. The MiniVNA units are between 2 and $500, (last time I looked) and very usable: http://miniradiosolutions.com/ There are Chicom copies on Amazon but I'd avoid them. Finally, there are some very impressive instruments that are still incredible buys next to the lab gear I'm used to, like the Siglent SVA1015X. https://smile.amazon.com/SVA1015X-Spectrum-Analyzer-Frequency-Generator/dp/B07FNQCWYB/ref=pd_ybh_a_13 I just find it hard to justify the cost of one of those.

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  13. Previous comments have listed that which I would be interested in, especially propagation.

    I would also be interested in channel splitting in the 8.33 kHz spectrum. Aviation stuff.


    Rick

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  14. Thanks. I got into packet in maybe 1987, so you were there a bit before me.

    Today I noticed a new toy in beta; source code not yet published that I see. One interesting thing they do is use it to run some benchmarks against common packet modulation techniques (Downloads, bottom of page).

    > IONOS HF/VHF/UHF Channel Simulator
    > The Amateur Radio Safety Foundation introduces the IONOS Simulator, an audio-processing, 1-4 path (ray) simulator that models common HF and VHF/UHF propagation channels. It is intended to accelerate modem and protocol design, analysis, optimization and comparison, but has other uses as well. It allows off-air laboratory testing and evaluation of radio protocols and modems using statistically-standardized channel characteristics that would be almost impossible to achieve with over-the-air RF testing. Automation features allow scripting for multiple test runs under automatic control for huge time and labor savings. Since no transceivers are needed, the device may also be used as an inexpensive operator training station for exercising and teaching digital mode software. The simulator is based on the well-documented Watterson model [1] used by many laboratory grade instruments costing many thousands of dollars.
    https://winlink.org/content/ionos_simulator

    Thanks for the cavity tuning info. I have a station monitor that I got from a friend's estate that I'm cautiously learning to use. The last thing I want to do is blow out the front end. I'm basically a software guy, so I go slowly on this kind of stuff.

    I found some W2AEW videos on youtube that should help a lot.

    73, Jim

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  15. I have been a ham since 1972, but now I am not very involved with much of the hobby. Mostly due to having so many other hobbies, and the costs of all of them.
    I went to a hamfest last year in my city, and I could not believe the prices that they were asking for gear that was out when I first became a novice. Drake, Collins, and the like, were asking priced at the same as or more than, what they cost brand new back then. While I understand the value of money is different, the equipment is not up to the standards of that coming out today.
    I am mostly using 2 meter FM, since it is the least expensive way of getting involved in the hobby. I had given all of my equipment to a missionary going to Togo, Africa a number of years ago, and so I didn't have any of my HF gear. I had several Heathkit rigs, my favorite being the HW 7. I know it had a lot of quirks, that were fixed with the HW 8, but I made a lot of contacts with that rig.
    I also had a receiver that I built by Heathkit, and used a Globechief and sometimes a homebrew transmitter.
    I have a QRP kit that I need to put together for 20 meters, and get an antenna up. I also need to get a straight key, since that is what I am most comfortable with. I have used an automatic bug, but it just is to easy to go to fast, and it takes some of the fun out of it.
    I think that one topic that I would like you to address, is just how the HF bands are being used, and some of the good and bad things on each of them. I ask this, because I know that on some bands, there used to be etiquette that was just assumed, and you were shunned if you misbehaved. Plus, which of the bands are people using most of the time for what type of contact, and qrp use, or for the digital modes, SSB, etc. I know I am not being very clear, but I hope you can understand what I am trying to ask. No matter, I want to tell you that your information on RF radiation was excellent, and it made me think again, about the kind of things that made me love ham radio when I was just a kid. The fact that it makes you to be responsible for your own equipment and it's operation, and police yourself. I have always tried to do that in all areas of my life, and so that was right in my wheelhouse.

    pigpen51 aka KA8KRV

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    1. I think that one topic that I would like you to address, is just how the HF bands are being used, and some of the good and bad things on each of them. I ask this, because I know that on some bands, there used to be etiquette that was just assumed, and you were shunned if you misbehaved. Plus, which of the bands are people using most of the time for what type of contact, and qrp use, or for the digital modes, SSB, etc.

      There's not a whole lot I can say about some of that. The digital modes and what frequencies they're used on is an easy one to ask your favorite search engine - I do it all the time. I've been operating a lot of FT8 and the WSJT modes lately; those frequencies are built into the program, but you can always add more frequencies.

      Likewise, there are QRP hangouts on all the bands - This is a good start.

      The broader question of which parts of the band are SSB and CW is in a chart you can get from the ARRL I've seen versions of that chart as giveaways at hamfests.

      This weekend is the CQ Worldwide DX contest, CW portion. From 0000 5/30 (tonight at 8PM Eastern) until Sunday clicks over to Monday on Sunday night, 8PM Eastern. The CW portions of the bands are likely to be busier than you've heard in quite a while. At night, 80 and 40 are sure to have DX. 20 is possible - maybe an hour or two after sunset and then again and an hour or two before sunrise. During the day, 20 and maybe even 15. 10 is pretty doubtful. I've worked a lot of new countries in that contest, usually waiting until the first 24 hours are up and the rate of new contacts is going down for the serious contesters. They're just as happy to work you for a contact point as you are to work them.

      That's a start...

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    2. Thank you for such a personal response. It was just what I was looking for. Now to just get off my butt and get busy. I like you am retired, but due to disability. I have a couple of chronic pain conditions, one being chronic daily migraines, caused by a family history and a rather high number of concussions from playing football in my younger days. And a broken back from a car accident at age 20. I am now 60. Like you, I am a Christian, I have attended Bible college, back in the 80's, for just one year. I also am a gun owner, and own several guns, both for concealed carry and for home defense, and also for deer hunting here in Michigan.
      I just want to thank you for taking the time to bother answering me personally. It means a lot,knowing that you have many other things to do. Oh, I forgot, I am a strong supporter of Israel also. I have been in contact with their ministry on several occasions, mostly to encourage the country that not everyone in America hates them. That was during the Obama years.
      So I wish you health, happiness, and good friends and family, all around you. Thank you once more,for your kindness.

      pigpen51

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