Part-15 Blogcasting

by Boomer

Intro <CLOAD>  ...   June 1, 2020


I decided to start an independent station, a blogging station, that is. Artisan Radio and Carl Blare are doing it, so let's start Trending. Actually, several other Part-15 operatives on the groups have websites and journals for their own stations on nice, top-of-the-line websites, but I can see the appeal of a writing format that's text-focused, simple and as DIY as some of our stations are.

I'll toss my hat in with good intentions. This might be the only post that gets written, but no, I have a few other ideas in the can.


Hospital Radio   ...   June 2, 2020


British TV show host Karl Pilkington said he got his start in broadcasting through "Hospital Radio". I got the impression that hospital radio was a faded glory now, maybe not even around, but no, I found it's still going, with two hundred stations still on the air, and an organization for them too! They operate through PA speaker systems and AM radio, so it sounds a lot like campus carrier current here.

They apparently didn't have college radio in Britain, so hospital radio did that function. Now it's been discovered again because of Covid-19, more folks in hospitals, looking for something simple in a live voice, taking requests.

Hospital Radio Wikipedia


Mellotron   ...   June 3, 2020


A friend sent me a video showing the Mellotron and how it operates. I've liked this keyboard instrument ever since I heard about it some years ago, and found out how it uses magnetic tape to play back samples of sounds. It's all analog, and you can hear artifacts in the sound, hiss, thumps, and uneven speed in the tapes, which gives unique character to the sound. It was all over the sound of 1970s rock, David Bowie's song, Fame, and albums by the Moody Blues.

She really does a good job explaining how the Mellotron works - YouTube video


Mark's Transmitter   ...   June 4, 2020


Mark, from WMRK in Toronto Ontario recently got a new transmitter. He's been an FM broadcaster with a Decade brand transmitter, but recently got a Talking Sign transmitter, fit for use in Canada on the AM band. Apparently Mark has the transmitter's antenna indoors, which usually leads to poor range compared to an outside antenna. Signals are trapped inside by lossy building materials and surrounded by electrical wiring which reduces the signal.

Operating low power transmitters indoors over time, I've noticed that more of the signal follows the power lines like a carrier current system, strong by the lines and near poles at a distance, but gone over open areas. I think the transmitter, when it's grounded to the electrical system. is sending a signal into the power line neutral, and some of it is reaching the power grid as unintentional carrier current! This might be what is getting Mark strong coverage of his whole 500 foot block, and weak signals outside of it, as shown on his hand-made signal map.

I came up with an idea to exploit this effect, a two sided tuner, fed by a 100 milliwatt transmitter. The top side would be the usual 3 meter whip and loading coil, and the ground side would go to a carrier current coupler connected to the neutral line outside and tuned to resonance there. The key to this would be to isolate any grounds on the system away from house grounds, which would mean the transmitter ground, as well as the neutral ground at the frequency you were using. A 1:1 balun could be used on the transmitter, and ferrite around the neutral line, to make a parallel tuned circuit with a capacitor to block the transmitter's signal heading for ground. At that point I could envision the neutral lines going out across the poles acting like a raised counterpoise ground return for the antenna, meanwhile acting as a carrier current system as well!

two-way-antenna-carrier-current-system

Click Picture for bigger size.. My contribution to James R. Cunningham Style Engineering! (Untested).


Inroads to SDR   ...   June 5, 2020


boomer-hdsdr-reception-6-5-20 All roads lead to SDR. It means Software Defined Radio, where a piece of radio hardware connected to a computer, with functions like tuning, bandwidth, and mode controlled by software on a screen. I've listened to SDRs on line, and have had an RTL USB stick for several years, but didn't get into it much since it only was receiving over 60 mhz. I've wanted to modify the stick for direct sampling mode, to receive longwave, AM broadcast and shortwave on it. I made a 4:1 balun on a ferrite bead with trifilar wind #30 wire. To bypass the tuner chip, I connected the wires from the balun to the ends of tiny capacitors, and it felt like trying to solder to the flat surface of a grain of salt. That's exaggeration, but not much.

Putting the stick back together, plugging it into a USB socket, installing the proper driver, I was rewarded with successful AM band reception after taking time to learn some settings. Articles warned that there could be images from FM signals getting into the radio, and indeed, I found them in the upper shortwave range. The remedy is to use a low pass filter that blocks signals above 30 mhz.

SDR may be the future, as dedicated radios drop in quality and become scarce, SDR will be available, and most radio fans will likely be using them. Click picture for larger size.


Regenerative reception   ...   June 6, 2020


kc6vdx-globe-patrol Long time Part-15 enthusiast and user Tha Dood started a conversation about 'regenerative receivers' in email. He's thinking about getting an MFJ-8100K kit, which receives shortwave frequencies. Since the first full radio kit I built was a regenerative radio, I had some thoughts. The following is excerpted from my letter back to Tha Dood.

I've built several regenerative radios over the years, to try out different circuits, 1 bipolar or JFET type, but my first was actually the Radio Shack Science Fair Globe Patrol tabletop receiver kit. In junior high, my science teacher was all the way into electronics, working on projects all the time before class, and had the chassis' of old TVs and radios in a junk pile right in the classroom. A hacker, maker and experimenter of his time, and I attached myself to him, and would go to the science room to check in, and have him look at my drawn schematics for off-the-wall devices I thought up..

The school funded supplies, and he got a couple of the Globe Patrol regen kits, and let me and another kid take them home to build. Mine worked, the other kid's didn't.. I had it for a week before taking it back to class, so that was my first regen, and first real powered radio kit beyond a crystal radio.

A ham's page about the Radio Shack Science Fair Globe Patrol


Part-15's sun is setting?   ...   June 7, 2020


I'm doubting it, but trying to figure out why the flight from the established website forums seems to be happening. Several other low power radio forums seem to be doing well, Antique Radio Forums is one, and Radio Museum has lively topics from posters around the world, in several languages. The HF Underground just started a new section on Part-15 operations this year.

Carl recently posted a link to Part-Fifteener WILW's blog of thoughts for March. I don't know much about WILW or the scene he's in, but he seems to be deeply involved in low power radio, and runs a couple of forums which he wants to merge, because they are "essentially lifeless." I note that one of the forums is for a popular hobby transmitter model, and the other is called the "Low Power AM Radio Network." Those sound a lot like topics that would also be covered at Part15.org or The MICRO-BROADCASTERS COMMUNITY Forum.

Hmm.. Could this type of low power home broadcasting be losing steam? Reading forums over the years, most participants seem to be interested in serving the local community through their stations, a worthwhile goal now that many other stations are run by national networks. The strength of the signal is important, as well as using audio compression, to give the station the most reach it can have within the rules.

There have been changes in listening, in my observation, more people 'consume' their audio through a smart phone or TV, than a radio which just does one thing. That leaves radio to some car listeners, older people, and radio fans, or those who want to hear shows for free and not have their listening habits tracked. I thought of social sites taking broadcasters' time and know that some have escaped to other sites, but that doesn't account for why antique radio, church parking lot radio and pirate broadcasting to a community all seem to be doing very well.

Maybe it's good to look at the origins of the Part-15 home broadcasting scene and what might have changed. What made the forums get started in early times, was it kit building, transmitter sellers promoting their units? It seems that there's been less equipment available over time. Is there hope to bring back an audience to home broadcasting forums? Site owners don't seem to be concerned about it, at least openly.




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