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Part 15 AM and FM Station Operation / My Experience so Far with the Schlockwood SW300

« on: January 30, 2025, 0102 UTC »

I did a little write-up on my newly acquired Schlockwood SW300 AM Field Strength and Modulation Monitor. Long story short - it's a crackin' little unit and I'm very happy with it. Another piece of gear, along with my SW200, Hamilton Rangemaster, and a few bits of ham radio gear that I will only get rid of just before I head up to the big radio shack in the sky -

https://aa7ee.wordpress.com/2025/01/26/the-schlockwood-sw300-an-am-field-strength-and-modulation-monitor-for-the-am-broadcast-band-and-amateur-use/

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Part 15 AM and FM Station Operation / Re: Low Power Broadcasting Book, James R. Cunningham .PDF

« on: January 26, 2025, 2026 UTC »

Interesting stuff. I haven't seen this one before. Lots to read and digest. I have only done a brief look-through, but will read more later. Thanks Dood!

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General Radio Discussion / Re: Boston AM pirate gets notification of unlicensed operation under PIRATE ACT

« on: January 16, 2025, 1642 UTC »

I'm not very informed on the new procedures since the PIRATE act was passed, but it doesn't look as if they are called NOUO's any more. What stands out though, is that this is for an AM pirate station! It almost warms the cockles of my heart remembering, as I do, growing up in the UK when AM pirates with strong signals that covered wide areas were common. It will be interesting to see how this story unfolds.

Also interesting (to me at least) is the acknowledgement in the letter that they are "investigating a complaint". We've known for a long time that the FCC usually only polices these infractions as a result of complaints, and don't go out looking for them. This would seem to support what is widely accepted as common knowledge. However, in the markets such as NYC and Miami that have a lot of FM pirates, I wonder if FCC teams go out actively looking for offenders? Seems as if it would be like shooting fish in a barrel.

Because they appear to be going after the property owner, does this mean that the station operator (if a separate individual) can potentially get off scot-free?

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Part 15 AM and FM Station Operation / Re: Ye Poor Man's AM Carrier-Current Coupling Unit! DIY'ers, run with it!

« on: January 06, 2025, 0324 UTC »

That's a lot of good info ThaDood. I have one of those Radio Shack audio isolation transformers. Guess I'd better hang onto it. Score!

Rich - I didn't hear any explanation of why it happens in that clip, other than him saying that the RF signal shares the wiring with the 60 cycle AC power, and that the hum can be all-pervasive. That's not really an explanation; just a general comment.

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Part 15 AM and FM Station Operation / Re: Ye Poor Man's AM Carrier-Current Coupling Unit! DIY'ers, run with it!

« on: January 03, 2025, 0351 UTC »

This made me think of something. With the more conventional Part 15 AM transmitters that use a regular antenna as the radiating element, most of us have learned that re-radiation of the transmitted signal by the AC wiring of the building leads to 60 cycle hum. With carrier current, the sole intent is for the building wiring to radiate the signal. This begs the question - isn't 60 cycle hum a big problem with this type of broadcasting, and how can it be avoided?

I have virtually no knowledge of carrier current broadcasting, so apologies for the rather basic question.

Good point about the lack of harmonic suppression.

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Amateur Radio / Re: Suggestoins on headphones for listening? Depends, but...

« on: December 31, 2024, 0408 UTC »

For me, I am using original AKG #K240 headphones, commonly used buy Baby Boomers in broadcasting time-line period. On a robust Kenwood transceivers, they really bring out great broadcast-quality audio that some AM'er have, as well as ESSB'ers. That's my personal favorite headphones.

I know this thread is old but for what it's worth, here's another vote for AKG K240's. I have two pairs of the K240 Studio, both of which I've had for years, and have replaced the earmuffs and cords on. They are not completely enclosed acoustically, so you don't lose touch with what's going on around you. Also, they are very comfortable to wear for long periods of time, unlike my 100 year-old Western Electric 509-W's 

PS - I notice that right now, they are on sale for a mere $49 from multiple outlets. If the quality hasn't changed drastically since I bought mine, that's a great deal.

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Part 15 AM and FM Station Operation / Re: MICROPOWER AM BROADCASTING – A SCRATCH-BUILT SSTRAN AMT3000

« on: December 28, 2024, 1819 UTC »

It's a fair question Rich. There were a few reasons. Firstly, I wanted to completely replicate the circuit of the original AMT3000 to see how my build compared with the "real" one that I used to own. It's a tried and tested circuit, so I figured it was a good starting point for any changes or mods I might want to make. My only transmitter that was in operation at the time was a Rangemaster, which is mounted outside and operating 24/7. I thought it would be cool to also have an indoor unit to play around with. I don't have a burning need for an extra outdoor unit, which also played into my decision to build this one as an indoor unit.

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Part 15 AM and FM Station Operation / Re: MICROPOWER AM BROADCASTING – A SCRATCH-BUILT SSTRAN AMT3000

« on: December 27, 2024, 0624 UTC »

Thanks ThaDood. I've benefitted a great deal from all the things I've read online over the years, so when I do something, I like to share.

You have a good memory Rich. I did find out that the enclosure used for the Rangemaster is this one -

https://www.mouser.com/ProductDetail/Hammond-Manufacturing/1590ZGRP123?qs=sGAEpiMZZMv151B%252BVDR3zBr88%252Ba5a7FeYoXfKyeAB0U%3D

I thought I'd start my build off as an indoor unit and go from there. If I did want to mount it outside, I'd also want to upgrade the inductors in the output network for a more efficient one wound on a large iron powder toroidal core, as used in the Rangemaster and AMT5000. I'd also want to include extra circuitry to allow the transmitter to be fed with balanced audio. Whether I'll ever get around to it is another matter though! 

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Part 15 AM and FM Station Operation / Re: MICROPOWER AM BROADCASTING – A SCRATCH-BUILT SSTRAN AMT3000

« on: December 24, 2024, 1906 UTC »

I was going to post a link to this here, but you beat me to it Chris. Thanks! There's not a whole lot of information out there for people who are interested in building their own Part 15 gear, as it's such a niche pursuit. For radio hams who are into homebrew, we are spoiled. There are tons of articles on building ham radio equipment, dating back to the birth of radio, as well as many kits available. Not so much with Part 15 broadcasting.

Building this transmitter was a useful exercise. When I owned an original one, years ago, I had nothing to compare it with. Now, I'm able to evaluate the AMT3000 in the light of a little more experience. I'm mostly happy with it, but like almost everything I build, it gives me ideas for future experiments. I'm not thrilled with the simple single-channel audio processing, so I want to try bypassing it and feeding the transmitter with processed audio from my SW200. I'd also like to try a more efficient inductor in the output network, a circuit so that it can accept a balanced audio feed, and put the whole thing in a rugged weatherproof enclosure for outdoor mounting - if I ever get around to it! 

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Part 15 AM and FM Station Operation / Re: Radio World interview of Bill Defelice, “Wannabes” Should Consider Part 15?

« on: December 05, 2024, 0137 UTC »

He says the transmitter challenge will not occur until after the release of several upcoming Part 15 broadcasting products.

As I said over in the other forum, I am quite keen to see what these could be. A new transmitter perhaps? An AMT3000 replacement, or perhaps even a Rangemaster/Procaster alternative? A transmitter would be my keenest wish, but I guess we will need to wait and see.

In the meantime, I'm sitting at the bench here, very gradually working on a scratch-built AMT3000 because I was silly enough to sell mine without realizing that one day, they would be hard to come by.

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Part 15 AM and FM Station Operation / Re: "New" Part 15 Station in Alameda, CA

« on: November 17, 2024, 0729 UTC »

"As compliant as is practical" 

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Part 15 AM and FM Station Operation / Re: "New" Part 15 Station in Alameda, CA

« on: November 16, 2024, 1848 UTC »

I guess this post could be considered a logging. Not many folk post loggings of Part 15 stations, so I'll put mine here. I think it's interesting to share information on how far away Part 15 stations can be heard. Yesterday, I was walking around the area of Oakland near where I live and was able to hear them. The signal was very weak, but identifiable, at a distance of 5.1 miles from the transmitter. Receiver was a handheld Belka-DX with the telescopic whip.

I'm curious to see if it can be heard at greater distances. I'll add to this thread if I hear it any further away. In the image, the vertical black line shows the direct path from the believed location of the transmitter (at the bottom) to my receiving location.

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Part 15 AM and FM Station Operation / Re: "New" Part 15 Station in Alameda, CA

« on: November 14, 2024, 0552 UTC »

ThaDood - yes, DDS is the way to go to replace a crystal, IMHO. The agile frequency module in the Rangemaster uses a little SMD clock generator IC that is programmed by 2 banks of DIP switches. I used to think it was a PLL circuit, but I looked at the IC in mine this morning and looked it up online. I think this is a slightly different method of frequency generation from DDS, but it seems to work well. You could pair up an Si5351 clock generator IC with an ATMega325 processor for a little circuit that would act as a crystal replacement. Adafruit sell an Si5351 breakout board, which you could team up with a cheap Arduino Nano. Then you just program whatever frequency you want into it. For greater stability, you can use a TCXO instead of the regular reference crystal.

From the point of view of circuit simplicity, I like crystals. Nowadays, for anything other than very specific frequencies, for which they are manufactured by the boatload, crystals seem to have gone the way of the dodo. I don't fully understand why Keith no longer uses crystals in his Rangemaster though. I'm a radio ham, and there are a few vendors who have bulk lots of crystals manufactured for specific popular frequencies in the ham bands, and sell them individually to hams - 7030, 10106, 14060, 21060, and 28060KHz, for example. I'm wondering why Keith couldn't have done this for the channels from 1590KHz thru 1700KHz? I believe that the crystals in the Rangemaster were HC-6/U types, with pins. I notice that the custom ham crystals that are now available are in smaller cans with wire leads - not pins. I wonder if it's the cans with pins that are no longer available for custom orders? The market for hams is probably bigger than that for an individual Part 15 transmitter builder, so it could also be the case that the minimum order required is too big for a Part 15 transmitter manufacturer.

As far as grinding your own crystals Rich, that was done with the older crystals that were in bigger holders that could easily be taken apart and reassembled. The FT-243 crystal was a popular size. The side plate on the holder could be unscrewed, and the little slab of crystal was held on to the wire connectors with a compression plate. It was a relatively simple matter to remove the crystal, grind it down a bit to increase the frequency, and reinsert it. You could even decrease the frequency a bit by rubbing graphite (from a pencil) on the side of the crystal. However, there was a limit to how much a crystal frequency could be moved with this method. You wouldn't have been able to move an AM BC band crystal one whole 10KHz channel - it's just too big of a frequency excursion.

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Part 15 AM and FM Station Operation / Re: "New" Part 15 Station in Alameda, CA

« on: November 13, 2024, 0452 UTC »

Very interesting day today. I did some listening to this station in the part of Oakland that is just across the water from Alameda. At some point, I may listen in enough different areas of Oakland so that I can draw a new coverage map. Today, I concentrated on a few specific areas and just one main street, Fruitvale Ave, in the Fruitvale area of Oakland.

Reception was good and very listenable in the area of the Embarcadero in Jingletown, by the waterfront. I then walked away from Alameda (and also away from the transmitter), up Fruitvale Ave. Without detailing the exact locations I was taking reception readings (because few readers will be familiar with this area), I found the following. Reception was good, with only smooth noise in the background that was not very noticeable, up to about 1.25 miles from the assumed transmitter location. From there to about 2 miles away, reception was fairly listenable, with about 40-50% noise on the signal. The signal became increasingly less consistent, with deeper nulls, but some surprisingly strong peaks until, at about 2.4 miles, the signal became discernible but not what I would call listenable.

What I was completely unprepared for was when I got home, I discovered that I could just about discern the station outside my house. The signal was just strong enough for me to make a positive ID from the music they were playing. Not sure if I'd have been able to adequately hear speech though. My house is 3.3 miles from the assumed transmitter location. Even more amazing, is that they picked such a clear channel, I can just about ID the station after dark from my house. It's definitely not listenable though!

When I first decided on the frequency I wanted to use for my station, thinking of antenna efficiency, I only looked at frequencies at or above 1600KHz. I now wish I had looked a little below too, as 1570 in this area is an excellent frequency for Part 15. It works well for CHRS, as many of the restored vintage radios they have in their collection, or that they have sold to locals who live nearby, will be able to receive the station - a good argument for them not choosing a frequency in the expanded portion of the band.

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Part 15 AM and FM Station Operation / Re: "New" Part 15 Station in Alameda, CA

« on: November 12, 2024, 1545 UTC »

I'm just happy that I came across something before you did Rich. You're the supreme documenter of all things Part 15! I only knew about it because it's right in my back yard, and I'm already familiar with CHRS.

I'm heading to the army surplus store in Oakland today, to look for a new pair of pants. It just occurred to me that it is right across the narrow channel of water that separates Alameda from Oakland, so I'll get a chance to see if coverage of the Radio Sausalito relay station extends to the mainland at all. Being a radio geek is fun!