A Different Type Of QRP

My radio interests have taken a different course in the last month or so and I’m not sure whether it’s appropriate to include them in this blog or not, so let me tell what I’ve been up to and you can decide;  I’d welcome your comments.

I had been earning my living as a DJ/announcer/voiceover guy since 1987 until last year when the paid work all came to an end for me. I really thought I’d gotten over the DJ bug and in some ways, I think I have.  As a youngster, I very much wanted to prove myself – to both myself and my peers.  Being perfectly honest, there was a need for a certain amount of ego gratification too. Well, I don’t feel the need to prove myself to anyone anymore and as for the ego gratification part – well, I think that age has cured me of the need for that.

But interests picked up at an early age never go away completely and so it was that a month or two ago I became interested in setting up a Part 15 AM broadcast station.

Most people reading this blog will know about the FCC regulations that cover Part 15 devices, which can be broadly divided into 2 types – non-intentional radiators and intentional radiators.  Non-intentional radiators are devices that emit RF as a by-product of what they do and then happen to leak some of it. This category includes the local oscillators of radio receivers and the crystal controlled clocks in computers, for example.  Intentional radiaters are devices for which the RF radiation is the main point of the device.  Baby monitors,  cordless phones and garage remote controls are examples of intentional radiators.

Part 15 regulations also cover something which is quite attractive to me,  and that is the ability to operate a low power unlicensed yet completely legal broadcast station. On the FM broadcast band, there is a strict field strength requirement at a set distance from the antenna that makes it unlikely you’ll be able to achieve a range much greater than 200 feet.  This is fine if you want to play music from your iPod on your radio, but you’re not going to build much of an audience with a Part 15 FM station. The criteria for transmitters on the AM broadcast band are much more lenient; instead of field strength measurements at a specified distance from the antenna, the main rules are that the input power to the final amplifier cannot exceed 100mW and the total length of the antenna and ground lead cannot exceed 3 meters.

100mW to a 10 foot antenna on the AM broadcast band isn’t much, but if you engineer the whole system for maximum efficiency, it can be possible (from what I’ve read) to achieve a range of up to a mile (or even more) from the transmitter. What makes this even more appealing is that the FCC allows the use of multiple transmitters to increase coverage. Place a few transmitters around the edge of your primary coverage area, and now you’re starting to cover a significant part of a city.  Some small town residents can cover a significant part of their entire community with one well-placed transmitter. The same discipline of maximizing the efficiency of the whole system that applies to QRP ham operating also applies to Part 15 AM operating. After all – it is also QRP. In fact quite a few operators of Part 15 AM broadcasting stations are licensed hams.

Many Part 15 AM broadcasters are either people who want to broadcast old-time programming to their restored antique radios, or Realtors with their “Talking House” transmitters broadcasting details of houses for sale to prospective buyers parked outside.  A smaller, but very enthusiastic subset of  Part 15 AM operators are the folk who run their own radio broadcasting stations.  The FCC don’t recognize these outfits as radio stations; they are simply classified as intentional radiators.

At this point, you’ve either completely tuned out or have at least some level of marginal interest. Here’s a picture to break the monotony:


Ant Radio broadcasting from the Pill Hill district of Oakland, California


Not a great photo I’m afraid.  At some point I’ll take a better lit and processed picture, but at least you can see what it looks like. This is where I do my ham operating too.  In the shelf unit to the left is the FT-817,  KK-1 straight key and Bencher paddle along with the Fort Tuthill 80 and 2N2/40 as well as my soldering station, 13.8V regulated power supply – oh, and my DVD player to boot! There is also my Signalink USB sitting on top of the Tut 80.

On the right is AM broadcast central. At the bottom is a Mackie mixer on a pullout shelf. Above it the Denon dual CD player (2 separate units – the control unit at the bottom and the CD trays in the unit above it.) The microphone is an EV RE27N/D. There is a Shure SM7 (also on a boom arm) out of sight of the camera for guests.  At the top of the rack are the 2 audio processing units.  The lower one is the first in the audio chain after the mixer.  It is an Aphex compellor which provides compression, leveling and peak limiting of the signal. Above it is an Inovonics 222 which provides pre-emphasis, a lowpass filter (to limit the bandwidth of the transmitted signal) and more peak limiting. It supports asymmetrical carrier modulation to modulate the transmitter to as much as 130% – another way to maximize the range of this QRP signal. The Inovonics 222 is quite popular with AM amateur radio operators to help them squeeze maximum efficiency from their signals.

When I’m not DJ’ing live (which will be most of the time) the computer runs the whole station in automation and so far, it’s not sounding too bad at all. I’m currently spending a lot of time recording and producing all the station ID’s as well as adding to the song library. When Ant Radio hits the airwaves, I’ll probably post an air-check so you can hear what my little broadcast station sounds like.

Maybe I’ll even get the occasional DX report 🙂


14 thoughts on “A Different Type Of QRP

  1. I found it interesting, too. I’m interested to know what, for you, is your driving interest in this? The communicating, creating the shows, or the technology, the radio? My interests are in the latter, which is why ham radio is more of an interest to me. If I wanted to do what you are doing then I think I’d use internet streaming rather than RF, which would make it possible to have a worldwide audience rather than one limited by 100mW to a 3 foot antenna. Have you considered that option? We have 3 WiFi internet radios at home which we often use to listen to American “FM” radio stations that we’d never otherwise hear.

  2. Jason – somehow I’m not surprised that you find interest in my post. You strike me as quite the renaissance man!

    Julian – It’s a little bit of everything really, though the one thing I get to do with a station like this which I can’t do with amateur radio, is to program it. I enjoy performing the production tasks and putting together all the audio elements that make up a broadcast radio station. I did look into streaming, but if I want to build up any kind of an audience it will start getting quite pricey to pay for the streams and the music royalties. That will then force me to treat the station as a business and try to figure out ways to bring in revenue to pay for the upkeep; something I don’t want to do.

    One thing I like about terrestrial broadcast stations as opposed to internet-based ones is that the audience are all in the same geographical area. There is a sense of community in the area in which I live, and if I can bring in one or two local musicians to play live on the air and perhaps a few area residents to talk about local events, I can turn it into a very local community station. Our neighborhood has block parties – Ant Radio could perhaps be the official station of the neighborhood association. The month to month cost of running it as a terrestrial station will be almost zero, so I can treat it as a hobby that serves my community, rather than as a business that needs to make money.

    Apologies for the wordiness, but I hope that explains things. I don’t believe that these kind of micro power unlicensed stations are allowed in the UK. This is a great gift that the FCC have given us.

  3. Interesting, Dave. Regarding the difference in allowable power from AM vs FM stations, I think the reason the FCC is more lenient on AM is because very few people can manage an efficient antenna on frequencies that begin just below the 160m band. Many hams can’t get on 160 for that very reason and if you’re operating an AM station on 600 kHz, any antenna would be 3x the size of the same one on 160. On FM – the 3m band – efficient (and gain) antennas are a simple matter.

    I’m curious what your programming format is and are you on 24/7 with the automation you mentioned?

  4. Part 15 regulations specify that the maximum length of the antenna and ground lead on the 510-1710KHz band cannot be more than 3 meters John, so all “serious” Part 15 operators are using roughly the same antennas – base loaded whips. If the antenna isn’t at ground level and the ground lead cannot be made very short, a choke is inserted in the ground lead close to the transmitter so that it doesn’t radiate; this seems to satisfy FCC inspectors. This is the most efficient antenna any Part 15 operator is allowed to use while remaining within the bounds of the FCC rules. You did hit on something by mentioning the relative sizes of an antenna for 600KHz and for Top Band. Most Part 15 operators transmit at the high end of the band, between 1600 and 1710 KHz so that they can maximize the efficiency of their already-compromised antennas.

    I didn’t make it clear in my blog that the station is not on the air yet. I have everything I need apart from the transmitter and antenna. Everything else is here – the automation software already partially programmed and the entire audio chain including full audio processing to feed the transmitter – just no transmitter yet. That will be the subject of a future post.

    The format is music intensive with news at the top of each hour (pulled from an internet feed news service). I haven’t yet found a way to describe the music mix, which is based purely on what I want to play. It’s a mix of classic rock and pop, with a few Americana/roots type songs thrown in and also some choice jazz and world music cuts. I have yet to add the jazz and world – that is coming in the next month or two. Every song has to be edited individually before being added to the playlist, so it is a very time consuming process. To give you an idea, here were the first 20 songs on the playlist this morning:

    The Clash – This Is Radio Clash
    20-20 – Yellow Pills
    Dramarama – Anything, Anything (I’ll Give You)
    David Bowie – Santa Monica ’72 – Life On Mars
    Bob Dylan – Hurricane
    The Kinks – Waterloo Sunset
    Fleetwood Mac – Dreams
    Led Zeppelin – Heartbreaker
    Cream – Sunshine Of Your Love
    Romeo Void – Never Say Never
    John Lennon – Grow Old With Me
    Jimi Hendrix – Still Raining, Still Dreaming
    The Dave Clark Five – Bits And Pieces
    The Doors – Touch Me [Take 3]
    The Isley Brothers – That Lady
    Bis – Young Alien Types
    The Ink Spots – I Don’t Want To Set The World On Fire
    Peter Gabriel – Modern Love
    Joan Armatrading – Me Myself I
    The Beatles – Anthology 2 Disc 1 – I’m Only Sleeping [Take 1]

    Thanks for the interest John. Based on the comments on this post, I think I’ll continue to provide my Part 15 updates in this blog. It will be a little while; I’m saving my pennies for the transmitter. Although there are a few good transmitters both ready built and in kit form on the market, there is one that stands head and shoulders above the others and naturally it is the most expensive one. If I’m only allowed 100mW to the final stage I’m going to make darned sure that I maximize this signal.

  5. Is there any “webreceiver” in your area, from which we can monitor your AM BC transmission ‘sort-of-live’via internet here in Europe?
    73 Mark, PA5MW

    1. I don’t believe that there is Mark. It would need to be within a mile of my house in order to pick up the signals, as this is going to be a very low range broadcasting station.

  6. Dave,

    Long story short, I’m back into amateur radio after a period of kid-raising inactivity. Did 31 years in radio before the bottom fell out for me 2 years ago. I’ve transitioned out but miss certain parts a LOT. Anyway–very cool to find a QRP fan and former broadcast guy via the web. I’ll keep reading.


  7. I identify with what you’re going through Danny. Not sure if I’ll be posting too much here in the future; I think the “blogging bug” might have left me, but if there are any major changes, I’ll be sure to post them here. Good luck in your journey!

  8. Hello Dave,

    Great post and I wish you the very best in this endeavor. A mile radius in a densely populated city can mean thousands of people listening to your station. These days, I find most AM stations spewing the same programing coast to cost, with the same information. I don’t even like the music. Putting a legal low cost station on the air will be a welcome change!

    Get some good music out there and do a good service for your local community. I wish we had one to listen to here.

    Please post more on this!

  9. Thanks John. I shelved this project shortly after writing this post but have recently revived it. It looks like my little AM station might well take to the airwaves before long. I checked out a few of the posts on your blog and we seem to share very similar views on the importance of quality and diversity in broadcasting. If only we could turn the clock back and somehow prevent deregulation…….

    I hope to see you on your blog very soon!

  10. What frequency are you on for AM? I am line of sight to Oakland, over here in SF. Also a QRP builder, but no room for antennas here. Saving to buy a Buddipole. String long wires when camping, etc. Plan to start operating QRP at Ft Funston, by the ocean on days off.

  11. I was on 1600KHz Ronald, but wasn’t able to put up a suitable antenna that would enable me to get out more than a few blocks, so now I’m thinking about building a QRSS transmitter for 30M and perhaps also a long 2M Yagi so I can hear EME. Not much money here, but plenty of ideas and time. I may come back to the AM broadcast band Part 15 idea at some point.

    Let me know when you plan to do any QRP outings – I can at least give you a QSO so you know your gear’s working!

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