Dave Richards AA7EE

May 27, 2010

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.

If you have any interest in this, I thoroughly recommend Hobby Broadcaster (link opens in a new window) – the site for Part 15 AM and FM broadcasters.  It’s run by broadcast engineer Bill DeFelice who also actively participates in and moderates a great set of forums. There are other sites that deal with Part 15 broadcasting,  but Bill really sets the tone in his forums with helpful friendly comments and advice as well as equipment reviews.  He also posts his online finds for those who are looking for deals on good affordable gear for their stations.

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 🙂

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May 25, 2010

I Finally Made It!

I finally made it – into print in a national publication, that is. It’s funny really – in my former career as a DJ/announcer/voice-over person, my voice has been heard on radio and TV in New York, Chicago, Los Angeles, London, San Francisco, Boston, Columbus and a bunch of other cities as well as on in-flight audio on airplanes.  I don’t think I’ve ever been mentioned in a national publication though and although it was a fairly brief mention, I got a real kick from seeing the Fort Tuthill 80 I made on the contents page of the June issue of CQ magazine:

This image belongs to CQ Magazine - hope you guys don't mind me using it.

That’s my Tut 80! I get a bit more of a mention on page 72, as does this blog (which explains the sharp spike in page views).  Thank you to Cam Hartford N6GA for the mention – a hearty welcome and congratulations on a fine first QRP column for CQ magazine.

May 24, 2010

Telescopic Fiberglass Masts – A Must for Every Ham

Well, I’ve been settled into my new place for a while now.  I’ve done a little bit of amateur radio (though not much) and embarked on a new project which, although not a ham radio project, is still radio related.  More on that in a subsequent post.

My new digs are in a 100 year-old house with an easy-going landlord.  The landlord part is key, as I have already erected one antenna, and have plans for one or two more.  I’ve often noticed that a shake-up in my lifestyle will cause a change in the interests I pursue, and this move was no exception.  Even though I felt that ham radio was about to take second place to something else, I still wanted to put up some kind of antenna for the HF bands.  A quick scout around the internet led me to the website of The Mast Co (link opens in a new window) with a great selection of telescopic fiberglass poles. The 32 foot heavy duty model seemed ideal for mounting on my balcony and attaching some kind of vertical to  so a few mouse-clicks, a few days of waiting, and an hour fiddling around on the balcony led me to this:

This is the pole in it’s retracted position with the top cap in place. I strapped it to the balcony with large plastic ties that I got from Home Depot. You can see that I’ve used cut-up pieces of old bicycle inner tube to protect the paint finish on the pole from being chafed by the ties and to cushion the pole against the faucet.  This is a first floor balcony at about 11 feet above ground, so the top of the pole is about 43 feet above ground.  The top of the pole is a little higher than the sloping roof of the house and the house is at the top of a small hill (Oakland is quite hilly), which works out quite well.  Anything sitting at the top of the pole (like an antenna) will have a good view of the east bay.

This doesn’t really show you much, but here’s a shot taken from ground level of the pole fully extended:

I ran a length of 26 gauge magnet wire from my window to the top of the pole and then down again to the other end of the balcony – a total length of about 75 feet. As soon as the wire gets through the window into my room it connects to a 4:1 balun after which about 15 feet of RG8 goes to the Z11 tuner and then the radio. I draped about 40 feet of wire around the perimeter of the balcony as a counterpoise and what do you know – it tunes up on all HF bands 80 thru 10.

Of course, just because an antenna tunes up doesn’t mean that it radiates well. To this date I haven’t done extensive testing, only having had 4 or 5 QSO’s. The furthest was on 40M (CW of course) with AD5WI in Pea Ridge, AR – a distance of 1547 miles. He gave my 5 watts a 599, so I might be on to something with this antenna.

The great thing about the telescopic pole is that it is very much a multi-purpose item.   According to Henry K4TMC, the proprietor of The Mast Co, this pole can support a lightweight HF dipole fed by RG8X (lightweight meaning made out of fairly light gauge wire with no traps).  You can also support a small beam if you attach it part-way down the mast.  This is a great all-purpose experimental antenna mast. To extend the pole, you just pull out the sections and twist them a little so that they stay extended – they hold together by friction.  It retracts just as easily. My mast has been up continuously for 3 weeks now with no problems. The poles are made to hold windsocks, and this one seems to handle wind quite well, flexing when it gets gusty, but staying up.

There are so many uses I can think of for a lightweight extending pole like this. Because it’s lightweight (5lbs for the heavy duty 32 foot pole), it doesn’t take a whole lot to support it. This particular one will most likely stay on my balcony and be used to support a variety of different antennas.  The next plan is to mount a vertical antenna for the MURS band at the top and use it to test the coverage of a couple of MURS handhelds that will be arriving here in a few days.  My friend lives a mile away and isn’t licensed, so we decided to play around with MURS as a way of keeping in touch.

If you have any questions about this mast, please don’t hesitate to ask.  I’m quite enamored with it. Henry mentions that this particular pole isn’t being made any more so when he runs out of his current stock, that’s it. Think what you could do with a lightweight and very portable 32 foot telescoping mast………

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