Radio Richmond – Testing Begins!

This past weekend I installed one of the Hamilton Rangemaster AM1000 transmitters on the roof of my house. The installation meets the requirements for power, antenna, and ground lead length making it a legal unlicensed station per the Part 15.219 rules.

I have good news and bad news.

The bad news first – nighttime coverage in unimpressive. After just a couple of blocks there is noticeable interference from distant stations on 1700 khz. This was not a total surprise however, I expected XEPE “San Diego” (actually Northern Mexico) to give me some trouble. And of course, the noise floor is pretty high in spots around here.

The worst noise problems are near overhead MUNI wires and near businesses. These noise problems are prevalent day and night.

The good news: Daytime coverage is considerably better.

I did an afternoon “range check” walk around the neighborhood with a portable radio. For those keeping score, it was a Grundig Yacht Boy 400. This isn’t most sensitive radio in the AM band but it’s OK. Most car radios are better in the AM broadcast band. Shown below is the “coverage area”.

Radio Richmond Daytime Pattern

Area where Radio Richmond can be heard comfortably with possibly some careful orienting of your radio.

I put it in quotes because it is possible to pick up the signal outside these boundaries. The marked area shows where the station could be heard with comfortable listening. In some spots you’d have to re-orient the radio for best reception but the signal was not hard to hear.

The area covered by the daytime pattern is approximately 0.2 square miles. That doesn’t sound like much, but given the population density of the Richmond District, this coverage represents a potential audience of about 5600 of my closest neighbors. Not too shabby!

I think I could achieve better coverage with a better ground. The short ground lead connects to the steel pipe the AM1000 is mounted on. However, I don’t know if there is electrical continuity with earth. And even if it did connect to “earth”  the soil around these parts is basically just sand. It’s not the good conductive soil that makes AM radio signals sing.

My first goal is full weekend, daytime programming.  I’ll publish a schedule when I can reliably meet that programming threshold.

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5 comments on “Radio Richmond – Testing Begins!

  1. RE: “I think I could better coverage if I had better ground. The short ground lead connects to the steel pipe the AM1000 is mounted on. However, I don’t know if there is electrical continuity with earth.”

    Sounds like you want to set up a good, legal Part 15 AM system, which is great. Here is some info that isn’t real obvious, but could be important in doing that.

    Some manufacturers of FCC-certified AM transmitters suggest mounting them “high” above the earth — maybe 25 to 35 feet, if possible.

    But if a Part 15 AM transmitter with its attached ~3-meter whip is installed at the top of a steel pipe, and the ground terminal of the transmitter is connected to that steel pipe, then the antenna will consist of an off-center fed dipole whose length might exceed the total 3-m radiating length permitted by FCC ¶15.219(b), depending on the length of that pipe

    That steel pipe will add to the radiating length of the 3-m whip, whether or not the pipe is grounded at its base.

    There was some discussion about this in a thread at http://www.radiodiscussions.com/showthread.php?649941-Willful-vs-Unintentional-Non-compliance-with-FCC-%A715-219

    Maybe just something to consider as you get your system operational.

  2. Mr. Fry makes a valid point. You might want to test/consider ground mounting the transmitter a few inches above the ground and then fan out a radial system from the ground lug of the transmitter. I seen and made comments about how long the wires for the radial system should be. I have always and maybe incorrectly so, thought the length should be slightly longer than the antenna is high. So maybe 12 to 15 feet, and a minimum 16 wires arranged like spokes of a wheel.

    Also at night sky-wave propagation is what making your signal sound weak because of signal pouring in. Hope this helps.

  3. Thanks for your comment. I understand the RF issue you describe of mounting on a steel pipe with the ground lead attached to same acting as an OCFD. There are couple of facts which I think mitigate the issue in this installation. First, the plumbing pipe to which the transmitter is mounted and “grounded” is not standing in free space, it is embedded in a multi-storey building. Any radiation from this pipe is right into the structure of the building and likely attenuated greatly. Second, (and an inspector might not care about this) but this location is the only one available. There is no opportunity on this property to mount the transmitter near the ground with a short lead to earth ground.

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