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FM ranging on the last day of analog teevee
Friday, June 12 2009
Gretchen and the dogs were in Willow all day preparing food with a vegan celebrity, so when I went out today on a mission to get supplies, I was all by myself. I found it a little strange to be driving around without two half-asleep dogs in the back seat.
Before I left, I switched on my FM transmitter so I could listen to its signal on the drive to P&T Surplus (41.915176N, 73.990463W). I was broadcasting at 87.9 MHz, which is not the usual frequency I use. I was using it because it doesn't lie outside my car radio's FM spectrum. Also, anyone complaining about interruptions in their licensed radio service as the result of my broadcasts would almost certainly be told they needed to buy a digital television tuner (today happened to be the last day of American analog television, and 87.9 MHz is within television Channel 6, one of the channels being abandoned). In terms of broadcast content, I'd picked Guided by Voice's Alien Lanes because I know it extremely well and because none of its songs are likely to ever be played on any local radio station. If a few notes from that album managed to break through the static hiss (both of the radio environment and of the low-fi technique with which it was recorded), I'd know I was still receiving a signal. As I started my drive, the signal dropped away rapidly about a quarter mile down Dug Hill Road, although it persisted in a degraded form all the way to Hurley Mountain Road, over a mile away. The signal improved somewhat as I headed north on Hurley Mountain Road, and improved dramatically on Wynkoop as the blocking effects of the mountainous terrain gave way to the Esopus plain. Still, the signal was pretty weak by the time I got to the Hurley Mountain Inn (over two miles from home). As a lark, I drove south down Old Route 209 through the neighborhood of Riverside Park and at some point I must have come out of the shadow of the highlands east of Dug Hill Road, because suddenly the signal was perfectly clear. At this point (41.914629N, 74.077635W) I was precisely two miles from home (as a crow might fly).
I took Old Route 209 to its end and then headed north on actual 209, the big road. The signal improved briefly and then faded as I approached Old Hurley. I reached Old Hurley via Russell Road and Schoolhouse Road (a route I'd never taken before) and from there I headed southeast via Zandhoek Road (which eventually turns into Dewitt Mills Road). Zandhoek gradually climbs a hill rising from the Esopus plain, and the higher I climbed, the stronger the signal became. It started to fade as I crested the hill, but it came back powerfully at the intersection
with Lucas Avenue
(41.91155N, 74.0558W), exactly three miles from home. The signal quickly faded from there, but I could still hear snatches of it beyond the Thruway. It died definitively once I'd crossed Route 32, 4.25 miles from home (41.887367N, 74.043624W) and increasingly below the broadcast horizon of my transmitter. From there I left my radio tuned to this otherwise vacant frequency, listening for pirate radio stations. Somewhat surprisingly, I didn't encounter any.
I had to say I was impressed with the results. Today's broadcasting had come from the J-pole, which I'd been able to accurately tune with a SWR meter once I'd gone and bought the proper PL-259 connectors from Radio Shack (the only retail source outside the internet; not even P&T Surplus had them). Satisfied with my J-pole, this evening I mounted it more permanently to the northwest corner of the solar deck. This put it more than ten feet higher than it was during today's earlier test drive, so I went on a second local test drive, this time bicycling northwestward on Dug Hill Road and using a weaker Walkman-style pocket FM radio. There are no terrain benefits in that direction, so the signal dies out much more quickly. But I was still receiving respectable transmissions at Reichel Road (41.933N, 74.1132W), a half mile away.
While I was out bicycling in the dark on Dug Hill Road, Gretchen was driving home from Willow and she recognized me, a bare-torsoed cyclist in the darkness, and she stopped and we chatted.
For linking purposes this article's URL is:
http://asecular.com/blog.php?090612 feedback
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