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Winter 2004 Issue |
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FM
Life on
900 MHz By Gary Pearce,* KN4AQ |
The Johnson mobile/base radio. (All photos courtesy Vester Scott, N8EKA) |
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Return with me now to those thrilling days of yesteryear. I’m talking about the 1960s, before anyone started making ham gear specifically for 2 meter FM. In those days, hams used converted commercial or public-safety radios from companies such as Motorola, GE, Johnson, RCA, and a few others. The radios were big, heavy, and full of tubes. In those pre-synthesizer days we re-crystalled the radios for a few local repeaters, tuned them up into the ham band, and had a ball. A four-channel radio was a luxury, but in most towns there weren’t four repeaters to choose from anyway. Those days live again, after a fashion, on 900 MHz. If you think 220 is a neglected band, pity the poor 900 op! There are now several good, brand-new 220 mobile radios to choose from, and a multi-band handheld with full power, at reasonable prices. However, nobody builds a 900-MHz ham radio, and the hams on 900 wouldn’t have it any other way—at least so I’ve heard. Like 2 meters in the 1960s, if you want to get on 900 FM (902–928 MHz, actually), you’ll be using radios designed for commercial use. Yes, the band’s been around for business use long enough that there is a fair amount of used, surplus equipment. You won’t find any tube rigs, though. It’s mostly small, under-dash mobiles and handhelds. The availability has spurred some interest and a few repeaters in the ham community. Most of the information in this report came from an article in the August 2003 SERA (the SouthEastern Repeater Association) Repeater Journal entitled “The 900 Band: There’s still time to do it right!” by Vester Scott, N8EKA. Vester is an assistant director for SERA from Georgia, and a big 900-MHz enthusiast. His point in the column is that the 900-MHz band could benefit from some planning and foresight that didn’t go into band-planning for 2 meters (or any of the other FM bands). We’ll get to that in a minute, but first, what’s 900 MHz like? Vester says it’s pretty similar to 440 MHz in terms of local propagation. A lot of hams actually have some experience in nearby spectrum—800-MHz cell phones. That and monitoring 800-MHz trunked public-safety radio around here tell me that you get the expected faster mobile flutter on noisy signals (just as 440 is faster than 2 meters). I’d expect simplex to be pretty pathetic. However, if you can get a repeater up in the air with a good antenna and feedline, it’s going to work well.
We are not alone on 900, though. There are
other two-way systems, pagers, data, and some Part-15 stuff such as
cordless phones and baby monitors to contend with. Vester says it hasn’t
been much of a problem. Ham radio is a secondary service there. We’re a
notch above the baby monitors, but below everyone else, including the
boxes that help the police find your stolen car. Click here to return to this month's highlights Click here to subscribe to VHF and read more about FM _________________ © Copyright 2004, CQ Communications, Inc. All rights reserved. This material may not be reproduced or republished, including posting to a website, in part or in whole, by any means, without the express written permission of the publisher, CQ Communications, Inc. Hyperlinks to this page are permitted.
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