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MFJ-868 SWR/Wattmeter
Jeff Liebermann wrote:
Actually, I lied. Two of those that I've repaired were attached to antennas. However, the locations are not conducive to having nearby transmitters. One is in the deep dark forest, where the nearest neighbor, much less nearest possible RF source, is about 1/2 mile away. The other lives in a nearby rural area. No forest, but also no nearby transmitters. However, it's possible that the transmitter in question may have been one owned by the hams in question. Keying a nearby HT or mobile might have been the culprit. Dunno. Attach a wattmeter to any VHF antenna on a mountain top with FM/TV transmitters, and you'll get a watt or more of RF indicated. Nice way to blow up the instrument. At this point, I don't know what is causing the failures. However, I do know what to do. Add a dummy load and buy some more diodes. If you do not short the center conductor (on the DUT) to ground immediately before connecting to the analyzer you risk discharging a large "capacitor" directly into the instrument. If I am at an antenna farm I am grounding all my test gear prior to putting it into service. There is a Ground lug on the 259B right next to the SO239. They provide a Type N adaptor with a new meter, too, BTW. |
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