My bargain eBay W-4 arrived over the weekend, but I didn't get a chance to try it out until today. Scratched up case, but otherwise intact, it looks like it has seen life and then sat on a shelf for a while.
Testing with the TR-7 and a Bird GigaHertz dummy load showed that it agreed within 10 or so watts with the internal wattmeter and with my HyGain 421B (hardly a lab reference) from 28 MHz down through 14 MHz. But when I got down to 7 MHz and below, all hell broke loose. I was getting forward power readings of from 500 Watts to 2000+ Watts, depending on the band, with anomalous reflected readings as well. Both the internal TR-7 meter and the HyGain meter showed nothing unusual. I have NEVER seen a wattmeter act like this. Having nothing to lose at this point, I carefully opened the sensor box for inspection. What I found was a 2.2 uF capacitor in series with a small inductor, soldered from the anode (the RF side!) of D1 in the forward power circuit to ground. I removed it immediatly and normal operation was restored on all bands, although it appears the meter needs calibration of at least the null capacitor. My best guess is that someone attempted to install a quasi-peak reading mod and screwed up. The meter was subsequently set on a shelf and left to collect dust when it started acting strangely. Ya learn something new every day. Seems like I've been getting all the strange ones lately. 73 -Jim -- Ham Radio NU0C Lincoln, Nebraska, U.S.S.A. TR7/RV7/R7A/L7, TR6/RV6, T4XC/R4C/L4B, NCL2000, SB104A, R390A, GT550A/RV550A, HyGain 3750, IBM PS/2 - all vintage, all the time! "Give a man a URL, and he will learn for an hour; teach him to Google, and he will learn for a lifetime." HyGain 3750 User's Group - http://groups.yahoo.com/group/HyGain_3750/ http://radiojim.exofire.net http://incolor.inetnebr.com/jshorney http://www.nebraskaghosts.org _______________________________________________ Drakelist mailing list Drakelist@zerobeat.net http://mailman.zerobeat.net/mailman/listinfo/drakelist
