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oh7ug Equipment

Static Discharge from Antenna Can Do Damage to Your Gear.

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Snow This Winter we have got a lot of snow in Southern Finland. A couple of weeks ago we had nearly -20 C cold and it was snowing. When I  turned on my rigs, there was a lot of static noise on the bands making QSOing impossible. Suddenly I saw the linear amp power/swr meter needles to bump erratically. I guessed it was the static coming from the antenna and switched the antenna off by turning the tuner panel antenna selector switch to an empty position having the amplifier on - that was a mistake.

I started hearing a static discharge sparking every second or so within the tuner. I disconnected the coax from the tuner an saw sparking 1-2 times per second at the N-connector between the pin and  the barrel. Then I grounded the antenna and turned off all my gear.

Linear Amplifier SWR Meter ProblemNext day snowing had ceased, I turned the rigs on, everything looked right. I tuned on 80m and saw that the linear amp meters did not show correct values anymore. The power out was barely 200 W and reflected around 30W. However the Antenna tuner meter showed normal 500/0 W (out/reflected). The same for all bands. No changes to any tuner settings from previous were needed to tune to 1:1 SWR with 500-600 W out by the tuner meter. Also the (exciter) Icom power output and SWR were as normal.

I guessed that the static arcing inside the tuner antenna switch had propagated a transient to the linear amplifier and somehow damaged the SWR circuitry.

Furher study with an e-mail and a call to Ameritron support suggested that the Germanium diodes at the amplifier SWR circuitry may be damaged. That was cured by replacing the diodes, but needed some adjustment to get the meters to show correctly again. More about that in a later article.ALS-600X Power/SWR Meter Board Repair I constructed a simple static charge bleeder inside a coax connector, and installed it at the antenna coax end using a t-connector. I also added a grounding switch to the antenna.

Lesson learned: Have a static charge bleeder installed to the antenna to prevent this happening again - and try to avoid working when it is snowing and cold..note that a static bleeder is not a prevention against lightning damage.Antenna Static Bleeder
Last Updated on Friday, 05 February 2010 13:14  

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