Friday, 3 May 2013

Remote operation for the IARU contest

In a bid to get onto at least 23cm during the upcoming contest this weekend I have 'bodged' together a system that allows me to connect the TS2000X over nearly 60m of coax to the 2x44 element yagi array and rotate the antenna from the new indoor shack.

I am using LogMeIN to access the outdoor shack desktop running PSTRotor lite and connected via an ERC controller to the Yaesu G1000DXC. This works very well.

I am keying the long single 23cm coax change over relay via the 'small' FSJ1-50 coax. Always wary of damage to the TS2000X I decided not to directly connect the open collector 23cm linear keying line to the coax. As the run is quite long there is a real danger of a significant voltage difference across the cable and subsequent damage to the keying transistor. Instead I have used a PNP bipolar to switch a small relay and the relay contact then provides a fully isolated keying line.

On receive I found it necessary to use an additional in-line low noise preamp in the outside shack to overcome some of the receive line losses. A VLNA at masthead does not provide sufficient gain to overcome the high line loss.
Similarly I needed to use my 2xM57762 driver amplifier to raise the maximum 2W I could get from the TS2000X, after the long run of FSJ4-50, to 15W to drive the MKU13200 amplifier. I have used a 5dB attenuator on the driver amplifier input to limit the output to 15W and therefore not damage the MKU13200A. The relay derived keying earth switches both amplifiers to transmit and changes the single coax feed relay from the TS2000X over from receive to transmit.

With this arrangement I can hear lots of beacons out to the east and generate over 200W on transmit.

View of the indoor shack operating position.

In order to monitor the outdoor shack, whilst all this setting up was being done, I looked around for a wireless web cam. Not being able to find one locally I looked at what could be done with my mobile phone. The free app ipCam turns my iPhone 4S into a perfectly good wireless web cam operating over the home WiFi network and by logging into the indicated web page ( on the app screen) on my iPad I could watch what was going on in the outdoor shack including checking the driver and linear were keying up, showing me the Bird meter indication ( no easy way to remotely reverse the slug to check SWR! though!).

Roll on the contest!

73 de Sam

The MKU13200A power amplifier and Bird in-line indicator

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