Friday 24 May 2013

W5HN 902/1296MHz Beacons

Last Friday I went with WA5TKU and AA5C to the TWU dormitory roof to maintain the W5HN beacons on 902 and 1296MHz. THe frequency and power had not been set/measured in a couple of years so the visit was overdue.
The 902.370MHz beacon was still producing 10W and was within 200Hz of its nominal frequency, not bad for an unovened crystal. The 1296.370MHz beacon was down at 1296,349MHz and had low power output. 2mW in fact, 30dB down on nominal. I tuned up the oscillator chain and got 2watts back, but it went again. The decision was made to remove the beacons and take them home for maintenance on test gear. While there AA5C removed his old microwave beacon package

The 902/1296 beacon was taken to Bobs, WA5YWC, as he was the closest available spectrum analyser. Investigation revealed that one of the airwound coils had moved and broken the connecting PCB track. Resoldering it produced a stable 3W. Both beacons were left at Bobs on soak test over the weekend.

On Monday morning the power was still the same, just needed to set the receiver. The beacon was taken to W5LUA's shack as he has receivers on both bands. Just in case the 1296 beacon's crystal was bad I dropped by the storage unit and retrieved the spare crystal. Installing the crystal we got back to 1296.380MHz (the original frequency from 2000) and the FSK was still good. The 902 beacon was moved to the matching 902.380MHz frequency

On Wednesday Wes and I  returned to the site and reinstalled the beacons, We also commisioned the Z3801 GPS locked reference which will be used as part of the upcoming 50MHz 6m beacon. We also investigated methods to integrate a 1W 10GHz amplifier into the 2/3/5/10GHz roof mounted beacon package

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