New Station Aerials and Noise Chasing
#5
Installed ...

    The nice and compact 38 cm 20 turn loops attached to the ridge board by a home brew bearing so they can be easily rotated, locked off or removed.

    The bearing is a couple of saddle clips and 20 mm dia plastic electrical conduit and a length of 16 mm steel tube cross drilled each end. One cross drilling has pin that rests on the top of the conduit, the other takes a bolt to hold the antenna frame into the bearing. The conduit has a couple of slots cut at the lower end enabling a jubilee clip to tighten it onto the steel tube locking it in place. To stop the conduit rotating in the saddle clips it is glued to them.

    The controller mounted in a "Really Useful Box" A4 paper storage box, plenty of space and translucent so the LEDs can be seen. Couple of L brackets stop it sliding off the purlin. Power is via 802.3af PoE full details in the PoE recommendations for System Blue thread.

    Raw input, no LP filtering, equal gains.

Using a Frequency Analyser app on a tablet showed spot carriers on 16.4 Noviken, Norway; 18.3 Rosnay, France (moves about, also uses 21.7 and 22.6); 19.6 Anthorn, England; 22.1 Skelton, England. Noviken (1000 miles) and Rosnay (528 miles) are far enough away not to be a problem. Skelton (18 miles) must have been off a few days ago as you can't miss it now and it gives a nice beat pattern with Anthorn (38 miles).  Anthorn is tremendous signal but can be almost eliminated on one loop by aiming its null in that direction. Unfortunately Skelton then comes in pretty strong. On the plus side they are only 27 degrees apart and the noise floor figures from the controller's web interface was the best way to find a compromise position.

    Hard filtering, LP filtering set to give equal noise floors and thus equal gains.

 This loop is on Ch 1 and will have it's best pick up almost exactly N-S but only by chance it's alignment is dictated by Anthorn and Skelton... Of course the now E-W (Ch 2) loop gets fairly hefty doses of those stations. Setting the LP filter to around 17 kHz brings the noise floor down to that of the N-S loop at the expense of a lot of information above the cut-off frequency. The horizontal loop (Ch3) is less affected by Anthorn/Skelton but also doesn't pick up as many strikes as the two vertical loops.

    Soft filtering, LP filters set to remove as little as possible and have equal but high noise floors. The 54 kHz LP filter is to remove the 60 kHz MSF time standard transmission that also comes from Anthorn.

There is plenty of scope for more playing between "hard" LP filtering or "soft" LP filtering with or without equal gains. As can be seen the hard filtering does produce rather rounded and slow signals compared to the soft filtering.

Then there is the E field...
Cheers
Dave.

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RE: New Station Aerials and Noise Chasing - by allsorts - 2016-10-13, 13:18



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