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Thursday, 22 December 2016

Noise Cancellation

Perhaps for those with a want to try and homebrew stuff... ok the devices are a bit older than those in the LZ1AQ active antenna setup
or a more recent derivation:

Along with the hint (think it was Clive? GM3POI) you make sure you isolate the TX antenna on RX so you do not  add noise from that source.

At Cornwall QTH, used 1m copper pipe loop made from section of LDF-450 with a broadcast cap across the gap, adjust for maximum noise (odd you actually want to peak the noise!). Usually the noise is largest when broad side to the loop too so you can DF it a bit too. I use J310 as the FET not the MPF102 as they were not available at the time.

I found worked better for point noise sources not broad 'all around' noise. I was chasing contacts on 80m at the time and couldn't hear the signals for the noise. BTW I am taking similar to E5 as there are local 80m fun and games.

Interesting section on LZ1AQ site where he uses SDR/Softrocks so don't forget to check out the links he gives too.

1 comment:

M1KTA said...

I'll post images when I can but I made up all the induictors in mine using T37 and T50 -6 and -61 material. The dual cap was a twin 500pF and had a 4:1 reduction drive, the 500ohm gain pot I used a multiturn pot. The combination means you have amazing ability to adjust the phase and amplitude of any noise. I found the loop works best if you have 'tuned' it for maximum noise too. I have thought about adding a 472KHz section and a special multiturn RX loop.