21 Jun 2014

WSPR non-reciprosity? More

As an experiment, I have reduced my TX so that the FT817 ALC is now barely moving. This is a bit lower than the usual setting. TX power as indicated on the FT817's meter is unchanged.

I'll monitor to see if reciprocity. is affected. I suspect not. The ALC was set at a lower setting at 1038z.


Chris M6CRD said...

Hi Roger. There's some interesting reading on area noise floor figures in the UTU document "Rec. ITU-R P.372-8" https://www.itu.int/rec/R-REC-P.372-8-200304-S/en (page 15+)
My money would be on those remote station's receiving conditions, but I understand your curiosity.
73. You're doing well.

Anonymous said...

P372-8 has very out of date man-made noise data from the 1970's. Since that time we have gone from hardly a PC in sight to many per household, Plasma TV's and very large numbers of SMPSU's ( almost in every appliance or in it's charger) Wall warts are now SMPSU's and much more numerous due to rechargeable tools, phones, toothbrushes, cameras and other toys for all ages.

We now have ADSL on phone lines that leaks noise, data over power devices and the hundreds of millions of LENG "low energy" bulb ( Light Emitting Noise Generator). All of these devices produce noise, some much more than others. Power supply switching speeds have moved up dramatically into the MHz range as people want smaller lighter cheaper....

From no data devices we have moved to many per household, clock rates are now GHz on chip with very fast edges on interconnects that are not always fully screened.

It is interesting to do your own survey, This evening we had 2 TV's, 5 PC's, 1 ADSL, 5 warts a charging and around 20 LENG's running so that's around 35 free running switchers in one home. That is not a worst case either.

Four decades ago you did tune "low to high across two" and you did not hear many carriers. Try it today and you might get 40 or more "carriers" in 2 MHz. But noise is not just 144-6MHz, that's also across all of the HF and VHF spectrum too.

So anyone using P372-8 for planning in an urban region is not best served. However it could be a very large task to try to quantify current noise levels.
This is certainly complicated by the way that time of day and other events- such as World Cup Football- change use patterns.

So if you do live on top of a little hill and your local noise is blissfully low think yourself very fortunate.