Other sources of hum sidebands...

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VK2XV's picture
Last seen: 5 years 2 hours ago
Joined: 2008/12/15 - 19:48
Other sources of hum sidebands...

G'day All,

In the interests of seeking to further understand some of the funnies we see on WSPR the following pictures might be of interest.

While the recent discussion has been resolved as being a problem at the transmitting station (thanks Tim and Paul), this should not be taken that the comments by Tim and others about problems at the receiver also causing multiple decodes are not valuable. Have a look at these pictures taken after Tim's signal had been fixed up...


Note at 07:04 Tim's fixed signal - strong and clean as a whisker (the two 'sidebands' close are not spurii from Tim, but legit signals from other stations). Note also the other strong station at 07:10 (ZL2FT ?), also strong and clean as a whisker.

At 07:12 to 07:26 on this picture I experienced a high level of power line interference (even put lines across the analogue TV picture). Note that this produces 50Hz 'sidebands' on ALL signals and is clearly identified by the continuous lines.

Please don't jump and say AHA!!! - as these lines were not present on my previous posts....(and the 'sidebands' were not on other stations' signals).

The second picture shows everything going back to normal...


So, even though in this recent case with Tim's signal it clearly was on the TX side, what Tim and others have to say regarding interference on the receive side causing double decodes is correct - it just wasn't in Tim's case.

So the clue is that if appears on only one signal it is likely to be on the TX side, while if it appears on ALL signals it is likely to be on the RX side.

Now for a bit of paranoia - note that the interference starts and stops exactly on the 2 minute WSPR period ?????

Hope this is a help.

Steve VK2SRO