20 Jun 2014

WSPR non-reciprosity?

Sometimes my software give some stations on WSPR quite decent reports as the signal decodes well. In these situations I am surprised not to be decoded myself as, even allowing for power difference, I should still be well above -30dB S/N. The reasons could be many:
  • The other station is just on TX only
  • The other station has a very high noise floor
  • The other station has a deaf RX.
Apart from these, I cannot think why I should not be copied.


G6AVK_QRPp said...

Hi Roger,
Just to let you know, the reason you get few spots from me is due to high noise level beaming in your direction at least (S4). I can normally get nice decodes of you when I beam east and the noise floor drops to a decent level, as does the aircraft scatter.

73 Colin - G6AVK

David (G0LRD) said...

Other possible causes:
- You are not putting out the power you think you are. I wonder if this might explain the non-reciprocity between us that we sometimes see.
- Aircraft Doppler might be hitting you worse than others owing to your proximity to flight paths from Stansted. Certainly this evening a lot of your 6m signals were quite badly disrupted.

Cheers, David G0LRD

Paul Stam said...

I had it once before, when I put down the ALC | audio input, suddenly I got reports. 73 Paul

David (G0LRD) said...

Roger's WSPR signals are very clean at my receiver so I don't think there is an ALC problem.

I thought of another possible reason for asymmetry: The frequency stability changing during receive and transmit. Most rigs are very stable during receive, but the short-term heat generation of transmit tends to cause drift on non-TCXO rigs. I think your rig Roger does this a little. Some, but certainly not all, of your transmissions show a slight slant and -1 drift reading.

Bob G3WKW said...

Also being off frequency at either end can lose band edges. I think you are reporting CN8LI about 25Hz lower than he is putting him right on band edge according to you. I have him 25Hz in. I used to find the most drift on receive in the cycle after a transmission. FT897 with cooling fans good for 100 watts permanently on on Tx at 5 watts out!It caused me to miss a few on 28MHz, several on 50MHz and completely useless at 144MHz. I now have phaselock to an external OCXO. Also previously I could not complete a JT9 QSO on 28MHz

Roger G3XBM said...

Usually I am giving other stations better reports than they give me. Appreciate I may be off in frequency a bit, but that is NOT the reason Bob. CN8LI is just above lower band edge with me currently.

G0LRD has just frequency calibrated one of my transmissions, so I should be able to offset a tad.