Triple spots

That happŠµned during last WSPR activity period (12 August) on 40m band. Once I've noticed the following sequence:

2009-08-12 22:14 UT2UZ 7.040190 -20 0 KO50cr 2 VK8CH PH57 11836 90
2009-08-12 22:14 UT2UZ 7.040147 -8 0 KO50cr 2 VK8CH PH57 11836 90
2009-08-12 22:14 UT2UZ 7.040104 -20 0 KO50cr 2 VK8CH PH57 11836 90

The first idea, came into brains, was that something wrong is with my equipment.

However, more triple sequences were seen that day:

2009-08-12 22:26 DH5RAE 7.040051 -24 0 JN68pv 5 VK8CH PH57 13063 77
2009-08-12 22:26 DH5RAE 7.040094 -13 0 JN68pv 5 VK8CH PH57 13063 77
2009-08-12 22:26 DH5RAE 7.040137 -23 0 JN68pv 5 VK8CH PH57 13063 77

2009-08-12 22:24 VK6BN 7.040099 -25 0 OF88ac 10 VK8CH PH57 2639 39
2009-08-12 22:24 VK6BN 7.040142 -14 0 OF88ac 10 VK8CH PH57 2639 39
2009-08-12 22:24 VK6BN 7.040185 -25 0 OF88ac 10 VK8CH PH57 2639 39

Looks like small parasite modulation.

The frequency difference is equal to 43 Hz in all the cases. I have no idea, what does that number correspond to?