first, I thought of this
signal as being the long-time unidentified NDB 'P' on 474 kHz...
...but half a day later, I
found it to be the russian naval station instead, transmitting
telegraphy, the 'P', and radioteletype one after another (as
it was transmitted, it's not a medley!)
(both: rb, 2008, in the baltic area).
So this 'P' is just a marker for the frequency.
look at this PPC from the collection of Patrick Robic (2009)
------------------------------------------------------------
Callsigns:
P
RMP
UNU3
Frequencies Morse Telegraphy:
474
583
3167
3181
3208
3212
3234
3264
3291
3594.8
3649
3699.5
3772
3807
3837
4031
4043
4051
4078
4222
4302
4475.9
4547.9
4558
4605
4828
4899
5111
5154
5213
5305.8
5394
5738
5862
5881
6328.5
6330
6496.4
6500
6728.3
6873
6909
6936
6968
6972
7033.8
7039
7632
7640
7935
7972
8471
8495
8680
9082
9373
10118
10872
10888
10908
11132
11418
12833
13528
13633
13635.8
15688
16016
16176
16332
17015.8
18720
18858
20488
20991.8
Frequencies Radioteletype:
474
3167
3208
3592
3807
Systems used:
50 Bd
75 Bd
?-50 Bd