26 March 2016

SVO SiTOR-B: a curious feature

SVO Olympia Radio (formerly SVA Athinai Radio) belongs to Hellenic Telecommunication Organization, S.A. (OTE) and is a telecommunications network that serves the needs of maritime security sector as well as the needs of commercial maritime communications  across the world.
At a first glance, its SiTOR-B broadcasts comply the standard 100Bd/170Hz that is common for such transmissions (pic.1) 

pic. 1
But looking closely at the signal there is a curious feature of the Sitor transmitter which is  evident in the oscillograms of the WF module (pic.2,3)

pic. 2
pic. 3
It is not clear what causes such behavior, if it's a requested feature or a transmitter "sign", anyway is present only in the Greek SVO SiTOR-B and in all their SiTOR-B bands (8, 12, 16 and 22 MHz/USB). 

update (from my Fb page):
Reed Gaede Ha! It's clearly a harmonic resonance in the exciter, modulator, or PA. Common flaw/issue in tank-tuned tube PAs, less so in broadband solid-state units. Their engineering department is slacking.