Russian Meridian military communication satellite constellation monitoring continues. More operational info has been gleaned from long term monitoring of the transponders on ~484MHz. As you can see from this animated GIF there's a lot going on here. [thread]
First, the Meridian constellation uses the 484.25MHz slot for it's North American apogee. Where the spacecraft hover over North America for about 6 hours each. 
Second, Meridian 2 which was placed into the wrong orbit due to a final stage malfunction during launch occupies the 484MHz slot all to it self as it slips in and out of sync with the rest of the constellation.
Third, on UHF even at my latitude of almost 50 degrees north I can hear the Russian apogee on UHF. The attenuation from trees etc are not a severe as on higher bands and allow for analysis of the signal. 483.75MHz is in use on the Russian apogee.
Fourth, when Meridian 4 and 7 come on they appear to start transponder transmissions on the opposite apogee frequency. The image below shows Meridian 4 starting on Russian apogee frequency and switching to North American one a few minutes later. [sub thread]
Fifth, the sidereal locked mean motion of the satellites Meridian 4, 6 and 7 is clear in the animation. Indicating they are actively in the satellite constellation. Where Meridian 2 is clearly not drifting out of sync. Hence why it has it's own frequency for ease of management.
The behaviour of Meridian 4 and 7 is directly related to the X-band TTY beacon believed to transmit a space craft ID. Upon start up these spacecraft use the generic ID frame, but as the UHF transponder switches to proper apogee freq. The s/c ID becomes unique.
The image above shows the sequence of the X-band beacon for Meridian 4 on start up. It starts with a carrier, then sends a generic frame used by almost all active Meridian's upon start up, on UHF 484 the opposite apogee freq is used.
Once the s/c makes the switch to a unique frame used only by that particular spacecraft, the UHF transponder switches to its respective apogee frequency. The timing of this switch is not exact for both bands but is very closely related. The image here provides a frame summary.
Meridian 6 is an outlier that doesn't conform to these general observations. It simply jumps into the UHF apogee frequency and X-band unique frame ID upon start up. Note no opposite UHF transponder behaviour and absence of X-band start frame.
The fact that Meridian 6 doesn't seem to comply with constellation behaviour is interesting as it could be the reason why Meridian 9 appears to be targeting this orbital plane and slot in the constellation and not Meridian 4 which is a much old satellite.
Lastly, the Meridian 3 'GAP' is present on both apogees. launched into Meridian 3's orbital plane M8 has not demonstrated any operational behaviour on 278, 484MHz or X-band. Observations by @uhf_satcom have showed limited C-band activity from M8.
@KN4QGM developed the decoder to display these frames.
Here's a week long comparison of the active Meridian constellation satellites in their fixed planes and the behaviour of Meridian 2 which is outside the constellation yet active. As you can see its apogee drifts around and it doesn't have a fixed ground track.
