This information is edited from a repost of an acig.org forum post by mrdetonator:
http://www.secretprojects.co.uk/forum/index.php/topic,25.msg59.html#msg59
БСВ (BSV)
For high/medium altitudes and all-aspect intercepts, to engage targets flying higher than the Mig-23 (Hc > Hs).
The maximum antenna elevation us is 6º (ΔH switch). (Note: Hs = altitude of the Mig-23, Hc = target altitude)
БСВ-ΔH4 (BSV-delta H4)
For high/medium altitudes, rear-aspect intercepts, to engage targets flying lower than the Mig-23 on the earth background (LD/SD mode) (Hc < Hs).
The minimum antenna elevation -4º (ΔH switch).
Differs from БСВ by using half of the PRF.
БСВ-ΔH1 (BSV-delta H1)
For high/medium altitudes, rear-aspect intercepts, to engage targets flying lower than the Mig-23 on the earth background (LD/SD mode) (Hc < Hs).
Differs from BSV-ΔH4 by using the pulse width of 1 µsec (search, track).
The signal is further processed, filtered out in the “differential clutter filter” (DKP)
СМВ (SMV)
For medium/low altitudes and all-aspect intercepts, to engage targets flying higher than the Mig-23 (Hc > Hs).
Indicated range scale on SEI is 30km(search, track). The pulse width of ~1 µsec(search, track)
МВ (MV)
For engaging targets flying lower than the Mig-23 on the earth background (LD/SD mode) (Hc < Hs).
It`s used only for rear-aspect intercepts, pulse width ~1 µsec(search, track), Beam width in search 1,5°.
The МВ mode uses the „SDC with external coherence“ technique to compare Doppler shifts between the target and earth background.
The antenna scan zone is locked in azimuth and elevation.
БСВ-СЦ (BSV-SC)
For high/medium altitudes and all-aspect intercepts, to engage targets flying higher than the Mig-23 (Hc > Hs).
The radar mode exploits the same form of doppler processing of the received signal as in the МВ mode, but on the background of radio-reflective clouds.
The antenna scan zone isn`t locked as in the МВ mode.