- 27 December 2005
- Reaction score
Image from PVO museum- allegedly an R-27R seeker
Who told you that is a SARH seeker?What business does any SARH seeker have, operating in "transmit" mode?
mrdetonator said:I think it wouldn`t work when all four antennas were passive. There has to be at least one transmitter on the board. The phase mono-pulse principle assumes that you have transmitter/receiver on the same place. If the aircraft radar was used for illuminating the target, those four antennas on the missile would receive "incorrect" phase signals to track the target.
crossiathh said:Regarding SARH:
you have a fifth receiver directed backwards receiving the "original" signal from the aircraft's radar. This signal was used as reference to compare the phase, enabling the extraction of the doppler shift.
Dilbert said:... I always thought it was used mainly for Doppler comparison and shoot-down capability, not for monopulse ... They are absent on R-27T, which is one way that we know that the heat-seeker doesn't have a datalink.
crossiathh said:Regarding SARH: Talking about the predecessor (R-23R/R-24R), also having a mono-pulse seeker with four receivers in the antenna
mrdetonator said:In case of the R-27 I wouldn`t dare that it uses monopulse homing seeker, active or passive one.
But the R-23R SARH seeker uses the continual wave(CW) beam provided by the KNP transmitter of the Sapfir-23E radar. AFAIK only the Sapfir radar itself uses a monopulse system to track target in space, but when the missile has to be prepared for launch, the radar switches to CW.
How would you call the R-23R seeker then, a mono-pulse continual wave?
Also please explain to me why would a missile seeker need doppler for homing on to a low-flying target or better, why is doppler needed for missile homing? The only one application for doppler on SAHR missiles I see in the radio proximity fuse. It compares the frequencies of the outgoing to the incoming waves and uses the doppler to determine the range to the target.
I thought the missile homing principle depends on shooter`s radar. The Sparrow is to be said to have either Cw or monopulse seeker (pulse illumination). In first case the shooter`s radar had to be equiped with a cwi trasmitter when homing the old Aim-7F. The upgraded Aim-7M features inverse monopulse seeker, because the illumination is done via pulse-doppler radar (STT mode). I`m not aware whether modern airborne radars have cw illuminators for homing SAHR missile.Dilbert said:I don't understand the above sentence.
crossiathh said:The doppler shift's bandwith which will be searched after launch is 60Hz.
Dilbert said:I agree with everything else above, but - 60 Hz?!? From a carrier frequency of 10 GHz? So if the target changes its closing speed by as little as, e.g. 10 km/h, the missile can't see it?!
mrdetonator said:I thought the missile homing principle depends on shooter`s radar. The Sparrow is to be said to have either Cw or monopulse seeker (pulse illumination).
The upgraded Aim-7M features inverse monopulse seeker, because the illumination is done via pulse-doppler radar (STT mode).
crossiathh said:Right before launch, the R-23 still on the APU-23M missile rail, the weapon system provides a bunch of information to the R-23R. The proximity fuse "Tschaika" receives information about when to activate and the approach rate.
The RGS is tuned on the litera(frequency) of the KNP transmitter. You are saying something different that it is tuned on the velocity of target (returned cw frenquency, which varies due to doppler.?????)crossiathh said:The RGS seeker's frequency oscillator will be tuned on the velocity of the target by the radar via the RBS module before launch.
At last I agree with that, the LOCK-ON is achieved after launch for the RGS and before launch for TGS. That`s exactly what the source is saying.crossiathh said:Lock-on after launch is used.......
The time after launch prior to proximity fuse activation depends on target type and target distance/aspect.
The AVM-23 supplies the "expected missile flight time" information when the launch button is pressed. The information is used to initiate the proximity fuse. That` what source is saying.overscan said:The time after launch prior to proximity fuse activation depends on target type and target distance/aspect.
Yes, but the optimal distance to detonate the proximity fuse differs depending on engagement type (headon/tailchase), target size, and possibly even speed? The host aircraft can supply this information.
at least we concur that "to initiate" means "turn on" .... ;D But that does not explain my question.overscan said:OK- then perhaps "initiate" means "turn on".
That way the proximity fuse isn't armed until its well away from you and your wingmen, reducing the chance of fratricide.
I agree that the Tschaika proximity fuse is doppler type. But this is independent to the seeker. Keep in mind that Tschaika uses doppler to measure closure speed, while the RGS seeker additionally needs doppler to identify and track the target. BTW, Tschaika is used with the R-23T too, where the seeker doesn't provide doppler information.mrdetonator said:My point is why the "Tchaika" is measuring doppler(closure rate) if the seeker is doing the same as well? The information from the seeker could be used to detonate the warhead when close to the target. The Tchaika proximity fuse then seems to be useless.
(R-23R/R-24R) don't have radiocorrection datalink.crossiathh said:Regarding SARH:
Talking about the predecessor (R-23R/R-24R), also having a mono-pulse seeker with four receivers in the antenna, you have a fifth receiver directed backwards receiving the "original" signal from the aircraft's radar. This signal was used as reference to compare the phase, enabling the extraction of the doppler shift.
: if "CW illumination is always the best for a conical-scan seeker" could you tell me the other modes of illuminations?The defining feature of a monopulse seeker is the ability to follow a jamming signal, regardless if it's pulsed or CW. Of course for normal operation, CW illumination is always the best, but it's not required by the monopulse seeker as it is for a conical-scan seeker.
Hi .overscan said:Hi Vadifon.
R-23/24 do not have radiocorrection datalink. They do have receivers facing backwards which receive the radar signal from the aircraft, which is used to compare with the signal from the target.