FWind Posted July 4, 2021 Posted July 4, 2021 AWG-9 in game± 133 knots of MLC and ± 100 knots of zero doppler filter, but APG-59 is ± 110 knots and ± 50 knots in the manual. Is the blind ranges of awg-9 the same or better than that of apg-59 in the real world？
Naquaii Posted July 4, 2021 Posted July 4, 2021 No. Afaik the data we've modelled the AWG-9 on are correct.
FWind Posted July 5, 2021 Author Posted July 5, 2021 (edited) 9 hours ago, Naquaii said: No. Afaik the data we've modelled the AWG-9 on are correct. Why AWG-9 have blind area is 200 knots wide in zero doppler filter, the blind area is 100 knots wide of AWG-10? Edited July 5, 2021 by FWind
Naquaii Posted July 5, 2021 Posted July 5, 2021 38 minutes ago, FWind said: Why AWG-9 have blind area is 200 knots wide in zero doppler filter, the blind area is 100 knots wide of AWG-10? All systems are developed out of their own specifications. You tell me! All I know is that our data say it was like we've currently modelled it and we're quite sure of the veracity of our data. It's quite possible they upgraded the AWG-9 later on in it's service life as our information is about the earlier Tomcats. But we're not going to change it without any evidence of it. 5
SgtPappy Posted July 6, 2021 Posted July 6, 2021 (edited) On 7/5/2021 at 5:25 AM, Naquaii said: All systems are developed out of their own specifications. You tell me! All I know is that our data say it was like we've currently modelled it and we're quite sure of the veracity of our data. It's quite possible they upgraded the AWG-9 later on in it's service life as our information is about the earlier Tomcats. But we're not going to change it without any evidence of it. Just out of curiousity - is the real F-14 blind speed tuneable with a knob? I know we have some gain knobs and the like that have no function in DCS due to game engine limitations and that this function might be one of them. Edited July 6, 2021 by SgtPappy
AH_Solid_Snake Posted July 6, 2021 Posted July 6, 2021 Not likely, the AWG-9 is really 1960s tech that was designed starting in the late 50s. So in order to get range gates and speed gates and all the "electronic" logic it actually requires a physical logic gate, its not handled in software. The reason jets of the F-14 or F-4 vintage don't have clever things like MPRF and very narrow gates is simply due to physical space limitations to fit all the permutations. 1
Naquaii Posted July 6, 2021 Posted July 6, 2021 9 hours ago, SgtPappy said: Just out of curiousity - is the real F-14 blind speed tuneable with a knob? I know we have some gain knobs and the like that have no function in DCS due to game engine limitations and that this function might be one of them. No, the MLC will always be the same as your own speed as that’s how fast the ground is coming at you and the zero doppler filter will always be at zero as it’s filtering out non-moving targets. The gain is what it sounds like and adjust gain (i.e. a sort of amplification setting), some of them not really making sence to implement in DCS as it is atm.
SgtPappy Posted July 7, 2021 Posted July 7, 2021 (edited) 23 hours ago, Naquaii said: No, the MLC will always be the same as your own speed as that’s how fast the ground is coming at you and the zero doppler filter will always be at zero as it’s filtering out non-moving targets. The gain is what it sounds like and adjust gain (i.e. a sort of amplification setting), some of them not really making sence to implement in DCS as it is atm. Ah understood, thanks! I understand that the hardware limitations of the time prevented the heterodyning of a low doppler signal to show up.. after all you can only fit so much non-digital hardware into a 60s processor. But I could've sworn I saw a series of DDD images which had the rejection doppler "tuned" such that you could keep the target tracked as its radial speed decreased at the cost of rejecting fewer things like trees moving in the wind. I could be mistaken, but I can't for the life of me find the image right now. EDIT: Just read in my handy Hughes Radar Handbook that the blind speeds are a strong function of the PRF, which, in the Tomcat's case is not very variable, only having low or high PRF and no medium PRF waveforms. However, I believe since its CW illumination is chirped (i.e. varying frequency) in order to determine range while locking. I am curious if its HPRF waveform is chirped as well or can be modulated in any way by the RIO? Edited July 7, 2021 by SgtPappy
Naquaii Posted July 8, 2021 Posted July 8, 2021 18 hours ago, SgtPappy said: Ah understood, thanks! I understand that the hardware limitations of the time prevented the heterodyning of a low doppler signal to show up.. after all you can only fit so much non-digital hardware into a 60s processor. But I could've sworn I saw a series of DDD images which had the rejection doppler "tuned" such that you could keep the target tracked as its radial speed decreased at the cost of rejecting fewer things like trees moving in the wind. I could be mistaken, but I can't for the life of me find the image right now. EDIT: Just read in my handy Hughes Radar Handbook that the blind speeds are a strong function of the PRF, which, in the Tomcat's case is not very variable, only having low or high PRF and no medium PRF waveforms. However, I believe since its CW illumination is chirped (i.e. varying frequency) in order to determine range while locking. I am curious if its HPRF waveform is chirped as well or can be modulated in any way by the RIO? Only thing you can really do is to remove the MLC filter by being in a look up situation, in that case it's only the zero doppler filter that affects the radar and for that to occur the target has to have a radial speed the same as yours moving away from you, i.e. a chase. The zero doppler filter is not removable as it's kinda inherent to being a pulse doppler radar, i.e. zero speed = no doppler. Blind speed depending on PRF is a totally different thing, that's regarding the existance of blind speeds as a function of PRF and frequency (https://www.radartutorial.eu/11.coherent/co13.en.html). Those blind speed zone are much smaller and not something modelled in DCS as it would need exact knowledge of PRF amongst other things. In the real aircraft the solution for those were to just wait for the target to reappear as the blind speed zones are small and as nearly no target has a constant radial speed they would reappear quite quickly. Chirp is a type of pulse-compression that's used with pulse radar, not pulse doppler radar. I guess modulation of CW radar can be called chirping but I'd just say that it's frequency modulation in general and that's used for some pure CW radars to kinda simulate pulses in the CW emission to get range. My guess would be that very few airborne radars use this as they use CW almost entirely for missile guidance illumination, not as a means of tracking. The AWG-9 as an example has a separate TWT and antenna built into the radar for AIM-7 illumination, not tracking. The CW illuminator is piggybacked onto the normal radar and illuminates what the AWG-9 tracks with it's normal radar. So no range information needs to be extracted from the CW, in fact the AWG-9 doesn't even listen to the CW, it has not receiver for it. 3
SgtPappy Posted July 8, 2021 Posted July 8, 2021 8 hours ago, Naquaii said: Only thing you can really do is to remove the MLC filter by being in a look up situation, in that case it's only the zero doppler filter that affects the radar and for that to occur the target has to have a radial speed the same as yours moving away from you, i.e. a chase. The zero doppler filter is not removable as it's kinda inherent to being a pulse doppler radar, i.e. zero speed = no doppler. Blind speed depending on PRF is a totally different thing, that's regarding the existance of blind speeds as a function of PRF and frequency (https://www.radartutorial.eu/11.coherent/co13.en.html). Those blind speed zone are much smaller and not something modelled in DCS as it would need exact knowledge of PRF amongst other things. In the real aircraft the solution for those were to just wait for the target to reappear as the blind speed zones are small and as nearly no target has a constant radial speed they would reappear quite quickly. Chirp is a type of pulse-compression that's used with pulse radar, not pulse doppler radar. I guess modulation of CW radar can be called chirping but I'd just say that it's frequency modulation in general and that's used for some pure CW radars to kinda simulate pulses in the CW emission to get range. My guess would be that very few airborne radars use this as they use CW almost entirely for missile guidance illumination, not as a means of tracking. The AWG-9 as an example has a separate TWT and antenna built into the radar for AIM-7 illumination, not tracking. The CW illuminator is piggybacked onto the normal radar and illuminates what the AWG-9 tracks with it's normal radar. So no range information needs to be extracted from the CW, in fact the AWG-9 doesn't even listen to the CW, it has not receiver for it. Very interesting, thanks so much Naquaii for clarifying that! That last bit about CW illumination was my second question but it all makes sense now, that it's only used for Sparrow illumination and not for tracking.
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