Home On Jam (HOJ)


ACCESS: Confidential
29 January 2006
Reaction score
Can some one explain to me , How effective in a practical scenario is the feature of Home On Jam (HOJ) useful.

A simple scenerio which I can think about is when a AAM is fired at a Target Aircraft , Lets say a AIM-120C is fired at a target aircraft , The Target aircraft carries external jammers and then tries to Jam the AAM or the data link between Air to Air Missile & Launch Platform.

I would like to think here in a very simplistic explaination of the above scenerio , that if the AIM-120C is jammed and the lock to the target aircraft is broken/jammed , The algorithm inside the AIM-120C would then try to lock on the jammer Aircraft as it is expected to do.

Ofcourse HOJ is just not limited to AAM , but anti-ship and other missile.
Is HOJ a wonder technology or is there is a way to spoof the HOJ feature ?
By its nature as a transmitter, ECM can be vulnerable to this kind of counter. However, HOJ cannot easily provide distance, only angle, and is less precise than a good radar lock, which is why it is used as a secondary mode.

As it is passive mode,the only easy counter is to stop transmitting. Obviously a continuously transmitting "noise jamming" signal is easier to home on than a deception jammer that transmits intermittently.

Home on jam seekers is one reason behind the increasing use of towed decoys. That way, the seeker homes on, not you, but the decoy hundreds of metres behind you.
So its the good old Noise Jamming which is vulnerable to HOJ , modern jamming techniques like DRFM jamming techniques, Frequency hopping etc are not vulnerable to HOJ.

Thanks for the reply
Top Bottom