you can replace it yes.
have a search on ebay for futaba 2.4ghz aerial - it's a micro co-ax fitment, so you will need to be careful when installing it.
I have used the 2.4ghz FAAST antennae on my KO 2.4ghz when that aerial wire broke. It's an easy repair, but you need to be carefule getting into the receiver and taking the old aerial off - for a small plug, the micro-co ax has a big grip.
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