The simplest was I can think of is to go ahead and by a handheld scanner from Radio Shack (I have a Pro-79) and then run a Male-Male cable from the headset jack on it to the tape deck, digital recorder, mini-cassette recorder, what ever you want to record with.
Since it is all consumer connections the impuence won't be an issue. Just make sure you have good batteries in the scanner and in the recorder. Since it is completely independent of the aircraft you can use in it in whatever you fly and not worry about having the right plugs, any plugs or matching impedence and it will be extremely portable too since it doesn't depend on any connections to the aircraft.
You just need to remember to either, A set the scanner to each frequency you wish to transmit when you change frequencies (That might be a pain especially in busy airspace, maybe take along a freind to do this
), or B go ahead an program in a set of frequencys that you commonly use (you will lose some transmissions if the scanner locks onto somebody else on another band transmitting).
Besides it isn't a bad idea to have an aircraft band scanner anyway, in case of a radio failure you can at least hear everybody else, even if you can't transmit.
My scanner was a middle of the road model at Radio Shack and set me back about 100 bucks.
L-188.....Former U.S. Army Signal Corps.
OBAMA-WORST PRESIDENT EVER....Even SKOORB would be better.