I'm putting an MRX into the panel of my RV-9A project. I would like it to attach to an external transponder type antenna. I've seen a VERY expensive cable available for doing this. I've been told that it's the price it is because it has an attenuator in it. Is there another way to attach the unit to an external antenna without using this high cost cable? Is an attenuator really required if the MRX is located several feet from the aircraft's transponder antenna?

Thanks

Kelly Johnson