I have a HPN-30118 Combined Notch Filter, which I use with a roof antenna for reception on the BCD536HP scanner. But I recently purchased the SDS100 handheld unit and wanted to occasionally hookup the external antenna. What's the best notch filter for hooking up two scanner radios. Even if I keep it hooked to just the base model 536HP, is the HPN-30118 still the best option in terms of performance and filtering? I would never use both radios at the same time but it's easier to have an extra cord rather than unplugging the base unit al the time.