Band pass filters
With any event and contesting station where comes a time when you need to use 2 or more radio on different bands and running at 400 watts. You soon realize that the second and third harmonic is knocking the front end of the second radio and vice visa.
To over come this problem band pass filters are used and have been for many years, these come in many forms but 2 common ones are coax stubs and W3NQN filters, both of these methods can be made quite cheaply if you source your parts well. As we have our workshop we started to make our own and Marcin M0GLV / SP4BHD undertook the task and made a great job as you can see.