@@MakeDoAndMend1 You seem very confused, is your transmit power 10 or 20 watts? in the video you show 20 watts on your power meter, and now you're saying it's 10, or 9,5. I didnt say 80% of anything anywhere so I dont know what that comment is about. So let me summarise, YOU showed a measurement with your VNA of insertion loss at 3.5 dB. 3dB loss equates to half power, ie 20 watts from rig and then 10 watts after filter. Is this not the situation? Is your VNA insertion loss measurement wrong? The figures dont agree. Also SWR is not measuring loss, it is meaningless in this context. I believe the design is fine, the problem is you haven't implemented it very well. Your performance measurements show this. You are getting too much insertion loss and wider bandwidth than you should. The design calls for copper or aluminium case, your galvanised steel will be lossy. You have smaller gauge wire than design, this also adds loss. You have used steel threaded rod on the tuning capacitors, these are lossy too, you should use brass.
The -3dB insertion loss is something to consider, but it is also a pretty aggressive filter - If you had a lot of noise from a pager station, or a local VHF trunking base station, this would cut it all RIGHT out.
It's open plan so it can be easily viewed at the radio club. Easier to pass from person to person and show it works rather than keep removing metal lid. It's a see through lid etc. George ❤
To be honest I don't know. However I would image due to the wavelength of 80metres. It would be oil drum size. The lower the frequency filters tend to be on ferrite rings. But even what I am doing makes my brain hurt. Cheers from old George.
