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With all those channels mixed together, it would be best to simply use
an A/B switch to switch between the two antennas. Ian. In message , SH writes Thanks for both you answers its nice to now i stil remember some theory eventhough its 10 years since i read some UHF theory (Ended up being a programmer :-)))) I think ill go for the notch version. I have made a lot of them and they are easy to build but I've noticed that it seams that 3 notches (adjusted to 3 diff freq.) is some kind of limit. When i put in no. 4 it seams that the overall loss increases. Do I remember correctly when i state that 2 nothes on the same freq. should be a 1/4 wave apart??? Best regards Svend Holby "Crazy George" wrote in message ... Ben Jackson has some good points. You need not worry about audio, usually, as the FM capture takes care of the weaker signal. So, filtering the video carrier and near sidebands is all that is necessary. However, in answer to your question, the way you connect bandpass filters in parallel is with power dividers, amplifiers, and power dividers again, backwards as summers. Otherwise, controlling the out of band input and output impedances of several in parallel is a monumental, but solvable task. Spice, anyone? -- Crazy George "SH" wrote in message ... Hi I have come up with one of those crazy DYI ideas which I would like to try to implement but one thing still remains. I have two UHF (TV) arial pointing in different directions and would like to connect them together through BP filters to minimize noise. BP = Bandpass Antenna 1: UHF channel (Europe) BP 1 ch 22-37, BP 2 ch40 -44, BP 3 ch 49 - 68/ or high pass Antenna 2: UHF channel (Europe) BP 1 ch 21 / or low pass, BP 2 ch38 -39, BP 3 ch 47 I have found formulas to design each section of BF but how to you connect several BP filters in parallel??? I have investigated some old TV filter and they have a coil (12 WDG) in and out of each BP section but is that the way to do it and how does it influence the design of each BP. The only approach that I can find is to split the signal into three (- 6dB ) then feed each into a BP filter and the Combine them again (-6dB). This will result in each BP section seeing 75 Ohms as they shouland they would not interfere with eachother. Ofcouse i would need a 20 dB amplifier to fix the loss. But is there a better way. Best regards Svend Holby -- |
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