Coaxial Notch Filter 56.7 Mhz
These filter are very easy to construct and require no final tuning. |
Filter Response
The filter response of the above circuit, shows that after fitting a small tuning network added between the coaxial cables. The improvement in notch depth at 56.7Mhz sank from -150Db to over -200Db the limit of the programs measuring capability. The tuning of the additional circuits do not effect the filters notch response, but does effect frequency's below 30 Mhz. Some compromise is necessary on 28Mhz but considers worth while in view of the improved performance. Just about readable at the bottom of the graph is a table showing measured responses. |