Multiple crystal front end filters board for 40M
- Details
- Category: Frontend Filters
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40M front end unit with 800Hz narrow Crystal filters for each kHz, from 7011 to 7025 kHz, all controlled from MCU |
This front end unit was designed by Sinisa, YT1NT. Year ago, I ordered 15 peaces of 6 pole crystal filters, 800 Hz wide ( +/- 3dB ) with central frequencies from 7011 up to 7025, on each kilocycle.
As you can see on diagrams below, filters are very narrow. Insertion loss is little bit higher than 3dB, and with this crystal filter in front of your receiver performance will be much better. You will dislodge intermodulation of near strong signals on the best possible way, as good, as will improve signal to noise ratio of you receiver. Actually, any average receiver will be become the best one. You will be very surprised having brand new receiver suddenly, capable to fight with strong signals, on the most crowded edge of the bands in major contest.
As this multiple crystal front end filters` board was built for WRTC, as the part of station automation project, switching of proper filter is controlled from MCU (Micro controller Unit) automatically, when frequency on VFO was +/- 499 Hz from central frequency of proper filter.
Signals for switching filters are BCD, and you can use 16 decimal to BCD IC as interface. But absolutely best solution is to have data about your frequency from CAT and to make it to be automatically. For that microcontroller interface will be needed.
Also on the board is attenuator from 1dB to 31 dB, in steps of 1dB and divider when you have two receivers on the same band.
This product will be available on the market soon. Client will decide about number of filters needed and filters frequencies. Boards can be produce for any band, or can have crystals from different bands, different bandwidth etc. Switching can be done manually or automatically.
It is LIFE TIME product, and can be used with any receiver.
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Schematic diagram
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