Difference between revisions of "70MHz filters"
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Higher power duty filters. | Higher power duty filters. | ||
| − | In CQ-TV 260 Charles G4GUO published a low pass filter using ATC capacitors to go in a die cast box. | + | In CQ-TV 260 Charles G4GUO published a low pass filter using ATC capacitors to go in a die cast box. |
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| + | [[File:4m_LPF.jpg|400px|G4GUO filter built by David M0YDH]] | ||
| + | [[File:4m_LPF_trace.jpg|400px|Spectrum analysis trace for this filter. Ref level was -14 dBm with a 10dB PAD. So -2dBm loss.]] | ||
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Mini-kits sell a [https://www.minikits.com.au/electronic-kits/filter-kits/vhf-lowpass-filters/LPF7-75M low pass filter kit] described as a 75MHz 7th order Chebychev Low Pass filter. | Mini-kits sell a [https://www.minikits.com.au/electronic-kits/filter-kits/vhf-lowpass-filters/LPF7-75M low pass filter kit] described as a 75MHz 7th order Chebychev Low Pass filter. | ||
| − | Band pass filters may present a problem. The [https://www.qrp-labs.com/bpfkit.html QRP-Labs 12m or 10m Band pass filter kits] may be a valid point for starting on experimentation for your receiver application. | + | Band pass filters may present a problem. The [https://www.qrp-labs.com/bpfkit.html QRP-Labs 12m or 10m Band pass filter kits] may be a valid point for starting on experimentation for your receiver application. The [[71_MHz|upconverter shown on this Wiki]] contains good filtering for receive already. [https://www.antennas-amplifiers.com/4m-70mhz-bandpass-filter-receiving Antennas-amplifiers off a bandpass filter covering 70-70.5MHz] with published characteristic curves. [https://pa3csg.nl/?page_id=62 PA3CSG] has a home built band pass filter which will tune to cover 70.5 -71.5MHz. 2021 update:- Mini-Circuits make an excellent low power Bandpass filter - the RBP-75+ which passes 50-72MHz signals and is for mounting on a PCB. Very low insertion loss. About £16 each or try your luck with an application to their EZ Samples programme. |
Latest revision as of 17:22, 17 April 2021
Low pass filters on 4m remove signals from e.g. the broadcast radio band beginning at 88MHz.
QRP-Labs sell a Low Pass Filter kit for 4m that may be suitable for 71MHz duty with the Portsdown TX.qrp-labs.com lpf kit
Higher power duty filters. In CQ-TV 260 Charles G4GUO published a low pass filter using ATC capacitors to go in a die cast box.
Mini-kits sell a low pass filter kit described as a 75MHz 7th order Chebychev Low Pass filter.
Band pass filters may present a problem. The QRP-Labs 12m or 10m Band pass filter kits may be a valid point for starting on experimentation for your receiver application. The upconverter shown on this Wiki contains good filtering for receive already. Antennas-amplifiers off a bandpass filter covering 70-70.5MHz with published characteristic curves. PA3CSG has a home built band pass filter which will tune to cover 70.5 -71.5MHz. 2021 update:- Mini-Circuits make an excellent low power Bandpass filter - the RBP-75+ which passes 50-72MHz signals and is for mounting on a PCB. Very low insertion loss. About £16 each or try your luck with an application to their EZ Samples programme.