FT-818ND Ceramic vs Optional Collins Filter YF-122S (FT-817ND, FT-857D)

Jarrad VK3BL demonstrates the performance differences between the FT-818ND&(also FT-817ND, FT-857D) Ceramic filter and the Optional YF-122S 2.3KHz Collins Mechanical Filter. The Collins Mechanical Filter offers a flatter passband, as well as overall greater passband power. This is a huge win for speech intelligibility, especially given the extra flatness is at the high frequency side of the passband (we tested in LSB). One interesting finding was that due to the Collins filter&ultimately less sharp skirts, if the PA is driven into significant distortion the passband power actually rolls off; this does not happen with the Ceramic Filter. This means that users of the Collins filter should place extra importance on their TX IMD performance, and avoid significantly overdriving the PA stage. The weakness was only noted when the IMD performance fell below -15dBc, an unacceptable figure for any Amateur radio irrespective of power output. Ultimately, we especially recommend the YF-122C Collins Filter to existing owners of FT-817NDs who are looking for a more significant upgrade than the FT-818ND offers. 73, Jarrad VK3BL & the RMR Team :)