Jim and the group,
Per notification sent to the group. I have added a folder in the 'Files' section with what information I have here regarding filters. No, I don't speak Japanese either!
Interestingly, the filter board in my FT-301D has UK, after-market units installed in the AM and CW positions. The after-market CW filter is a 250 Hz bandwidth unit, whereas the stock Yaesu part is, I believe, 600 Hz bandwidth. Presently, I have this three-filter board installed in my FT-301, which I have recently finished repairing. It sounds nice on all modes. I have not yet done the ELCON mods to improve the matching around the IF filters.
My FT-301D is still in pieces. I need to re-fit the VFO which I had apart to fix and assemble and install an ELCON replacement digital display board. The filter board in the D has only two units fitted - the Yaesu stock SSB and CW ones. The picture I posted to the folder shows the links needed on the board for the AM receive signal path to pass through the SSB filter in the absence of a dedicated AM one.
One experiment I intend to try on this two-filter board is the trick that is commonly used on Drake TR-7 radio.There's a roofing filter (XF301) on the IF unit, separate to and ahead of the mode-specific / channel filters. XF301 is shown as type '9M20A', so I'm guessing it's 20 kHz BW at the nose. I intend to make up and test a 'dummy' AM filter, comprising a 'T' pad attenuator (500-Ohm Z, 6 dB loss), with 150 Ohm series arms and a 680-Ohm shunt arm. 20 kHz is really way too wide for AM on congested bands but might be usable.
Like you, I am also curious as to the differences between and FT-301D and an FT-301AD. I have never seen the AD variant here in the UK. Maybe the AD just had the last of the model changes rolled-up into the production run. Somewhat like the FT-101F (which, again, I have never seen an example of on this side of the pond) vs. FT-101E.
Regards,
Mark, G4FPH.
