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Author Topic: Substitute a ceramic filter for a mechanical filter?  (Read 466 times)

WB6BYU

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Re: Substitute a ceramic filter for a mechanical filter?
« Reply #15 on: July 01, 2021, 05:54:58 PM »

The IF transformers may have a limited range
of adjustment, depending on the design.  I’ve
tried some that would only tune 10 kHz or so.
In that case, you may need to remove the
internal capacitor and use an external one
of a slightly smaller value.

VE7RF

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Re: Substitute a ceramic filter for a mechanical filter?
« Reply #16 on: July 18, 2021, 06:33:30 PM »

At a minimum you would need to match the input and output impedances for the ceramic filter and adjust for the difference in loss in the filters. They’re probably not the same as for the mechanical filter.  But doesn’t Yaesu use Collins mechanical filters?  It’s something to look at.

Both my yaesu  FT-1000D and also my  FT-1000MP-MKV  use collins mech filters in the 455 IF.  Murata filters are used at the higher IF's, but only for AM...and wider ones can be  also be used for AM.   I replaced the  oem collins mech filter ( think is 2.6 khz)  with a wider 5.7 khz  collins.  But that was for a one off application for  ESSB use.  The higher IF oem 2.4 xtal filter was replaced with a 6 khz, 8 pole inrad.  ( yaesu also offerd a 6 khz  xtal filter, for another radio, for am use, same if, and also works).  That only works on the MKV, since the  cxr osc can easily be tweaked to handle it.  Cxr osc will handle up to a 9 khz filter, but that's over the top.

ALL the collins mech filters were made in... Mexico !  (dunno when collins started making mech filters in Mexico, I think the early  90's...quality was excellent).
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W2EAF

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Re: Substitute a ceramic filter for a mechanical filter?
« Reply #17 on: July 20, 2021, 11:24:17 AM »

WB6BYU
The IF transformers may have a limited range
of adjustment, depending on the design.  I’ve
tried some that would only tune 10 kHz or so.
In that case, you may need to remove the
internal capacitor and use an external one
of a slightly smaller value

I going to try the Xicon 42IF100-RC transformers, which have no internal capacitor. Spec sheet says center frequency is 796 kHz with a primary inductance of 360 uH at 455kHz. Hopefully I can get them to work. Only about a buck a piece and they are actually in stock at Mouser. And for now I'm going with the Collins 500 kHz filter I got on eBay. If I can get this IF section working, the rest should be pretty straightforward. Famous last words!
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