Re: Fix for Spurs and Harmonics on V3 Board

Dale Hardin

Curt, the pinout on the Axioms is symmetrical across the pins, so they can go on either side of the board.  I'm putting off ordering the toroids and caps for the mods in the hope that someone on the list who has done the mods will have extras available.  I would like to see a photo of the added V5 LC filter to see what is involved.  I am just about finished with some mods of a TenTec Century 21.  I added an AGC, and additional preamp, a Hi-Per-Mite filter (w/o amp) and am working on a digital dial.  With that effort and a long trip in October, I won't get to the uBitx until November.  I probably should have bought a V5 and called it a day, but I really love to build and modify stuff, so a V3 got me.  Up until about four years ago I had a nice HP spectrum analyzer, but got rid of it because I used it so little and it took up too much room.  I really appreciate your comments on this effort.  Regards, Dale 

On Mon, Sep 16, 2019 at 6:44 PM Curt via Groups.Io <> wrote:

Yes remnants of many experiments here on this list. Those axicom relays may get your harmonics compliant or very close. Watch pinouts before you put them on the underside, they should work okay on top side. Some added the shielded inductors on the 45 MHz crystal filters, and obtained lower mixer spurs in conjunction with those axicoms. The v5 LC filter did nothing to improve mixer spurs on my v4.

That trap idea was difficult to tune even with a spectrum analyzer, so hence came the shielded inductors.


Dale Hardin
24750 State St. Unit 487
Elberta, AL 36530

Dale Hardin, KS4NS
Elberta, AL

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