> Hans said:
>
> >I do not know whats inside the filter but if you are lucky
> >it is a ladder filter with no ferrite transformers that degrade
> >the filters big signal performance.
Peter replied:
> I did a lot of work on IMD in crystal filters back in the mid 1970's. The
> ferrite transformer business I found interesting, since I was never able
> to find a filter where the ferrite transformer was the problem - and this
> was working with a number of filter manufacturers. I read about it in Ham
> Radio magazine, but that was all.
It's amazing what a single incorrect article can start.
Because of stuff in ham books, people think:
1.) Folded unipoles improve antenna ground system system
efficiency.
2.) Ferrites cause noticeable signal distortion if used anywhere in
the system
3.) Parasitics cause tube and bandswitch failures.
> Sherwood are still in business - they have a web site.
.......and still are selling quality filters
> Tom, what signal generator, wanted signal input level, wanted signal SNR
> and rx bandwidth do you use to measure blocking 1 kHz away?
Homebrew crystal oscillators with attenuator pads, 10 dB s/n, 250
Hz.
I haven't found a commercial generator yet (not in my budget
anyway) that is useful for close spaced tests (unless it is the weak
signal source).
73, Tom W8JI
w8ji@contesting.com
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