Re: Filter problem

Liz Tuddenham wrote:

Dave Platt wrote:
>

Is there any chance you can make enough room in your setup for
something of the following sort?
>
https://www.pa0nhc.nl/IMDfilter/EN/Notch/Single/HelicalNotchfilters2mEN.htm

>
That's exactly the sort of thing I had in mind.  The author's dimensions
of 4" diameter and 6" high might be a bit of a problem but I could try
scaling it down and adding more turns to the helix.  Perhaps a piece of
35mm copper pipe would make a good starting point.
>
A length of thinner pipe would be easier to accommodate, so perhaps I
could experiment with something intermediate between between a coaxial
stub and a helical resonator.

"Coaxial Resonators with Helical Inner Conductor" may help. Fig. 1 shows
a shield less than 2" in diameter and about 4" high. (Its height was
eyeballed.)

<https://iontrap.duke.edu/files/2025/03/Coaxial_Resonators_with_Helical_Inner_Conductor.pdf>

Danke,

--
Don, KB7RPU, https://www.qsl.net/kb7rpu
There was a young lady named Bright Whose speed was far faster than light;
She set out one day In a relative way And returned on the previous night.