[600MRG] Vacuum variable capacitor, low-pass/band-pass filters

[John Langridge]

Max gain systems is another Vac Cap supplies that NI7J was
recommending a few years ago:

https://mgs4u.com/#Vacuum

73/GL

jl

On 6/21/19, Frank O'Donnell <600 at inkbox.net> wrote:
> Hi all,
>
> I'm a fairly new ham and very new to 630m, currently in the process of
> getting a station together.
>
> I have a new Elecraft K3S (major birthday this month), and recently
> bought a 100w 630m class D amp from Ken Roberson K5DNL. Due to the great
> number of trees and lack of clear space for radials on our city lot, I'm
> following an excellent suggestion to look into putting up a vertical
> loop antenna rather than the inverted-L that I first had in mind.
>
> At this point, I'm working on the following questions -- any advice or
> suggestions would be greatly appreciated:
>
> 1) Depending on how it's hung, the final circumference of the loop could
> vary between about 100 and 130 feet. Using AA5TB's loop antenna
> spreadsheet, it appears that I will need a range of about 1548 pF to
> 2136 pF capacitance to tune the loop across the entire 630m band. I have
> zero experience so far with vacuum variable capacitors, and although I
> see them listed for sale on eBay and elsewhere, I'm reluctant just to
> pick one and hope it's suitable. Does anyone have suggestions for a
> source, possibly even for a specific cap?
>
> 2) In case I need to supplement the above capacitances for any reason,
> is there a type of fixed cap that works well for this? For HF work I've
> been using silver micas in transmitter antenna tuning circuits.
>
> 3) Although I have a fairly good external low-pass filter for receiving,
> I often run several SDRs with different antennas at a time, and would
> like to get some additional low-pass filters and experiment with
> bandpass filters. I saw a favorable reference to filters by Clifton
> Labs, which apparently was acquired by DX Engineering, but I'm not clear
> on which of their current offerings would be best for 630m and below.
> Any suggestions on filters, either prebuilt, kit or homebrew plans?
>
> It would also be interesting to hear from any K3/K3S owners -- as a
> newbie on that front I have a few things I'm wading through as well.
>
> Thanks for any guidance,
>
> Frank K6FOD
>
>
> ______________________________________________________________
> 600MRG mailing list
> Home: http://mailman.qth.net/mailman/listinfo/600mrg
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:600MRG at mailman.qth.net
>
> This list hosted by: https://www.qsl.net
> Please help support this email list: https://www.qsl.net/donate.html
>