China vacuums capacitors

[jord4231]

Hi Just wondering if anyone has had any experience with these?
https://www.aliexpress.com/item/1005005910772893.html

Can't find anyone who's using them for radio related projects anywhere

I have built a balanced L matching unit and the Jennings vac cap I have its a bit too high at minimum C for my needs.
This one fits my requirements but I do wonder about it's mechanical longevity seals etc...

Cheers
 

[A.Z.]

sorry, can't help with those, but the issue with vac caps is the sealing and "how long" they'll mantain it...

as for your Jennings min capacity, did you consider adding a switchable series doorknob to them to lower it when needed ?

[A.Z.]

alternatively, you may consider something like the attached, it can be configured as either a T or an L match using S1 and S2; the C3 and C4 fixed caps will have the same value as the max value of C1 and C2 and can be inserted in both configs (L or T) if/when needed; when in T config they'll help reducing losses

[jord4231]

alternatively, you may consider something like the attached, it can be configured as either a T or an L match using S1 and S2; the C3 and C4 fixed caps will have the same value as the max value of C1 and C2 and can be inserted in both configs (L or T) if/when needed; when in T config they'll help reducing losses

Thanks for the reply, I've experimented with series capacitors and while it works I think it will just be easier to get something that goes to around 10p rather than 50p I have linked a video for the project so far if you are interested.

https://youtu.be/PkCmKlOmHHU?si=NObs60NmXud0xFVb

Thanks again
Jordan

[A.Z.]

see here

http://ur4ll.net/#caps3_1

[A.Z.]

also see

https://elektrodump.nl/en/49-variable-vacuum-capacitor