Bandpass filters and RF shields...

Hello Bill,

Does that shield cover thoroughly connect to the wall sections? Meaning by more than just one spot? If not that might be a point to look at.

How does the removable part of the sheild connect to the fixed part? What's it made of? Can you post photos somewhere?

-- Joe Legris

Ooooooo.... I don't know nothing about this stuff but I can fantasize, or have a Glenda. It's all black magik anyway and you are having a Barbara yourself so you don't really need the Tom.

If the ground stuff on your board is sorted then...... Ummmm. OK, to me it sounds like what you might want to do is sort of separate the input and the output grounds of your filter on the board.

Then your RF shield plate thing should have those pin bits that solder in the board so it makes the ground connection between the two halves.....

And then you mill a slot across the top of the plate between the physical location of the output of the input and the input of the output of the filter

DNA

Thanks for the pointers guys -- that really did the trick: better soldering of the shield walls to the ground, and the shield walls to the shield top!

-Bill

billcalley wrote:

Is the shield grounded ALL THE WAY AROUND the bottom? Not just in one or two places, but completely around? How about the top? Is it just pushed on or is it too soldered all the way around?

Jim

What kind of components are you using for the L and C?

Yes, thanks Jim, that was the problem exactly! I guess RF currents were riding on the shield, destroying the stopband response. Now I will solder all of my shields 100% around before test (even though this makes tweaking an issue...).

-Bill

RST Eng> Is the shield grounded ALL THE WAY AROUND the bottom? Not just in one or

Depending on how you built your filter, you could try placing it inside a length of copper tube. A technique I have used with great success on

billcalley a écrit :

You could place the shield on opposite side :-)

NOt really. Several folks sell copper mesh (sort of like window screening) that can be tack-soldered, then "mooshed" into making a slightly larger "mesh" that a tweakie tool will fit into. While I know it won't work at 2.4 gig, at VHF I've got a ferrite slug epoxied to one end of a toothpick and a brass slug epoxied to the other end. Bringing the ferrite near a coil will up the inductance and bringing the brass near the coil will down the inductance. Just a trick I learned from an old time RFer.

Jim

There was a time when those sticks were handed out with, e.g., radio kits, RF parts manufacturers, etc. so the old time RFer wasn't even needed to learn the trick. :-)

Wow ! I haven't heard anyone mention "Tuning Sticks" for many years.

I still have one from, I think, a 19 RT set maintenance kit. Anyway WW2 era. About six inches long, black Bakelite rod, with a powdered iron bit on one end and a brass one on the other.