Resistive Card Supplier / Waveguide Bow Vane Attenuator design 1

[microwavemark]

I am looking for a supplier for resistive card used in a Waveguide Bow Vane attenuator. I am not sure even what the material is called! All I know is that the resistance is measured in Ohms per square...

Basically I am trying to come up with a simple design for a variable attenuator, so any help there would also be much appreciated. Tunable from 0 to 40 or 50 dB ideally.

 

[Higgler]

Resistance card
_________________________________________________________________________Steve is a one man shop.

Work: 858-486-1810
Fax: rcard
Other: steve vekes
E-Mail: astscy@aol.com

or rcard on a circuit board (preferred location)

http://www.ohmega.com/OhmPly.html,

this is a large company, although we recently tested their rcard values and they were 35% too high.

There is also a manufacturer in Florida, couldn't find the link, they make rcard in small sizes 4"x8" range.
Window coverings to filter the sun are also rcard.

I think you can also use magnetically loaded RAM glued to a circuit board. Ask the standards about that Emerson and Cuming, Cumingcorp., and ARC.

kch

 

[logbook]

Sorry I can't be of any help on this one, but I am curious. "bow vane" had no hits on google, which is unusual for something which already exists. What is the structure?

Presumably the lossy material thickness is relevant because of the skin depth.

 

[microwavemark]

Hello Logbook,

It is probably they way the resistive card is used.
A strip of it is placed in the waveguide, secured at each end against one H wall and a pin or screw is used to bow the vane in to the path of the microwave RF, thus attenuating the signal.

 

[logbook]

Ah, got it! I have seen them done as flaps though slots and parallel sheets slid sideways, but not as you described. Interesting.

A key problem is power. If you want to dissipate a lot of power the substrate stability is critical. I think these things can be made from nichrome films on mylar, but I don't know if it would be good for bending, especially if there were a lot of operations.

 

[microwavemark]

I have have found the manuafcturer of the Ohmega-Ply resistor material but they only supply it in 60 squre feet quantities.

Does anyone know of any smaller amounts available anywhere? Say, a couple feet of 100 Ohm per square?

Thank you

 

[Higgler]

Try Steve Vekes, he has smaller supplies. He usually has a list he Faxes you, typically he has 500 different options and 1-50 square feet per option.

Work: 858-486-1810
Fax: rcard
Other: steve vekes
E-Mail: astscy@aol.com


kch

 

[microwavemark]

Has anyone got contact details for Steve Vekes, I have googled his name and searched the white pages but nothing came up.....

Thanks,
Mark

 

[Higgler]

Did you try the phone number above? or the email address?

kch

 

[logbook]

I'm guessing the phone number given is in the USA. If you are not in the USA you would need a few prefix digits.

 

[Higgler]

Yes, correct, it's in the USA. There is definitely a company in Florida, I think West Palm Beach that sells very small quantities (4"x12") as a standard production product, and I know they sell 100 ohm per square. Do a Google search for it.

Also, purchase some home window tinting at your local hardware store. It'll look identical to what you'll purchase for 100x the cost. $20 US for 50 square feet.

I recently purchased two kinds and measured approximately 10 and 30 ohms per square. The window tint also has glue on it, essentially a protective layer to prevent you from scratching the surface. If you scratch Rcard, it'll change your performance greatly, so handle it extremely cautiously since you can not see a scratch and can only measure it electrically.


kch

 

[Higgler]

finally found the source,
svmicrowave has a standard product in rcard.

http://www.svmicrowave.com/pdf/resistive.pdf

they give a power rating on them too, which is nice.
5" wide pieces.

kch