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INTERNAL FINISH ON WAVEGUIDE (COPPER)

 

CAN ANYONE TELL ME WHERE I CAN FIND A COPY OF THE FOLLOWING SPECS? IAW SM-A-949104 SM-A-949284-1

DAN ESTABROOK
DELTAMICROWAVE - OXNARD, California, USA

Dan,

Although I am familiar with the specifications of all sorts of waveguide (standard, coin-silver, copper, stainless, flexible, corrugated, etc... WR-22 to WR-3 mostly), I have never seen a specification with the letters you have listed. Could this be a non-US specification? There are ASTM specifications on finish that you can find at www.astm.org, and there are MIL specification finishes that you can find using a search engine at www.dscc.dla.mil/Programs/MilSpec/

If this is for a customer who has requested that you meet this specification, you might ask them for a copy of the spec they are referencing in their RFB. It is not what I would think of as a run-of-the-mill finish standard. Are you at liberty to divulge the intended application?

Ronna Erickson
- Amherst, Massachusetts

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IAW is an acronym for "in accordance with". Leave out the IAW when you're doing a search for the specs.

Bill Reynolds [deceased]
consultant metallurgist - Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.

Yes, IAW means in accordance with.... but the SM-A is not a prefix I have ever seen in waveguide standards or specifications. MIL-W-85/3-xxx, or MIL-STD-xxx is what you may see for military standards. A federal standard would have FED-STD-xxx. You might see BS2871/C.103 for British Std. you also might see ASTM B188. Most US waveguide manufacturers use the military standards for historical reasons. National Institute of Standards and Technology (NIST) in its former incarnation as NBS performed tests on WR-15 waveguides with a variety of finishes. However, no standards were issued from that work. For a flange finish, commercial manufacturers have used 16 microinches. The primary thing to remember about surface finish quality on waveguide is that it depends upon the frequency of use. A WR-22 waveguide does not require as smooth a finish as a waveguide for WR-8 band. It is a very simple task to determine the surface finish required for the job, but if the customer has quoted a standard in the RFB (for whatever reason), they should be willing to spell out what they need. Another important aspect of the waveguide interior would be the radius at each corner. This is critical for proper RF performance.

I would like very much to know what the specification quoted in the letter above says.

Ronna

Ronna Erickson
Radio Astronomy, University of Mass. - Amherst, Massachusetts