[Moon] How to build a Wave Guide high power dummy load?

[Anders M. Thorrud]

Hi,
Thanks to all that replied to my msg. re. Dummy Load.
The power is 500++ watt. 
 Last year I planned to build a high power Wr-137 to 7/16 coax connector and use of 4 meter 1/2" LCF hardline to the feed, but a Guru on TWTA's
warned me not to use any  kind of coax instead of wave guide. I believe some of you might be interested in his explanation so here it is:

QUOTE: 
Hello Anders,
just something about arcing : We delivered a 600W TWTA for 8 GHz to a university for plasma generation.
They used coax for the final end to the plasma generator. Arcing occoured, and that flash was running with sound 
speed towards the power source. It was stopped at the vacuum window of the TWT - but burnt it within seconds.
We experienced  it  also by destroying TWTs and one detonated circulator. If you can not avoide coax, install an arc detector at the wg
output of the TWT. It will switch off the TWTA within milliseconds in case of arcing in the coax section with arc moving 
towards the TWT. We have that kind of protection  also in wg-only commercial transmitters !
If using coax, it should be as big as propagation inside allows. Preferably Flexwell, it can be pressurized with dried air.
I know, all no easy task - but safety is our main concern at these expensive "toys" because  new TWTs are not affordable.
Unquote

So I will stay away from coax. And to fabricate a WR-137 Dummy load myself seems unrealistic now that I have all the replies here
on Moon-net. I have also searched E-Bay for WR-159 and 187 dummy loads which are within the freq.range of 5.7Ghz, but nothing
found in my price range.

So will stick to my original commercial C-band feed for the offset dish I will use and pay attention to the direction of radiation sugested by
W3LBI.
73, Anders, LA8LF