[NLRS] Waveguide transitions

[W0ZQ at aol.com]

Hi John.  I think a lot of our microwave experts are in Dayton this weekend.  
  I do know that WR90 is indeed 0.400 x 0.900 ID .... perhaps some of those 
dimensions that were given to you were OD ?  I know that some WR90 flanges are 
bigger, like 0.500 x 1.000, in order to take a 0.050 thick wall (x2 = 0.100) 
on a mating section of waveguide.   I think WR75 is usable at 10368, but there 
should be WR90 stuff out there, keep looking.

Regarding the horn vs dish thoughts, we've found that the 19" dish is a very 
good compromise between gain and aiming.   You should be able to achieve about 
30 or 31 dB of gain yet the beam isn't too narrow ... aiming is not that 
difficult, but it does take some practice.   I think the beam width is about 5 or 
6 degrees or so .... its sounds narrow, but like I said, with practice aiming 
isn't as tough as it sounds.   A bigger dish provides more gain, but aiming 
starts to get more critical .... I've already noticed this on my second system 
that has a 24" dish (not to mention that its heavier).

Regarding what to use for a jumper from the transition, most of us are using 
semi ridig UT-141 coax.  Its OD is 0.141".   At 10GHz the specs are 0.42 dB 
loss per foot and its good for at least 100 watts.   The run from my feedhorn to 
my SMA relay is maybe 2" and the run from the relay to the transverter 
receive input is maybe another 3".   My runs on the transmit side are somewhat 
longer .... I optimized placement to make the receive side lines as short as 
possible.   Depending on which version of UT-141 you have you can make some pretty 
sharp bends with it too.   With just a little practice its easy stuff to work 
with.   DEMI sells it for $2.00 per foot (as I recall) along with the needed 
SMA connectors.   I know DigiKey sells SMA connectors but I don't think that 
they sell UT-141.   

73, Jon
W0ZQ
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