[NLRS] New 10 GHz Player

[tosca005 at umn.edu]

LMR240 is *NOT* equivalent to RG-58...

Loss at 10368 MHz, per Times Microwave web site:
  http://www.timesmicrowave.com/cgi-bin/calculate.pl

RG-58......... 1.7 dB per 3 feet, 5.8 dB per 10 feet ** note
RG-8X......... 1.7 dB per 3 feet, 5.5 dB per 10 feet
LMR-200....... 1.1 dB per 3 feet, 3.6 dB per 10 feet
LMR-240UF..... 1.0 dB per 3 feet, 3.4 dB per 10 feet
RG-8.......... 1.0 dB per 3 feet, 3.3 dB per 10 feet
LMR-240....... 0.8 dB per 3 feet, 2.8 dB per 10 feet ** note
LMR-400UF..... 0.5 dB per 3 feet, 1.8 dB per 10 feet
LMR-400....... 0.5 dB per 3 feet, 1.5 dB per 10 feet

UF suffix refers to "Ultra-Flex" variety of the Times Microwave product. 
LMR-400 is about the biggest size that accepts an SMA connector without any 
adapters.

Physically, LMR-195 or LMR-200 is about the same size (but lower loss)
 as RG-58.

Physically, LMR-240 is about the same size (but lower loss)
 as RG-8X

Physically, LMR-400 is about the same size (but lower loss)
 as RG-8

Otherwise, I basically agree with Donn (not much surprise there!) - if 
possible, have the first gain stage (preamp) as close to the feed horn as 
possible to keep noise figure as low as possible, then you can tolerate 
quite a bit of loss back to the transverter itself if necessary. Many of us 
have mounted the transverter on the sidearm of the feed assembly, but back 
of the dish would also work if the preamp and PA are close to the feed horn 
and the transverter needs to be further away...

73 de W0JT

On Dec 21 2008, Donn Baker - WA2VOI/0 wrote:

> Re: LMR 240... Question: Where's the RECEIVE pre-amp ? If you don't have 
> a pre-amp then the receive path is from the feed horn, thru the T/R 
> relay, thru the 3' of LMR-240 to the XVRTR... maybe 3 dB of loss (LMR 240 
> is basically RG-58 ! At 10GHz ??!) That means youv'e LOST 1/2 of your 
> receive signal before you get to the receiver and your RX noise figure is 
> AT LEAST 4.5-5 dB. Maximizing the TX is the least of your worries... if 
> YOU can't hear'em it doesn't matter if they're receiving you at 20 over.
>
> On the other hand, if you have the Pre-amp, TX amp, and T/R relay at the 
> feed horn, LMR-240 (again, RG-58 -- shudder !) to the XVRTR doesn't 
> matter. You will need at least 16-18 dB of gain in the RX pre-amp to 
> overcome the cable losses and set the noise figure of the entire system 
> to the NF of the pre-amp. That most likely means a 2-stage pre-amp.
>
> While its a matter of preference, I'd recommend the back of the dish 
> rather than a tripod leg for the mounting location of the rest of the 
> stuff. Makes the whole packge easier to move around, and faster to get 
> working. (At least if you're going to be a Rover... less of a problem if 
> you're only to set up once or maybe twice in a day.)
>
>73 Donn
>WA2VOI/0