[amsat-bb] satellite flexible rotor-section coax question

[Zach Metzinger]

On 8/27/18 4:45 PM, Miles via AMSAT-BB wrote:
> I installed two 80 foot sections of LMR 600-UF from the shack to top of 
> the tower.
> 
> I have the option of installing a tower mounted preamp, but just added a 
> Female to female N-Connector at this spot.
> Preamp are in the Shack.Higher loss, but I have not Fried a Preamp in 15 
> years.
 >
> I had to replace the two 20 foot sections of LMR-600-UF.They were full of water. 

I'm going to take the contrarian viewpoint (again). A LNA in your shack 
is not going to do you justice if you've already set the noise figure 
with a long, expensive, attenuator.

160' of LMR600UF = ~$320

80' loss @ 150 = 0.8dB
80' loss @ 450 = 1.3dB

Let's add in 0.5dB of loss for various connectors, and the best you can 
do is something like a NF of 1.8dB at 2m, and about 2dB up at 70cm. So 
much for that fancy 0.5dB NF preamp, right?

Why not spend that money on a _good_ or _cheap_ (pick one) LNA, 
RG-8X/RG-213 at half the price, and add some power to overcome cable 
loss in the shack? Good grounding goes a long way to protecting your 
LNA, which should be off during storms.

A preamp (LNA) belongs at the antenna, not in your rig. That is, unless 
you've attached the rig directly to your antenna. :-)

--- Zach
N0ZGO