[time-nuts] Trimble recommends RG-59 Antenna Cable.

[Bob Camp]

Hi

Low noise receiver inputs are often mismatched to optimize noise figure. Receiving antennas may / may not be well matched to a given impedance. That all makes the mismatch loss a bit of a random thing. Some of the early Trimble docs mention that they saw essentially no mismatch loss when they swapped 50 ohm for 75 ohm cable.

I'd strongly recommend that you use quad shield satellite TV coax rather than RG-59 though.

Bob

On Apr 30, 2012, at 2:23 AM, Robert Atkinson wrote:

> Hi Ken,
> This is correct. Some other documents explain the rationale. Basically for long runs the loss caused by the mismatch is less than the higher loss per foot of 50R coax of a similar size. Even better than RG59 is the high performance cable used for cable TV and satellite installations. This is cheap and low loss at 1.5GHz. This also also explains the F connector on the Thunderbolt. It would also be intersting to measure the actual impedance of some GPS receivers and antennas.
>  
> Robert G8RPI.
> 
> 
> ________________________________
> From: Ken Kubick <kenkubick at hotmail.com>
> To: Time Nuts <time-nuts at febo.com> 
> Sent: Monday, 30 April 2012, 6:58
> Subject: [time-nuts] Trimble recommends RG-59 Antenna Cable.
> 
> 
> Hi Time-Nuts guys,  I was reading the Trimble Thunderbolt manual section 2.1.3 (Antenna Cable).  Trimble recommends using RG-59 cable which is 75 ohm coax.  Is this a typo or is this correct?  I thought that the Trimble Thunderbolt would use a 50 ohm cable and antenna.
> 
> Thankyou
> 
> Ken Kubick
> 
> kenkubick at hotmail.com                         
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