[time-nuts] ThunderBolt question

[Wes]

A 1.5:1 SWR = ~14 dB return loss.


On 6/5/2020 6:42 PM, Tom Holmes wrote:
> Dana...
>
> I think that you are neglecting two important mitigating factors.
>
> 1. the cable loss at 1575MHz, even for a 25' run of RG-6, reduces those
> reflections quite a lot from one end to the other.     It amounts to 2 - 3
> dB in 25', depending on cable quality.
>
> 2. a 1.5:1 SWR is not a very big reflection to begin with, on the order of
> 20% of the incident power, about  7 dB. I am rounding a lot here just to
> keep the math easy...for me.
>
> By the time a reflection has made the round trip from the receiver back to
> the antenna and them back to the receiver, which is how the delay would have
> to manifest itself, it will be down at least 15 dB from its original self,
> and probably more. Given the coding of GPS signals which allows several
> satellites to share a common frequency band, that is not going to be much of
> a problem. And if only one end of the path actually is 75 ohms, then there
> won't be a delayed signal.
>
> Tom Holmes, N8ZM