[time-nuts] ideas so far for first GPS, NTP project
jimlux at earthlink.net
Sun Aug 19 02:42:48 UTC 2012
On 8/18/12 6:23 PM, J. L. Trantham wrote:
> I use one like this (theBay item 270881742870) and it works well in NW
> Florida under some trees. I could get better performance if I had it up
> higher but it serves my purposes. There are also ones with higher gain out
> there as well, up to about 40 dB IIRC.
Yeah, but gain isn't a big deal. It's designed to overcome the loss of
the transmission line to the receiver. What's important is the noise
figure of the LNA, more than the gain. Most receivers have a 1 bit
quantizer, so all you really care is that the signal from the antenna is
big enough that the "antenna noise" dominates over the receiver noise.
If I had to guess, I'd say that as long as the antenna/preamp gain is
more than the loss in the cable (and power dividers, etc.) by some few
dB, you're fine.
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