[time-nuts] GPS Antenna Feed Line Decision
attila at kinali.ch
Sun Sep 3 14:43:27 EDT 2017
On Sun, 3 Sep 2017 12:32:31 -0500
Clay Autery <cautery at montac.com> wrote:
> - I saw in some aviation references where pilots claimed that they
> achieved "better performance" by running their antennas at higher
> voltages. (Overclocking the antenna amp? Who knows.) But it piqued my
> interest, especially since the PCTEL antenna I have will "run" from
> below 5VDC through 12 VDC and has an even higher survival voltage.
There are a couple of LNA chips around that work at 3.3V and 5V.
Usually they exhibit better performance (higher amplification and
less degradation with frequency) with higher voltage. You should
not run those chips at higher voltage then spec'ed, though.
An antenna with a 5V-12V rating has most likely a local LDO, thus
it will not benefit from higher voltage, beside having more heat
generated localy, which might or might not stabilize temperature.
> Bottom Line: I'll read/research/design and build until I come up with a
> supply that meets my needs. Just off the top of my head, a linear
> supply that charges a battery or batteries that provide the top voltage
> or voltages in multiple ranges which are then regulated/filtered to
> provide dead flat DC at the desired levels.
> I am not an engineer or an expert of any kind. I'll have to go learn
> all this. <grin>
The supplies for LNAs are usually quite benign given two constraints:
1) Low frequency (0Hz to bandwidth of signal) noise is low
2) High frequency noise within the signal range is low.
It is usually quite easy to achieve 2) by using some L-C filter.
But 1) is a bit harder as it also includes 1/f noise, temperature,
(upstream) supply and load effects.
You know, the very powerful and the very stupid have one thing in common.
They don't alters their views to fit the facts, they alter the facts to
fit the views, which can be uncomfortable if you happen to be one of the
facts that needs altering. -- The Doctor
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