[time-nuts] Rooftop antenna and splitter

[Bob kb8tq]

Hi

Often the “puck” that comes with a demo board is set up to only work when
directly connected to the board. No long cable runs, no splitters, no lightning protection
to all add a bit of loss here and there. It also is a good bet that whatever is supplied
“free” with the demo board came from the low bidder.

About all we have to go by is a line in the spec that talks about 40 db max and 30 db 
typical as being the “recommended” gain characteristics. The more common numbers
would be 20 db typical and 30 db max for sort of telecom devices we all are used to working with. 

The lack of a “minimum” spec generally is because the problem is actually far more complex
that a simple gain number. Things like antenna element gain matter. Gain delta between 
overhead and horizon matters. LNA noise figure matters. Since these are multi band 
devices, gain delta between bands matters. 

All of that assumes the antenna is sitting on a pole with a perfect view of the sky in all
directions. Does this gizmo get used under tree cover? Do birds land on it? Does snow
and ice pile up on it? How well should it work in those conditions? ( Looking out at the 
multiband antennas here with ice and snow rapidly piling up on them yet again …..)

All I’m suggesting is that if you have a choice between antennas up around 40 db and
ones down below 30 db …. the higher gain is a lot more likely to do the job. Since you
can get the higher gain devices for not much money, there’s not much downside. 


Bob

> On Jan 29, 2019, at 3:09 PM, Achim Gratz <Stromeko at nexgo.de> wrote:
> 
> Bob kb8tq writes:
>> The first one is designed to mount on a ground plane (which is fine if it is going 
>> on a truck or airplane). It also is a bit low in gain for what I *think* the F9 is looking
>> for. 
> 
> The only antenna that u-Blox themselves advertise for use with the
> (eval) F9P module is an unassuming 28dB gain puck (ANN-MB, not seen it
> anywhere for sale so far).  So I don't think that the gain matters very
> much for this module unless you have to compensate for distribution
> losses, at which point you'll probably end up with the more typical
> 35…41db gain figures for fiyed installation antennas.
> 
> Interestingly enough the antenna is mentioned in a comparison with two
> other multi-band patch antennas here:
> 
> https://www.ardusimple.com/ardusimples-oem-antenna-vs-u-blox-tallysman/
> 
> You can apparently buy one from their store, with or without an
> accompanying F9P RTK-module.
> 
> 
> Regards,
> Achim.
> -- 
> +<[Q+ Matrix-12 WAVE#46+305 Neuron microQkb Andromeda XTk Blofeld]>+
> 
> SD adaptation for Waldorf microQ V2.22R2:
> http://Synth.Stromeko.net/Downloads.html#WaldorfSDada
> 
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