[time-nuts] ground plane for cheap helix antennas?

Bob Camp kb8tq at n1k.org
Fri Jul 24 07:25:27 EDT 2015


> On Jul 23, 2015, at 1:38 PM, Alan Ambrose <alan.ambrose at anagram.net> wrote:
> Hi, is there any benefit in adding a ground plane to these simple timing antennas? e.g. GPS-TMG-26N
> http://www.antenna.com/apg_products.cgi?id_num=11740
> In which case, how big? And I'm imagining immediately underneath the antenna? This ublox note suggests probably not?

It very much depends on: 

1) Exactly what your antenna actually has in it (it may or may not be a helix, most are not). 
2) Precisely how the ground plane is arranged relative to the antenna (machined choke rings are a good idea …)
3) What sort of multi path you do or do not have in your your antenna location
4) The elevation mask you have set on the receiver
5) How many sat’s you can see at a time 
6) Which sats (and when) are impacted by multi path

> http://www.u-blox.com/images/downloads/Product_Docs/GPS_Antennas_ApplicationNote%28GPS-X-08014%29.pdf
> The 58503A sitting on this atm gets '4.3us/initial 24 hours' prediction although I have seen it around 2.2us. Also max ~110 'SS’.

That’s not a good way to evaluate this sort of thing. The prediction algorithm is not set up for this kind of stuff. A plot of your location
is a much better way to check things out. 

> Also is it helpful to increase the elevation mask?

If your multi day location plot shows trouble with low masks, then yes increasing it is a good idea. 

By far the *best* idea is to have a good location estimate.


> TIA, Alan
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