[time-nuts] GPS antenna selection

Thu Aug 4 22:32:23 UTC 2016

Hi Herbert,

just look the loss of the cable at 1500 MHz, and you will start to cry 
at 1500MHz tha cable will have cca 30dB for a 30meter long 
piece....basically that RG174 looks very nice with that small antenna 
but that is the only positive aspect. Meinberg in Germany has one 
up/down converting system, which makes it possible to go more than 50 meter.
On the other hand if you could stay on the balcony and use the cable 
which came with the antenna, 2m  to 3 meter,  you could have a good 
working system, but with 15m RG174  is asking to much. For 1500 MHz BNC 
is not the best solution,
73
KJ6UHN
Alex
P.S.: wo ist diese "Austrian countryside"

On 8/4/2016 2:29 PM, Herbert Poetzl wrote:
> Dear fellow time-nuts!
>
> I'm currently investigating my options regarding
> GPS antennae (of course for time related purposes)
> and I'm really confused by the variety they come
> in ... (my apologies in advance for the long post).
>
>
> Setting:
>
> I'm living in a three storey house with a sloped
> roof, a covered balcony and a larger garden with
> huge trees on the Austrian countryside (Europe).
>
> I've walked around with my smartphone (older one)
> and I get a GPS position fix within 35s in the
> garden (nine satellites shown), within 100s on
> the balcony (also nine satellites), and not a
> single satellite can be seen indoors.
>
> The obvious choice would be to put the antenna on
> top in the middle of the slanted roof for a perfect
> sky view, but this brings a number of problems as
> the roof is very hard to reach and quite high.
>
> I have my 'lab' at the floor where the balcony is,
> so I'm considering putting an antenna there and
> run about 5-15m of coax cable to the GPS receiver.
> The advantage there is that the antenna would be
> somewhat protected (it still gets very hot during
> summer and very cold during winter, but no rain
> and no snow) and easy to reach for maintenance.
>
> The third alternative would be to put the antenna
> somewhere in the garden and have a rather long
> cable running to the house and up to my lab.
>
>
> Antennae:
>
> Looking on eBay and Amazon shows a huge pricerange
> for active GPS antennae with and without cable.
>
> It seems to start at about 10 bucks with rather
> small black boxes [1] designed for cars, probably
> containing a 25x25 ceramic GPS antenna and an
> amplifier, progresses over very interesting out-
> door constructions for boats and whatnot [2] in
> the 20-100 bucks range and finally tops with high
> end devices [3] way above 100 bucks.
>
> The information about the cheap devices is usually
> very scarce, but typically boils down to:
>
>   1575.42 +/- 5MHz
>   24-28dB LNA Gain with 10-25mA at (3-5V)
>
>   7dB f0 +/- 20MHz
>   20dB f0 +/- 50MHz
>   30dB f0 +/- 100MHz
>
> They seem to use RG174 and come with SMA as well
> as BNC connectors (and a number of others as well).
>
> The mid range devices seem to use larger antennae
> with smaller tolerances (+/- 1MHz) and larger
> voltage ranges for the amplifier (3-13V).
>
>
> Questions:
>
>   - What are the key specifications which need to
>     be verified before buying a GPS antenna?
>
>   - How can they be compared based on incomplete
>     specifications?
>
>   - Is a place on the roof or in the garden worth
>     the trouble over the covered balcony?
>
>   - Are there any typical pit-falls or general
>     tips and tricks regarding mounting and cable
>     connection to the receiver?
>
> Many thanks in advance and my apologies again for
> the rather lengthy post. Please feel free to point
> me to previous discussion regarding this topic.
>
> All the best,
> Herbert
>
>
> [1] http://www.ebay.com/itm/99-Good-GPS-Antenna-SMA-Screw-Needle-10m-Super-Signal-Navigation-DVD-Antenna-/171802461614
>      https://www.amazon.com/Waterproof-Active-Antenna-28dB-Gain/dp/B00LXRQY9A
>
> [2] http://www.ebay.com/itm/Standard-Horizon-XUCMP0014-GPS-Antenna-f-CP150-CP160-CP170/331364914004
>      https://www.amazon.com/Garmin-010-12017-00-GPS-GLONASS-Antenna/dp/B00EVT2HSE
>      https://www.amazon.com/SUNDELY®-External-Marine-Antenna-connector/dp/B00D8WAVTC
>
> [3] http://www.ebay.com/itm/NEW-FURUNO-GPA018-Gps-dgps-Antenna-/182223355414
>      https://www.amazon.com/Garmin-nmea-2000-orders-over/dp/B0089DU96A
>      
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