Re: [time-nuts] GPS splitter
Hi
There is a poorman's way of making a -3dB splitter using lengths of cable of characteristic impedance equal to the system impedance. That is to say using only 50Ω cable in a 50Ω system. It is a variant on the well known square four-port quadrature hybrid. In the standard hybrid with ports A,B,C & D, with a signal entering at A, half the power (-3dB) emerges at B and the other half at C and in principle nothing emerges at D. The outputs at B & C are in RF phase quadrature with C lagging. The four sides of the square are all of length λ/4. The sides BC & DA are of 50Ω cable whilst sides AB and CD are of cable with characteristic impedance 50/√2=35.35Ω. The poorman's version is to replace the low impedance sides (AB & CD) with λ/8 lengths of 50Ω cable and add λ/8 open ended shunt stubs of 50Ω cable at each corner. As a splitter port D should be terminated with a 50Ω load. The OC ends of the stubs should be shielded with caps but in a way that doesn't significantly add end capacitance. This poorman's hybrid is rather narrow-band but adequate to cover the GPS L1 band (1575MHz). Three such hybrids may be joined to form a 4-way splitter which in principle has -6dB from input to each output. There is no DC path from inner to ground.
John Ponsonby
Hi
There is a poorman's way of making a -3dB splitter using lengths of cable of
characteristic impedance equal to the system impedance.
[]
John Ponsonby
---===
.. or a ready-made, and smaller item:
http://www.ebay.co.uk/itm/1GHz-3GHz-2-4GHz-Power-Splitter-Combiner-2-Way-SMA-/141740586696
I use this successfully for 1.09 GHz ADS-B splitting.
Cheers,
David
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv
Hi
If you don’t mind shopping a bit, the Minicircuits two way GPS splitters shipped out with every
TBolt and a variety of other Lucent gear. They show up at very cheap prices sometimes …
My suggestion is to spend the $20 and just get one of the eight way Minicircuits L band units.
That way you have some spare outputs.
Bob
On Jun 18, 2017, at 2:50 AM, David J Taylor david-taylor@blueyonder.co.uk wrote:
Hi
There is a poorman's way of making a -3dB splitter using lengths of cable of characteristic impedance equal to the system impedance.
[]
John Ponsonby
---===
.. or a ready-made, and smaller item:
http://www.ebay.co.uk/itm/1GHz-3GHz-2-4GHz-Power-Splitter-Combiner-2-Way-SMA-/141740586696
I use this successfully for 1.09 GHz ADS-B splitting.
Cheers,
David
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv
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On Sun, 18 Jun 2017 07:50:17 +0100
"David J Taylor" david-taylor@blueyonder.co.uk wrote:
.. or a ready-made, and smaller item:
http://www.ebay.co.uk/itm/1GHz-3GHz-2-4GHz-Power-Splitter-Combiner-2-Way-SMA-/141740586696
I use this successfully for 1.09 GHz ADS-B splitting.
Please be aware that this is a Wilkinson splitter and thus has a DC
path connecting all three ports. You will need to add a DC block
at one of the receivers.
Attila Kinali
--
It is upon moral qualities that a society is ultimately founded. All
the prosperity and technological sophistication in the world is of no
use without that foundation.
-- Miss Matheson, The Diamond Age, Neil Stephenson
"David J Taylor" david-taylor@blueyonder.co.uk wrote:
.. or a ready-made, and smaller item:
http://www.ebay.co.uk/itm/1GHz-3GHz-2-4GHz-Power-Splitter-Combiner-2-Way-SMA-/141740586696
I use this successfully for 1.09 GHz ADS-B splitting.
Please be aware that this is a Wilkinson splitter and thus has a DC
path connecting all three ports. You will need to add a DC block
at one of the receivers.
Attila Kinali
---======
In practice, what would happen if you didn't have the block?
Say with two identical receivers?
David
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv
Hi
On Jun 18, 2017, at 11:17 AM, David J Taylor david-taylor@blueyonder.co.uk wrote:
"David J Taylor" david-taylor@blueyonder.co.uk wrote:
.. or a ready-made, and smaller item:
http://www.ebay.co.uk/itm/1GHz-3GHz-2-4GHz-Power-Splitter-Combiner-2-Way-SMA-/141740586696
I use this successfully for 1.09 GHz ADS-B splitting.
Please be aware that this is a Wilkinson splitter and thus has a DC
path connecting all three ports. You will need to add a DC block
at one of the receivers.
Attila Kinali
---======
In practice, what would happen if you didn't have the block?
Say with two identical receivers?
As long as they both are powered up, noting much. If one looses power, it might try to power
up the other one via the antenna feed. With most receivers, even that would likely just be an
odd occurrence / no damage caused. The fear is that you have a receiver that would be damaged
by the back feed. With eight receivers into a coupler, there could be quite a bit of current available.
Bob
David
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-taylor@blueyonder.co.uk
Twitter: @gm8arv
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Hi,
On 06/18/2017 05:37 PM, Bob kb8tq wrote:
Hi
On Jun 18, 2017, at 11:17 AM, David J Taylor david-taylor@blueyonder.co.uk wrote:
"David J Taylor" david-taylor@blueyonder.co.uk wrote:
.. or a ready-made, and smaller item:
http://www.ebay.co.uk/itm/1GHz-3GHz-2-4GHz-Power-Splitter-Combiner-2-Way-SMA-/141740586696
I use this successfully for 1.09 GHz ADS-B splitting.
Please be aware that this is a Wilkinson splitter and thus has a DC
path connecting all three ports. You will need to add a DC block
at one of the receivers.
Attila Kinali
---======
In practice, what would happen if you didn't have the block?
Say with two identical receivers?
As long as they both are powered up, noting much. If one looses power, it might try to power
up the other one via the antenna feed. With most receivers, even that would likely just be an
odd occurrence / no damage caused. The fear is that you have a receiver that would be damaged
by the back feed. With eight receivers into a coupler, there could be quite a bit of current available.
As you power up, there can be a bit of a rush-in power.
Lack of isolation can cause antenna power detection to be confused.
Two driving one antenna => too little current => judged as unconnected.
One driving antenna and other GPS => too much current => judged as short
circuit.
If you have different voltages, it might be bad for the low-voltage device.
Cheers,
Magnus
Hi
It also depends a bit on weather the original designer anticipated odd things happening on
the antenna circuit. The answer to that one is …. errr …. not always. Some designs have the
antenna supply tacked straight into a bulk regulator that feeds a bunch of stuff. Other designs
have an indépendant regulator for the antenna. Even with the independant regulator, one needs
to know how much that regulator “likes” an over voltage on the output.
Bob
On Jun 18, 2017, at 11:56 AM, Magnus Danielson magnus@rubidium.dyndns.org wrote:
Hi,
On 06/18/2017 05:37 PM, Bob kb8tq wrote:
Hi
On Jun 18, 2017, at 11:17 AM, David J Taylor david-taylor@blueyonder.co.uk wrote:
"David J Taylor" david-taylor@blueyonder.co.uk wrote:
.. or a ready-made, and smaller item:
http://www.ebay.co.uk/itm/1GHz-3GHz-2-4GHz-Power-Splitter-Combiner-2-Way-SMA-/141740586696
I use this successfully for 1.09 GHz ADS-B splitting.
Please be aware that this is a Wilkinson splitter and thus has a DC
path connecting all three ports. You will need to add a DC block
at one of the receivers.
Attila Kinali
---======
In practice, what would happen if you didn't have the block?
Say with two identical receivers?
As long as they both are powered up, noting much. If one looses power, it might try to power
up the other one via the antenna feed. With most receivers, even that would likely just be an
odd occurrence / no damage caused. The fear is that you have a receiver that would be damaged
by the back feed. With eight receivers into a coupler, there could be quite a bit of current available.
As you power up, there can be a bit of a rush-in power.
Lack of isolation can cause antenna power detection to be confused.
Two driving one antenna => too little current => judged as unconnected.
One driving antenna and other GPS => too much current => judged as short circuit.
If you have different voltages, it might be bad for the low-voltage device.
Cheers,
Magnus
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