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GPS receiver board - can I remove the SMA connector?
- Thread starter loadlover
- Start date
You may find the SMA connector has a 50 Ohm impedence.
If you remove it you will have to match the impedence.
But I would measure it to see if it has or not. There might be a 50 Ohm resistor next to it on the board.
Martin
If you remove it you will have to match the impedence.
But I would measure it to see if it has or not. There might be a 50 Ohm resistor next to it on the board.
Martin
Hi Martin,
I'm sure it is 50 Ohm impedence. Would I need a signal generator and oscilloscope to measure this, or is there simpler way? And what would I replace it with that wouldn't weigh much?
A 50 Ohm resistor should be all that’s required.
Martin
Martin
Sorry, I'm not sure what is meant here.
The SMA is not terminated. So it appears as an open. The line to it and the SMA will appear as appropriate for a 50 Ohm characteristic impedance, but at the SMA, with no load plugged in, it's an abrupt open.
If the board is intended to be run with the antenna on either connector without termination on the other, as I'd guess, then I'd guess removing the connector is likely fine.
I'm not particularly an RF black arts guy, so happy to be corrected.
The SMA is not terminated. So it appears as an open. The line to it and the SMA will appear as appropriate for a 50 Ohm characteristic impedance, but at the SMA, with no load plugged in, it's an abrupt open.
If the board is intended to be run with the antenna on either connector without termination on the other, as I'd guess, then I'd guess removing the connector is likely fine.
I'm not particularly an RF black arts guy, so happy to be corrected.
Yeah that's kinda what I was thinking. To clear one thing up, you're supposed to use one connector or the other, not both simultaneously. Bearing this in mind, what do we think?
And yes, RF does seem to be a black art.
Didn't see a part number, but assuming this is a GPS or similar. The antenna is receive only.
Somehow on the board they have arranged that you can plug a receiving GPS antenna into either connector and the other, open one isn't an issue. I'd presume this is mostly by just keeping the line short, though it feasibly could have two inputs to the module.
Termination can be important? Absolutely: In RF even more so than audio. if transmitting or don't want reflections from open/shorted lines.
Summary:
Don't think we are in any transmitting situation, hence a lack of termination is not going to be an issue to the module safety.
The "other" connector is normally open, so removing it, carefully so as to not mess with the board too much, is likely just shortening the line a little, shortening a rather short stub off the line being used: used antenna connector to module.
Seems very likely to be ok.
Disclaimers: Never looked at how these modules provide the two inputs. Not an RF guy (even less than previously).
You could try asking UBlox.
Somehow on the board they have arranged that you can plug a receiving GPS antenna into either connector and the other, open one isn't an issue. I'd presume this is mostly by just keeping the line short, though it feasibly could have two inputs to the module.
Termination can be important? Absolutely: In RF even more so than audio. if transmitting or don't want reflections from open/shorted lines.
Summary:
Don't think we are in any transmitting situation, hence a lack of termination is not going to be an issue to the module safety.
The "other" connector is normally open, so removing it, carefully so as to not mess with the board too much, is likely just shortening the line a little, shortening a rather short stub off the line being used: used antenna connector to module.
Seems very likely to be ok.
Disclaimers: Never looked at how these modules provide the two inputs. Not an RF guy (even less than previously).
You could try asking UBlox.
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