GS1000 and noise

Gamma spectacular, theremino adapters, non-sound card based, etc...
Post Reply
User avatar
pilgrim
Posts: 74
Joined: 06 Nov 2017, 03:28
Location: Italy
Contact:

GS1000 and noise

Post by pilgrim » 26 Sep 2018, 21:20

Hi all,
I have some noise problems with my setup and I ask your help.
If I connect a Bicron P-12 (a low impedance socket) to a GS1100 PRO, without any probe,
Setup.jpg
if I exceed 1200V PRA reads several counts per second.
I made some tests at different voltage, if I increase the voltage the situation gets worse.
Here there are some screenshots at 1200, 1300 and 1400 volts; I've always used the PULSE SHAPE ACQUISITION for these tests.

P12 @ 1200V
P12-300 sec @1200 v - Copia.JPG
P12 @ 1300V
P12-3000 sec @ 1300 v - Copia.JPG
P12 @ 1400V
P12-2200 sec @ 1400 v - Copia.JPG
As you can see the CPS get lower after several minutes, so at the same voltage, the situations gets better after 10 or 20 minutes.

Then I made the test with the same setup with a Bicron P-14 and this problem comes out after 1400v.

P14 @ 1500V
P14-1100 sec @ 1500 v - Copia.JPG
Under 1200V I PRA reads no counts with both sockets.

I tried to swap the USB ports (USB supply and USB sound card) but the problem persists.
I also tried to use the original laptop sound card instead of a DeLock USB soudcard and the problem comes out at 1500v.
P12-900 sec @ 1500 v original sound card - Copia.JPG
I know that the GS1100 should be used at 1100 V, but I ask you if there's a way to fix this problem, because I'd like to use the GS at 1250 V with the P-12, so the voltage I have to set on the GS could be 100 - 150V higher than the voltage shown on the GS display (due to the low impedance of the socket).

Thanks
Daniel, Italy

User avatar
Steven Sesselmann
Posts: 613
Joined: 27 Apr 2015, 11:40
Location: Sydney
Contact:

Re: GS1000 and noise

Post by Steven Sesselmann » 27 Sep 2018, 08:16

Daniel,

It sounds like you are observing some over voltage arcing. The weakest link is probably your BNC connectors or the cable itself.

Check if the cable is a proper RG58/C with PE core, the cheaper antennae cables with foam core are no good, they can arc inside the cable.

The next thing to check are the BNC connectors, I only use those to save cost, as it is good enough up to 1100V in dry weather (officially rated for 600V). On my GS-2000-PRO I use the proper SHV connector, which is good for 3kV.

Try replacing the connectors, and/or cable.

Steven
Steven Sesselmann | Sydney | Australia | gammaspectacular.com | groundpotential.org | rephopper.com | beejewel.com.au |

User avatar
pilgrim
Posts: 74
Joined: 06 Nov 2017, 03:28
Location: Italy
Contact:

Re: GS1000 and noise

Post by pilgrim » 27 Sep 2018, 13:24

Steven,
this is the SHV cable I use on the GS110 :
https://www.ebay.it/itm/BNC-Male-To-RP- ... Sw2gxYx1Ic
If it's not a quality cable, do you have a trusted seller to suggest me for the cable and for a good SHV connector ?
Daniel, Italy

User avatar
Steven Sesselmann
Posts: 613
Joined: 27 Apr 2015, 11:40
Location: Sydney
Contact:

Re: GS1000 and noise

Post by Steven Sesselmann » 27 Sep 2018, 14:27

Daniel,

It looks like the person selling the cables knows what they are doing, so we can assume they have used a reasonable quality RG58 cable, this leaves the BNC connector as the weakest point.

Have you tried listening for noise with no cable connected?

If you narrow the problem down to the BNC connector, I can send you a new back plate with an SHV connector.

Steven
Steven Sesselmann | Sydney | Australia | gammaspectacular.com | groundpotential.org | rephopper.com | beejewel.com.au |

User avatar
pilgrim
Posts: 74
Joined: 06 Nov 2017, 03:28
Location: Italy
Contact:

Re: GS1000 and noise

Post by pilgrim » 27 Sep 2018, 14:57

This evening I'll do the test with no cable and I'll let you know.

Thank you.
Daniel, Italy

User avatar
pilgrim
Posts: 74
Joined: 06 Nov 2017, 03:28
Location: Italy
Contact:

Re: GS1000 and noise

Post by pilgrim » 28 Sep 2018, 02:41

Steven,
I've just made the test you suggested :
As you see in the picture, with the GS @ 1500V with all cables connected, no problem;
GS110 Test_2.jpg
Without SHV and signal cables, no problem;
Without SHV cable, no problem;
Without signal cable, no problem;

In a nutshell PRA reads the counts only with sockets plugged.
Do you think the problem could be the in BNC connector anyway ?
Daniel, Italy

User avatar
Steven Sesselmann
Posts: 613
Joined: 27 Apr 2015, 11:40
Location: Sydney
Contact:

Re: GS1000 and noise

Post by Steven Sesselmann » 28 Sep 2018, 07:26

Daniel,

Sounds like the problem is in the socket. Open it up and have a look, maybe a loose wire or some dust causing it to arc.

Re-solder any loose wires and clean the parts with some isopropyl alcohol.

Steven
Steven Sesselmann | Sydney | Australia | gammaspectacular.com | groundpotential.org | rephopper.com | beejewel.com.au |

User avatar
pilgrim
Posts: 74
Joined: 06 Nov 2017, 03:28
Location: Italy
Contact:

Re: GS1000 and noise

Post by pilgrim » 28 Sep 2018, 14:21

Ok Steven, I'll try as you suggested.
Thanks for your help.
Daniel, Italy

Post Reply

Who is online

Users browsing this forum: No registered users and 1 guest