Bad phase noise

Locator: IO91SU
Location: Luton, Bedfordshire
Post Reply
G4CPE
Posts: 39
Joined: Mon Oct 31, 2016 3:59 pm

Bad phase noise

Post by G4CPE » Mon Mar 19, 2018 3:36 pm

GB3TZ on 2326 MHz has been getting progressively more difficult to receive over the last 12 months. Because we have had some aerial issues we assumed that this was the reason for the poor reception. Recently I took a look at the signal I received on the spectrum analyser at home and concluded that the signal strength was good and that the reception should be a lot better. I removed the SR Systems coder tray and brought it home for a coat of looking at. What I discovered was that the O/P was noisy and difficult to decode. I traced the problem to a o/c electrolytic capacitor on the SR Systems coder board. This capacitor has been replaced and the coder tray refitted in TZ. Result TZ back to its old self and easy to receive on small aerials in the Luton area. 73 Arthur G4CPE

G3VZV
Posts: 16
Joined: Mon Feb 25, 2008 12:38 am

Re: Bad phase noise

Post by G3VZV » Wed Mar 21, 2018 2:04 pm

Hi Arthur,
Congratulations on your usual superb fault finding skills.... I will put a dish back up over the weekend and have another look:)
73
Graham
G3VZV

G4CPE
Posts: 39
Joined: Mon Oct 31, 2016 3:59 pm

Re: Bad phase noise

Post by G4CPE » Thu Mar 22, 2018 2:20 pm

Hi Graham
Good luck with that, I will be interested in the result.
73 Arthur

G4WIM
Posts: 128
Joined: Thu Jan 29, 2015 8:36 pm

Re: Bad phase noise

Post by G4WIM » Thu Mar 22, 2018 8:11 pm

Hi Authur,

Out of interest, was what the function of the capacitor you replaced ? Coupling or de-coupling ?

Regards Tim

G4CPE
Posts: 39
Joined: Mon Oct 31, 2016 3:59 pm

Re: Bad phase noise

Post by G4CPE » Fri Mar 23, 2018 8:54 am

Hi Tim
The capacitor was a decoupling capacitor on the 5v line. The oscilloscope revealed a large amount of ripple on the 5v line which was causing the poor quality o/p from the coder. The cap was a 550uf which I replaced with a 1000uf because that is all I had in the shack. The faulty cap did not show any signs of being faulty ( no bulging ) but was definitely o/c.
73 Arthur
G4CPE

G4WIM
Posts: 128
Joined: Thu Jan 29, 2015 8:36 pm

Re: Bad phase noise

Post by G4WIM » Sat Mar 24, 2018 5:30 pm

Thanks for that - seems to be quite a plague of faulty electrolytics at the moment. I read some where that a Chinese manufacturer didn't quite get the recipe right leading to a spate of premature failures.

Post Reply

Return to “GB3TZ”