Quieter power supply for Trimble Thunderbolt? - Page 1
Forum section: electronics / general

author: elroy
author_rank: Regular Contributor
timestamp: May 14, 2019, 02:55:10 am
content: Recently I bought a ~2001-vintage Trimble Thunderbolt from eBay that came with a small power supply. When I run it near my radio gear, there's a significant amount of noise on some bands such as 40 meters.I suspect the PSU is a switching power supply. Are there any quieter supplies that work well with the Thunderbolts?

author: tkamiya
author_rank: Super Contributor
timestamp: May 14, 2019, 07:56:41 pm
content: I have Thunderbolt cousins with Nortel brand name.I've used lab supplies (switching power supply but very high quality) and open frame linear power supply with good results. Many commercially produced GPSDO has switching power supplies inside them, but they have filters on output side to remove ripples and noise.Mine (Nortel GPSTM) has built-in power regulator inside the case. It basically takes 24V to 48V and down-convert them and cleans it up. So theoretically, I can use any power supply with up to 100mV p-p ripple/noise.Most common recommendation here on forum is, to stick with linear supplies and you can't go wrong. With switcher, use with care or you take your chances.

author: elroy
author_rank: Regular Contributor
timestamp: May 15, 2019, 01:06:48 am
content: Thanks.I have some Jameco low-noise linear wall-warts -- a couple that produce 12vdc, and one 5vdc. What if I connect the minus output of one 12vdc psu to the plus output of the other, and tie those together to ground, then use the remaining plus and minus for the +/- 12vdc that the Thunderbolt requires? And then connect the 5vdc psu to the + and gnd where required for the Thunderbolt? I assume that the DC output of the wall-warts is all floating relative to the AC input, but I wouldn't want a nasty surprise.

author: tkamiya
author_rank: Super Contributor
timestamp: May 15, 2019, 01:58:39 am
content: Is your power pack regulated? Can it supply sufficient power? While crystal oven is warming up, it will consume good amount of current. I think 2 amps?I also doubt 12 volt supplies are isolated from each other. Typically, ground are all tied together.

author: texaspyro
author_rank: Super Contributor
timestamp: May 15, 2019, 05:31:05 am
content: Quote from: elroy on May 15, 2019, 01:06:48 amA VERY bad assumption... many/most tie the output - to the wall plug ground.

author: elroy
author_rank: Regular Contributor
timestamp: May 15, 2019, 05:56:17 am
content: Quote from: texaspyro on May 15, 2019, 05:31:05 amIn the case of these Jameco psu's, the AC end is 2-prong (no ground prong), and they're equal-sized. Just checked with my Fluke multimeter, and I get infinite resistance between either minus or plus DC out and either AC prong. Having said that, though, I'm inclined not to test it.

author: MiDi
author_rank: Frequent Contributor
timestamp: May 16, 2019, 10:29:22 am
content: Quote from: texaspyro on May 15, 2019, 05:31:05 amAt least in Europe this is not allowed, it is only allowed to tie secondary to earth.With two plug wall wart the earth is not connected.But almost all smps have a Y capacitor from mains to secondary to reject emi.The impedance from secondary to mains deacreses with rising frequency.

author: elroy
author_rank: Regular Contributor
timestamp: May 19, 2019, 06:37:58 am
content: For what it's worth, based on a recommendation from another Trimble Thunderbolt owner, I ended up buying an International Power IHBAA-40W linear supply from Mouser. It wasn't cheap, and it outweighs the Thunderbolt by several times, but it puts out a very clean +5vdc and +/-12vdc with no fuzz on the HF waterfall.