RA0SMS active mini-whip power supply

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Paul
Posts: 77
Joined: Fri Feb 17, 2017 9:52 am

RA0SMS active mini-whip power supply

Postby Paul » Wed Jul 19, 2017 4:30 pm

Hi
I have one of the subject mini-whips. Power requirements stipulate 12 - 14V/300ma and it has worked pretty well on a good quality switched regulator power supply at 12V.
I have recently replaced this psu with a presumably superior bench type 13.8V/5-7amp regulated power supply unit, the output of which is on spec and does work with the RA0SMS supplied RF isolating transformer.
However, I have concluded that it actually performs better on the original switched unit than on this 13.V one.
Can anyone suggest why this may be the case.

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DanubeBCL
Posts: 168
Joined: Sat Jul 02, 2016 12:39 pm

Re: RA0SMS active mini-whip power supply

Postby DanubeBCL » Wed Jul 19, 2017 4:51 pm

Hi Paul,
I can't explain. Normally there should be no such difference, except that the "bench" PSU should create no noise (if it's linear).
What is the difference you noticed? More noise? Weaker signals? More "ghost" signals (intermodulation)?
What brand/type is the "bench" PSU?
73s Heinrich

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Paul
Posts: 77
Joined: Fri Feb 17, 2017 9:52 am

Re: RA0SMS active mini-whip power supply

Postby Paul » Wed Jul 19, 2017 5:15 pm

Hi Heinrich
Thanks for the response.
I do not know the brand (Regulated DC power supply with short circuit protection) - purchased quite a few years ago, but it did check out on spec.
Neither psu appear to be "noise generators," but the 13.8V unit produces weaker signals than the 12V original, using the rsp's built-in lna produces very variable and unsatisfactory signal quality, whereas when using the 12V supply the signals are noticeably cleaner and the lna more effective in use.
The only RFI that I suffer is I believe from the 3 phase overhead cables about 50M from my little antenna farm.
Needless to say the 12V supply is back in use at the moment- I'm happy - just a bit puzzled.

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DanubeBCL
Posts: 168
Joined: Sat Jul 02, 2016 12:39 pm

Re: RA0SMS active mini-whip power supply

Postby DanubeBCL » Wed Jul 19, 2017 5:31 pm

Paul wrote:just a bit puzzled.
Me too, Paul. The linear PSU should not have an influence on the signals. Difficult to say, why it has. But I wouldn't worry. If your switched PSU is OK then use it.
Yes, I know the trouble with the "overhead" power lines. I do not have high voltage lines here, but our old houses here are supplied with wires on top of the roofs. Needless to say that these lines transport all the RFI noise from the houses across the whole settlement.
73s Heinrich

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OH2BUA
Posts: 30
Joined: Mon Aug 29, 2016 8:58 am

Re: RA0SMS active mini-whip power supply

Postby OH2BUA » Thu Jul 20, 2017 1:10 pm

Hi,

is there possibly a difference between your power supplies in a way that one 'passes' the ground to the mini-whip power adaptor, and the other doesn't?

73, Jukka

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Paul
Posts: 77
Joined: Fri Feb 17, 2017 9:52 am

Re: RA0SMS active mini-whip power supply

Postby Paul » Thu Jul 20, 2017 1:34 pm

Thanks for your interest Jukka
Not as far as i am aware.
Either psu is connected to the same, earthed socket and connected by barrel plug to the RF isolating transformer, which is also grounded to my common earth system which is connected to copper a rising cold-water main.
this is the best option that I have so far.
Best Wishes
Paul

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OH2BUA
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Joined: Mon Aug 29, 2016 8:58 am

Re: RA0SMS active mini-whip power supply

Postby OH2BUA » Thu Jul 20, 2017 1:50 pm

Do you happen to own a multimeter? If you have, you can check if there is connection between the earth terminal of the AC plug and the DC minus of the power supply?

The UK plug (if you are in UK) is a little bit strange and also frightening thing for me:)

73, Jukka

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Paul
Posts: 77
Joined: Fri Feb 17, 2017 9:52 am

Re: RA0SMS active mini-whip power supply

Postby Paul » Thu Jul 20, 2017 3:22 pm

Thanks for the suggestion Jukka.

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DanubeBCL
Posts: 168
Joined: Sat Jul 02, 2016 12:39 pm

Re: RA0SMS active mini-whip power supply

Postby DanubeBCL » Thu Jul 20, 2017 4:21 pm

OH2BUA wrote:is there possibly a difference between your power supplies in a way that one 'passes' the ground to the mini-whip power adaptor, and the other doesn't?
I also have already thought of such a scenario. But Paul's bias T has an isolating transformer in the RF path. This should reduce the influence of ground from the PS.
But without knowing the exact setup it's difficult to guess what is wrong here.
73, Heinrich

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OH2BUA
Posts: 30
Joined: Mon Aug 29, 2016 8:58 am

Re: RA0SMS active mini-whip power supply

Postby OH2BUA » Thu Jul 20, 2017 5:52 pm

I happen to know the mini-whip construction well. The one and _only_ point to be grounded is the ground tap of the (antenna) power adapter. No ground loops allowed.

73, Jukka

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