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Re: Re: Re: LF: MF/160

To: "RSGB LF group"<[email protected]>
Subject: Re: Re: Re: LF: MF/160
From: "dhchurch"<[email protected]>
Date: Mon, 23 Oct 2017 20:07:18 +0100
References: <[email protected]> <CAA8k23Q5V3OQcE6E1pAT0ZNuADgahJZ5HhE7BfHBX5pgR0j+vQ@mail.gmail.com><[email protected]> <CAA8k23TjLUHt6MAT0Zgi6obi0eYti7736s0jy8iX7pkMyOx2yA@mail.gmail.com>
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Hello Andy 
 
The idea of using any SMPS in, or near, the shack is somewhat abhorrent. It is possible to introduce a series circuit in a linear PSU which is not exactly a regulator but has a hum cancellation circuit, something that used to appear in an ancient National Semiconductor publication. I'd love to try it but just haven't left any room in my PSUs, they're stuffed full, including a cooling fan. A couple of 100Hz side bands are at least predictable, my PA has,  but there is one regular transmission on LF which has all manner of spurii making reception here somewhat variable.
 
I think Dave, GW8GLO, has a system which promptly knocks off his transmitter SMPS when going into Rx mode, maybe this is the way to go.
 
73, Hugh, M0DSZ
 
----- Receiving the following content -----
Receiver: rsgb_lf_group
Time: 2017-10-23, 10:12:17
Subject: Re: Re: LF: MF/160

Its a difficult call - I have a similar problem with my 700 Watt 137kHz Tx.   30dB hum sidebands corresponds to 3% ripple, which in the main scheme of things is not that much.   It would need an enormous reservoir capacitor to make a serious reduction.  

Either that or design the Tx to run from 50V and use a SMPSU instead of raw rectified AC

Andy  G4JNT

On 23 October 2017 at 10:03, dhchurch <[email protected]> wrote:
Mal, I think a little attention should be paid to, perhaps, your power supply. The 100Hz sidebands, as I recall from earlier this week, should be much lower in level. Seen on Spectrum Lab at one stage, they were less than -30dB in comparative level. 
 
73, Hugh, M0DSZ
 
----- Receiving the following content -----
Receiver: rsgb_lf_group
Time: 2017-10-22, 22:44:59
Subject: Re: LF: MF/160

You're so strong, Mal,  I'm getting decodes on your hum sidebands

21:36  G3KEV  0.475804  -27  0  IO94sh  5  G4JNT  IO90iv  384  189  2017-10-22 21:36  G3KEV  0.475704  +3  0  IO94sh  5  G4JNT  IO90iv  384  189  2017-10-22 21:36  G3KEV  0.475604  -29  0  IO94sh  5  G4JNT  IO90iv  384  189  2017-10-22 1

Andy   G4JNT

On 22 October 2017 at 19:25, mal hamilton <[email protected]> wrote:

NICE CONDX 160M THIS EVENING VK7DIK  REPORTING G3KEV WSPR MODE

LOOKING GOOD FOR MF/630 M ALSO

TNX REPORT DE MAL/G3KEV

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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