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From: <jrusgrove@comcast.net>
To: <rsgb_lf_group@blacksheep.org>
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Date: Tue, 24 Oct 2017 10:10:29 -0400
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Subject: Re: LF: MF/160
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The problem can also be on the receive station end ... i.e. not using an isolation transformer
between receiver and sound card input if ground loops are present.

Jay W1VD  WD2XNS  WE2XGR/2


----- Original Message ----- 
From: "Chris Wilson" <dead.fets@gmail.com>
To: "dhchurch" <rsgb_lf_group@blacksheep.org>
Sent: Tuesday, October 24, 2017 9:16 AM
Subject: Re: LF: MF/160


Hello Hugh,

I am assuming the regular transmission you refer to is mine Hugh? In
case you or anyone else here thinks I have ignored your multi
frequency reports, I have not. I have, in recent weeks, used a G0MRF
amp, a G3YXM and my W1VD amp, all of which have their own dedicated
LPF assemblies. I have used U3S exciter, and used my Kenwood TS-590 as
well. I have used each of them on a SMPS, two high end commercial
linear supplies, and on a bank of car batteries, and have tried two
different matching transformer arrangements and two different loading
coils. You still see multiple TX frequencies from me, only their level
changes, which is expected as the amps have different power
capabilities.


I also have SA screen shots from an in calibration HP8568B analyser
which shows sidebands to be well down and no real spurious emissions.
So, I feel have gone the extra mile in time and cost to address this
and short of moving I am at a loss to as to what more I can do and why
you  see  this,  when other very close stations apparently do not, and
nothing  untoward shows on the G3YXM grabber which isn't that far away
from me.

Regards, Chris Wilson

Monday, October 23, 2017, 8:07:18 PM, you wrote:

>
>
> 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 -----
> From:   Andy Talbot
> 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 <dhchurch@lineone.net> 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


-- 
Best regards,
 Chris                            mailto:dead.fets@gmail.com