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" <[email protected]>
To: "dhchurch" <[email protected]>
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 <[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
--
Best regards,
Chris mailto:[email protected]
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