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]