We are using Stanford Research SR780 and SRS785 FFT spectrum analyzers.
We obtain this peak in every measurement we do. By connecting an
unshielded wire and moving it it is obvious that the FFT is the culprit.
Are we the only ones in this case?
Bye
Jean-Pierre Coulon <coulon@cacas.pam.oca.eu>wrote:
We are using Stanford Research SR780 and SRS785 FFT spectrum analyzers.We obtain this peak in every measurement we do. By connecting an unshielded >wire and moving it it is obvious that the FFT is the culprit.
Are we the only ones in this case?
Bye
It could be the horizontal deflection frequency pf the CRT display.
Some of the magnetic field from the deflection coils will escape
through the front face of the CRT and can couple into your
signal wiring. I have seen this effect in other makes of FFT
analyzer.
We are using Stanford Research SR780 and SRS785 FFT spectrum analyzers.
We obtain this peak in every measurement we do. By connecting an unshielded >wire and moving it it is obvious that the FFT is the culprit.
Are we the only ones in this case?
Bye
Hint: Don't use unshielded wires in place of shielded scope problems. >Unshielded wires are also known as antennas.
We are using Stanford Research SR780 and SRS785 FFT spectrum analyzers.
We obtain this peak in every measurement we do. By connecting an unshielded >wire and moving it it is obvious that the FFT is the culprit.
Are we the only ones in this case?
Bye
Hint: Don't use unshielded wires in place of shielded scope problems.
Unshielded wires are also known as antennas.
We are using Stanford Research SR780 and SRS785 FFT spectrum analyzers.
We obtain this peak in every measurement we do. By connecting an
unshielded wire and moving it it is obvious that the FFT is the culprit.
Are we the only ones in this case?
Joerg <news@analogconsultants.com>wrote:
On 6/17/26 11:50 PM, Jean-Pierre Coulon wrote:
We are using Stanford Research SR780 and SRS785 FFT spectrum analyzers.
We obtain this peak in every measurement we do. By connecting an
unshielded wire and moving it it is obvious that the FFT is the culprit.
Are we the only ones in this case?
Self pollution? I was never fond of Stanford Research analyzers. The
kicker was a case where that expensive thing could not find a noise peak
in the audio range but my lowly netbook with a 1st gen Intel Atom CPU
and 18(!) bit sound chip could clearly find it.
Joerg <news@analogconsultants.com>wrote:
On 6/17/26 11:50 PM, Jean-Pierre Coulon wrote:
We are using Stanford Research SR780 and SRS785 FFT spectrum analyzers.
We obtain this peak in every measurement we do. By connecting an
unshielded wire and moving it it is obvious that the FFT is the culprit. >>>
Are we the only ones in this case?
Self pollution? I was never fond of Stanford Research analyzers. The
kicker was a case where that expensive thing could not find a noise peak
in the audio range but my lowly netbook with a 1st gen Intel Atom CPU
and 18(!) bit sound chip could clearly find it.
Do you mean 8 bits?
Most audio was 16 bits though?
On 6/17/26 11:50 PM, Jean-Pierre Coulon wrote:
We are using Stanford Research SR780 and SRS785 FFT spectrum analyzers.
We obtain this peak in every measurement we do. By connecting an
unshielded wire and moving it it is obvious that the FFT is the culprit.
Are we the only ones in this case?
Self pollution? I was never fond of Stanford Research analyzers. The
kicker was a case where that expensive thing could not find a noise peak
in the audio range but my lowly netbook with a 1st gen Intel Atom CPU
and 18(!) bit sound chip could clearly find it. Oh, and that netbook had >cost me a fraction of what the client had paid for that analyzer. Their >engineers stood there in disbelief. They initially didn't believe it. So
I said "Slow down that fan over there with your palm and a rag and watch
the peak on my laptop screen". One of them did ... "Oh S..T!"
john larkin <jl@glen--canyon.com>wrote:
On Mon, 22 Jun 2026 09:24:06 -0700, Joerg <news@analogconsultants.com> >wrote:
On 6/17/26 11:50 PM, Jean-Pierre Coulon wrote:
We are using Stanford Research SR780 and SRS785 FFT spectrum analyzers.
We obtain this peak in every measurement we do. By connecting an
unshielded wire and moving it it is obvious that the FFT is the culprit. >>>
Are we the only ones in this case?
Self pollution? I was never fond of Stanford Research analyzers. The >>kicker was a case where that expensive thing could not find a noise peak >>in the audio range but my lowly netbook with a 1st gen Intel Atom CPU
and 18(!) bit sound chip could clearly find it. Oh, and that netbook had >>cost me a fraction of what the client had paid for that analyzer. Their >>engineers stood there in disbelief. They initially didn't believe it. So
I said "Slow down that fan over there with your palm and a rag and watch >>the peak on my laptop screen". One of them did ... "Oh S..T!"
SRS used 7-segment LEDs, spelling out letters!, way after everybody
moved to LCDs.
Their pushbutton menus were crazy too.
https://www.thinksrs.com/products/sg380.html
Their clock generator is OK, except for the klunky user interface.
https://www.thinksrs.com/products/cg635.html
The internal architecture is sorta weird.
Somebody once wrote a novel without using the letter "e".
Somebody should write a novel in 7-segment text.
Joerg <news@analogconsultants.com>wrote:
On 6/22/26 11:07 PM, Jan Panteltje wrote:
Joerg <news@analogconsultants.com>wrote:
On 6/17/26 11:50 PM, Jean-Pierre Coulon wrote:
We are using Stanford Research SR780 and SRS785 FFT spectrum analyzers. >>>> We obtain this peak in every measurement we do. By connecting an
unshielded wire and moving it it is obvious that the FFT is the culprit. >>>>
Are we the only ones in this case?
Self pollution? I was never fond of Stanford Research analyzers. The
kicker was a case where that expensive thing could not find a noise peak >>> in the audio range but my lowly netbook with a 1st gen Intel Atom CPU
and 18(!) bit sound chip could clearly find it.
Do you mean 8 bits?
Most audio was 16 bits though?
Even back before 2010 most laptops sported 24-bit sound chips but mine
had only 18 bits. That's why some of their engineers scoffed and thought
I'd never find anything with that. Until I did.
On Mon, 22 Jun 2026 09:24:06 -0700, Joerg <news@analogconsultants.com>
wrote:
On 6/17/26 11:50 PM, Jean-Pierre Coulon wrote:
We are using Stanford Research SR780 and SRS785 FFT spectrum analyzers.
We obtain this peak in every measurement we do. By connecting an
unshielded wire and moving it it is obvious that the FFT is the culprit. >>>
Are we the only ones in this case?
Self pollution? I was never fond of Stanford Research analyzers. The
kicker was a case where that expensive thing could not find a noise peak
in the audio range but my lowly netbook with a 1st gen Intel Atom CPU
and 18(!) bit sound chip could clearly find it. Oh, and that netbook had
cost me a fraction of what the client had paid for that analyzer. Their
engineers stood there in disbelief. They initially didn't believe it. So
I said "Slow down that fan over there with your palm and a rag and watch
the peak on my laptop screen". One of them did ... "Oh S..T!"
SRS used 7-segment LEDs, spelling out letters!, way after everybody
moved to LCDs.
Their pushbutton menus were crazy too.
https://www.thinksrs.com/products/sg380.html
Their clock generator is OK, except for the klunky user interface.
https://www.thinksrs.com/products/cg635.html
The internal architecture is sorta weird.
Somebody once wrote a novel without using the letter "e".
Somebody should write a novel in 7-segment text.
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
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