Hi Everyone,
I just created a simple website to share pictures and some text for the
analysis (including FFT) that I did on the unknown RFI Jeff (W4DD) is
trying to identify and I included known power line RFI for comparison
purposes so everyone understands my equipment capability, etc. Here is the
link to my simple website for this case:
https://sites.google.com/view/w4ddunknownrfi/home
I hate guessing what a RFI source is and will leave that up to others.
Note: I recently had a major breakthrough using my laptop based SDR
receiver to produce real time results similar to that of the Radar
Engineers model 243 and/or near field captures using an oscilloscope with
appropriate antenna and I was preparing to share my findings in the near
future. To help Jeff (W4DD) out I told him to use the very wide bandwidth
which is the key to my recent discovery and I mention this on the website
and I will follow up about my system in the near future. This very wide
bandwidth may have been discussed in the past by others but if it is I
don't think it's a well communicated requirement/need as normal
conventional receiver AM bandwidths are typically not adequate and SDR
receivers now provide us great flexibility and the bandwidth required.
Just FYI,
Don (wd8dsb)
On Wed, Nov 26, 2025 at 7:50 AM Don Kirk <wd8dsb@gmail.com> wrote:
> Hi Mike,
>
> I too did FFT using both my oscilloscope and a software based audio
> oscilloscope and will post them on a website and share it with the group in
> just a little bit. I also did it on a known power line RFI source that’s
> arcing 2 times per half cycle for comparison.
>
> Standby.
>
> Don wd8dsb
>
>
> On Wed, Nov 26, 2025 at 7:40 AM Michael Carter via RFI <rfi@contesting.com>
> wrote:
>
>>
>> I generated a FFT spectrum estimate of Jeff's 'Noise 1a 20 kHz BW' audio
>> file and attempted to post it to the reflector, forgetting of course that
>> this reflector doesn't allow image content embedded in posts. I sent that
>> email direct to K9YC and W4DD, and hope that Jeff can add it to his Google
>> Drive page.
>>
>> For anyone wishing to generate their own spectrum estimate, I used
>> Audacity with FFT size 8192 points, Hann windowing. The 60 Hz line and its
>> harmonics are prominent.
>>
>> 73,
>> Mike, K8CN
>> ________________________________
>> From: RFI <rfi-bounces+mike.carter=unh.edu@contesting.com> on behalf of
>> Jim Brown <jim@audiosystemsgroup.com>
>> Sent: Tuesday, November 25, 2025 11:12 PM
>> To: Rfi List <rfi@contesting.com>
>> Subject: Re: [RFI] RFI Signature
>>
>> CAUTION: This email originated from outside of the University System. Do
>> not click links or open attachments unless you recognize the sender and
>> know the content is safe.
>>
>>
>> Can you do an FFT of this, Don?
>>
>> Jim
>>
>> On 11/25/2025 5:09 PM, Don Kirk wrote:
>> > One is the oscilloscope display of your noise which I called "RFI
>> > being investigated" when you were using 20 KHz bandwidth. T
>>
>>
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