Thanks for the clarification Jim.
I think the RF energy is present in both. Depending on the turn on time of
the device, that will generate noise across a wide BW, similar to what a
lightning pulse does (no repetition there, just fast turn-on time). The
switching rate of any internal SMPS will also generate energy at multiples
of the switching frequency. When I scanned across the Aircraft band, I
didn't see much of an increase (aka the HT receiver has an AM BW of 6KHz and
step rate of 25KHz so I sample 25% at a time). After looking across 10MHz,
25KHz at a time, I would expect to eventually land on the SMPS frequency but
I saw pretty minimal peaks.
For 28MHz, I'm looking for any noise increase across 120KHz. Assuming the
Switching rate is less than this (seems like 20-40KHz is common), I should
see a spike in the display. There was none noticed.
This does bring up an interesting question. How is the LED string really
powered. There's not a lot of room in the tubes. I assume they are not
powering the LEDs off of the line voltage directly but I have not seen the
internals. If anyone has dissected one, it would be interesting to know for
sure.
-----Original Message-----
From: RFI <rfi-bounces+w4dd09=gmail.com@contesting.com> On Behalf Of Jim
Brown
Sent: Tuesday, November 10, 2020 1:03 PM
To: rfi@contesting.com
Subject: Re: [RFI] Hyperikon LED Tube Info
Thanks for your work and your post, Jeff.
There's one VERY important problem with your method in attacking devices
like this. Your method is great for power line noise, which is impulse
noise, and thus present at all frequencies. The noise electronic devices
produce is NOT impulse noise, and is rarely present at all frequencies.
Rather, it shows up at harmonics of the square waves that the noise source
uses. For electronic sources, we must use a receiver that can listen on the
ham bands where noise is a problem.
73, Jim K9YC
On 11/10/2020 6:32 AM, Jeff (W4DD) wrote:
> HT set to 137MHz / 3 element 137MHz Yagi / 45dB attenuator (this is my
> standard power line noise hunting arrangement) positioned at 5Ft from
> the fixture.
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