Re: [RFI] Sitting position and RFI ...

["QRV@kd4e.com" <QRV@kd4e.com>]

I'm inferring that it's coming from the UHF LNA or the cellphone 
repeater device
but am puzzled as to how.


Perhaps it's bouncing off the wall behind me, or the ceiling?


I'm in a metal structure.


Just tried leaning in different directions ... there is an angle where 
it happens
and one that does not.


It doesn't happen unless I'm sitting in my office chair (which has an 
unplugged
roller massager on it) - I tried standing then crouching - as if seated 
- no static.

Our 6'4" 300lb son just got home and was standing in the doorway - suddenly

the effect ceased. Had him step away - it returned.


So, conclusion is that the signal is originating in the next room and is 
bouncing
off the wall behind me ... and the combination of my body and the chair is

combining to reflect it on to the HT antenna.


WDYT?


On 1/31/22 4:53 PM, Michael Carter wrote:
> David,
>
> You didn't conclusively identify the signal source that was opening
> the squelch.  However, your body may be the necessary
> attenuator to prevent the squelch opening in just
> the right body posture.  A slight shift in posture is
> enough to increase the squelch-breaking signal
> strength at the HT.
>
> For what it's worth, I use my body as an absorber
> when DF'ing RFI sources with a 135 MHz handheld
> receiver and a simple helical whip.  The body absorption
> is sufficient to remove the whip's null direction ambiguity
> when held horizontal and swung in the azimuth direction.
>
> 73,
> Mike, K8CN
> ------------------------------------------------------------------------
> *From:* RFI <rfi-bounces+mike.carter=unh.edu@contesting.com> on behalf 
> of QRV@kd4e.com <QRV@kd4e.com>
> *Sent:* Monday, January 31, 2022 3:55 PM
> *To:* RFI@contesting.com <RFI@contesting.com>
> *Subject:* [RFI] Sitting position and RFI ...
> 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.
>
> Riddle me this ...
>
> I'm sitting at my desk and my handheld is sitting on a wood shelf
>
> just behind the HP laptop.
>
> The HT is on and set to monitor 146.670 (it has long thin flex antenna).
>
> All of a sudden the squelch opened to static.
>
> I walked around with it and it seemed that the source might be the
>
> inline UHF amplifier that feeds two rtl-sdr devices, or the cellphone
>
> repeater. Note: Both devices are located on the other side of a 4x8'
>
> steel door from the handheld, laptop, and me.
>
> When I sat back down at my desk it was quiet, then when I moved,
>
> it started, again.
>
> Yup, it's responding to the position of my body relative to the laptop
>
> and mouse.
>
> Sitting back, away from the desk opens the squelch, leaning forward
>
> quiets it.
>
> WDYT?
>
> David KD4E
>
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