WATERFALL of the WATER HOLE INTERFERENCE

[David Eckhardt]

The second port of the splitter is now fed to the AirSpy R2.  The PC is running SDR#.  The HI emissions are easily viewed just to the right of the AirSpy LO as a fuzzy vertical line on the last group of images.  8 MHz span is not wide enough to ccapture the full spread of the interference.  I am not sure much more information can be gleaned from this presentation of the interference, but have a look at the enclosure.    

Dave Eckhardt - WØLEV

[David Eckhardt]

I believe I sent you the original email on this issue which defined my setups.  There is a NooElec preamp at the antenna which claims 0.5 dB noise figure and a gain of 40 dB.  I measure the gain more like 38 dB. 

I need the preamp to see the HI line, but certainly not to detect the interference.  It measures a peak of -43 dBm on the spectrum analyzer connected directly to my wideband horn sitting the the radio room window with no preamp other than what is internal to the spectrum analyzer.  The horn is connected to the SA through about 6 to 8 feet of RG-58.  The specified gain of the horn at 1.5 GHz is 6 dBi (3.8 dBd).   My window is also low-E which attenuates 1.5 GHz by an unmeasured amount. 

Neither the R8600 or the SA need an external preamp to easily detect the interference.  I could even run both without their internal preamps and still easily detect the interference, but not the HI emission.   

Dave - WØLEV

On Tue, Dec 28, 2021 at 10:59 PM Greg Ella <grege...@gmail.com> wrote:

Are you using an external preamp and H Line filter?  Are you able to see this interference with your Icom R-8600 without

an external preamp and filter?

Greg

On Tue, Dec 28, 2021 at 3:46 PM David Eckhardt <davea...@gmail.com> wrote:

The second port of the splitter is now fed to the AirSpy R2.  The PC is running SDR#.  The HI emissions are easily viewed just to the right of the AirSpy LO as a fuzzy vertical line on the last group of images.  8 MHz span is not wide enough to ccapture the full spread of the interference.  I am not sure much more information can be gleaned from this presentation of the interference, but have a look at the enclosure.    

Dave Eckhardt - WØLEV

--

Dave - WØLEV

Just Let Darwin Work

[Hamish Barker]

are you sure that isn't coming from the pc?

the pulsed bands seem to indicate a square wave around 30kHz pulse frequency. might be a switch mode power supply (could be an LED driver also, maybe a streetlight? or a variable speed motor drive.

Can you localise the bearing by rotating your antenna?

On Wed, Dec 29, 2021 at 11:46 AM David Eckhardt <davea...@gmail.com> wrote:

The second port of the splitter is now fed to the AirSpy R2.  The PC is running SDR#.  The HI emissions are easily viewed just to the right of the AirSpy LO as a fuzzy vertical line on the last group of images.  8 MHz span is not wide enough to ccapture the full spread of the interference.  I am not sure much more information can be gleaned from this presentation of the interference, but have a look at the enclosure.    

Dave Eckhardt - WØLEV

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[Jeremy Waller]

Re:  8 MHz span is not wide enough to ccapture the full spread of the interference.

There is a way of getting a wider bandwidth.

1. You will need multiple receivers each tuned to an offset frequency such that the pass bands overlap by about 10% of the bandwidth.

 Initially the LO's need not be phase locked.   The spectra may be "stitched"  to indicate the overall spectrum.

2. A more difficult exercise is to combine the  outputs of the receivers to synthesise a single wide band signal. I did this exercise (not at all pleasant), as part of my job,  with 3 receivers (IF = 21.4 MHz.).

Jeremy

[David Eckhardt]

But Terry, I receive the interference coincident with the R8600 on the horn pointing out the window connected to the Rigol spectrum analyzer.  Totally different system!  That's why I set up that for a sanity check.  It's not the NooElec preamp with intermod.  It's really there.

Dave - WØLEV

On Tue, Dec 28, 2021 at 11:58 PM Terry Bullett <tbul...@skybeam.com> wrote:

Dave,

That you can still see the interference without the preamp shows that it is in-band.  To be even more sure, I would use one of the 1420 MHz bandpass filters at LTO, right at the antenna and without the preamp.  I have no clue about the IP3 of that first stage in the preamp.  I know Ted is struggling with interference using the same device. 

There is also a 0.5dB NF amplifier from MCL used by the STEM students at LTO.  I think it’s probably more robust than the nooelec.  

Terry Bullett  

On Dec 28, 2021, at 16:17, David Eckhardt <davea...@gmail.com> wrote:



[David Eckhardt]

I'd encourage you to explore this whole thread.  It turns out the severe Water Hole interference is likely caused by the second harmonic of the 710 MHz cell handset usage.  More RFI in the Water Hole!!

Dave Eckhardt

WØLEV

---------- Forwarded message ---------
From: Terry Bullett <tbul...@skybeam.com>
Date: Wed, Dec 29, 2021 at 8:40 PM
Subject: Re: WATERFALL of the WATER HOLE INTERFERENCE
To: David Eckhardt <davea...@gmail.com>, Greg Ella <grege...@gmail.com>
Cc: Bascombe J. Wilson <jay.w...@vodec.net>, Meinte Veldhuis <mei...@frii.com>, Ted C <hm5...@hotmail.com>, Marc Clarke <clark...@gmail.com>, Phil Burk <Philli...@comcast.net>, <celestia...@mindspring.com>, Hare, Ed W1RFI <w1...@arrl.org>, Dave <da...@nk7z.net>

Dave,

You start by turning radio astronomy into a multi-trillion dollar per year industry. 
Then buy more lobbyists than the cell phone companies, to pay for a majority of the corruption in DC.
Then you might see some action. 

Terry 

 
On 12/29/21 11:54 AM, David Eckhardt wrote:

Greg, I just confirmed that 710 and 1420 happen together.  At least on the SA with the horn.  I was sweeping from 700 MHz through 1.5 GHz, and, yep, there are the two signals about the same strength even though the horn is rather insensitive at 700 MHz. 

I just witnessed both frequencies being written simultaneously.  The spread of one set of pulses at nominally 710 is 11.33 MHz and at 1420 it's 28 MHz wide.  Not quite 2X of the 710 frequency, but close enough.  So, yes, it's the cell network - handsets.  ROYAL GROUCH😫😕........

What do we do to get FCC off their duffs on this one??  Crystal clear they the 700 MHz handsets are polluting the Water Hole with their second harmonic which is supposed to be virgin territory. 

Dave - WØLEV

Dave - WØLEV

On Wed, Dec 29, 2021 at 6:04 PM Greg Ella <grege...@gmail.com> wrote:

Not a lot of physical space inside of modern cell phone handsets for effective harmonic filters.

Digital cell phone handset transmissions have a distinctive sound, if you listen on AM somewhere within the

bandwidth of the handset TX.  You might give a listen down around 710, and compare it to what you hear at 1420.

My QTH overlooks the intersection of 392 and 287, which gets quite busy during rush hour.  We also have a 700 MHz cell tower nearby, so handsets will be active in that

band.  I plan to do some simultaneous monitoring of 710 / 1420 with antennas pointed at that intersection, to look for correlation.

Greg Ella

N0EMP

On Wed, Dec 29, 2021 at 10:30 AM David Eckhardt <davea...@gmail.com> wrote:

Thanks, Greg, for the sleuthing.  So, cut to the chase, we owe the interference to the hand cell phone units.  GGGgrrrrrrr...........  So, does FCC have to require far better filtering on the hand units to keep the second harmonic out of the Water Hole???  Fat chance of that ever happening......😖😫😕📵

I will have a look at 710 MHz today and report back. 

However, what I am receiving is 24/7 at generally very well defined intervals of nominally 43 minutes.  Yesterday, when I took the waterfall data was an exception.  The rep interval seemed a bit random and some were minutes apart - very atypical to the usual 43 minute rep rate.  We did recently come home with a smartphone, Samsung, through Consumer Cellular, but it is sitting on equipment in the OFF state since we don't have cell service here at home.  I've had this interference off and on well before that came home with us.  I haven't even put phone numbers into it as we purchased it predominately for traveling. 

Dave - WØLEV 

On Wed, Dec 29, 2021 at 3:34 PM Greg Ella <grege...@gmail.com> wrote:

Here is a study of cell phone handset harmonics and interference to a radio telescope:

http://www.naic.edu/~phil/rfi/cellphone/lbw_dome_19aug05.html

These tests were done on 2005, before the 700 MHz takeover.

Greg Ella

N0EMP

On Tue, Dec 28, 2021 at 10:38 PM Terry Bullett <tbul...@skybeam.com> wrote:

If it comes down to cell phone companies vs any other spectrum users, the cell companies will win.  Even over DoD. 

Terry

On Dec 28, 2021, at 20:28, Greg Ella <grege...@gmail.com> wrote:



I've been listening tonight with my 8600 just outside Fort Collins.  Discone antenna with a mast mounted preamp

intended for over the air television.  Not designed for 1420 MHz, but seems to have some gain there.  I hear

occasional interference that looks like the waterfall pics that Dave sent.

I cut the frequency in half to 710 MHz.  Same signals, but much stronger.  4G LTE band 12 and band 17 uplinks (handset to tower)

span across 710 MHz.  See here: https://en.wikipedia.org/wiki/LTE_frequency_bands

I think you are seeing the second harmonic from cellular handsets operating on 4G LTE bands 12 and 17.

If this is true, and you simultaneously monitor 710 and 1420 MHz, you will see coincident signals.  Also,

if you monitor in a town or near a busy roadway, you should see very little between midnight and 0400 local time,

with peaks around rush hour and midday.  Research project for Star Kids?

I dropped SARA from this reply, because my email bounces off of them.  Dave, please forward to SARA if you

deem appropriate.

BTW, the second harmonic of band 13 covers the GPS L1 frequency.  I listened there, and guess what?

Greg Ella

N0EMP

[Marcus D Leech]

That’s unfortunate. I know that manufacturers of bass stations equipment for this band were required to put in filtering specifically to protect the 2nd harmonic. But I think the regulators generally caved for handsets. 

Sent from my iPhone

On Dec 29, 2021, at 4:26 PM, David Eckhardt <davea...@gmail.com> wrote:



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