Internal noise on 160 meters - Flex 6600M

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  • Updated 4 weeks ago
Anyone seeing this noise on 160 meters with dummy load or no antenna connected ?  It varies in level with RF Gain settings.  It also varies in level when in WIDE mode.  I am opening a ticket.


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Joe N3HEE

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Posted 1 month ago

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Joe N3HEE

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This is what it looks like in WIDE mode.
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K1UO - Larry

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Here is what mine look like obn a 6600 ....  Swapped it out with a friends 6400 and the spurs were gone.
https://helpdesk.flexradio.com/attachments/token/06vCBhXpHAXLE73A047bEEdQO/?name=K1UO+160M+Birdies.PNG
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Joe N3HEE

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Thanks Larry.  Your noise spurs are different than mine but still not good.  Did you have spurs with 2.3.9 firmware ?
(Edited)
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K1UO - Larry

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Hi Joe,       I have had these through at least the last 3 firmware updates.   I should mention that the 6400 did have the large single spur on it like your picture shows.  My picture was taken in a much narrower bandwidth on the Panadapter and only start to show after s/n base  drops below -120dbm on the pan...  which happens a lot with my RX array or Beverages.
(Edited)
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Joe N3HEE

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Yes, I noticed mine when I started using my RX antenna a week ago.  Flex engineering is looking into the issue.  
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NA0B

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Some monitors produce that type of noise. That was my case, when I used a cheap 24" monitor.
When I moved to an all-in-one computer, presumable with better RF shielding, the noise went away. I had it in all bands. 


(Edited)
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Joe N3HEE

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It's not my monitors.  I don't have this noise on my K3.  Pretty sure it's internal to the Flex.  I opened a ticket with Flex.  
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Bill -VA3WTB

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Because the K3 can not pick up the noise does not mean the Flex can't.
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Joe N3HEE

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I made a little sniffer loop antenna and connected it to the K3.  I can hear the noise on the K3 when I get the sniffer antenna close to the rear of the Flex.  It's S5 on the K3 when sniffing the rear panel of Flex.  Flex engineers are looking into this issue now.  
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K3SF .

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just fired up my 6600M, not seeing any such spurs here on dummy load or on grounded antenna setup...

Paul K3SF
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Joe N3HEE

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Thanks Paul.  What version firmware are you running ?
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K3SF .

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i am running v 2.4.9
and
my 6600M  had the PEN updated done by Flex
and
at that freq the preamp is set to zero
and
i run my power supply at 14.0 vdc
(Edited)
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W8WD

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Joe,
I have a single spur at 1.82857 which is about -105dbm. I don't remember seeing it when I originally got my 6600M. Maybe its not related but I definitely can say noticed it after the PEN heatsink upgrade. 

Brian / W8WD
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Joe N3HEE

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I have one around 1827 but not as loud as the one at 1837.  What version of firmware are you running ?
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W8WD

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I am running v2.4.9, but I have seen the similar results with earlier versions. 
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NA0B

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FWIW, I just checked my Flex6600M. I don't have any spurs in 160m. I run v2.4.9.115.

(Edited)
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W8WD

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Joe,
I was able to replicate multiple spurs by changing the displayed spectrum width several times, there were relay noises in the radio as I changed the bandwidth and at some point the multiple spurs occurred. They were much larger than my original spur at 1.82857 mhz. Rebooting the radio caused them to disappear and then only the 1.82857 MHz spur @ about -105dbm was present.

Brian / W8WD 
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Joe N3HEE

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Thanks Brian.  Yes, the spurs will come and go when moving between WIDE panadapter widths.  However the primary (larger) spur does not change much.  Flex engineers are studing the issue. 
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Barry Simpson

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I have a loud internal spur on or about 1.828. I say about because the frequency is power supply voltage dependent. At first I thought that it was just a problem with the power supply but I have tried three different supplies with the same results.

It is exactly the same strength into a dummy load or with an antenna connected and is definitely internally generated I would suggest somewhere near the front end.

I have done some playing around and I have found that after a few changes to the Receive antenna source I can make the spur go away at least for a while.

I normally use antenna 1 input for transmit and receive. If I then tap on receive antenna 1, then receive antenna 2, then antenna 2 and finally back to antenna 1, the spur disappears on the final move back to antenna 1. It may not be that exact sequence but it always seems to work but then the spur comes back sooner or later.

Hopefully my non-scientific findings may give the Flex team a clue as to what is happening.

Barry Simpson VK2BJ
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Robert Lonn

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I took a picture of my 6600M this morning, Both bands using the same antenna, Carolina Windom.. 
Using the latest Software..

Robert


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Joe N3HEE

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Flex engineering has identified the noise as a third-harmonic of one of the switching supplies that can show up in 160m.  They have an ECO to address this issue which will move the harmonic out of the 160m band. I will be sending the radio back to Flex to have the ECO applied. 
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K1UO - Larry

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Hi Joe,  I just watched your noise demo for the 6600 on 160 meters and even though my noise signature looks a slightly different it is actually also being generated internally.  I had to chuckle to myself as you described the exact actions I took to try and find the source.  You even tried a couple I never thought of!   Anyhow hopefully this ECO (which i had not heard about until you mentioned it) will fix this problem since 160 is my favorite Band.  C U in the cw piles for VK9X!
Thanks for sharing the information and videos.
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Joe N3HEE

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Larry, In troubleshooting this noise issue I found another issue you may encounter.  When using RXA input for a receive antenna you may find about a 10 db degradation in signal and signal to noise ratio while the signal is routed through the bandpass filters.  I found much better receive performance via RXA input when using WIDE mode on 160 meters.  I also found many of the noise spurs disappear in WIDE mode.  This degradation issue does not present itself when using ANT 1 input.  The noise floor and signal levels are equal when switching between WIDE and bandpass filters engaged.  I will document in a video and submit another support ticket. 

I am also very active on 160 meters.  See you in Stew Perry this weekend ! 
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Ed Stallman

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Hi Joe , Larry and the group . I too am a 160m enthusiast with a Flex 6600 . So following with entrust ! For RX on the TB using the YCCC 9 Circle connected to RXA,  for my country location this works well for me. My spurs look exactly as Larry shows in his posted link. FW is 2.3.9 ... When I see these spurs, sending a single dit with the paddle will make them go away most of the time 
GL TB contest and DX , Ed N5DG
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Joe N3HEE

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Hi Ed. 

Not sure why sending a dit makes the spurs go away ?  That may be noise from an external source you are triggering on and off with your transmitter. 

Check your receive signal levels and signal to noise ratios with RXA and WIDE setting on panadapter.  See if you have 10 db improvement in WIDE mode.


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Ed Stallman

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Joe 
I have the RX antenna on a 75 Ohm A/B switch , so while seeing the spurs on the 6600 and switching to the K3 with Panadapter, it's gone . I seen early on that with out WIDE my SNR was not as good so leave it wide all the time. I made 2 screenshots . I'll see if I can post them here . I'm only seeing 3 to 4 DB improvement when in wide.  
(Edited)
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Joe N3HEE

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Thanks Ed !  This confirms what I am experiencing.  I see about 10 db improvement in WIDE.  My spurs are much stronger.  Flex knows about the issue and I will send the radio back to have ECO applied when I get a break in my contest schedule.  There is an issue with an onboard switching power supply causing spurs in the 160 meter band.  
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K1UO - Larry

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Hi Joe,Ed,

I just tried the Wide mode trick and RXA noise floor does indeed drop about 10db to -130 or -131 on the s meter when connected to the HI-Z 8 circle RX array  and 50Hz wide filter and the spurs nearly completely disappear!   Go back to the Band Filters and everything deteriorates.
  I already have a ticket in for the spurs but did not notice this aspect using wide Mode.   I wonder if I should open another ticket or add to the first since i have not returned the unit yet.

NOTE:  I just added this info to the existing ticket.
(Edited)
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Joe N3HEE

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Thanks Larry. I will also open a new ticket for this issue.  I already gave Tim a heads up this was coming.  
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Tom Worthington

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Hello all,
6600M, 2.4.9
I don't do 160 at the moment but I checked with a dummy load. My noise floor is about -140 dBm for a 5 kHz BW, about S1 with a 500 Hz BW.  I did find a band of hash, S6, at 1.850 MHz,  about 15 dB above the noise floor that goes away when I turn off my MFJ-4245 power supply and run on battery.  I see no other spurs.  Running with 16 dB preamp gain. I also noticed a change in the noise floor when I tuned up and the radio switched to wide but when I added the preamp gain the difference went away.  When I connect my 40/80m dipole I start to see some spurs.  I have had a lot of trouble with spurs from LCD displays, especially on 2m (10m transverter), I gave up my nice new (cheap) LG displays and switched back to two HP displays with built in power supplies.
73 and Aloha, Tom, NH6Y
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Joe N3HEE

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Mahalo Tom.  We will have to see what Flex engineers have to say about this.  Aloha  -Joe N3HEE