Hum on transmitted signal

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  • Updated 1 month ago
I received my 6600 M today, and got right to familiarizing myself with it. I made a few quick contacts and I was told that there was hum on the signal. I looked at it on two other transceivers and on both panadapters you could see the hum superimposed on the signal the hum is there in CW, tune, and SSB. I tried a different power supply, all of them Astron linear supplies, and the issue persisted. I even put a scope on the output of the power supply to look for ripple and there was Virtually none. Could this be something about the SDR architecture and the 6600 that I’m not familiar with? Any help would be appreciated I also have a screen issue, and I wonder if this is something that others have observed. In the upper left hand corner of the screen there is a light area, what you might see if you put you finger on an lcd screen. It is there all the time. There is no such abberation on the Maestro I bought to go with the 6600m.
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Al Matthews

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Posted 1 month ago

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mikeatthebeach .

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Not normal.... Have 6600M here and No Screen/No Hum issues 
Try a 50ohm dummy load --- Is it RF getting into DC Lines - etc
Might suspect RF getting into it on Transmit - Ferrite Cores can fix that ! 

Regarding the screen issue - attach a jpeg so we can see it to comment 

73 Mike
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mikeatthebeach .

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Al, 
 
Also if you have the Astron Linear Supply too close to the Flex
perhaps the AC Field of the transformer is causing issues with
the 6600M with an AC Field from the transformer induced Hum

If you have a DC Battery in lieu of the AC supply that would eliminate
that factor as an issue of the hum 

Mike
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Al Matthews

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Hi Mike, I am using an Astron VS-50m linear supply. It is about 10 ft. from the 6600m. I tried the Astron 50 amp switcher that I also have. No difference.
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K3SF

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a 10ft long DC power cable...seems like a perfect place to pickup RF and to have a very large voltage drop....

the flex input voltage is critical.

There are some s/w utilities to measure the input voltage...

see thread
https://community.flexradio.com/flexradio/topics/voltage-drops-chart

https://community.flexradio.com/flexradio/topics/flex-meter-v1-2

http://k5fr.com/DDUtilV3wiki/index.php?title=Main_Page

these s/w tools will measure the voltage inside the radio

Paul K3SF







(Edited)
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Bill -VA3WTB

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What is you DC power at the power connector on the Flex while in transmit at a 100w
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Bill -VA3WTB

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Al, I don't think you are going to get any further here, I would open a help ticket tonight.
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Burt Fisher

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You have the same name as K1LTJ who I knew as a kid 58 years ago and look like him. I have a Flex 6400M. I think we are the only two still alive and active from that group from Norwalk area.
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Al Matthews

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We're still alive?
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Bill -VA3WTB

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Al, start by disconnecting things from the radio one at a time and use tune button to transmit. Something connect to the radio causing a ground issue.


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Al Matthews

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Bill, I removed everything one at a time, but the hum is still there
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Al Matthews

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Good point Bill. I unplugged everything but the ethernet and power connector. (obviously). I then unplugged the ethernet cable, no change. I am running 1 watt into a dummy load.
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Al Matthews

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Here are the pix and a short video of the problems. I have also included a video so you can see and hear the problem. I do appreciate the help and suggestions. Any more ideas on what I might try? 

Al / K1LTJ







Here is the picture of the light area that never goes away in the upper left corner of the screen. There seems to be some of this a the bottom center as well.

(Edited)
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Ken - NM9P, Elmer

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You may want to do a factory reset, as per the manual, and see if perhaps the processors glitched when booting up and something got set incorrectly.
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Al Matthews

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Ken, I tried the xvtr port, but no change the hum is still there. I did a factory reset, but no change. The manual says to hold the power button from the off state until it blinks white. It turned white, but never blinked. I also tried downgrading the software without a change.
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Bill -VA3WTB

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Did you put in your help ticket yet,,time is wasting.
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Al Matthews

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Yes, I put one in Bill, so I hope to hear from them. I’m not sure if I’m ok with repairing a 5hr old $6000 (with gpsdo etc) Radio. This must be unusual, I have never bought a DOA transceiver in 59 yrs as a ham.
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Al Matthews

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And thanks for all the help everyone has offered. This is a great group.
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mikeatthebeach .

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Al,
 
Saw your video, if you get AC buzz with a Battery you should contact help desk

Also, the white Flare Up in the Upper Right of the screen most likely
will not show when SSDR is running. I suspect it is because of more
pressure in that corner due to mounting or shifting of the Touch Screen

Mine has a slight White Flare-Up in that area, but not seen when Display is active
or Booting Up. ( White Flare-Up in left upper Corner is on mine as well ).
Some may be more noticeable than others is my guess 

Possibly during shipping this can be aggravated, my guess this can be
fixed by a mechanical readjustment by Flex if you sent it back to fix the Hum
Issue

Maybe a ribbon Cable ground got loose during shipping to cause your Hum Issue
( Try with a DC Battery ). If your 6600 goes back, both Issues can be addressed
with a Help Ticket to Flex.

73 Mike

(Edited)
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Dennis ODell

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Does the buzz change character or level if you raise or lower the touchscreen backlight illumination?
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Al Matthews

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I changed the touchscreen illumination Dennis, but it had no effect.
(Edited)
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Wayne

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Looks like at the factory either the touch screen or the backlight were mounted slightly off the correct position then missed during the qc process before it was shipped. You need to open a helpdesk ticket to get an rma and maybe while its there they will verify if the hum you are hearing is due to the rig or your shack environment. Be sure to describe to them exactly how to observe the white you are seeing or they may miss it when they try to make it repeat.
(Edited)
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Al Matthews

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This is a great group of helpful people, with some great ideas on things to try. Thanks to all of you.
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N8SDR

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Al,  have you disconnected the Ethernet cable and tried as well ( didn't see that mentioned) , I'm curious as I have seen some routers and switches which are noisy and i wonder if that is getting into the radio via the cable. If it does away try another cable if its the newer style with the metal grounding around the connector try one without it a standard type 5 will suffice. If it also drops and reappears with another cable then start looking  down the line at the devices which are plugged into the router and or switches including other computers and such. Some of it comes into the network system via the cheap non filtered power adapters they use. Ground loops between the network devices can also cause issues.
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Al Matthews

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Thanks for the suggestion. Yes, I tested with only the power and dummy load connected. The problem was not affected by removing the Ethernet connection.
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Burt Fisher

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How about a battery?
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Terry AB2UE

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Try plugging astron power supply into a 3 to 2 prong adaptor as a test to see if hum goes away.
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Burt Fisher

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Did you ever fix it?
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Al Matthews

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Yes Burt, Tim has been a great help. It is an intermittent problem, and they will look into it for me. The support with Flex is great.
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Burt Fisher

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Yes one gets great help from Flex, Neal too. I had a strange large waveform on various bands. I thought it was the 6400M but I took a KX3 outside and it appeared to be RF emanating from a nearby campground. 
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Ken - NM9P, Elmer

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The noise generated by some RV charge controllers can be horrendous. My neighbor’s camper trailer charger used to wipe me out a few weekends a year as they charged up before and after several weekend trips. Then they sold the camper.
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Cosmos (Alan KB5CUS)

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Al...  I haven't seen mention of what mic you are using & if you have checked if you have the Mic Bias on or off/ also +20Db boost on / off. Also if your using a Dynamic Mic, Bias needs to be off & have properly wired  adapter cable . Do you have another mic you can try ??

OPPS...  Sorry..  I didn't see that you got it going....   LOL
(Edited)