6300 transmit hum

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  • Updated 5 years ago
I took delivery on a new 6300 last week and put it on bench a couple days ago.  My audio reports were not good (slight hum) and bassy).  Maxing out the 500 and higher EQ helped the bassy but hum persisted and audio was still not great.  I was using a Heil 780 mic and tried my EV 320 and finally the handmic. With monitor on I can hear the noise and if I check the box in setup that allows you to watch audio signal during RX I can see it on the panadapter and level meter without transmitting and with no microphone attached.

Hoping I am doing something stupid but I really suspect its a faulty radion.

Any ideas?

Rich

kd0zv
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Rich McCabe

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Posted 5 years ago

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KY6LA - Howard, Elmer

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First Guess .....

RF in the Shack

Second Guess.. what are you using for a DC Power Supply and what is it's maximum power rating?
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Rich McCabe

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Hi Howard.  Well the noise is there with power turned down completely and the Level indicator is indicating audio when with no mic attached and not TX. Its jumping between zero and 6 bars right now without mic attached.

The power supply is a RS35M and seems to be functioning fine
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David Altekruse

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Hum and audio problems are classic ground loop symptoms.  

-David, N1DNA
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KY6LA - Howard, Elmer

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The RS35M is an excellent supply and more than adequate for the 6300

However they are known to sometimes have failed capacitors that can cause hum when they get a bit older... suggest if you have a scope look at the power supply to see if it is clean...

Is the hum on receive too or only when in transmit mode?
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Rich McCabe

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Here is a screen shot. No microphone and not TX at this point.
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Rich McCabe

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No hum on receive Howard. Powers everything else fine including my Icom 8500 wideband receiver.

I am concerned that there is audio activity on level meter with no mic attached !
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KY6LA - Howard, Elmer

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Looks very much like RF in the shack on Transmit...

Suggest you read my paper on "How to Build a Quiet Station"

https://www.dropbox.com/s/kffp92esffo3zy5/How%20to%20Build%20a%20Quiet%20Station%20V2.pdf?dl=0

Unfortunately things like Ethernet Cables and Computers pick up RF even when transmitting small amounts of power..

Heading to the USC / Nebraska Holiday Bowl Game Now.. GO TROJANS>.. 73's
(Edited)
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Rich McCabe

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There is no transmitting going on in the shack. That audio level is showing up on receive with no mic attached.

Thanks for help and have fun at game.

73
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K1UO - Larry

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Hi Rich,    Go in to the SETTINGS Tab (TOP left row) and in to the RADIO SETUP view and check the PHONE Tab and disable the  LEVEL METER during receive.
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Rich McCabe

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Larry, is this normal on the flex to show the flickering level during receive.  I am trying to diagnose my hum issue and thought what I was seeing during receive was the same buzz? That is why I have that turned on.
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K1UO - Larry

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Rich,  I cant recall and cant check because I have the radio remotely on my LAN and using DAX for all the audio so I cant check.  Are you getting hum during receive or just transmit?


You could disconnect everything on the rear panel except the Ethernet cable and power to see if that eliminates a possible ground loop.

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Ken - NM9P

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Start by checking your mike line. It sounds like you may have it wired up incorrectly. The shield should be connected to the connector ground. Then then look at the mike diagram. There is a mike- and a mike+, do not connect the Mike minus and shield together. It will ruin the shielding, making it more prone to hum and rf on the signal.

Then try dropping the 63 Hz level all the way down. Check your Tx audio level on voice peaks. The meter should never go red or over the 0 dB mark. Make these adjustments with the processor/compressor OFF. Then add the compression without adjusting the Mike levels any more. Just a start. Let me know what you find.
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Ken - NM9P

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Next.... Turn power all the way down. Put on phones. Hit PTT and adjust Downward Expander until background noise just drops.
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K1UO - Larry

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OK ..I pried my rig out of cw mode to one of the SSB modes and I enabled the level meter and I see one green bar on the level meter but no deflection...  do you by chance have VOX enabled?

  
(Edited)
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Rich McCabe

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 Larry its just TX. For now I am going to assume the level flicker shown in my picture is normal without audio.

The only thing connected to back of radio is the power, feedline and Ethernet.

I notice the noise/hum is more pronounced on the Heil 780 than the hand mic.

Noise is same  into dummy load and 1/2 wave and does not change when I move the power level from left to right (full power).

It is not 60 cycle and sounds more "juhhhhhhh" .

I just ran a ground wire between PC and 6300 and picked up more noise that sounded more 60 cycle.

This forum is great !

Thanks
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Jay / NO5J

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Rich 
The ground wire you added between the PC and the 6300 created a ground loop so that's why you got more hum doing that. The ground wire from each component should not be daisy chained each component should have it's own connection to a common ground point. My shack to my ears is relatively quiet but I do have fans in the PCs and fans in the radios and amps the microphone picks those up the downward expander eliminates those noises. How close are you working the mic? the PR781 can be worked very close its internal pop screen is effective enough, so remove any external pop screens if you use them, and start out with you lip right against the metal screen on the face of the mic and back away enough to avoid the thumps caused by you lip bumping the mic. that will let you reduce the mic level setting a bit more. The less you have to use the gain in the level controls and mic preamp the better. I keep a newborn sized white tube sock on my PR781 as a spit guard to avoid spitting directly into the mic and also as a lip guard to avoid becoming an unintended personal ground loop. Looks a bit silly but when visitors show up I just pull that sock off and pretend to polish the mic with it, thats also a good time to swap it with the other sock in the pair and send that one thru the washing machine. hi hi The mic is on a boom arm so I just lean a bit forward and pull the mic right up against my lip and then relax so the face of the mic is never more than 2-3 inches away. The PR781 is designed to be talked into, and not side talked.

The  "juhhhhhhh"  your hearing might just be nothing more than background noise in the room being amplified by the radios preamp.
(Edited)
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Rich McCabe

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Jay,  all my gear is grounded to a common bus however the PC is ungrounded (thus the loop).  I need to get a ground wire on it but have been busy with building a new shack setup.

I close talk my mics and they are on a boom. I have given up on the PR780 for now as the  ElectroVoice RE320 seems to be a better mic for this application.  I have been using the boom setup for over 10 years so getting pretty good at using it at 1-2" distance so thats not an issue. 

I am reasonably sure the Juuuhhhh is computer noise and may go away with grounding the PC.
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Jay / NO5J

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I run a ground strap from one of the PC PSU screws on the back of the PC. The screw closest to the AC cord receptacle to be specific. But still put Ground loop isolators on all the line inputs to eliminate those ground cross-connects. If your speakers connect directly to the radio you avoid that loop too. PC speakers powered by a wall wart supply have the connector on the input cable floating it's ground connection also eliminating it's loop. Your aware of that I'm sure. just restating it for anyone new to running transceivers that use powered speakers and PC connections, that might read this. If there is Hum heard in your audio there shouldn't be, and you don't have to live with it. 
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Rich McCabe

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Thanks Jay. I will get rid of it noise one way or another.

I am not sure which route I am going to go with audio yet. I do not want an extra set of speakers for the Flex so I ordered a iPlus from W2IHY and that will switch my mics, amp and speakers. My experience with W2IHY stuff is that he does a good job with RF isolation so hoping that takes care of it.  I also have a line isolator out for delivery right now as I might add a switch and use the PC input allowing me to listen to the Flex and my other radio(s) at same time.

Just been a while since I have had to ground the computer for anything !
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Jay / NO5J

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Its been grounded all along, through the AC Line cord safety ground. Which is the why of the ground loop. If you aren't hearing it don't worry about it though. it's usually pretty obvious. So maybe your almost, or just past done with fixing it.
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Rich McCabe

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Ken,  its a new Heil Yaesu cable and the sheild was connected to the same ground the PTT is. I tried clipping that ground yesterday with no help at all. I soldered it back about 1 hour ago.

No change in noise with power change. I using headphones and monitor to test.

No vox

Yes the downward expander takes it out but trying to find culprit of the noise.

Not running and EQ at the moment. No compressor either and noise is there even with mic level at 75 % on level meter.

Just noticed noticed noise is there with Downward expander on when I am talking but it does take it out when I am not.
(Edited)
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Tim - W4TME, Customer Experience Manager

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Was the cable shield connected to the mic connector shell?
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Rich McCabe

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Tim the shield is/was connected to pin #5 along with the PTT ground. It seems to be working OK at this point with the EV RE320 but the heil 780 is just requires just too much EQ for my liking.  The radio is a little anemic from a punchy standpoint so it it permanently attached to my amp. I have plans to connect it to my EQ plus as soon as I get a cable built.

Basically at this point people cant hear me very well on the 6300 but if I switch to the 7800 (at 100 w) I am instantly Q5.  So I have some tweaking/stuff to figure out.
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Ken - NM9P, Employee

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Don't be afraid of using the EQ on the 6000, that's what it is there for.  A half hour's work with the EQ and mike levels, while recording yourself on another receiver will yield fantastic results.  There have been many posts on the subject, some of them specific to the PR-781 mike.  I use a PR22 which has a similar response pattern.  (I think the 780 may need more high frequencies added to it)  Search the forum and you will get some good starting places for your settings, both for Rag-chew and DX settings for the 6000 and PR-781.  But, before you ADD Highs, DROP lows.  Your zoomed panadapter is also a good tool to visualize if you have way too much or too little of any particular frequency band.  Then listen, listen, listen on a second receiver, NOT through the 6000 monitor and headphones because that is not a post-processed sample.  It is close, but not exactly what you sound like.
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Rich McCabe

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Good tips Ken. I have to admit I just straight to adding hights from 1K up. As a matter of fact I have 1k and above maxed out.  I will say when I switched to the RE320 mic all of a sudden I felt I had something to work with.  I will listen on the 7800  and I will try zooming the pan adapter too.

Thanks !  And Happy New Year.

By the way even though I am not where I want to be with the rig, I still think its awesome. 
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Ken - NM9P

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With no EQ and that Mike, you will be VERY bassy and prone to more hum.. Also, when changing mikes and eq settings, it is necessary to readjust mike levels so that you are not overpowering things. Sometimes what sounds like hum is just the normal background noise greatly amplified due to excessive Mike levels.
(Edited)
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Rich McCabe

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You know...

Even though I got a hum report first day I am not sure I actually have that. I am going to test online shortly. 

I just recorded my audio via SmartSDR even though I am not sure that is a valid test and it sound clean.  I tried listening my signal on my 7800 but its hard to tell.

Very bassy for sure.
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Jay / NO5J

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Rich
I think your seeing normal operation as far as whats displayed. What your seeing with the microphone level indicator is normal. My radio shows the same indication in receive with no microphone connected. What the meter is indicating is the "Peak" reading currently seen. which is a reading of current microphone level is "Less than -40 dBm" in other words its saying that it doesn't see a signal. I've got the 20 dBm boost enabled so in my case its indicating that it see's no signal above a -60 dBm. If the downward expander is enabled, that reading amounts to "Zero". when I disable the downward expander the peak bar fluctuates between -40 and -30 dBm with a mic  connected and selected and my normal mic level setting of 75 what its hearing is the receive audio coming out of the speakers if I mute the speakers, the level drops to "Peak is less than -40 dBm" again. Record your audio and listen to it if you suspect RF or hum on your transmit audio.  Hum from speakers and headphones indicates a ground loop, do you have everything grounded properly? 
(Edited)
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Rich McCabe

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On 160 now and no hum to other stations. So maybe I got a bad audio report and the hum I am hearing appears to be on my headphones only.

I am pretty sure everything is grounded well.  The basic rundown is Astron supply, powerpoles on everything. No wall warts for anything. Everything with a ground lug like tuners, radios, amp, etc is ground to a bus bar on back of desk which goes to a 8' ground rod 6' outside shack. That ground rod is bonded back to dual ground rods at panel as well a UFER ground (new code thing).

So I think I am OK but I have to agree the headphones deal sounds like ground loop at this point.

One more question.  If I turn on DAX I can receive though PC but have no audio control from SmartSDR at that point. Just PC soundcard control.  Normal?
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Jay / NO5J

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If I understand your question, yes that is normal, think of the DAX channels as "line" level connections. you can adjust the levels with the DAX control panel. SmartSDR can be adjusted to do what you want and all of its sliders affect things. DAX is next piece in the audio chain the DAX sliders only vary the amplitude of the signal into and out of DAX think of it as a software audio amplifier whose input and output connections can be changed with software.  really DAX is just Virtual Patch cables with level controls so you can match SmartSDR to other connections that run in software on your PC. but they are digital wires so the don't degrade the signals riding through them, as far as hum on the headphones is concerned I still think that would be a ground loop issue. Can the hum be heard if you record the mic audio with SmartSDR and play it back?
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Jay / NO5J

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Bill Roberts

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I made several 40 SSB contacts today, some under strong, good S/N condx. Everyone said great audio, no echo or hum. Still, I have the echo and grrrrr in the monitor.
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Bill Roberts

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I made several 40 SSB contacts today, some under strong, good S/N condx. Everyone said great audio, no echo or hum. Still, I have the echo and grrrrr in the monitor.
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Tim - W4TME, Customer Experience Manager

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Bill - I recommend you open a HelpDesk support ticket on your issue so we can investigate further. 

For details on how to submit a HelpDesk support ticket, please refer to the following URL: http://helpdesk.flexradio.com/hc/en-us/articles/202118688-How-to-Submit-a-Request-for-Technical-Supp...
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Bill Roberts

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Thanks Tim.  Dudley sent me an expedited RMA number and shipping label yesterday.  I boxed my 6300 along with the Heil mic cable and ferrite beads (in case there's any question about the cable) and dropped it at the UPS store this morning.  Thanks for the great support.
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Rich McCabe

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Have to say Flex service is pretty impressive.  I am sending mine back for a look as well.
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George Molnar, KF2T, Elmer

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One thing folks having audio issues might want to consider is building a terminator to act in place of the microphone. An open mic line could pick up random shack stuff (monitors, etc.) and provide a low-level of modulation. With a resistor (of mic impedance) using short leads in a shielded shell, you might see some improvement. At least for testing to rule out radio issues.