Maestro TX Audio has Hum

Cal N3CAL

I've been told by others that I have a hum on my transmit audio while using my Maestro.   I've confirmed the issue using FDX and listening on a second slice.  I'm using a Radiosport RS60CF Headset with M207 mic cartridge along with the Radiosport cable hooked to Mic-2 and Phones on the Maestro.  The Hum is only there while using the supplied Flex wall plug-in power supply.  I have no hum if using only a USB battery or using external 12V from my shack power supply.  The Flex power supply measures 12.1 Vdc out.

Here is a waterfall shot of my TX audio while using the Flex 12v power supply,  you can see the hum / noise on the left side of the waterfall : 

Here is a waterfall shot of my TX audio on a USB battery only you see the hum/noise is gone:


Is this a known issue that has already been documented or is this a possible bad power supply? 

Cal/N3CAL
 

David Decoons, wo2x

Cal, try running the Maestro on the power supply that was included with it, not 12 volt shack power. See if that improves things.

Dave wo2x

Chris DL5NAM

It's the Flex power supply. There was before some days a thread here.

wb5xx

WO2X. Re-Read the original post and then Re-Read your answer.

David Decoons, wo2x

Oops, my bad. Too quick reading it. Is the Maestro supply plugged straight in the wall or through a power ****? I know you need to use a brick with grounded AC plug. Dave wo2x

Cal N3CAL

The Maestro supply is plugged directly into a three prong wall socket. 

Cal/N3CAL

David Decoons, wo2x

Carl, give Dave at Arlan Communications a call tomorrow. He is very good to deal with and can help you get to the bottom of it. I thought I remember there were some issues with initial batch of the right angle cables.

I'm using the RS-60CF with M350 electret element and the Maestro right angle dual 3.5mm cable. Running 50 - 3500 bandwidth for rag chew and no issues.

Make sure you have Maestro bias off as the M208 is a dynamic element. Also check to ensure the cables are firmly plugged into MIC-2 and Phones.

73

Dave wo2x

Cal N3CAL

Dave, 

Thanks for the reply but my name is Cal not Carl!   It seems you are not reading through my original post!  The headset works fine with a USB Battery in the Maestro as well as a external 12 volt power supply (NOT THE Flex Supply).   How could the headset cable be the issue if it's working  with USB Battery power etc. (Picture 2)?  Sorry but I don't follow.  

Maestro bias is off and the element as listed in my original post is a M207 dynamic mic.  +20db is selected. 

Cal/N3CAL

David Decoons, wo2x

Sorry Cal but I am using my phone and don't have my glasses :-) I had the same issue early on and Dave sent me a replacement Maestro cable. Hum with the included power supply but not on battery or shack 12 volts. Try one more thing, while transmitting with the hum present touch the CW key jack on back of Maestro and see if the hum reduces. When I had the issue it would reduce quite a bit. Dave

Cal N3CAL

Touching the CW key jack on the back while transmitting does reduce the hum.  With the hum present there are two spikes peaking at about -60 db on the left of the display.  Touching the key, pwr spk, or line out jacks on the rear reduces the spike on the display to -80db but it's still there.   

Cal/N3CAL

David Decoons, wo2x

Ok this looks like a ground/ground loop issue. Check with Dave at Arlan Communications to see if that might be one of the early cables.

The RadioSport cable with dual 3.5 mm right angle connectors uses the phones shell connection for ground.

Dave wo2x

Steve (N9SKM)

There was someone else that had an issue on the flex and his shack PSU. Slapping a ferrite on it for him cleared it up it seems. I havent used the Flex power adapter yet just my shack supply on it.
Or possilbly the headset cable issue mentioned above is what the deal is.

Tim - W4TME

The supplied AC switching power supply, while grounded through the AC mains, may be a little noisy, as all switching power supplies are.  As Steve (N9SKM) suggested, a few turns on a ferrite core should fix you right up.

Cal N3CAL

Tim,

The supplied AC switching supply came with 2 ferrite cores installed on them already!  The cable is rather short and if I wrap any more cores on it will be too short for any practical use.  This issue is far from solved.  I'm very disappointed.

Cal/N3CAL

Steve K9ZW

@Cal/N3CAL

I improved some similar issues when I made sure my electrical supply grounds were actually well grounded.  Seems they weren't and it helped when they were corrected.

BTW Like the camo-tape job on your vertical.  Effective in the photo.

On my Maestro power supplies I did substitute longer mains power cords, which might be a way to give you some more working length.

73

Steve K9ZW

Cal N3CAL

I added a large Mix31 Ferrite Core and it didn't help at all!  The Flex Power Supply is useless!  It's a piece of junk!  This is very disappointing!   Sorry but I'm getting very frustrated. 

Cal/N3CAL

Bert

I had the same problem with the Maestro supply....extremely noisy including AC hum. Tried two different Maestro supplies and both were noisy. Replaced them with an Astron switching supply and is quite as a church mouse - no noise, no hum. I too was disappointed as the Maestro supply fit my installation requirements - the Astron does not.