Reports of echo on ssb

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  • Updated 5 years ago
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I have had reports of a very faint echo on my transmitted SSB audio.  What confuses me is that it is present at the 100 watt level but goes away when I put my Ameritron ALS-600 on line.  Hence, it does not appear to be RF in the audio related.

Running a Flex 6300 and SSDR 1.3.84.  Also using the Flex-supplied Heil balanced to Foster connector cable.  Mic is a PR 781.  The radio is connected to my I7 computer running Windows 8.1 via a D-Link gigabit router.  I have 31 mix torroids on the mic cable, speaker cables (sharing Bose Companion IIs with my Flex 5000), power supply in/out cables, etc.  The antenna (GAP Voyager IV) is at least 100 feet from the house.

Any ideas?

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Bill Roberts

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  • Just fine!

Posted 5 years ago

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Ken - NM9P, Elmer

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Q:  Are you using the speakers, and do you have the MON function turned on?  

You might be getting direct re-transmission from speaker to mike, which when you have the amp on is being covered up by the noise from the amp's cooling fan.

Just a theory.

Ken - NM9P
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Bill Roberts

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No Ken.  Monitor is off.  Got the report with the amplifier running in standby.  There was only one report.  I've made several contacts on both 80 and 40 since then and no echo reports.  Who knows :-)  Thanks
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Peter Bentley

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Hello Bill

I pointed out some months ago on the 'Community' that this can be an issue with the 6000 series.

Usually it is never noticed by the receiving station mainly due to poor signal to noise ratio, but is most evident by the operator especially if you are monitoring your outgoing transmission with high quality headphones, where you may be experiencing a dynamic range of 80 db or more.

It is definately there as some acoustically alert operators will tell you, but for me is around 40db or more below the peak audio level.

I do not believe it is the effect of any 'rf' feedback as it can be experienced at rf drive levels of only
1 watt.

It is generally known and accepted that 'ringing' does occur in digital circuitry where overdriving is present, however I do not believe that this is the cause here.

To be honest its no big deal for me, careful adjustment of the audio drive levels can largely mitigate it and unless you are working a station who is receiving you at 9 plus 30 or so, then its unlikely to be detected even if they were looking for it.

For me it is not an issue and is fairly insignificant when you consider how brilliant the rest of the radio and its software are !!

regards

G4BIM
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Steve N4LQ

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On 80m I get echos quiet often but on CW. This is atmospheric related. It's a fraction of a second and I've experienced it for decades. It's only noticeable to myself when using QSK and can get so annoying that I must turn QSK off. The condition happens at night and you never know when it will hit and how long it will last. Certainly the same thing can happen with SSB but of course I can't hear it myself however another station certainly could under the right conditions.
Since this happened to you only one time I would suggest ignoring it. I can't explain the amplifier deal...Perhaps the band changed while you were experimenting with it.
73 Steve N4LQ 
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Al K0VM, Elmer

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Bill,
  One often overlooked cause can be DC related.  Does your mic system have ANY DC  ground paths external to the radio? If so, then it is possible that a portion of the Power Supply current is flowing through that circuit as well.  With an amp on, the drive from the 6500 is reduced and the is less DC current flowing.   ( For SSB, the peak power supply current roughly tracks the RF envelope. ) 

AL, K0VM
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Roy - W5TKZ

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Hi Bill,
I recently had the very same problem. On my 6300, it was quite pronounced on 80 meters and was reported by several of my contacts on a local net. Had the problem with or without the amp. (It should be noted that I am in the nearfield with my 80 meter dipole.) 
I did all I could to track the problem as RF related, but finally gave up and filed a HelpDesk ticket. After talking with FRS engineers, I sent my unit back for service.
  In the meantime, I reworked my station. Moved things around to get more separation and better cable layout. I also replaced all the grounding system. I found some corrosion on the ground contacts. Not bad, but I replaced the whole thing anyway.
  When I got my unit back from service, I set it on a card table in the middle of the room with only a dummy load and power supply. No ground other than the house wiring. Result: No echo in the monitor headphones.
 FRS claims they did not make any repairs. However they did leave me with a default EQ setting for my Heil Pro 6 headset.
  I have the unit back in my shack now and there is just the smallest hint of an echo. Reports from other stations verify no echo. I have modified my EQ slightly to give more highs.

Let me suggest you try my "middle of the room approach" and if you still have a pronounced echo, file a Helpdesk Ticket. The engineers are there to help and they will.

Good Luck and 73,

Roy - W5TKZ          
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Bill Roberts

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I will try rerouting transmission and audio lines.
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Bill Roberts

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Official Response

Think I found the cause...  the BOSE Companion II speakers!  If I have two sets of cables going into these speakers (regardless of "side" as in left L&R input VS the pair on the right side) I have rectified and amplified RF.  If I disconnect one set of cables (from either right or left) the RF goes away.  This happens on all HF bands (160 - 20) that I have antennas for.  It happens with or without my 600 watt amplifier.  I have interchanged the shielded "powered speaker cables" that came with the speakers and the Belkin ones I bought two weeks ago.

So apparently, the un-elegant solution is to connect only one set of audio output cables at a time; plug in the 6300 when I want to use it and the 5000 when I want to use it.  BTW, both sets of audio cables are wound around large split beads at both ends.  Also, both radios are connected to the same ground bus.

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Roy - W5TKZ

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Glad you found your problem, but check with your contacts for an echo. If they hear it, your problem could be more serious.

73
Roy - W5TKZ 
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Tim - W4TME, Customer Experience Manager

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What you created with the dual connection is a classic ground loop between the FLEX-6000 and the FLEX-5000.  Ferrite beads will not resolve that issue, you will need isolation transformers.
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Al K0VM, Elmer

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I agree with Tim, Its a classic DC ground loop problem.  One solution is a power supply for each radio and the power supplies must not have a connection between the negative terminal and ground ( or safety ground ). The other solution is to transformer isolate each audio path to/from the radios.  

It is easy to forget that on SSB the power supply current changes rapidly nearly in step with radio PA current and has audible components.  If a portion of the current flows through audio lines ( due to a ground loop ) the an echo may be induced.

AL, K0VM
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Bill Roberts

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Thanks again. Any suggestions on a ready source for appropriate isolation transformers? BTW, I am using separate switching supplies.
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Tim - W4TME, Customer Experience Manager

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How much do you want to spend? Jensen is the "top shelf" brand for 600 ohm 1:1 audio transformers.  From there you can work your way down through midrange transformers to the ones they sell at Radio Shack.  Some of the midrange products are ones from Rolls, Art, EBTech, Whirlwind.  Google "audio isolation transformers"
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Steve N4LQ

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Just to clarify....This sounded like an echo but actually the speakers were picking up transmitted RF and playing it through themselves. It sound like an echo but was actually caused by latency in the transmitter. I would think SSB would sound "donald duckish".
I tried using my Bose the same way but with the 6300 and K3 combo. With the K3 plugged in I got a nasty hum. Both rigs are grounded to the same ground and use the same power supply. 
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John n0snx

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Bill don't waste your time and money on the one in your link... Tried it and it didn't do the job. 
(Edited)
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Bill Roberts

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Well guys, for whatever it's worth, I received two PAC SNI-1-3.5s.  I inserted one into the computer speaker output on the 5000, problem gone.  Removed the item, symptom came back.  Tried inserting a 2nd PAC SNI-1-3.5 on the 6300 and got a buzz.  So far, I've left one of the devices on the 6300.  Tested on the 4 bands I have a resonant HF antenna for (160 - 20) with both the exciter and amplifier and the problem remains gone.  I'll keep the 2nd PAC SNI-1-3.5 for a few days and send it back to Amazon if no further need arises. 

Also, didn't note any distortion or frequency response differences with the device in or out.

In the last few days, I've read more about ground loops.  Thought I understood them before.  Guess I have more to learn. 

73