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.
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
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 !!
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
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. )
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
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.