6400 RFI issue-
When I run the amp at 400-600W, I get reports of RF on the audio
on LSB 80M. I have 3 other rigs that do
not have the issue. I have a Balun
Designs RF isolator in line. I have 31
mix donuts on the mic cord, LAN cable, power cable, etc. All radios use the same coax cables &
power supply. The RF is there with the supplied
mic & a Heil HM12 and home made XLR cable.
I have not tried a full reset of the 6400.
Pretty much at my wits end. Any suggestions?
All I can think of are grounding and feed line radiation. You might experiment with changing the length of the ground wire to the Flex and changing the length of the transmission line from the amp to the antenna. Also, regarding grounding, I don't know your situation, but improving the grounding lay out to the extent possible could be helpful.
I would use only one antenna at a time to see if your rfi issue goes away. if it does the repair is simple a alpha delta coax switch on the output of your atu and let the a/d do the switching if you would like to talk on the phone my number is 781 944 7543 73 Ray NR1R
I completely disconnect the unused coax/antenna. I then insert the unused PL259 into a shorted SO239 to ensure no induced RF gets back into the shack. Also, I have 2 sets of active speakers in the shack. A pair of Fostex 6301B's for the 6400 & just above them I have a pair of wood cabinet M-Audios connected to my computer. No RF comes out of them. I have an old Field Strength meter near the window & that barely shows any movement at the 600W level. The Balun Designs 1116di is one of the best isolators on the market. ???? I have 2 Icoms, a Kenwood and a Yaesu (I recently sold) that did not have the issue. I used the HM12 on the Kenwood & Yaesu with appropriate Heil cables & a SM30 on the 2 Icoms.
Also RFI may be getting into the DC power cable to the radio.
So eliminate things one by one.
if your radio is grounded to a common ground then temporarily remove the ground for a test.
If you have a friend HAM close by can you take it to there QTH and test it?
It is an OFC Y cable. Has gold contacts on the 3.5mm stereo jack & has a silicone sheath. I know those details may not speak to the shielding, but it feels/looks like a quality product. It does split to 2 RCA jacks so the "balanced" connection is lost at the Fostex 1/4" psuedoXLR jack. Because of your comment, I added 3- 31 mix donuts to the cable and I'll give that a try tonite or tomorrow.
I previously added ferrites on the power cable also, to no avail. My other radios do not have ferrites on the power cable & they haven't been an issue.
The only unique things to the Flex is the LAN cable & mandatory active speakers & psuedoXLR mic connector.
At this point in your search process I would suspect it as a potential cause. I have had various RFI issues when rig used Ethernet connections. I installed fiber converters at each end of
Ethernet cable and since no issues when running legal power.
Pair of converters on eBay was <$30.
I am not familiar with fiber converters. I will take a look.
I should have mentioned earlier, that there was a time a few months ago, that I did not have any RF complaints. Also, I have not made any changes to the shack, antenna systems, router, cables, etc.
Can someone who hears you strong record you and send it to you? then you can post the recording hear?
I am open to other suggestions.
Everyone who hears me says it sounds like RF. At 100W or less, the 6400 by itself seems to be clean.
I put the amp on (Acom 1500 running 4-600W), I get the roughness.
I use that amp & everything else the same (minus the LAN,Speakers, mic cable) with another rig, no problem.
The problem with random wire antennas is that they are, well, random. You may have unluckily selected a length of wire that causes a very high RF voltage at the feedpoint. That might be very hard to filter out. Adding some length (1/2 wavelength) to the wire might shift the feedpoint to a current node and help with your problem.
Alternatively, you can experiment with adding a clip-on ferrites to the wire that would electrically change its length. Or a couple of turns of wire through a toroid core. That may seem counter-intuitive (adding a RF "filter" to your antenna wire), but all you're doing is adding some inductance and changing the resonant length. Your tuner should be able to handle the impedance change.
I am liking the LAN cable as the culprit and maybe the speaker cables. I have not had a chance to get on the air to check out the effect of the additional ferrites & relocation of the LAN cable.
I am surprised at the number of users who have commented on the LAN cable as being a problem.
Also, I am not entirely sure I don't have a problem using the 6400 barefoot. I need to have good band conditions to connect with the local hams I talk to to see if I sound good at 100W.
I'll report back then & thanx for all the replies.