Using a Bird dummy load and Mix 31 beads on all coax and audio cables, I'm still getting RF into the line input of a powered PA speaker I'm currently using with the radio.
Since the level of the interference goes up and down with the PA's volume control, it appears the RF is being rectified in the PA mixing buffer amp ahead of the main volume control. While I may be able to fix it by opening up the PA and bypassing the inputs with .01 or thereabouts caps, I'm curious if anyone else has seen this happen, and if there's an easy fix.
I haven't had time to open the PA and put a scope on the input to see how much RF "fuzz" is on it. That would be a direct indicator.
... and for what it's worth, I don't experience the issue using the same gear and cabling with several other radios, just the 6300.
My experience with Flex radios has always shown them to be sensitive to RF. Is the speaker you are using RF shielded? I'm using Bose Companion 2 speakers and get no RF interference. I also have a non-shielded set of speakers hooked to another computer in the shack and they often squalk when I operate with high power.
I have a new 6500 and had the same problem. I solved it by using audio isolation transformers in between the radio and the powered speakers.
As the speakers I have use RCA jacks for the input, I used a preassembled isolator cable made for car stereo systems ( used between preamp level outputs from a head unit and a power amp input). Works like a charm.
Gary - W8EEY
The speaker isn't shielded, no. What is interesting, though is that I get the "RF" (assuming it is that) in the audio even with the 6300 connected to a Bird Termaline dummy load with a known good cable. I can't imagine the 6300 being THAT sensitive to external RF... :-)
Once I know more about the nature of the problem, I'll put packaged transformers on the list for possible fixes.
I haven't been using the 6300 lately, but the issue just popped into my head today and I thought I'd ask about it here. It's a strange one. It doesn't seem to matter much what frequency I use, what antenna, a dummy load or what if any amplifier. Given how unlikely that all sounds I'll try to look into it over the next few days. Too darned busy...
Good find on the power supply! I'll try to find a 120-120V isolation transformer in my junk and give that a try.
Somewhere in the boxes I should have one or more Jensen transformers left over from a previous life, if that turns out to be the problem.
It does seem that the 6300 is exceedingly sensitive, especially since I can detect rectified RF in the audio when the radio is connected directly to a quality dummy load. Also, my shack is not in the near field of any of my antennas, and my feedlines (all unbalanced) are choked to excess with Mix 31 ferrite both at the near and far ends.
All that aside, I have yet to find enough time to do much experimentation. I should have a few 600:600 Jensen transformers in my junk, but I need to find them. RF grounding is another issue that I should address, although my experiment with the dummy load isn't encouraging.
It's also possible that there's something wrong with this particular 6300 itself, although I'm not ready to test that as an assertion yet.
Thanks and 73,
Powered speakers can be problematic. I have found with my 6300 that all RF woes from my Bose Companion Series II speakers were related to poor cabling from 6300 to speaker. I replaced the stock cable with a high quality double-shielded cable and the RF problems disappeared as expected.
So what I am saying is you might be able to put isolation transformers on them or/and toroids on leads and get the rf out but it might be you still have issues with something else. If you do not have a field strength meter (I have found this cheap cb meter I found is a valuable part of my shack) borrow one and start sniffing you setup with it. I run 1500 watts on tune with my field strength meter set to max senativity and the meter barely moves.
I use rg 223 coax for all jumpers up to the tuner then good quality rg 213 from there on. I clean all my so so 239 and pl259 with a brass brush and a good cleaner and tighten all with a final twist with pliers. Of course good ground with one point grounding from all equipment. My ground connection is checked with a meger
Like I said at the beginning the rf on the speaker might be light a cough telling you have a cold.
I replaced the Astron SS-30M switching power supply I've been using all this time with a trusty dinosaur Astron VS-35M, and the RF in the powered speaker output is gone!
Before we start with the "I told you so's", please bear in mind that three other rigs (including my Apache Labs ANAN-100D) work perfectly from that supply and environment with no ground loop or RF problems of any kind. The 6300 (as far as I can tell) cannot practically be made to work with it.
At the end of the day, I'm just happy to not have monkey chatter in the powered speaker output, so I'm not going to pursue this any further. Consider yourself warned, though - if you want to keep your sanity, use that SS-30M on your other rigs.
Let the speculation begin... ;-)