RFI and ANAN-100D DC Power Cable

(from this posted thread)

I am having problems with transmit audio tearing at mid and high frequency. Originally I thought the RF is getting in to the audio but after several actions , there is no sign or indication of RF floating in the shack. I have tried, multiple different Microphones using front Mic IN and Real Line In input but with the same results. (KE3VG)

The problem is/was RF leaving the ANAN-100!

Study the schematics for the ANAN-100D and you will see that there is hardly any filtering where the DC power enters the PA board. Unlike an Icom or Kenwood hf transceiver, there are no torroids or chokes to adequately isolate the PA from the power supply source. Look at any of the transceivers from the traditional manufacturers, and you will see the extensive filtering on the DC input cabling to their respective PA boards.

Even Flex discovered this issue early on, as their dc power cables now have a filter of some sort on them.

I suspect RF is leaving the ANAN via the dc power cable, and getting into your dc supply and/or any other equipment which may be connected to the same dc supply. Especially if you are using an Astron or similar power supply which is known for poor and inadequate bypass filtering.

My symptoms were identical to yours. If I transmitted and recorded my audio with the RF output level set to zero, the audio was crystal clear. Once I set the drive level to 10 or so, you could hear the audio start to sound raspy, and once I went higher than 25 or more, the audio went to hell, and was just as bad all the way up to full drive (100).

I pulled my hair for a few days, initially suspecting RF getting into my W2IHY equipment. Yet this same equipment has been used on many other transceivers, and other than the new ANAN, everything else in the shack had remained the same. Prior to the ANAN, I have never had any issues with RF in my shack. In addition, the antennas are all almost 200ft away, so that was of no concern..

I then began to suspect that maybe something was amiss with the station power supply, which is an Astron VS-50M. Yet this same supply would power my IC-7600, TS-2000, and other rigs just fine, even with the W2IHY equipment connected to this same supply.

Once I isolated the ANAN-100D onto its own 23a switching supply, and left the rest of my shack connected to the primary station supply, I no longer had any issues. The audio has been crystal clear, and no further issues. Further investigation and testing revealed that RF was leaving the ANAN and traveling up the DC power cable, and entering the power supply. Then it was either modulating the voltage regulator circuit of the power supply, or continuing on to the W2IHY equipment. The voltage appeared to remain stable, so I suspect that the latter was the case. Furthermore, if I used VAC and fed my tx audio into a Focusrite 2I2 box, then into the SDR software via VAC, I never had any issues. So either the RF was getting into the W2IHY stuff, or, more likely, it was travelling back into the Angelia board portion of the ANAN and affecting the audio op-amps or codec chip.

Once I switched to the separate power supply ( a Samlex 1223), I have not had any issues whatsoever.

So you may want to investigate your power source and try running the ANAN off a different supply. Worse case, as a test, run the ANAN off a battery if you can, as a test……

thanks for your suggestion. I connected Anan to separate power supply and problem disappeared. You are absolutely right about the RF is leaking through the DC power lead in to power supply and penetrate other devices connected to it. Looking at the schematic, there is not enough RF filtering, definitely not like my Ftdx 5000MP, which was the source of all the problems.

Now the problem is solved, spend almost a month to fix it but finally the yahoo group came through and found the solution so I am very glad that I posted the problem here. Most of the suggestions were already implemented but the one you suggested was right on money, since we all come from traditional knob radios, we hardly ever experienced this type of problem so this is something was a learning lesson for me and may be for all other users.

As you have said, Flex radio has been though the same problem and they implemented the filtered DC cord, Apache-lab may need to do the same thing, that will reduce so much pain and make operator experience much more pleasant.

This problem was probably exacerbated by poor bonding between case and the middle and top metal plates.

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