TS-480HX RFI and the Mic...

[WB4LCN]

PREFACE: I've read many of the forum messages from a while back that dealt with RFI and the Mic being sensitive to it. I'm aware that others are having a problem with it.

However, I'm having an issue with RFI in the mic too. But, I'm guessing that the issue is because I have both RemoteRigs in the same area in the shack? I use the MC-90 desk mic with the TS-480HX. Whenever I mic, I get RFI into the mic, however, when I put my hand around the mic, the RFI goes away. My hand acts as a shield or a ground to wick off the RFI, away from the mic. If I was going to keep everything here, I probably out to ground the RemoteRig boxes and the mic. But...

I'm guessing that once I finish testing and take the radio 13 miles away to the remote location, I won't be plagued with RFI any longer. Am I correct?

dave

[dj0qn]

Dave,

I have personally never experienced RFI problems with several TS-480 setups.

Have you:

a) Made sure that the radio RRC and TS-480 are not running off of the same 12v power supply?

b) Have you tested your control RRC and TS-480 control head from another part of the house?

73,
Mitch DJ0QN / K7DX

[WB4LCN]

Everything works great, except for the RFI issue. I can lower the Output Power from 200w down to 100w and there's only an occasional problem with RFI. Not at all at 50w.

a.) I'm not running the TS-480 and the RRC off the same power supply, but both power supplies are running off the same power strip.

b.) I have not checked operation in another part of the house. I'll try that tomorrow.

I don't think this is an issue, but I'm using CAT-6 cables where the User Manual calls for a CAT-5 cable. That should be OK, right?

Again, with the remote radio body and the antenna 13 miles away, there isn't any RFI to get into the mic, correct?

dave

[dj0qn]

a) Try not running off of the same power strip.

b) Good idea

No problem using ethernet CAT 5, 5a, 6 or 7, the other ones are actually better.

If this is really an RFI problem on the audio, it would likely be coming into the cable between the radio RRC and TS-480 body, not the mic. Make sure there is a ferrite core on this cable.

73,
Mitch DJ0QN / K7DX

[WB4LCN]

Thanks Mitch,

You suggest that the RFI is possibly coming in through the cable between the TS-480 and the RRC?

QUESTIONS: If that's the case, shouldn't the mic already be isolated through the Internet? Shouldn't my ability of 'grounding' out the mic when I grasp it; should that not effect the RFI interference?

I have each piece of the rig grounded, except for the actual RRC boxes, the TS-480 control panel and the mic.

BTW, one side of my dipole antenna is coming over my shack about 20 feet overhead. It's a low antenna and the main reason I considering remote operation. Could that add extra sensitivity because of the close proximity?

dave

[dj0qn]

Hi Dave,

Let me try to answer your questions as best that I can, others are welcome to join in:

- If there is an RFI problem on your audio, then it would most likely be this cable. The mic location is irrelevant, since
the RFI would occur on the radio side. All the internet is doing is acting like a long extension cord.

- It sounds like you may have a ground loop problem, if covering the mic solves some of the problem. That is why I
suggest trying it from a different room in the house. It is important also to keep the radio and its RRC on separate
12v supplies, even separate AC outlets in some cases make a difference.

- The antenna can always be an issue, that is a completely separate subject beyond the scope of this forum. This
depends upon a number of factors. I suggest that you get local assistance if you haven't already to make sure
that your antenna is correctly optimized.
 
I am not an RFI expert, but am trying to give you simple ideas where to look. You need to start trying to look for the
source of the problem by attempting variations on your setup.

73,
Mitch DJ0QN / K7DX

[WB4LCN]

Thanks Mitch. Very helpful. I'm glad it's all working. I am just testing at home right now, but soon the remote rig will be in a better environment. I live in an older house that still has the two prong A/C socket, not three. Grounding has, indeed, been a problem in the past.

Thanks man!

dave

[EA7EU]

Hi!

In my remote QTH I have ALL the cables with several ferrites on it. Also big ferrites are added to the coax (10 units at least).

Also using HP with the Expert I have no problem, before the ferrites were added "sometimes" I can feel the RFI problems.

On 40 and 80 meters with the ferrites RFI disappears but on 160 meters a commun chocke 1:1 was added and gets absolute NO RFI after that.

Mni 73

Pedro
www.ea7eu.com

[dj0qn]

Thanks, Pedro, that's why I mentioned adding ferrite cores a couple of postings ago.

The bible on RFI was written by Jim Brown, K9YC. You can download his document at:
http://audiosystemsgroup.com/RFI-Ham.pdf

Or a list of all his documents at:
http://audiosystemsgroup.com/publish.htm

This document would certainly interest many others on this forum.

73,
Mitch DJ0QN / K7DX