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Old 07-04-2014, 08:15 PM   #1
n4xyz
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Default Rfi feed back in my ic-706

Hi, I don't know if this is the right bucket but I need advice from experienced RV hams. I installed a fiberglass push-up pole 31 feet, on the ladder of my 5th wheel. It is feed with an Icom AH4 tuner grounded to frame feed from an IC-706mk2g. On 40m I have terrible feedback RF getting in the mic. I put clip on needs on the coax and tuner control at both ends. The operating position is in the rear of the 5er, only about 5 feet away. What are my options to reduce the rfi. Seems to work ok on other higher bands.

Thoughts would be appreciated.

Dave N4XYZ
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Old 07-04-2014, 09:39 PM   #2
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Quote:
Originally Posted by n4xyz View Post
Hi, I don't know if this is the right bucket but I need advice from experienced RV hams. I installed a fiberglass push-up pole 31 feet, on the ladder of my 5th wheel. It is feed with an Icom AH4 tuner grounded to frame feed from an IC-706mk2g. On 40m I have terrible feedback RF getting in the mic. I put clip on needs on the coax and tuner control at both ends. The operating position is in the rear of the 5er, only about 5 feet away. What are my options to reduce the rfi. Seems to work ok on other higher bands.

Thoughts would be appreciated.

Dave N4XYZ
By "clip on needs" I think you mean clip-on ferrite beads. If you meant something else, you'll have to explain.

If the RF is getting into the microphone, it may be that it's being picked up by the microphone cable. Try wrapping that cable five or ten turns through a ferrite toroid at the radio end, or at the mike end, or at each end. Depending upon the size of the connector, this may require a rather large toroid. To see whether RF is being picked up by the mike cable, you could wrap it temporarily in aluminum foil, grounded to the radio at the radio end and connected to nothing at all at the microphone end. If that cures it, it's RF picked up by that cable, for sure. The foil is not suggested as a permanent fix -- just as a diagnostic tool.

Clip-on ferrites aren't totally worthless, but on 40 meters (a fairly low frequency) they likely don't add enough inductance to have much effect. Several turns through a toroid will be many times more effective than any clipon, for several reasons. For example, three turns would add nine times as much inductance as a perfect clipon. But you could try the clipons first since you have them and it's easy.

This assumes there's no RF on the outside of the radio itself. If there is, work on that first. Ultimately you may have to replace those clipons with toroids.

Of course you have grounded the radio itself directly to the frame of the trailer, and not with just any old skinny wire but with a nice fat, thick braid. That ought to go without saying, but I guess it doesn't hurt to ask.
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Old 07-05-2014, 07:28 AM   #3
n4xyz
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Default Rfi feed back in my ic-706

Carl
Thanks much for the reply. Yes I meant to type split beads. I am on the road and that is what I have. I will have to order several toroids when I get home and try those. Today I will try the foil on the mic cord. I don't have a separate radio ground. I have the coax braid grounded to the frame as it comes through the floor. I sure can add a separate ground and see if it makes a difference.
Thanks again and I will post my progress.
73
Dave,
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Old 07-05-2014, 09:09 AM   #4
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First are you sure it's coming in on the MIC?

In my coch the radio and the tuner are perhaps 15 feet (Bee-line) apart, there is another RF device at the rear of the bus that gets it's power via a toggle switch in the ham shack.. As I talk EVEN with the switch off, I can see the 12 volt LED assembly power on indiator flashing. The wire, which runs down therough the floor, along the frame rail and up into the rear cap then back in via the real back wall, to the amp is picking up enough energy to light the lamp... My Kenwood TS-2000 seems not to be bothered by it, but (Nor is anything else in the house) but.. That light flashes.
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Old 07-05-2014, 09:32 AM   #5
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Just a thought. The ladder is probably not grounded to the frame. (mine isn't) Ground braid from the ladder to the frame, about 5 turns,(6 inches in diameter), of coax where it connects to the antenna, Take the feed line braid off the frame and instead ground the radio, tuner, and anything else connected to the radio. Had that 40m problem on my Icom. Grounding fixed it.
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Old 07-05-2014, 01:01 PM   #6
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All, thanks for the thoughtful replies. I checked all my connections and found a loos coax fitting on the incoming line through the RV floor. Also renewed the ground to the plate that has the bulkhead fittings at the feedthrough point. Problem seems to have gone. I made several QSOs on 40 and had good audio reports. Higher bands are still Ok. I will continue to try to improve my setup. I am trying to make a portable station that I can be setup and be on the air in a small amount of time. Don't operate mobile just portable from the 5er.
Again TNX
73
Dave
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Old 07-05-2014, 04:39 PM   #7
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Ground the 706 with the lug on the back. What is the antenna a dipole? If it is try a 1:1 at the antenna feed point. That tuner will match a way out of tune antenna but that does not make the antenna efficient so you'll have a lot of stray RF floating around. Got access to an antenna analyzer?
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Old 08-16-2014, 02:49 PM   #8
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Use a resonant antenna and don't use an amplifier.
If you amplify crap - all you will have on the other end is a bigger pile of crap.
Many people tries to overcompensate for a lack of antenna by using a amplifier.

Antenna tuners / trickers, does not make the antenna resonant, it just tricks the radio into thinking that the antenna is resonant..
Sounds like you have a antenna problem...

www.hypowerantenna.com

Try their ocfd - 80 meters..
It will work everything from 440 mhz to 80 meters, ex 15, 30, 60 - since they are not a harmonic of 10 / 20 / 40 meters..
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Old 12-13-2015, 10:13 AM   #9
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I am with Mr. Ham, I have always relied on resonant antennas and with 30 years in the hobby have never owned a tuner other than what was in my radio. (TS-450S and TS-940S).
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Old 12-13-2015, 05:03 PM   #10
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If you are using an IC 706 with a remote face many people leave out the tiny screw that holds the remote wire to the radio it is the ground shield for the remote cable!
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