Author Topic: TS-480 and RF feedback  (Read 5177 times)

sm0mdg

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TS-480 and RF feedback
« on: 2010-05-10, 01:22:47 »
I have come to understand that the Remoterig + TS-480 combination is sensitive to RF feedback. I get a lot of feedback, and on lower bands I can't even run 10 watts without feedback. I am using a separate power supply as described in the TS-480 setup. I tried ferrites, different power sources and grounding the radio in the station ground without any noticeable improvement. When connecting the mic direct to the radio everything is fine and all feedback is gone...

Any specific ideas for the TS-480 on how to get rid of the feedback?

73 de Björn,
SM0MDG
SE0X

« Last Edit: 2010-05-10, 09:39:46 by sm0mdg »

sm2o

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Re: TS-480 and RF feedback
« Reply #1 on: 2010-05-10, 12:25:25 »
Tyvärr får man nog betrakta det som en bristfällig konstruktion från Kenwoods sida, det konstiga är att ingen annan Kenwood station verkar ha det problemet. Synd på en för ändamålet så bra station. I normala fall så räcker det med att separera matningarna nått annat skall inte behövas. Det är ju också den ablsolut vanligaste radion till Remoterig boxarna, så det funkar bra för dom allra flesta. Se också till att du inte har USB kabeln ansluten till datorn från Radio RRC.n när du testar då får du samma problem. Jag skulle tro att du får tillbaka mycket RF till schacket från antennen, en RF choke ute vid antenn löser nog problemet.

73 de mikael

sm0mdg

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Re: TS-480 and RF feedback
« Reply #2 on: 2010-05-10, 18:17:18 »
I am not surprised that I get RF feedback on lower bands, but on higher bands it should not be a problem and I have never experienced it before with any radio. I also noticed the feedback when testing the setup on a small balcony antenna in the city, but as I was powering all units from the same PSU I though that was the problem.

Anyone with ideas how to cure the TS-480 from RF feedback?

73 de Björn,
SM0MDG
SE0X


HB9AZT

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Re: TS-480 and RF feedback
« Reply #3 on: 2010-05-10, 21:18:53 »
Never had any problems with RF-Feedback and TS-480, even when running 1 kw remote and using a windom antenna. A few things to check:

How is grounding of the station done, is there a good ground link, not only the ground of the power net?
What kind of antenna are you using? Symmetric antennas are much more uncritical for RF-feedback, longwires and windoms can be critical. Always prefer symmetrical antennas.
Under my operating table there is a sheet metal as ground, every part of the rig is connected to that sheet metal via a short, thick cable.
Check your rf-cable shieldings, lousy pl-259 connector, not fastened connectors, etc.
use rf-chokes for the antenna cables and put a choke in any wire coming from the ts-480
use shielded network cables
shorten all cables by winding them up.

73 de Mark, HB9AZT

sm0mdg

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Re: TS-480 and RF feedback
« Reply #4 on: 2010-05-11, 22:11:47 »
Hi Mark,

Thanks for the feedback. The station has a ground system with two ground rods outside the shack and all equipment grounded. Cabling is Aircom Plus or RG213 with good quality connectors soldered both tip and shield. The high band antenna is a SteppIR and for 80/40 a wire vertical with 16 ground radials and a RF Choke on the Coax.

My K3 and other radios have been working fine with only occasional RF feedback on 40 using high power, but with the TS-480 the setup is extremely sensitive to RF Feedback, even at lowest power of 5 watts on 40.

When disconnecting the audio cable to the Remoterig interface and connecting the microphone directly to the radio there is no feedback.

73 de Björn,
SM0MDG
SE0X

M0BPQ

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Re: TS-480 and RF feedback
« Reply #5 on: 2010-05-16, 15:38:14 »
Bjorn and co:

I have a similar problem. Using my FT-847 everything works just fine, but with the TS-480 I can run 100W between 18 and 28MHz, then only 50W on 14MHz, 25W on 40m,and less than 10W on 80m. My antenna is an inverted L with a tuner at the base and I have ferrite on every cable. Again, this is fine 80-10m @100W with the FT-847.

73
Steve

sm0mdg

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Re: TS-480 and RF feedback
« Reply #6 on: 2010-05-19, 22:28:31 »
Here's an update on the feedback problem:

I have been able to remove all feedback on most bands by turning the setting for "Codec inp preamp" in the Remoterig control unit to "No" and then re-adjust the microphone level to 25 without speech processor and 55 with speech processor activated.

With those settings I have reduced the RF feedback to a minimum on all bands except on 40 meters where I still have occasional feedback when the speech processor is in line.

I have asked Mike how this affects the S/N ratio on the link and waiting for an answer, but so far the audio reports received have been positive.

73 de Björn,
SM0MDG
SE0X

DF3FX

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Re: TS-480 and RF feedback
« Reply #7 on: 2010-05-21, 07:11:35 »
Many thanks for the hint with preamp.

With the beginning of Sporadic E Season on 6m I've been reported extremly bad modulation but great signal on that band.
The Rest of the bands (10m down to 160m) work 100% fine with 100W and great audio reports.

Will try to play with codec preamp to see if I could solve the problem.
Unfortunatly I have no station near my remote QTH able to receive on 6m so that
tests will have to be done with strong sporadic stations :-(

73's

Félix
« Last Edit: 2010-05-21, 07:14:21 by DF3FX »
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RRig with Ts-480 SAT - Distance 1000km :-)
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M0BPQ

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Re: TS-480 and RF feedback
« Reply #8 on: 2010-05-25, 11:49:39 »
Thanks for the helpful discussions guys,

I have just turned my codec preamp off as suggested and everything seems to be OK on the meters. I will try to make some QSOs to confirm what I can hear on my local rx.

For the record, I have my mic gain set to 51 and speech proc to 35 using the stock hand microphone.

Many thanks folks, es 73 de
Steve
M0BPQ