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Author Topic: ic-718 tripping off  (Read 704 times)
WB1DJC
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Posts: 10




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« on: July 16, 2005, 06:57:29 AM »

I have new (2 week old) IC-719. When i transmit on 20 meters it trips off like the power supply shuts it down. If I reduce the pwr output to 95 watts It works fine but not at High pwr setting.  The swr meter on the tuner is 1.2.  At the reduced pwr setting I will show 100 + watts out with a very low swr. It doesnt seem to have this problem on any other band. I am using a long random wire antenna with a roller inductor tuner.

Mike, WB1DJC
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KZ1X
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Posts: 3228




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« Reply #1 on: July 16, 2005, 07:07:04 AM »

What power supply are you using?
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WB1DJC
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Posts: 10




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« Reply #2 on: July 16, 2005, 07:09:53 AM »

Astron 23 amp with pwr and swr meters
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AA4PB
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Posts: 12893




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« Reply #3 on: July 16, 2005, 07:58:19 AM »

Its probably a matter of your grounding (counterpoise) system not being effective on 20M. You are getting RF on the radio and power supply chassis. Try changing the length of the random wire. If its close to some multiple of 1/4 wavelength then the current in the counterpoise will be high and therefore require a lower impedance counterpoise. If you change the wire length to move it closer to a multple of 1/2 wavelength then the feed impedance will go up and the current in the counterpoise will be reduced.

Alternately, connect a 1/4 wave (on 20M) insulated wire as a tuned counterpoise to the radio or tuner ground connection. This will provide a low impedance ground path for 20M.
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KZ1X
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« Reply #4 on: July 16, 2005, 08:34:38 AM »

" Astron 23 amp with pwr and swr meters"

The SS-20M ?  Need the model number ... the switcher will be more apt to cut off than the linear version.

Anyway, 'PB is on the direct track, but what he might have missed saying is that your rig, supply, and AC connections probably ARE your counterpoise.  

Assuming you can add ~33 feet of wire to your random length, do so.  If not, why not provide a "ground" to your tuner and some ferrite on your DC power leads?  

Several ways to solve this problem.  Trouble is, many of the possible solution will just shift the issue to another frequency.  

Lowering your power output is one of the solutions, and nobody can tell the difference between 75W and 100W.  However, if there's enough RF on the rig and supply to trip the latter off at 100W, even at 75W you'd probably still have enough to get into your audio chain, just as annoying.  

Best to really solve the problem instead of simply mitigating it.  Any chance you might put up another kind of antenna?
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KX8N
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« Reply #5 on: July 16, 2005, 09:05:58 AM »

I would guess that AA4PB has it right.
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KP4HE
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Posts: 22




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« Reply #6 on: July 16, 2005, 02:15:38 PM »

This problem I had with not only a IC 718 that I had but also with a TS 450 and a TS 570.  
Your problem is with the RF leaking into the the Power Supply's Protection circuit.
Astron will ask you to verify the contact of the ground cable to the casiss of the power supply.  But, that didn't help in my case.  
I simply separated the power supply as far away from the radio as possible.
You haven't stated any antenna location or type of feed line.  
Are you using an Antenna tuner?
Does the power supply shut off or the radio shuts off?
Did you check the voltage output from the power supply when this happens?

David KP4HE
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KB4QAA
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Posts: 2407




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« Reply #7 on: July 16, 2005, 09:36:20 PM »

I had a similar problem with an IC-718 at Field Day this year.   I was working 40M and when other stations would transmit, the 718 would shut down.  

The problem was NOT with the power supply, as it was still on.  I don't recall the P/S brand. RF was obviously getting into the radio and knocking out the integrated circuit controls.  

I was not impressed with the 718 performance.   In addition to cutting on and off, the front end became overloaded when other stations transmitted and throughout the weekend I got complaints that the 718 was doing the same to other stations.   None of the other rigs had problems interfering each other, and we didn't have any problem last year before the 718 showed up.  

The 718 IS the bottom of the line entry radio. Is it really weak?

Bill.
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K6AER
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« Reply #8 on: July 17, 2005, 11:01:38 AM »

Place sone .01 caps between the output connections and ground.
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AA4PB
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« Reply #9 on: July 18, 2005, 04:52:53 AM »

It is not normal for there to be enough RF in the shack to trip off either the radio or the power supply. Ideally you want to correct your antenna/counterpoise problem to keep the RF out of the shack rather than applying "band aids". Bypassing and chokes or beads might fix that problem but then you'll be dealing with the next problem like RF in the mike lines or intermittant CW keying. The RF belongs outside the shack:-)

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WB1DJC
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« Reply #10 on: July 18, 2005, 06:02:22 AM »

Thanks to all who have replied its been a big help and I have added some length to my antenna and that seems to have done the trick, I am also going to install a GR5 in the next few days.

Thanks again all

WB1DJC
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