The Electronics Universe
Over The Air => Home Brew And Tech Forum => Topic started by: longhaireddwb on February 16, 2014, 07:52:37 PM
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Hi all. I have bought an Icom 718 that I was going to put in the Peterbuiult. I started checking it all out and the one thing that bothers me is that the SWR meter reads 1.0:1 no mater what band the radio is on or what antenna I'm on. Lets say I'm on 10m on the radio and I'm on a 80m wire it still shows 1.0:1. Something is very wrong and working on HF radios is a bit out of my abilities.
I thought I was also having a problem with the TX but that turned out to be a coax issue.
The other problem I'm having is the microphone. It always sounds muffled badly. I found a couple mods on line but they didn't seem to help much so I put it back to stock. I read that a diff element can be put in the mic for better, cleaner audio but now cant find the info.
Anyway, If I could get some help on finding the problem with the SWR meter in this radio would be a great place to start. I work long hours and don't get a chance to check in on the forum on a daily basis but in time (and lots of it) I think I could walk thru whatever needs done.
Thanks , Jerry...
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Hey Jerry,
I will pull the schematic one night this week and look over that SWR circuit.
Two things. It is missing the signal or the adjustment pot could be bad that calibrates the circuit.
I know you have a scope so this may be a good test to learn what is going on by using that scope.
I will have to reseach that mic issue.
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Thanks for the help RT.
I found two diodes (SMT) on the back of the filter board that have to do with the SWR.
As far as the pot, Its possible. I tried to do the settings menu adjustments for the swr but it did nothing. Hope I was doing it right. I think I found the info in the service manual.
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Anything yet on this issue? Anyone?
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Have you tried a full reset on this radio?
Reason I ask is that there is really not a lot of seperate stuff between the swr and rest of the metering circuit