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Author Topic: Problems with AH-4.  (Read 374 times)
IK0PRG
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Posts: 4




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« on: September 16, 2004, 08:50:07 AM »

Hi OM!!!
I have recently installed a IC-706 and AH-4 in my car using with whip antenna about 2,5m (surplus). All worked fine to any bands from 10 to 40 meters and I work many station around the world with good signals.
Now the AH-4 are foulty. When press the tune botton the AH-4 tune the whip. After tuning, when I start TXing, the SWR gets higher and higher and then goes way up and up and down. If I reduce the power output at the minimum all work fine with minimum SWR. I check and is OK: ground connections, coax, tuner to antenna mount connection, antenna and, in other words, all the installation. If I shunt the tuner and connect directly the RTX to the antenna mount using a resonant antenna all work fine: so the problem is in the tuner.
I think that propably may be some soldering or relay foulty.
I have't the schematic diagram, so find the foulty is very very difficult.
Anyone could help me?
Thank you in advance.
73 de Roberto IK0PRG
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K0BG
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« Reply #1 on: September 16, 2004, 09:38:26 AM »

Have you taken the top off and looked inside the coupler? You might find the problem easier than you think. If it is a capacitor, it will be very evident. The inductors seldom fail.

However, this sounds like a bad relay, and if it is, the insides will look discolored. It's a pain to replace them, but it can be done. Replacement parts can be ordered from Icom.

I have a schematic of the unit, but it is a VERY large jpeg and you'll need Photoshop or similar program to open it. The file is 1 Mb.

Alan, KØBG
www.k0bg.com
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IK0PRG
Member

Posts: 4




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« Reply #2 on: September 16, 2004, 10:14:43 AM »

Bob, thank you for replay!
Yes, i have look inside the tuner: the capacitor and the coil are like new while any discolored points are in the relay cases.
I will try to take to pieces the PCB for look in the rear side.
I haven't any problem to receive large file, so I please you to send both to the following e-mail address roberto.corgiolu@enel.it and ik0prg@arrl.net.
Thank you again.
73 de Roberto IK0PRG
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N8BOA
Member

Posts: 90




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« Reply #3 on: September 17, 2004, 11:45:39 PM »

It almost sounds like a heat issue but I would go back and re-connect everything new ground wire (use big stuff)new ring connetors the works. For grins run some radials out and try a longer peice a wire. The idea here would be to use a deferent set of coil capacitors in the AH-4 since it would be tuning a deferant antenna impedance. Back to the heat if a capacitor got hot it's vaule may change and the resonate freq would shift check to see if this is the case i.e. it was at 1:1 at 7.100 now it is 1:1 at 7.050 maybe if this is the case hold the key down get her good and hot then run your fingers down the line of caps and find the one that is hot and replace it. squrit some frezz it on it to see if it swings the other way
good luck and please keep me in the loop I have a HA-4 too
N8BOA
Sean  
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K0BG
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« Reply #4 on: September 18, 2004, 08:59:24 AM »

Patrick, I would have taken this off-line, but you didn't post your e-mail address.

The problem is a relay as Roberto's e-mail to me indicated. Even if he would have added length to the antenna (or shortened it for that matter), the problem would still be a problem. The AH-4, like all auto-couplers, uses a binary switching scheme to hunt for a solution. Although adding or subtracting length might have temporarily alleviated the iffy relay, sooner or later it would have failed altogether.

Alan, KØBG
www.k0bg.com
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IK0PRG
Member

Posts: 4




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« Reply #5 on: September 20, 2004, 01:51:18 AM »

Thank you at all for help!!!
I have find the problem: is the ball mount insulator.
Using a resonant antenna or low power output we had any problems because the voltage at the antenna base is relative low. Instead, when use a not resonant antenna whit 100W output the voltage at the antenna base was very high and the  ball mont don'g guaranty the required insulation and spark to the car ground. I have enlarge the hole in the car where the mounting ball is through installed and wrap the mounting ball screw whit HV tape increesing the insulator. Now all work fine. The  mount  is Hustler SSM-2 and is not new of this kind of problem!!!
73 de Roberto IK0PRG
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