The results of your tests are normal for an internal tuner. I would try a 50
ohm dummy load to see if you can reproduce the problem your buyer had. The
tuner should be able to match 50 ohms on all bands in addition to the 3:1 loads
that Jerry suggested.
The range of internal tuners varies considerably by manufacturer, so the buyer
may have had unrealistic expectations based on his experience with another rig.
My TS-870S would match a wider range than my FT-1000MP Mark V. The Elecraft K2
and K3 tuners have a much wider range (10:1 SWR or more).
Jim AD4J
On Jan 25, 2011, at 11:44 PM, Jerry Flanders wrote:
> He might have expected it to load his bedsprings on 160 M like some
> of he better external tuners can do.
>
> ICOM specs the tuner to only handle 17 - 150 Ohm loads (3:1 SWR). One
> way to verify ATU operation is to use three 50 ohm dummy loads, first
> connected in series, then in parallel. Just check it on all bands to
> see if it can cope.
>
> Jerry W4UK
>
> At 10:46 PM 1/25/2011, Jeffrey Clarke wrote:
>> Content-Type: multipart/alternative;
>> boundary="----=_NextPart_000_000F_01CBBCE1.A5FE21B0"
>> Content-Language: en-us
>>
>>
>> Hi All,
>>
>> I sold a radio to this guy (my IC756PRO) and the day it's delivered
>> to him he calls and tells me the internal antenna tuner in the radio
>> is not working right. He was unwilling to have someone look at it at
>> his own cost (he wanted me to pay for that) so I told him to send
>> the radio back to me and I refunded his money.
>>
>> I got the radio back tonight an hooked it up. I have 160 , 40 and
>> 20 meter antennas that are cut for the CW bands. The SWR is higher
>> in the phone parts of the band. The internal tuner worked just fine
>> when I turned it on the tune out the slight mismatches in the higher
>> parts of those bands. I also hooked up my 135 foot zepp with 450
>> ohm feeder line to a DX Engineering 4:1 balun and went directly to
>> the radio on the 50 ohm side of the balun. I was able to get the
>> antenna to tune across the whole 80 meter band. I wasn't able to
>> get it to tune with that setup on 20 meters. I would imagine the
>> impedance is more complex using that antenna on 20 meters and up.
>>
>> I'm trying to determine if I really have a problem with the internal
>> tuner. This guy supposedly hooked the radio directly to a dummy
>> load to test the internal tuner. Is this really a good test ?
>>
>>
>> Thanks, Jeff KU8E
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>
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