[ICOM] ICOM 736 on 60 meters

[Larry Benko]

Have you changed anything on 80m such as antenna, antenna length, 
feedline length etc. that might explain why it currently does not tune 
above 3.9MHz?  Otherwise I don't know what it might be without taking 
the antenna tuner apart.

Good luck.

73,
Larry, W0QE

On 3/15/2012 2:50 PM, D C *Mac* Macdonald wrote:
> Actually, Larry, the problem with 746 tuner is ONLY at
> or above 3.900 MHz. Radio works fine on all 80 meter
> frequencies (without tuner) and tuner works on any
> 80 meter frequency below 3.900,000 MHz.
>
> If tuner mode is engaged, you can hear received signals
> drop (greatly) when you tune up from the bottom and the
> display hits the 3.9 point. Again, all is okay when tuner
> is not selected.
>
> * * * * * * * * * * *
> * 73 - Mac, K2GKK/5 *
> * k2gkk at hotmail.com *
> * (Since 30 Nov 53) *
> * Oklahoma City, OK *
> * USAF, Ret (61-81) *
> * * * * * * * * * * *
>
>
>
>> Date: Thu, 15 Mar 2012 11:35:26 -0600
>> From: xxw0qe at comcast.net
>> To: icom at mailman.qth.net
>> Subject: Re: [ICOM] ICOM 736 on 60 meters
>>
>> Mac,
>>
>> I doubt it. The basic issue is straightforward. If the 80m low pass
>> filter (which obviously passes all signals through 4.0 or probably
>> 4.3MHz) has significant loss at 5MHz (60m) then the low pass filter
>> causes the power transistors to see bad SWR, low power output, and high
>> DC power consumption. This will not be fixed by the tuner which is
>> between the low pass filter and the antenna. Does this make sense?
>>
>> The tuner issue may be something completely different. Generally the
>> Icom tuners are a type of high pass Tee network with the inductance
>> being fixed depending on the radio frequency. It is possible that the
>> tuner with the inductor value set for 40m may have damaged some
>> capacitor in the tuner which is why you now see the problem below 3.9MHz.
>>
>> I have used a 746Pro on 60m often including the internal tuner without
>> any ill effects so far. Obviously the original 746 is somewhat
>> different but both radios use the 40m low pass filter on 60m.
>>
>> 73,
>> Larry, W0QE
>>
>> On 3/15/2012 10:38 AM, D C *Mac* Macdonald wrote:
>>> Hi, Larry.
>>>
>>> My IC-746 (original) had its tuner function fail
>>> above 3.90000 MHz. Works fine below that freq.
>>> Radio works fine 3.9 plus either to dummy load
>>> or LDG tuner.
>>>
>>> I wonder if use on 5 MHz may have caused the
>>> tuner failure. Any ideas? We may have to retract
>>> my comments at the end of your page.
>>>
>>> * * * * * * * * * * *
>>> * 73 - Mac, K2GKK/5 *
>>> * Oklahoma City, OK *
>>> * * * * * * * * * * *
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