[ICOM] ICOM 736 on 60 meters

Larry Benko xxw0qe at comcast.net
Thu Mar 15 13:35:26 EDT 2012


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 *
> * k2gkk at hotmail.com *
> * (Since 30 Nov 53) *
> * Oklahoma City, OK *
> * USAF, Ret (61-81) *
> * * * * * * * * * * *
>
>
>
>> Date: Wed, 14 Mar 2012 21:22:29 -0600
>> From: xxw0qe at comcast.net
>> To: icom at mailman.qth.net
>> Subject: Re: [ICOM] ICOM 736 on 60 meters
>>
>> Thanks for remembering me :)
>>
>> Take a look at http://www.w0qe.com/60m_operation.html and pay close
>> attention to what frequency the radio switches the 80m TX filter to 40m
>> filter. If the radio wants to use the 80m low pass TX filter on 60m you
>> will most likely find that the radio draws too much power has has low RF
>> output. After "opening up" the radio you can hear relays click when the
>> output filter is changed.
>>
>> 73,
>> Larry, W0QE
>>
>> On 3/14/2012 8:11 PM, D C *Mac* Macdonald wrote:
>>> A paper on Icom rigs that are or aren't capable of
>>> being put on 60 meters was authored by Larry, W0QE.
>>>
>>> The Icom IC-736 is NOT covered, so I don't know if
>>> that rig can be expanded to cover 60m. It all depends
>>> upon how the various bandpass filters are placed in
>>> the spectrum.
>>>
>>> That website suggests you write to Larry with any
>>> questions. He MAY have a definitive answer for you.
>>>
>>> You also may wish to consider contacting Icom to ask
>>> your question.
>>>
>>> http://www.bnk.com/w0qe/60m_operation.html
>>>
>>> * * * * * * * * * * *
>>> * 73 - Mac, K2GKK/5 *
>>> * k2gkk at hotmail.com *
>>> * (Since 30 Nov 53) *
>>> * Oklahoma City, OK *
>>> * USAF, Ret (61-81) *
>>> * * * * * * * * * * *
>>>
>>>
>>>
>>>> Date: Wed, 14 Mar 2012 21:00:57 -0500
>>>> From: wa9vrh at dishmail.net
>>>> To: icom at mailman.qth.net
>>>> Subject: Re: [ICOM] ICOM 736 on 60 meters
>>>>
>>>> HI Gary,
>>>>
>>>> Thanks for the information!
>>>>
>>>> 73 Larry WA9VRH
>>>>
>>>>
>>>> On 3/14/2012 8:32 PM, Gary P. Fiber wrote:
>>>>> That radio is old enough you have to open it for all band transmit.
>>>>> It was called a "MARS" modification in those days. likely www.mods.dk
>>>>> will have that information.
>>>>>
>>>>> Gary K8IZ
>>>>>
>>>>>
>>>>>
>>>>> On 3/14/2012 1:25 PM, Larry WA9VRH wrote:
>>>>>> Hi All,
>>>>>>
>>>>>> How do I unlock my 736 so it will transmit on the new 60m frequencies?
>>>>>>
>>>>>> Thanks!
>>>>>>
>>>>>> Larry WA9VRH
>   		 	   		
> ----
> Your Moderator: Dick Flanagan K7VC: icom-owner at mailman.qth.net
> Icom Users Net: Sundays, 1700Z, 14.316 MHz
> Icom FAQ: http://www.qsl.net/icom/
> To support QSL/QTH.net: http://www.qsl.net/donate.html
>


More information about the Icom mailing list