[ICOM] ICOM 736 on 60 meters

[D C *Mac* Macdonald]

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 *
> > * * * * * * * * * * *