[1000mp] AMP Question

[Garry Shapiro]

John:

Your experience leads to your conclusion. Mine leads to a different one.

Some years ago, I was invited to operate the Cal QSO Party (CQP) at K6VX 
(SK) in remote Siskiyou County. Ray had an FT1000D driving a homebrew 
4-1000A GG amp with untuned inputs. Ray used a footswitch to key the amp 
manually after the VOX tripped on CW or SSB, but I found this a huge 
impediment during the contest and cajoled him to control the amp with a 
relay, which he did. I used the internal tuner on the Yaesu.

In that instance, the Yaesu's tuner hunted each time the rig keyed. That 
was a lot of hunting, with apparently disastrous effect. When Ray 
invited me back, it was on the condition that I bring my own gear. He 
told me the tuner had broken and the repair had cost him hundreds of 
dollars.

The key is apparently whether and how often the internal tuner hunts. In 
your case, it is not much. In the case cited above, it was too much.

Garry, NI6T



w3jxp at comcast.net wrote:
> I use the internal tuner with my SB221 all the time. The SWR on 17, 15, and 12 meters is higher than I would like. There is no bad effects. The tuner does not "hunt". It tunes once and doesn't change again until I change bands. I also have used it with an older amp with a pasive input (no tuned circuits) and it worked just fine with that too. I think that using the built in tuner with an amp  will cause some sort of damage is an old wife's tale.
>
> --
> John Passaneau, W3JXP
> State Collage, Pa.
>
> -------------- Original message -------------- 
> From: "Win" <w0lz at winlyn.us> 
>
>   
>> Not to draw this out, but I have to wonder if this is true in CW mode. 
>> Modulation is either 100% or nothing. It would seem that the input Z would 
>> remain the same and not cycle the tuner. Am I off base? 
>>
>> Win, WoLZ 
>>
>>
>>
>> ----- Original Message ----- 
>> From: "Garry Shapiro" 
>> To: "All about Yaesu 1000mp" <1000mp at mailman.qth.net> 
>> Sent: Thursday, May 03, 2007 8:05 PM 
>> Subject: Re: [1000mp] AMP Question 
>>
>>
>>     
>>> The impedance is nonlinear--and so voltage and current do not have a 
>>> constant relationship. 
>>>
>>> Rob Atkinson wrote: 
>>>       
>>>> Hi, 
>>>>
>>>> I guess I don't understand how the Z of a load can change with the power 
>>>> delivered to it unless the components affecting the Z are underated for 
>>>> the power. maybe i'm missing something? sorry. 
>>>>
>>>> 73 
>>>>
>>>> rob / k5uj 
>>>>
>>>>
>>>> On Thursday, May 3, 2007, at 10:09 AM, Rod Elliott wrote: 
>>>>
>>>>         
>>>>> Dick... 
>>>>>
>>>>> I use a Mk5 Field to drive an AL-1200. No problems... works great. 
>>>>>
>>>>> In my experience the SWR presented to the Field by the amp's input is 
>>>>> always well below 2:1, even if the output of the amp is not perfectly 
>>>>> matched. The Field has no problem with that. 
>>>>>
>>>>> One precaution... do NOT use the Field's internal antenna tuner when 
>>>>> driving the amp. (The amp's input impedance varies with drive level... 
>>>>> you don't want the Field's tuner to strip its gears trying to follow 
>>>>> your voice! ) 
>>>>>
>>>>> 73 
>>>>> Rod VE3UW 
>>>>>
>>>>>           
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