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Re: Latest Sherwood table

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Joe Subich, W4TV-4

Re: Latest Sherwood table

It has been a known (documented by W8JI with fix) issue since the
FT-1000D. The noise blanker contains a dual gate MOSFET connected
to the IF that runs all the time. Instead of disabling the MOSFET,
the second gate is simply biased into an "off" state when the NB
is turned off. Unfortunately this allows the first gate to be
overdriven by strong signals which creates IMD that is coupled
directly back into the IF.

The FT-2000 uses the same noise blanker circuit as the FT-1000,
FT-1000D, FT-1000MP, etc.

73,

... Joe, W4TV

On 1/3/2011 2:31 PM, Jan Erik Holm wrote:

> Is this a known issue with the FT-2000?
> /SM2EKM
> ------------
> On 2010-12-31 23:31, Joe Subich, W4TV wrote:
>>
>> or issues of IMD generated in the noise blanker (even when the NB
>> is off).
>>
>> 73,
>>
>> ... Joe, W4TV
>>
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Jan Erik Holm

Re: Latest Sherwood table

Yes I know all of this about the FT-1000, this was
NOT the question.

I have never heard that the NB in the 2000 is problematic.
Maybe it is maybe it isn´t, I just like to find out.

It seems you just assume it´s problematic since it uses
as you say the same circuit as in the 1000. Since you
did bring it up, is this the case or do you know something
else?

/Jim
--------------
On 2011-01-03 21:09, Joe Subich, W4TV wrote:

>
> It has been a known (documented by W8JI with fix) issue since the
> FT-1000D. The noise blanker contains a dual gate MOSFET connected
> to the IF that runs all the time. Instead of disabling the MOSFET,
> the second gate is simply biased into an "off" state when the NB
> is turned off. Unfortunately this allows the first gate to be
> overdriven by strong signals which creates IMD that is coupled
> directly back into the IF.
>
> The FT-2000 uses the same noise blanker circuit as the FT-1000,
> FT-1000D, FT-1000MP, etc.
>
> 73,
>
> ... Joe, W4TV
>
>
> On 1/3/2011 2:31 PM, Jan Erik Holm wrote:
>> Is this a known issue with the FT-2000?
>> /SM2EKM
>> ------------
>> On 2010-12-31 23:31, Joe Subich, W4TV wrote:
>>>
>>> or issues of IMD generated in the noise blanker (even when the NB
>>> is off).
>>>
>>> 73,
>>>
>>> ... Joe, W4TV
>>>

Jan Erik Holm

Re: Latest Sherwood table

Sure that is logical. OK this is good information, TNX
Seems they never learn.

If you would have put it like this in the first place
I wouldn´t have said anything.

73 Jim
-------
On 2011-01-04 07:16, Joe Subich, W4TV wrote:

>
> > It seems you just assume it´s problematic since it uses
> > as you say the same circuit as in the 1000. Since you
> > did bring it up, is this the case or do you know something
> > else?
>
> It has been 18 months since I have had a FT-2000 on my bench.
> When I did, I did not perform IMD testing but I did study the
> schematic (Service Manual) to determine that the noise blanker
> amplifier had the same unswitched design as the FT-1000 and
> FT-1000MP (and MK V).
>
> It is insanity to assume that identical circuits that operate
> one way in two (three) different models of Yaesu transceiver
> will suddenly operate differently in a fourth model.
>
> 73,
>
> ... Joe, W4TV
>
>
> On 1/4/2011 12:54 AM, Jan Erik Holm wrote:
>> Yes I know all of this about the FT-1000, this was
>> NOT the question.
>>
>> I have never heard that the NB in the 2000 is problematic.
>> Maybe it is maybe it isn´t, I just like to find out.
>>
>> It seems you just assume it´s problematic since it uses
>> as you say the same circuit as in the 1000. Since you
>> did bring it up, is this the case or do you know something
>> else?
>>
>> /Jim
>> --------------
>> On 2011-01-03 21:09, Joe Subich, W4TV wrote:
>>>
>>> It has been a known (documented by W8JI with fix) issue since the
>>> FT-1000D. The noise blanker contains a dual gate MOSFET connected
>>> to the IF that runs all the time. Instead of disabling the MOSFET,
>>> the second gate is simply biased into an "off" state when the NB
>>> is turned off. Unfortunately this allows the first gate to be
>>> overdriven by strong signals which creates IMD that is coupled
>>> directly back into the IF.
>>>
>>> The FT-2000 uses the same noise blanker circuit as the FT-1000,
>>> FT-1000D, FT-1000MP, etc.
>>>
>>> 73,
>>>
>>> ... Joe, W4TV
>>>
>>>
>>> On 1/3/2011 2:31 PM, Jan Erik Holm wrote:
>>>> Is this a known issue with the FT-2000?
>>>> /SM2EKM
>>>> ------------
>>>> On 2010-12-31 23:31, Joe Subich, W4TV wrote:
>>>>>
>>>>> or issues of IMD generated in the noise blanker (even when the NB
>>>>> is off).
>>>>>
>>>>> 73,
>>>>>
>>>>> ... Joe, W4TV
>>>>>