[Elecraft] P3SVGA

[Joe Subich, W4TV]

Jim,

with the pick-off point clearly *before* the noise gate, the NB can
not possibly provide any *blanking* to the P3.  There may certainly
be artifacts due to changes in the impedance (loading) seen by the
P3, but that is a *big difference* from real banking.

Please study the schematics before you claim the hardware blanker
*works* for the P3.

73,

    ... Joe, W4TV


On 2014-08-18 2:54 AM, Jim Brown wrote:
> Joe,
>
> I don't want to be confrontational and I greatly value your engineering
> mind, but I'm quite certain that the wide K3 NB DOES affect the P3
> display. I work a lot of JT65 on 6M, and there are several strong
> signals (not of overload magnitude) near me. The NB DOES create
> artifacts that result in multiple decodes, and corresponding stuff that
> is quite visible in the P3 display, and that is not visible when the K3
> NB is off.
>
> 73, Jim K9YC
>
> On Fri,8/15/2014 2:35 PM, Joe Subich, W4TV wrote:
>>
>>> I often study the screen of my P3, which DOES show reduction of noise
>>> when the wider NB is active. 2-4 dB is typical for the types of noise
>>> for which it is effective.
>>
>> 2 - 4 dB may be due to upsetting the impedance at the IF feed but given
>> the circuit topology it is not possible for the NB to provide effective
>> blanking to the P3 with the noise gate *after* the IF pick-off point.
>>
>> 73,
>>
>>    ... Joe, W4TV
>>
>>
>> On 2014-08-15 5:13 PM, Jim Brown wrote:
>>> On 8/15/2014 11:29 AM, Joe Subich, W4TV wrote:
>>>> Jim, that information is incorrect.  The K3 NB can not possibly have
>>>> any impact on the P3 or P3SVGA as the IF pick-off is at the output
>>>> of the first mixer - *before* any noise blanker gate.
>>>
>>> Joe,
>>>
>>> I've never studied the schematic or signal flow in the regard, but I
>>> often study the screen of my P3, which DOES show reduction of noise when
>>> the wider NB is active. 2-4 dB is typical for the types of noise for
>>> which it is effective.
>>>
>>> I appreciate the alert to the existence of the P3 NB. I last updated
>>> firmware about six months ago, and it was not in that version. It does,
>>> indeed, work pretty well.
>>>
>>> 73, Jim K9YC
>>>
>>>
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>
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