[Elecraft] P3

[Jack Smith]

The Z10000B buffer amp PCB at 8 MHz has an input impedance dominated by 
4.7K to ground and about 2 pF shunt capacitance. The 200 ohm resistor is 
in series with the input and is not of significant concern in the input 
impedance relationship.

Even with a reasonable length of coaxial cable between a Z10000 and the 
K3's IF output port, the Z10000 has sufficiently high input impedance to 
not appreciably load the IF port, so there is another 5 or 6 dB  gain 
pickup over measuring the IF port level with a 50 ohm instrument such as 
a spectrum analyzer.

Jack K8ZOA


On 2/16/2010 11:03 AM, Joe Subich, W4TV wrote:
>
>    
>> I'd like to see some specs for the P3 to know that it really
>> has the sensitivity to do this.  The IF OUT mod regains ~10
>> dB of the signal lost in the original design but I believe
>> that still leaves ~7 dB that may be lost, according to Jack
>> Smith's measurements:
>>      
> ~7 dB is correct when the IF out is driving a 50 Ohm load.
> Drive a high impedance load (e.g., the 200 Ohm input of Jack's
> amplifier) and the "loss" is 1 dB.  I believe Jack has a more
> complete explanation in the Z-10000 amplifier manual.
>
> 73,
>
>     ... Joe, W4TV
>
>
>
>
>    
>> -----Original Message-----
>> From: elecraft-bounces at mailman.qth.net
>> [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Bill W4ZV
>> Sent: Tuesday, February 16, 2010 10:18 AM
>> To: elecraft at mailman.qth.net
>> Subject: Re: [Elecraft] P3
>>
>>
>>
>>
>> Kok Chen wrote:
>>      
>>>
>>> Spectrograms, such as "waterfalls," make use of your
>>>        
>> eye-brain system
>>      
>>> to help find signals that are below the noise level,
>>>        
>> especially when
>>      
>>> signals are drifting and don't allow temporal averaging methods.
>>>
>>> <SNIP>
>>>
>>> With the addition of some special filtering, you can make a
>>>        
>> waterfall
>>      
>>> see even deeper into the noise when the signal is not drifting.
>>>
>>>        
>> I'd like to see some specs for the P3 to know that it really
>> has the sensitivity to do this.  The IF OUT mod regains ~10
>> dB of the signal lost in the original design but I believe
>> that still leaves ~7 dB that may be lost, according to Jack
>> Smith's measurements:
>>
>> http://cliftonlaboratories.com/elecraft_k3_and_panadapters.htm
>>      
> #What_then_is_the_transfer_gain_of_the_K3_
>
> 73,  Bill
>
>