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: [email protected] >> [mailto:[email protected]] On Behalf Of Bill W4ZV >> Sent: Tuesday, February 16, 2010 10:18 AM >> To: [email protected] >> 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 > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
