[Hammarlund] SP-600 First report, HC-10 question.

[Rodney Bunt]

I was reading your post about the SP-600.

I have a SP-600JX-17 with the RED knobs, one of them has a big ugly score acrossthe face of it. In
you look for knobs, if you find one of the RED knobs, could you let me know, please.

I have installed the IF gain mod myself, doesn't do much, unless you have a real strong signal, I
run it at maximum gain anyway.

Regarding the IF out on the SP-600, it is a "cathode follower" or buffer circuit, and has a 680
Ohm output impedance. The idea of the cathode choke in the installation instructions is to provide
a high impedance source, so that the "T" trap will have the sharpest response.

To simulate this high impedance from the IF out of the SP-600 connect a choke from V16A pin 8 to
the 680 Ohm resistor this will leave the DC conditions unchanged yet present a high impedance
source to the HC-10. (check the DC resistance of the choke and add resistance to make up the 680
Ohms to maintain the DC / bias current)

The filter is only used to remove birdies etc....

REgards,

Rodney
VK2KTZ
rodney_bunt@yahoo.com




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