[R-390] 8640B

[wa4aos at aol.com]

 Yes, As Don has pointed out TWICE, the external reference for the 8640B is 5Mhz and 10 Mhz as I had mistakenly stated earlier; sorry for my error ! !   I  made that conversion in my distribution box for a number of HP units I have that require 5 Mhz external reference as opposed to 10Mhz used on many other devices in my lab. 

My point was to give my two cents worth with regard to the quality of the 8640B as it pertains to most HF alignment issues. It's a very good sig generator and can be bought at a reasonable price. It's great for almost any application that I have needed it for during the last 10 plus years that I have been restoring  receivers.

Since we need to NITPICK, the 8640B does NOT go much below 450 Mhz out. I have two 8640's that go to around 435 and two that go down to about 445; Perhaps revision differences. I have the option that allow all of my generators to go above 1Ghz. If you are working on receivers with lower IF's and need to do alignments then another generator will be best. 

With regard to blowing up the internal counter by over-driving it. The owner can adjust the input level accordingly with an attenuator. However, for most of my applications, I have not had to attenuate an input signal. I would expect most users of such equipment would be INTELLIGENT enough to not exceed those parameters without the need to install a plug to prevent them from doing something stupid; just saying.. read your manual ! ! !

I should have made it clear that the external reference is 5 MHz for the 8640B but did not really plan on delving into the optional nicessities of my set up in that post. The external refenence is really not needed since the 8640B is very accurate on it's own. I use an external reference(s) to make the many pieces of my equipment closely agree with each other. 

As they say:

A man with a clock always knows the time
A man with two clocks is never quite sure..

73,
Glenn WA4AOS
DSM Labs