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Heath-Zenith (Heathkit) Frequency Counter Model SM-2420
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OK, thanks, I do have a manual for it, and according to the manual I have to let it warm up for about 20-30 minutes because of it having a crystal oven inside of the unit, which that was one thing I forgot to do with this thing, also I did check the switch on the back and it was switched to the external time-base rather than the internal time-base so I switched it to the internal time-base settung, and I tried both the "A" input and the "B" input and they both didn't give me any sort of reading (but then again it was probably because I didn't wait 20 minutes for it to warm up).
And its good to know I could use a 75 Ohm BNC cable with this unit because that was cheaper than the 50 Ohm one was.

I did do the modification where I took the AF Input jack and wired it straight to the oscillator so it completely bypasses the Attenuator and has a constant full volume signal.

See the quote below.


Quote:[Image: https://philcoradio.com/phorum/attachment.php?aid=22108]    Hi Captain, you can do as you said and just connect the RF OUTPUT to the frequency counter and then adjust the generator to your desired frequency, the disconnect it. My experience with my SG-8 is that it’s not very stable, necessitating constant readjustment. My alteration allows constant monitoring of the generator frequency without constantly connecting and disconnecting the counter to the RF output. Up to you. If you want to do the change, disconnect the AF INPUT jack from everything circled in red, add a .001mfd cap to the jack and the other end to the circuit with the green arrow! Now, no matter what setting you use for the attenuators, the counter always gets full signal level. Using BNC jacks makes it easy to connect a modern lead with BNC ends to the input of a modern frequency counter. This is a fairly quick and inexpensive change to your SG-8!


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RE: Heath-Zenith (Heathkit) Frequency Counter Model SM-2420 - by captainclock1988 - 05-04-2020, 09:11 PM



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