Nixie Tubes

[w3jn]

With a .1 second refresh rate, you won't notice a lag.  With a 1 second time base, you certainly will.

[w8khk]

Another thing that dawned on me was say if I use a counter board from a counter or something is that it would probably behave like an ordinary frequency counter. If I'm using it as the frequency readout for the tuning dial then I can't wait for the stupid thing to lock up to display the frequency. It needs to immediately change as I tune the dial. It says the heath 650 is a frequency display, but I wonder if the change is immediate?

You have complete control of the count time duration and interval.  The interval you set between counts determines how quickly the display is updated when you tune your oscillator.  Use a longer count to get higher resolution - ie: low-order digits.  Simply move the decimal point as you change your time base selection. 

I found a rather interesting article in QST for April '74.  On page 34 is part II of an article by Wes Hayward, W7ZOI, entitled "A Competition-Grade CW Receiver".  He installed a HB counter, using 7-segment LEDs, not nixies, inside the receiver.  Most of the receiver sections are shielded, but the counter logic is not.  He designed it using a 2.0 MHz clock so the spurs would not lie in the ham bands of interest.  Then the novel approach he used was to gate signal from the crystal oscillator to the divider chain, such that the chain was inactive when no count is in progress.  The oscillator is the only logic running continuously.  This virtually eliminated the interference problem.

[w3jn]

No reason the Heath counter won't work below 3 MHz.   In its intended application it doesn't need to though; there are no oscillators in the Heath SB-series under 3 MHz.

Use at least 74LS ICs in the first two dividers if you need to go to 55 MHz.  Regular 74xx TTL craps out between 15-20 MHz, depending on the chip.

[John K5PRO]

I used to have a HP counter that used Nixies that wasn't big. It was about the size of the Heathkit 650 seen here. I don't remember the model, but it was a 10 MHz top end counter I believe. I gave it to a friend few years ago.

[w3jn]

Why do all that?  The driver ICs will drive the nixies directly.  There's absolutely no reason whatsoever to add FETs - the ICs are much smaller than 10 FETs will be.  You can build the whole counter on one board, nixies included.

[w3jn]

Why not just run each 4 bit line from the counters to the decoder/driver mounted at the base of each nixie?  That way you're only sending 5V thru those cables instead of 180V.

"Better" is the enemy of "good enough" and it's certainly true here.  I can't fathom what you have against using the 74141s to drive the nixies directly - it's been done in hundreds of designs very successfully.