Re: [time-nuts] schematics of frequency counter

Hi Thanks for the suggestion. I will do some experiments with the front end :) 2014-12-25 4:32 GMT+08:00 Bob Camp kb...@n1k.org: Hi Very interesting !! Thanks for sharing. As you can see from the Fluke schematics, the input amplifiers on counters can get quite complex. I would

Re: [time-nuts] schematics of frequency counter

Hi Charles Bruce I'm not good at analog circuits. My circuit is modified from wenzel's, since RF pnp transistor is harder to get. I would like the front end works at 300MHz. My questions: 1) why the difference of DC bias of the 2 NPN matters? I thought only the frequency part is useful to a

Re: [time-nuts] schematics of frequency counter

Hi, On 12/26/2014 02:38 PM, Li Ang wrote: Hi Charles Bruce I'm not good at analog circuits. My circuit is modified from wenzel's, since RF pnp transistor is harder to get. I would like the front end works at 300MHz. My questions: 1) why the difference of DC bias of the 2 NPN matters? I

Re: [time-nuts] LNA and Alias

Hi, I have just found the culprit The AD7760 eval board in charge of the ADC task, is equipped with a little 40 MHz clock witch seems to generate a beat note with my 10Mhz noise measurements setup. I have discovered the origin of the problem after disconnecting the LNA from the measurement

Re: [time-nuts] Another use for a Trimble Thunderbolt

Authur wrote: Take a look at the plot where I adjust a rubidium standard and see what you think. I think it is a great idea, and shows that LadyHeather and a modified TBolt can make a great high end, stand alone Time-Nut tester without the need of a reference osc or offset osc, or any other

[time-nuts] EZGPIB / ProfiLab

Hi, I am using EZGPIB to capture data via HP3325A and HP3478A and it works great ( thanks Jack ). Ulrich Bangert in the EZGPIB manual suggests that EZGPIB and ProfiLab can run concurrently. Does this mean that I can plot data via ProfiLab in near real time ( without exiting EZGPIB and plotting

Re: [time-nuts] schematics of frequency counter

Hi Don’t go to crazy on the front end. You can spend a year optimizing something like this. The objective is to see if the front end is a big problem now. It’s very easy to get to many things going on in a project. That makes it hard to complete. All front end circuits will work better with

Re: [time-nuts] schematics of frequency counter

Hi On Dec 26, 2014, at 9:21 AM, Magnus Danielson mag...@rubidium.dyndns.org wrote: Hi, On 12/26/2014 02:38 PM, Li Ang wrote: Hi Charles Bruce I'm not good at analog circuits. My circuit is modified from wenzel's, since RF pnp transistor is harder to get. I would like the front

Re: [time-nuts] LNA and Alias

Hi The nature of a ADC with a built in digital front end filter is to have multiple passbands centered around the ADC clock and it’s harmonics. Put another way - the chip has zero rejection at clock * N where N = 1,2,3,4,5…. They may also have zero rejection at other frequencies (like clock /

Re: [time-nuts] schematics of frequency counter

Li Ang wrote: RF pnp transistor is harder to get. I would like the front end works at 300MHz. My questions: 1) why the difference of DC bias of the 2 NPN matters? I thought only the frequency part is useful to a counter, amplitude information is useless right? You want the circuit to switch