Trying to get a copy and paste RF tool made that deals with PF, Coil Q, and fast rise times. Beau S?
rwgast_logicdesign
Posts: 1,464
in Propeller 1
So first off I want to makes a Time Domain Reflector, im pretty broke and im trying to use what I have on hand. I watched a video from w2aew on making a TDR he basically Manhattan styles a 74ac14 the point is the frequency can be really low but the rise time has to be ultra fast, next he just adds a bunch of 220 ohm resistors on the outputs to get a 50 ohm impeadence. I have some 74lvvc244an line drivers. I don't use 74xx chips very much unless its with like an old z80 or something, so most my collection is 74LS I have tons of LS chip maybe 50 different kinds. Im having a bit of a hard time reading the data sheets though... Im guessing Tph (propigation time) is the rise/fall time, would that be correct? If so w2ae2's hex inverter is anywhere from 3 to 10ns while my 74lvc244 is <||=2ns? I have plenty of hex inverters may 15 or so but they are all 74LS.
Secondly I have a Uni-T ut71E 40,000cnt DMM this meter is pretty good its speced about the same as a 30,000 count Agilent for much cheaper, its major down fall is it has BAD input protection, im scared to use it for anything more than 12, but thats ok its a great electronics meter and my fluke is a great electrical meter which I trust to probe 1000v, I don't think id ever use the uni-t at its claimed 1000v! Sorry kind of rambling, but anyone needing a nice desktop meter in the 130 range should check it out, along with a DMM check and a few opamps you can get it dead on to the LSB with its closed box calibration after adjusting a few pots. its drift in a year is almost insignificant. Besides it data loging, via internal flash or USB the features I really loved were the 40mhz frequency counter, which I tested with a CML output TCXO and a 5v pull up, it was dead on the 28.800 frequency, The capacitance is suppose to be 1pf to 4mF. I actually have some huge caps close to 4mF and they all read well along with all the standard nF an uF sizes. I don't know if I trust it under 10nf though.
I have also been working on Phils AM radio project and trying to understand a bit more about manipulating I&Q values. My first goal is to eventually get the radio to tune from 1hz up to the top of AM and then go from there maybe adding a DDS etc. The thing Is I want a VERY low Q 500uH coil. I wrap coils all the time and just test there value with an arduino, it works quite well especially if you tune the frequency.... Im guessing it is better than an EBAY LC/ESR 20 dollar special.
So lets get to the point, why all this rambling about transmission line, low value caps, and the Q of inductors in the prop 1 forum.
i would like to make a multi tool and I don't want to waste a ton of time doing it! I remember I got a program from peter jacki that tested caps about 4 years ago... the problem is, is that it used VGA or Composite I think, the hardware was simple just an RC time circuit and you used the known value of the resistor to calculate the cap size. Well I dont really want to write code..... maybe modify but not start from scratch... I cant find peters code in obex. What I would like to do is use a metal foil .05% resistor to measure caps and send them via terminal or 16x2 maybe 4 LCD. Secondly I have NO idea how to test Q or even the permeability of a core, it would be nice if anyone has a Q test function. Until RF I only used coils for switchers and 2nd degree LC filtesr didn't worry about Q very much. I want a high high Q for the tank circuit on the antenna in the AM project that way im not so focused on a certain frequency. What im having a hard time understanding is if feright or air gives a better Q, I know Beaus huge coke can formed air coil is high Q, so what makes a low q coil, with higher L, and is air actually a better Q the freight? Lastly I Q factor?
Right now im really trying to copy and paste a bunch of stuff so I have a usable test tool for small caps, tdr, inductance and q, I can easily port the inductance code from arduino if there is none in obex. after I get it all going I would like to go back through and do alot of it in C and PASM along with adding more features like Z measurement and an adjustable clock generator, maybe DDS to. I think it could be a handy budget ham tool, kind of like a Bus Pirate for RF lol. But at the moment I just want to plug in a pre made prop board add the appropriate connectors and copy and paste if possible.
Secondly I have a Uni-T ut71E 40,000cnt DMM this meter is pretty good its speced about the same as a 30,000 count Agilent for much cheaper, its major down fall is it has BAD input protection, im scared to use it for anything more than 12, but thats ok its a great electronics meter and my fluke is a great electrical meter which I trust to probe 1000v, I don't think id ever use the uni-t at its claimed 1000v! Sorry kind of rambling, but anyone needing a nice desktop meter in the 130 range should check it out, along with a DMM check and a few opamps you can get it dead on to the LSB with its closed box calibration after adjusting a few pots. its drift in a year is almost insignificant. Besides it data loging, via internal flash or USB the features I really loved were the 40mhz frequency counter, which I tested with a CML output TCXO and a 5v pull up, it was dead on the 28.800 frequency, The capacitance is suppose to be 1pf to 4mF. I actually have some huge caps close to 4mF and they all read well along with all the standard nF an uF sizes. I don't know if I trust it under 10nf though.
I have also been working on Phils AM radio project and trying to understand a bit more about manipulating I&Q values. My first goal is to eventually get the radio to tune from 1hz up to the top of AM and then go from there maybe adding a DDS etc. The thing Is I want a VERY low Q 500uH coil. I wrap coils all the time and just test there value with an arduino, it works quite well especially if you tune the frequency.... Im guessing it is better than an EBAY LC/ESR 20 dollar special.
So lets get to the point, why all this rambling about transmission line, low value caps, and the Q of inductors in the prop 1 forum.
i would like to make a multi tool and I don't want to waste a ton of time doing it! I remember I got a program from peter jacki that tested caps about 4 years ago... the problem is, is that it used VGA or Composite I think, the hardware was simple just an RC time circuit and you used the known value of the resistor to calculate the cap size. Well I dont really want to write code..... maybe modify but not start from scratch... I cant find peters code in obex. What I would like to do is use a metal foil .05% resistor to measure caps and send them via terminal or 16x2 maybe 4 LCD. Secondly I have NO idea how to test Q or even the permeability of a core, it would be nice if anyone has a Q test function. Until RF I only used coils for switchers and 2nd degree LC filtesr didn't worry about Q very much. I want a high high Q for the tank circuit on the antenna in the AM project that way im not so focused on a certain frequency. What im having a hard time understanding is if feright or air gives a better Q, I know Beaus huge coke can formed air coil is high Q, so what makes a low q coil, with higher L, and is air actually a better Q the freight? Lastly I Q factor?
Right now im really trying to copy and paste a bunch of stuff so I have a usable test tool for small caps, tdr, inductance and q, I can easily port the inductance code from arduino if there is none in obex. after I get it all going I would like to go back through and do alot of it in C and PASM along with adding more features like Z measurement and an adjustable clock generator, maybe DDS to. I think it could be a handy budget ham tool, kind of like a Bus Pirate for RF lol. But at the moment I just want to plug in a pre made prop board add the appropriate connectors and copy and paste if possible.