help with some electronic terms - Electronic Circuits Projects Diagrams Free

ulot · 23rd June 2008, 04:49 PM

I'ld like to know the meaning of some electronic terms and values

1)what does the unit dBuV really mean?

2) what does a filter Q-factor really mean, i mean its effect on filter performance

3) what does filter selectivity stand for.?

4)if i have an Op-amp based filter, how do i calculate its SNR?

quixotron · 23rd June 2008, 08:23 PM

Well I ain't a filter guy but,

1: dB uV means that whatever signal level you're measuring is referenced to a uV. and since we are dealing with rms voltages, we need to to take 20 times the log of the ratio of your signal level to 1 micro-volt. Antenna engineers, like me, use these measurements to predict field strengths in terms of ERPs.

Example. S1= 1056uV therefore, S1 in dB uV = 20 * log(base 10) (1056 uV/1 uV) = 60.5 dB uV

2: To be continued...

MacFeegle · 24th June 2008, 10:46 PM

2) Bandwidth is equal to the resonance frequency divided by Q; (BW=f/Q). Therefore the higher Q a filter has the lower the bandwidth.

3) I believe a highly selective filter is called that because it passes (or blocks) a narrow range of fequencies, ie narrow bandwidth and high Q.

rjvh · 25th June 2008, 02:24 AM

Quote:

Originally Posted by quixotron

Well I ain't a filter guy but,

1: dB uV means that whatever signal level you're measuring is referenced to a uV. and since we are dealing with rms voltages, we need to to take 20 times the log of the ratio of your signal level to 1 micro-volt. Antenna engineers, like me, use these measurements to predict field strengths in terms of ERPs.

Example. S1= 1056uV therefore, S1 in dB uV = 20 * log(base 10) (1056 uV/1 uV) = 60.5 dB uV

2: To be continued...

What is ERPs ?

Robert-Jan

Yes i did look in wikipedia but still have a question mark, maybe a more simplistic explanation will explain it for me

ulot · 25th June 2008, 09:12 PM

thanks for the tips but what about measuring signal to noise ratio?

mneary · 26th June 2008, 02:15 AM

To measure SNR, terminate the input with no signal, and measure the output. This is the noise. Then apply a signal. This is the signal. The ratio (20 log(Vn/Vs)) is SNR.

This does not take distortion into account which would be SINAD.

Externet · 3rd August 2008, 06:12 AM

Hi.
dBuV :
- dBu means voltage based decibels unloaded or unterminated; that is, with no reference to impedance, and the reference is 0.7746 Volts RMS.
- dBuV means the same unloaded voltage based decibel but with a one volt RMS reference instead of the 0.7746 V RMS.
That is, 0dBuV = 1 volt RMS ; 0dBu = 0.7746 V RMS

Do not confuse u for unterminated with µ for the micro symbol. If is not written as dBµV; is dBuV as for unterminated, not microVolts.
If you were unable to write dBµV in your question and you truly meant decibel microVolts, 0 dBµV = 1µV

Q is for 'quality' , believed to be the the best the least resistance an inductor has in its winding

Selectivity is the sharpness of the curve a filter circuit provides, being capable of passing or rejecting a frequency without affecting or being affected by other nearby frequencies.

Miguel

ericgibbs · 3rd August 2008, 07:48 AM

Quote:

Originally Posted by rjvh

What is ERPs ?

Robert-Jan

Yes i did look in wikipedia but still have a question mark, maybe a more simplistic explanation will explain it for me

hi R-J,
Its Effective Radiated Power.

http://www.tasma.org/radiated.pdf

http://uk.search.yahoo.com/search?ei...diated%20power

Space Varmint · 3rd August 2008, 05:55 PM

Q = Xl / R that's inductive reactance divided by resistance.

Kryten · 8th August 2008, 08:14 AM

Iv got a filter "book" by TI that I will post when I get home from work.. (I couldn't find on ti web)

Kryten · 9th August 2008, 03:10 PM

I didnt find the TI one but i have a couple of others about filters..

Here you go

Space Varmint · 9th August 2008, 06:46 PM

Quote:

Originally Posted by Kryten

I didnt find the TI one but i have a couple of others about filters..

Here you go

By Golly I cannot save them. That sucks!

You wanna hear one of the great tragedies of my life...I took a 1 & 1/2 year correspondence course from Nat'l Radio Institute before I went back to school. It had a huge section on "Attenuators,Equalizers & Filters". This thing showed you how to break down a filter where you could analyze every arm & leg impedance in a complex latter network. I had my books stored at my folks house and neglected to pick them up a couple of years. Well they decided to remodel the basement and it was only one or two small boxes, and instead of calling me, they just took it upon themselves to throw my books in the garbage. Heart breaking story. I still love them though.

neon · 27th August 2008, 12:16 PM

Quote:

Originally Posted by ulot

I'ld like to know the meaning of some electronic terms and values

1)what does the unit dBuV really mean?

2) what does a filter Q-factor really mean, i mean its effect on filter performance

3) what does filter selectivity stand for.?

4)if i have an Op-amp based filter, how do i calculate its SNR?

1] means uv ratio in decibels it is a measurement it can be modulation ratio or other ratios.
4] you cannot calculate the SNR it is a spec given for a device to inply the maximun SNR it can achieve. It will vary form IC to IC inclusive variation of its own family.
2] as explained below is sharpness of the filter response.

3] filters ca be designed to pass and/or block frequency by design therefore the term selectivity.

Kryten · 15th October 2008, 04:38 PM

Hi i finally found the TI amp thing

PhillDubya · 15th October 2008, 06:45 PM

Similar to what Space Varmint states...

Q = ω L / R = (1/r)(√L/C); where ω = ωo = cut off frequency

I.E. a RATIO of reactance to resistance.

A way to visualize it is...a cut off intensity of a slope; or how "drastic" the cut off slope is.

Imagine graphically a high pass filter, with the side's slopes increasing of decreasing. Increase in slope, = increase in Q; conversely, decrease in slope, = decrease in Q.

Thread Tools
Show Printable Version Email this Page
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

Similar
Title	Starter	Forum	Replies	Latest
electronic help plz	evan_ellerbe	Electronic Projects Design/Ideas/Reviews	6	28th November 2007 07:09 PM
Electronic Tag	ryans63	Electronic Projects Design/Ideas/Reviews	3	2nd November 2007 03:48 AM
Hello, I'm new to Electronic circuits, how do I get info. on electronic tach for m.c.	pwotoole	General Electronics Chat	17	16th May 2007 06:33 AM
Soldering terms ques	kentken	General Electronics Chat	5	5th July 2004 07:13 AM
audio electronic mixer & electronic voice substitute	kartel	Electronic Projects Design/Ideas/Reviews	0	7th November 2003 03:39 AM

23rd June 2008, 04:49 PM	#1
ulot	help with some electronic terms I'ld like to know the meaning of some electronic terms and values 1)what does the unit dBuV really mean? 2) what does a filter Q-factor really mean, i mean its effect on filter performance 3) what does filter selectivity stand for.? 4)if i have an Op-amp based filter, how do i calculate its SNR?

23rd June 2008, 08:23 PM	#2
quixotron	Well I ain't a filter guy but, 1: dB uV means that whatever signal level you're measuring is referenced to a uV. and since we are dealing with rms voltages, we need to to take 20 times the log of the ratio of your signal level to 1 micro-volt. Antenna engineers, like me, use these measurements to predict field strengths in terms of ERPs. Example. S1= 1056uV therefore, S1 in dB uV = 20 * log(base 10) (1056 uV/1 uV) = 60.5 dB uV 2: To be continued... Last edited by quixotron; 23rd June 2008 at 08:27 PM.

24th June 2008, 10:46 PM	#3
MacFeegle	2) Bandwidth is equal to the resonance frequency divided by Q; (BW=f/Q). Therefore the higher Q a filter has the lower the bandwidth. 3) I believe a highly selective filter is called that because it passes (or blocks) a narrow range of fequencies, ie narrow bandwidth and high Q.

25th June 2008, 09:12 PM	#5
ulot	thanks for the tips but what about measuring signal to noise ratio?

26th June 2008, 02:15 AM	#6
mneary	To measure SNR, terminate the input with no signal, and measure the output. This is the noise. Then apply a signal. This is the signal. The ratio (20 log(Vn/Vs)) is SNR. This does not take distortion into account which would be SINAD.

3rd August 2008, 06:12 AM	#7
Externet	Hi. dBuV : - dBu means voltage based decibels unloaded or unterminated; that is, with no reference to impedance, and the reference is 0.7746 Volts RMS. - dBuV means the same unloaded voltage based decibel but with a one volt RMS reference instead of the 0.7746 V RMS. That is, 0dBuV = 1 volt RMS ; 0dBu = 0.7746 V RMS Do not confuse u for unterminated with µ for the micro symbol. If is not written as dBµV; is dBuV as for unterminated, not microVolts. If you were unable to write dBµV in your question and you truly meant decibel microVolts, 0 dBµV = 1µV Q is for 'quality' , believed to be the the best the least resistance an inductor has in its winding Selectivity is the sharpness of the curve a filter circuit provides, being capable of passing or rejecting a frequency without affecting or being affected by other nearby frequencies. Miguel __________________ Abolish the deciBel ! Last edited by Externet; 3rd August 2008 at 06:46 AM.

3rd August 2008, 05:55 PM	#9
Space Varmint	Q = Xl / R that's inductive reactance divided by resistance. Last edited by Space Varmint; 3rd August 2008 at 05:58 PM. Reason: Wrong symbol

8th August 2008, 08:14 AM	#10
Kryten	Iv got a filter "book" by TI that I will post when I get home from work.. (I couldn't find on ti web) __________________ The best is yet to come Good enough - its perfect !! 2 Gig of free online backup space cq cq de LA3BNA

15th October 2008, 04:38 PM	#14
Kryten	Found it Hi i finally found the TI amp thing __________________ The best is yet to come Good enough - its perfect !! 2 Gig of free online backup space cq cq de LA3BNA

15th October 2008, 06:45 PM	#15
PhillDubya	Similar to what Space Varmint states... Q = ω L / R = (1/r)(√L/C); where ω = ωo = cut off frequency I.E. a RATIO of reactance to resistance. A way to visualize it is...a cut off intensity of a slope; or how "drastic" the cut off slope is. Imagine graphically a high pass filter, with the side's slopes increasing of decreasing. Increase in slope, = increase in Q; conversely, decrease in slope, = decrease in Q.