to be honest all your videos blow my mind away. I had 2 classes of DSP in computer eng, where i did good actually. but this is really hard stuff to understand.
w2aew I know. This is also why I’m watching your channel, but having a family and all, studying electronics is something I have to do in my spare time.
Thanks for this "enlightenment". You also opened the door for me on transmission lines. I have tried to wade through the transmission line section in the ARRL manual but never could grasp what the heck was going on. That ARRL article is very poorly presented and too complicated in my humble opinion. Thanks again. Great video's!
Thanks, that was very informative as always! I remember some of that from over the years and electronic training and hands on but it was a great refresher also, I forgot a lot of that over time. Keep up the videos and I will be watching and learning.
I have an old HP141T and HP8443 TG in great working condition. As an excercise I'm trying to look at the bandpass wave form for my Icom 761 455kc 500 hz cw crystal filter. The wave form I am seeing is not the textbook bandpass wave form as displayed in the ARRL Handbook. I looked online and found the impedance of the IC765 cw filter I'm looking at is supposed to be 1000 ohm. How would one display the proper wave for as seen in the ARRL manual? Matching transformer? Thanks for your very clear simple explanations. I never could grasp the concept of coaxial stubs from reading the gibberish in the ARRL manual. You made it sound easy. I wish those who put the ARRL Handbook together could incorporate more practical explanations for field technicians instead of being oriented to those with electrical engineering degree's. I have used coaxial tuning stubs to lower the swr on dipole antenna's on Field Day but never truely understood how it worked.
Hi, I'm a student and your videos helped me a lot. Thank you. One topic that I dont understand very well is how to design a crystal oscillator. Can you do a video on this topic or can you recomend me a good tutorial?
It is unusual that inches are used instead of the metric system in the calculation of lambd/4 in coaxial cable = 1947"?/f (MHz). Frank Frank Reiser Video/Audio Service Caldwell, NJ.
Thanks alan, for another great video. One (beginner) question in regards to the notch filter: why does it filter the third harmonic and not the second?
At even multiples of quarter wavelength, the input impedance equals the far end termination - so an open is an open, and a short is a short. For odd multiples of quarterwave length, the impedance is inverted.
Thanks for another very informative video. What is your take about PC based spectrum analyzer and tracking generator such as Signal Hound as cost effective alternative (pros/cons)? Also wanted to thank you for your ARRL Antenna Handbook recommendation in response to my comment to your last video. I ordered the book as I strive to improve my antenna theory knowledge and appreciate everything I learn from your very well prepared videos and look forward to more.
The HP 8560E has a 1st LO output SMA connector and an IF input so that the HP 85640A tracking gen. can be connected as a separate unit. Theoretically that can be done in any SA, right?
For testing filters, sometimes I use the "poor man's tracking generator" by simply feeding amplified wideband noise into the filter and seeing the response on the spectrum analyzer. Would it be fair to say that the setup in this video is equivalent to doing an amplitude measurement |S21| on a vector network analyzer?
Im curious, isnt a tracking gen prettxy much the same as having a simple sweep gen connected with its sweep (ramp) output to my scopes X input and probing the output of a filter connected to my scopes Y input?
Hi, Nice video, Thanks. I have a nice HP 8566 SA but no tracking generator. If you have time at some point, could you do another similar video, sweeping an IF filter and describe the responses? 455KHz would be great and ubiquitous. Perhaps a second filter that is not working as it should would be helpful for comparison to one that is. 73, Glenn WA4AOS
Thank You for the video! What is the main difference between a spectrum analyzer with Tracking generator and a System Network Analyzer such as a HP 8753D ?
There are a few main differences. The SA+TG solution can only show the magnitude of the insertion loss/gain of a device. It can't show any input/output loss (reflections) unless you use an external directional coupler. A vector network analyzer can measuring transmission and reflection parameters on both ports, including magnitude & phase.
This video was amazing!!!! Holy crap!!! My question.....what causes the signal rejection @ 1/4 wavelength? Is it some type of destructive cancellation due to internal reflection in the conductor or something???
+Brian Streufert Yes. If a 1/4 wavelength long line is open at the far end, the reflection is virtually 100%. Thus, when the reflected signal arrives back at the input, it is delayed by 1/2 wavelength (1/4 wavelength down to the end, and 1/4 wavelength back). A sinusoid delayed by 1/2 wavelength is the same thing as a 180 degree phase shift - it is basically inverted. So, at the driven end, the incident signal is destructively cancelled by the reflected signal at the input.
Hello Alan. Once again I am learning a lot from your videos. Thank you for your time. I Live in NYC and as you can tell my transceiver is being bombarded by AM and FM Broadcast signals. How would I go about spacing the T for the bands that I want to reject. Can I couple the t's together and have one 1/4 wave stub next to the other or do they have to be spaced at a certain interval. I would rather not buy a professional low pass filter. Thanks again.
Stub filters are probably not be best thing to use in a transceiver situation because they will add an impedance discontinuity that will affect the matching for the transmitter.
@@w2aew Thanks again. I made the 1/4 wavelength coaxial transmission line stub filter and I was able to knock all FM Broadcast right out of my RTL-SDR Dongle.
Hi Alan, thank you so much for those amazing videos. Just one quick question, how can I sweep from high frequency to low frequency instead of sweeping from left to right?
+Rhonda Song All tracking generators and spectrum analyzers I've seen always track low to high. However, many signal /. function generators have VCF inputs that can be driven with a falling sawtooth to sweep high to low. Or, mix the output of a TG with a mixer and fixed LO, and the image on the opposite side of the LO will sweep in the opposite direction.
Please bear with me. I'm trying to learn about Spectrum Analyzers and tracking generators. I don't see the need for the tracking generator. Why can't you just take the LO freq of the spectrum analyzer, through some sort of fancy adjustable buffering amp, and use its signal to analyze your notch filter or other device under test?
Thanks for another excellent video. In your video, the tracking generator output appears to be a clean sinewave with constant amplitude even though it was sweeping from 5 MHz to 100 MHz. In my experiments with signal generating circuits I have found it difficult to vary the frequency by much more than a factor of 3 or 4. So starting at 5 MHz might allow me to sweep to 15 or 20 MHz. How do tracking generators sweep such a wide frequency range? Thanks.
w2aew Thanks again. ALC would explain a flat response across the spectrum. I have an old HP 8557A spectrum analyzer that scans from 10 KHz to 350 MHz and it is not synthesized. It appears to be a design from the 1970s and uses discrete analog solid state components. So it baffles me that it can sweep such a wide frequency range with an LC circuit using a varactor.
Thanks again Alan, I went to the HP8557A service manual and found that the spectrum analyzer uses two mixers. The first local oscillator is indeed a transistorized LC circuit with a varactor diode. It operates from 521.4 MHz to 871.4 MHz. The second oscillator is fixed at 500 MHz. Therefore the IF is 21.4 MHz. I am guessing that the 871.4 being only a factor of 1.7 higher than the lower frequency makes this possible.
@@w2aew my delta loop called for a 1/4 wave of 72 ohm line from the vee, backwards to the 50 ohm line for matching purposes, which im still kinda fuzzy why really. my first loop really in 30 years of being a ham
@@jeremycole3008 This site gives a brief explanation of how a 1/4 wave line does an impedance tranformation: www.everythingrf.com/rf-calculators/quarter-wave-transformer-impedance-calculator The 72 ohm line will transform the approx 100ohm input impedance of the loop down to 50 ohms
Hi Alan, Don't know if you've seen this video of the Tektronix vintage museum in Oregon. I think it's a cool timeless collection of everything Tek. Particularly funny (I think) is the Tek "you done good" and the "you screwed up" awards! (add youtube.com) watch?v=aavW_n3XyUI Cheers, Nelson
to be honest all your videos blow my mind away. I had 2 classes of DSP in computer eng, where i did good actually. but this is really hard stuff to understand.
Once again outstanding. You are my personal UA-cam college Professor.
Thanks
Thank you for taking time sir to create this video and clearly explain. Most appreciated.
WOW! once again a top notch high end educational gold nugget on youtube. THANKS A LOT!
Excellent, I followed it 100 %, your presentation hit and explained all of the highlights. 73 de K0UA
Man, you make me wish I had studied electronic engineering instead of computer science. I love your watching your videos.
It’s never too late!
w2aew I know. This is also why I’m watching your channel, but having a family and all, studying electronics is something I have to do in my spare time.
Thanks for this "enlightenment". You also opened the door for me on transmission lines. I have tried to wade through the transmission line section in the ARRL manual but never could grasp what the heck was going on. That ARRL article is very poorly presented and too complicated in my humble opinion. Thanks again. Great video's!
Outstanding tutorial as always! Thank you!
Excellent!! I've been hoping to see you do a video explaining tracking generators. Also, nice to see your Advantest in action.
👍Thank you sir.
Thanks, that was very informative as always! I remember some of that from over the years and electronic training and hands on but it was a great refresher also, I forgot a lot of that over time. Keep up the videos and I will be watching and learning.
I have an old HP141T and HP8443 TG in great working condition. As an excercise I'm trying to look at the bandpass wave form for my Icom 761 455kc 500 hz cw crystal filter. The wave form I am seeing is not the textbook bandpass wave form as displayed in the ARRL Handbook. I looked online and found the impedance of the IC765 cw filter I'm looking at is supposed to be 1000 ohm. How would one display the proper wave for as seen in the ARRL manual? Matching transformer? Thanks for your very clear simple explanations. I never could grasp the concept of coaxial stubs from reading the gibberish in the ARRL manual. You made it sound easy. I wish those who put the ARRL Handbook together could incorporate more practical explanations for field technicians instead of being oriented to those with electrical engineering degree's. I have used coaxial tuning stubs to lower the swr on dipole antenna's on Field Day but never truely understood how it worked.
Hi,
I'm a student and your videos helped me a lot. Thank you.
One topic that I dont understand very well is how to design a crystal oscillator.
Can you do a video on this topic or can you recomend me a good tutorial?
Man oh Man you make good videos..
great video
Thank u for the video. But its the first time in my life i see calculation of frequency with inches for wavelength, and i am old in the business.
great video thanks
It is unusual that inches are used instead of the metric system in the calculation of lambd/4 in coaxial cable = 1947"?/f (MHz).
Frank
Frank Reiser Video/Audio Service
Caldwell, NJ.
Inches and feet are not at all uncommon in Amateur Radio / USA anyway.
Hi Alan, I love to watch your detailed videos. Thanks a lot for your effort. By the way, the links for Note pdf is not working anymore.
I've corrected the link: www.qsl.net/w2aew/youtube/Basics_of_Tracking_Generators.pdf
Thanks alan, for another great video. One (beginner) question in regards to the notch filter: why does it filter the third harmonic and not the second?
At even multiples of quarter wavelength, the input impedance equals the far end termination - so an open is an open, and a short is a short. For odd multiples of quarterwave length, the impedance is inverted.
Thanks for another very informative video. What is your take about PC based spectrum analyzer and tracking generator such as Signal Hound as cost effective alternative (pros/cons)? Also wanted to thank you for your ARRL Antenna Handbook recommendation in response to my comment to your last video. I ordered the book as I strive to improve my antenna theory knowledge and appreciate everything I learn from your very well prepared videos and look forward to more.
The HP 8560E has a 1st LO output SMA connector and an IF input so that the HP 85640A tracking gen. can be connected as a separate unit. Theoretically that can be done in any SA, right?
For testing filters, sometimes I use the "poor man's tracking generator" by simply feeding amplified wideband noise into the filter and seeing the response on the spectrum analyzer. Would it be fair to say that the setup in this video is equivalent to doing an amplitude measurement |S21| on a vector network analyzer?
Yes, I'd like an answer to that as well.
Im curious, isnt a tracking gen prettxy much the same as having a simple sweep gen connected with its sweep (ramp) output to my scopes X input and probing the output of a filter connected to my scopes Y input?
Hi,
Nice video, Thanks. I have a nice HP 8566 SA but no tracking generator.
If you have time at some point, could you do another similar video, sweeping an IF filter and describe the responses? 455KHz would be great and ubiquitous.
Perhaps a second filter that is not working as it should would be helpful for comparison to one that is.
73,
Glenn WA4AOS
Thank You for the video! What is the main difference between a spectrum analyzer with Tracking generator and a System Network Analyzer such as a HP 8753D ?
There are a few main differences. The SA+TG solution can only show the magnitude of the insertion loss/gain of a device. It can't show any input/output loss (reflections) unless you use an external directional coupler. A vector network analyzer can measuring transmission and reflection parameters on both ports, including magnitude & phase.
This video was amazing!!!! Holy crap!!!
My question.....what causes the signal rejection @ 1/4 wavelength? Is it some type of destructive cancellation due to internal reflection in the conductor or something???
+Brian Streufert Yes. If a 1/4 wavelength long line is open at the far end, the reflection is virtually 100%. Thus, when the reflected signal arrives back at the input, it is delayed by 1/2 wavelength (1/4 wavelength down to the end, and 1/4 wavelength back). A sinusoid delayed by 1/2 wavelength is the same thing as a 180 degree phase shift - it is basically inverted. So, at the driven end, the incident signal is destructively cancelled by the reflected signal at the input.
:-) That is exactly what I visualized in my head. I impress even myself at times! HA! Thank you for the reply!
Hello Alan. Once again I am learning a lot from your videos. Thank you for your time. I Live in NYC and as you can tell my transceiver is being bombarded by AM and FM Broadcast signals. How would I go about spacing the T for the bands that I want to reject. Can I couple the t's together and have one 1/4 wave stub next to the other or do they have to be spaced at a certain interval. I would rather not buy a professional low pass filter. Thanks again.
Stub filters are probably not be best thing to use in a transceiver situation because they will add an impedance discontinuity that will affect the matching for the transmitter.
@@w2aew Thanks again. I made the 1/4 wavelength coaxial transmission line stub filter and I was able to knock all FM Broadcast right out of my RTL-SDR Dongle.
what about 1/2 wave length
Hi Alan, thank you so much for those amazing videos. Just one quick question, how can I sweep from high frequency to low frequency instead of sweeping from left to right?
+Rhonda Song All tracking generators and spectrum analyzers I've seen always track low to high. However, many signal /. function generators have VCF inputs that can be driven with a falling sawtooth to sweep high to low. Or, mix the output of a TG with a mixer and fixed LO, and the image on the opposite side of the LO will sweep in the opposite direction.
When I measure an RF cable, I measure like 0.8 dB loss at 900 MHz and 1.2 dB loss at 2.4 GHz.
Not uncommon.
@@alanwolke6253 Why is the cable loss higher at higher frequency? Is it caused by inductive reactance?
Two main effects are due to skin effect and dielectric loss, both of which are frequency dependent.
Please bear with me. I'm trying to learn about Spectrum Analyzers and tracking generators. I don't see the need for the tracking generator. Why can't you just take the LO freq of the spectrum analyzer, through some sort of fancy adjustable buffering amp, and use its signal to analyze your notch filter or other device under test?
Thanks, do you have plans to do any videos with the Tek Y400?
Thanks for another excellent video. In your video, the tracking generator output appears to be a clean sinewave with constant amplitude even though it was sweeping from 5 MHz to 100 MHz. In my experiments with signal generating circuits I have found it difficult to vary the frequency by much more than a factor of 3 or 4. So starting at 5 MHz might allow me to sweep to 15 or 20 MHz. How do tracking generators sweep such a wide frequency range? Thanks.
Most likely a built-in factory calibration that compensates for amplitude variation as it sweeps - maybe a lookup table, or even an ALC loop.
w2aew Thanks again. ALC would explain a flat response across the spectrum. I have an old HP 8557A spectrum analyzer that scans from 10 KHz to 350 MHz and it is not synthesized. It appears to be a design from the 1970s and uses discrete analog solid state components. So it baffles me that it can sweep such a wide frequency range with an LC circuit using a varactor.
Is it really using an LC circuit and a varactor? That would be a very wide range for that type of VCO.
Thanks again Alan, I went to the HP8557A service manual and found that the spectrum analyzer uses two mixers. The first local oscillator is indeed a transistorized LC circuit with a varactor diode. It operates from 521.4 MHz to 871.4 MHz. The second oscillator is fixed at 500 MHz. Therefore the IF is 21.4 MHz. I am guessing that the 871.4 being only a factor of 1.7 higher than the lower frequency makes this possible.
is there a 32 mhz signal of any kind at the open end of the coax cable?
Yes, of course there is. It only appears as a short at the input.
ok
@@w2aew my delta loop called for a 1/4 wave of 72 ohm line from the vee, backwards to the 50 ohm line for matching purposes, which im still kinda fuzzy why really. my first loop really in 30 years of being a ham
@@jeremycole3008 This site gives a brief explanation of how a 1/4 wave line does an impedance tranformation:
www.everythingrf.com/rf-calculators/quarter-wave-transformer-impedance-calculator
The 72 ohm line will transform the approx 100ohm input impedance of the loop down to 50 ohms
@@w2aew excellent, than you kindly. 73 N9IZX
Hmm...I thought it may had been considerably older.
How old is that spectrum analyzer?
Hi Alan,
Don't know if you've seen this video of the Tektronix vintage museum in Oregon. I think it's a cool timeless collection of everything Tek. Particularly funny (I think) is the Tek "you done good" and the "you screwed up" awards! (add youtube.com) watch?v=aavW_n3XyUI
Cheers, Nelson
You have to have an export license to ship these things into a non-NATO country...