#45: Sweep Generator Basics and Receiver Alignment
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- Опубліковано 1 лют 2025
- This video discusses the basics of a sweep generator, and how it can be used to observe the alignment of IF filters in a receiver. The video starts out by briefly discussing the frequency response characteristics of typical IF transformer cans, and how you and "manually" observe their response using a simple signal generator and a scope. Then, the fundamentals of a sweep generator / oscillator are discussed, and how these can be used to observe the "shape" of the frequency response of a resonant circuit like an IF transformer. The benefits of using a sweep gen, including the ability to observe whether multiple IF transformers in a single IF chain are aligned, or to see the "shape" of the skirts of a filter, is shown. While the video shows just a single IF can as an example, these same techniques can be used to align a receiver's IF by injecting the signal at the appropriate point in the IF, and monitoring its response.
MAY GOD BLESS YOU. I'm 72 and starting to get back into electronics. I've ALWAYS had a hard time understanding how to use test equipment. But, YOU, have made it clear. Where were you 50 years ago when I was starting out? So THAT'S the difference between just an RF signal generator and a sweep generator and what they do. It seems so simple now.
I gotta check to see if you have any more videos posted.
+Mystery47 Well, 50 years ago, I was 3. Probably wouldn't have been much help to you! And yes, I have over 230 videos posted...
Same here have not done electronics tuning in over 40 years....really good video
I'll be 48 in a couple of days, got into electronics as a very young child, especially radio, been a ham radio operator for nearly 30 years, and I am just now REALLY getting into electronics. NO AGE is too old to learn! Good luck!
This video demonstrates why should teaching more practice in technical schools, like the way in this video.
Thank you for your comment. So 28 years old is not too late to start. Good luck!
I agree with previous comments, Alan is one of the best teachers on UA-cam. Alan, Paul Carlson(Mr. Carlson’s Lab) and Joe Smith have electronics/electrical engineering skills far beyond most humans. These three gents have taught me some very helpful lessons in their videos. Thank you for sharing your knowledge. I’ve learned more from videos on here than I ever did in a classroom for the most part. Learning how to build and tests circuits is the best experience anyone will get, guys like you and the others I mentioned show us how. 👍👍👍
Ben Eater too..
Thank you Alan, your videos are great help in electronics for beginners like myself. I am currently an Intermediate Ham Licence holder in UK, and studying towards my Full licence exams. You have a great skill of delivering very easy to uderstand instructional videos.
I appreciate your demonstrating basic concepts in ways that absolute beginners can grasp. Though I had an idea what a sweep generator WAS, it wasn't until I watched this video that I could see how I might USE it.... Like testing and tweaking filters for audio circuits, as I'm not (yet) into RF circuits.
Nixie based displays are absolutely awesome, and so are all your videos Alan thanks
Wow, Alan, you really nailed it! This is the first utterly clear visualization of the concept of alignment that I've ever seen.
So cool! Thank you Alan. Do you have to physically remove the IF transformer from the radio to do this alignment though? That would seem to be excessive if it were the case.
Fantastic video Alan. I setup my signal generator to sweep a high pass filter that I assembled. The results are spectacular. Keep up the excellent work.
Most straightforward presentation of this topic I've seen. Love the Nixie Tube freq meter. Reminds me of the Heathkit one.
I built a Heathkit tube-based SW radio in 1968. Can't recall what I used to tune the IF. But to align, the book called for dialing up WWV (then NBS, not NIST)
Thanks for taking the time to produce this tutorial.
I really enjoy your videos but I'm having a little trouble understanding how you are triggering on the sweep to get that image. Are you using the ramp or pulse on a second channel and setting it as an external trigger your scope. Could you please outline your connections to the scope. Thanks for this great video.
I am viewing more and more of your presentations. I just finished the oscilloscope post you gave to the antique radio group. That was a great one. I have a tek 475 and a rigol 1102. I just got a used B&K 4040a generator from EBAY and I am following your videos. Tnx a lot for sharing. .
Thanks much for another great class! I needed this for working on a few older radios. Loved how well the scope shows you exactly whats going on.
Another interesting, very clear video. A sweep generator is a huge help for filter checking or design, checking "Q"-etc. The uses for tuned circuits are limited only by imagination. Does not have to be real fancy either -from old boatanchors like Eico's and RCA's to newer used BK's, HP's and Waveteks, etc -if you can afford a nice DMM you can usually afford a sweep generator for your typical purpose. Markers are a nice feature. I think your videos are super for helping people see possibilities!
Excellent. Head and shoulders above most other videos on this topic.
Thank you for your clear and concise exposition of the subject. The preparation and quality of your presentation makes the concept easy to understand. You increased the value of my test equipment. Much appreciated!
Well done Alan. As always, your videos are thorough and well thought out.
Cheers, I would never of though about that way of measuring without this video
I love this video, you are a very good teacher. It would be great if you did a series of videos on how to use a spectrum analyzer for the absolute beginner to advanced use. The use of attenuators and when to use them, the dangers of connecting the analyzer in the wrong spot in the circuit. The do's and don'ts. Thank You
I'll consider that. I already have a few on the use/operation of a spectrum analyzer.
Great video. A Contribution for the education in Electronics of future generations !
I have bought an old thandar sweep generator and am in the process of repairing it. Your video was useful. The one I have has a different looking ramp it goes up and down at the same rate. I’m not sure i have the setup correct but have it going into channel 1 or X input on the Tek scope. This moves the dot symmetrical from left to right and the back right to left at the same rate. I have the actual output from the filter into channel two. Unfortunately there no manual available so just working through it. Great video. Regards Chris
The best of the best tutorials here! Thanks! I really enjoy watching your videos!
Thank you. The vid on DB explaining training actually helped me in my job the last week or two so thanks.
Nice! So, my is my check in the mail? LOL!
Needing to set up my FRG7 this is one of my favourite vids, thank you.
Very nice video that shows the virtues of having test equipment at your disposal.I have a feedback function generator with sweep facility and its invaluable coupled with the versatility of the oscilloscope to correctly align the freq response of a given receiver..excellent video sir.Take a bow.Regards Roger M0TDM.
WOW. I finally get it ! Thank you.
Your video's great on helping folks use their scopes! I have one that came over on the Ark... Going through your video's is telling me I might have a problem.
I had a "sweep generator" once. I can't remember the make or model, but that was way back in 1974. It was specifically targeted for working on TVs, and not as generally useful as what you're showing here. Not only that, it wasn't even spec'd to deal with the then-current 40-some-odd MHz TV IF frequencies, but the earlier 25-some-odd-MHz frequencies. I don't recall when or how I parted ways with that beast, but I don't believe that I was all that upset about it at the time. :-)
This is cool because at work I use a $30k HP 83650B sweep generator with the optional 83651 unit., but at home I have a HP 3324 which is both a function generator and a sweep generator.. synthesized though.. and somewhere buried in my to do list is a HP8601A sweep generator. Yay to power supply issues. I really have to get working on my old R71A which is slowly going deaf to both AM/MW and HF frequencies. Love your videos.
Excellent video. Thank you so much for this information.
Real knowledge and skills, real video.
Thanks
Thank you for linking a "Visual Face" to topics that I wonder about! Greatly Appreciated!
Excellent Video, agree with other commenter's. Always learn some thing new from your videos.
Great tutorial and explanation. WIthout the luxury of a mentor in my quest for better and greater repair capability this tutorial was REALLY helpful! Thank you. j
A couple questions: what are the probabilities of IF cans such as these going out of "tune" in either newer or older tuners? And is the tuning of IF cans a normal part of receiver alignment? That is normally found in re-alignment procedures?
Keep up the great tutorials! I'd love to be able to call you at times! :-)
Edz
Thanks for video I had always shied away from sweep gens befor but have read about them in the past. A picture is worth a thousand words! Dan N9DH
Very lucid and detailed explanation. Thanks.
EXCELLENT Just what Im looking for! Restoring an RCA 1947 era radio receiver.
Exactly what I needed. Thanks a lot! As always crystal clear explanation 😃. awesome 👍
Be forewarned not to physically couple the signal generator directly to the radio mixer grid, you will load the circuit and distort the curve getting poor results. Loosely couple using a loop of wire laying across the AM LOOP. DISABLE THE OSCILLATOR ! Monitor with a scope or meter at the secondary of the 2nd IF can. Use minimal signal level.
Thanks... had been wondering if I really needed a sweep generator, when I didn't even know how to use one.
No problem. Instead of suggesting a topic, I just made a video here in my lab/shack that suggests a few things I might like to see you talk about/expound on, on your bench, with your equipment. It is on my channel and it is regarding the HP 652A test oscillator.
Hi, very instructive video indeed. Thank you very much. I'm trying to learn how to properly align AM and FM radios myself and i'd like to know how to properly hook up an oscilloscope @ the end of an IF chain without influencing the tuned frequency of that chain by having too strong of a coupling/loading. So, it would be nice to know what kind of probes are suitable for the above and also when tuning the FM portion what kind of generating equipment is needed considering that in FM we are dealing with stereo signals and we want to keep the distortions low when tuning the discriminator coil for instance. And how one can measure the level of distorsions while doing it if there is only an oscilloscope at hand? Thank you.
Many thanks for this very clear video. Couple of questions: If we have two IF transformers I understand you recommend probing the output of the second transformer and hopefully checking there the effect of both transformers. I guess it would be the same if we probe the output of the first nd adjust and then the second. And second questions: it seems that in this setup a marker generator (which is required by the service manual of the radios I am trying to adjust) is not needed as we know the min and max sweep frequencies and hence all the intermediate ones (if it is a linear sweep).
Ideally you would want to probe "one stage away" from the one you are tuning to avoid potential for the probe affecting the resonant frequency.
Very good tutorial! Thanks for posting.
I have been trying to work out how to view the slope response of an IF strip on my scope with a sweep generator. Your explanation and use of the pulse/ gate output has explained how I can use this as a start stop reference. Could you just confirm you are triggering off the pulse output on the signal generator? Thanks.
thank you w2aew for all this interesting and excellent material.
That nixie frequency counter is very nice!
its a thing of beauty!
You can manually (without sweep) get a curve shape by marking the output vs frequency on graph paper. This could be important for someone without the sweep equipment available who needs to occasionally check the pass curve of a filter or IF stage with a flat top. It is a bit time consuming, but it works.
Very clear and to the point love your work,
This is a great video and explained very well. Question, how would I do this when the IF can is in circuit?
Worth watching repeatedly.
Great video, you make things easy to understand, never thought of doing this, sweep jen, is now
on the to get list. thanks Dave W4GSM
Got me a Hammarlund HQ-129-x that needs an alignment. I did it by ear so far, but now I can do a more quantitative alignment.
The question I have is: How can I increase the gain in the RF so I can hear the stations it picks up?
Awesome demonstration
At time index 5:37 you mention the sig generators Trig/Sync output is a really "handy one to have" - can you mention how we might take advantage of that? I'm learning to use my HP3336c and it has a Sync/TTL output. Great teaching, thank you.
Another suggestion for future videos: I don't understand how to use the scope to view stable traces of very slow freq, like one or two hertz. An example: I have been using a scope to analyze a problem signal that pulses about one pulse every two seconds, so I am using the scope at its lowest sweep rate. The pulse duration is very short, just a blip. Is there a way to somehow "freeze" the blip to study its shape , using an older analog scope?
Thank you Alan. Priceless!
I have acquired several new sector antennas that unfortunately have no identifying marks as to manufacturer, model, frequency, etc. Based on other information I have I am fairly certain that they are either for 900MHz, 2.4GHz, 3.5GHz, 4.9GHz or 5.8GHz use. I am not sure how I can tell for sure which band though. I have an HP 8565A spectrum analyzer as well as a variety of scopes. Do you know of a way that these tools might possibly be used to help identify these antennas? Thanks!
your vids are excellent
How about tuning IF xformers in a non functioning boat anchor (8 tube Hallicrafters s-85), 3 if transformers. Can't successfully inject a signal because there's no speaker output. So, I would like to eliminate the IFs as a potential source of problems by tuning them up. This eliminates that aspect and allows focus on other issues to resolve the problem. So, In radio IF diagnosis without AF output would be helpful. Maybe this is too unconventional, but that's where I am with this radio right now. Don't want to pull all the IFs if I can avoid it. I know that wiring, etc will change the sweet spot to some degree, but knowing I'm close will be helpful, right? Thanks for a great video on sweep generation uses. Best regards.
If you have a scope, you can monitor the output amplitude of the IF stage on your scope as you tune it.
Thanks much for the response. That's good news. So, hook the scope across the secondary or Grid to ground ? Thanks again for your great videos.
Thanks for another great video Alan. Question: you seem to be showing us the ramp and gate waveforms _before_ setting the sig generator for sweep mode. Certainly before you set the start and stop points. I must be missing something.
Also, how different would these waveforms, or process, be using FM? maybe an idea for another video?
Is there a capacitor across one side of that inductor can for a LC circuit? Or are you just seeing the inductor's response by its self?
Awesome explaination!!!❤👍👍
I have tried your method in audio filter- it looks great. But what about phase shift? Is there a way to represent phase shift on analog or DSO ?
it is possible to probe the input and the output, and compare the phase shift of the output with respect to the phase of the input.
So if I am aligning a radio, let's say an AA5 for example, where would I connect the sweep gen and the scope? Would I connect the generator to the plate of the converter tube (with a DC blocking cap) and the scope to the grid of detector tube with the radio on? Or would i just tune each individual IF can with the radio off?
I have a national nc300 on the workbench right now that I finished re-capping last night. I want to do an IF alignment next. Using this procedure do I do the second IF first, and then the first IF Can? I'm curious as to your thoughts...
very useful video, please let me know that there was any capacitor connected as shown in the schematic at primary side?
Ohh- what would be cool is a video on using a sweep frequency generator and a scope to do component curve tracing/matching. Also for those with minimal equipment -using a signal generator and a scope to use lissajous patterns to do frequency determination/comparison and cool stuff like that.
Also, I've heard you can determine the resonant frequency of a circuit using an LCR meter. Is that correct? How would you set that up?
Is the measurement on the scope differential: Add, Invert?
Any special precautions to minimize loading of the can by the scope?
I didn't use a differential measurement. Loading can be minimized by using a good, properly compensated high frequency 10x passive probe, and by probing downstream from the can you're tuning as much as practical.
Thanks for the excellent video!
Hi Alan
I recently purchased a used BK Precision 4040 sweep function generator and was able to reproduce most of what you did in this video. Is there a simple way or circuit to introduce a marker at a given frequency.
Thx again
1:53
Great video as usual.
Is there a video for aligning the transmiting and receiving frequencies between the base and the handset of a cordless phone ?
Bloody hell look at your set up ducking hell! That’s epic
Thank you for your effort w2aew. Just clarify something for me here please..... By the looks of it, your example describes AM Tuner with 455kHz IF. The frequencies (Start & Stop) you applied, were between 2,000 & 4,000 MHz. Was it only for demo reasons? cause, in this case, I would expect you to apply signals 200kHz (Start) and 600kHz (Stop) to see the Max signal peaks at around 455kHz? Please confirm that this is right. Thank you.
Yes, this was only for demo purposes, because the only IF-cans that I had were these 3MHz units.
I am seeing this 9 years later. Thank you. It would be great if we can see this technique used in an actual receiver to show, where to inject signal, where to read and what we have to worry when the "cans" are in circuit. A future video? Thank you! VA3GPJ
I suppose if you can measure the spacing you get an idea of the selectivity or Q with this sweeping idea? With a wide spacing being not so selective. For example how could you reduce the skirt width to make the can more selective? This is absolutely fascinating. Do you know where I could get a low cost signal generator that will give me a sweep with ramps etc. I would like to do this but I don't have much money. (tiny income).
I had no idea you can have this much fun with a signal generator. I have to get one now.
in CW mode what does CW stand for?
very similar to the procedure you would use to tune like a duplexer for a repeater ??
that would make a great video too,,
For broadband signals it is often necessary to tune the center frequencies to different equally spaced values to avoid rejecting information far from the carrier frequency. Television and high bit-rate digital are two examples.
thanks for getting back. what would be the width of the sweep? at 10.7Mhz, what would be the recommended start/stop freq?
OK, thanks Alan. I thought that was the answer but wasn't sure. Can the scope camera connections on the old mainframes (like 7904, etc) easily be adapted to use/sync modern digital cameras with for that purpose? Know anyone who does that?
Hi Alan,I want to repeat your layout using a BK4007B DDS sweep generator, an IF 455kHz can, a freq meter, & BWD analog 2 Ch scope. With Gen centred on 455kHZ & Start 425kHz, Stop 485kHz fed into one coil of the can (no connection to 2nd coil as you made) & output to Ch1 & sync from gen into Ch2. This shows the sine signal & sync signal on scope. When switched to sweep the varying sine signal is visible. Question: How did you connect up to primary & secondary of the can to give you the bandpass selectivity curve? Did you use X/Y mode? Your video is excellent. Jack VK1ZAD
Ideally, the IF can should be loaded as it would be in the actual circuit. Apply the sweep gen to the input, and probe the output. Use the sweep sync to trigger the scope, and adjust the scope's horizontal scale to show the entire sweep duration of the sig gen, and then you should see the response of the filter shown the the shape of the 455kHz envelope. Alternatively, if the sweep gen has a sweep voltage output (probably not if it is a DDS), then use that to drive the X input of the scope running in XY mode.
I think the center frequency you measured still have to be calibrated due to the input capacitance of the oscilloscope or the output capacitance of the generator, is that right?
That's why it's a good idea to inject the signal one stage before, and measure one stage after the stage that you're adjusting (when possible)
I have a Elenco Kit of a transistor radio that needs to be tuned. I have a oscilloscope and a audio generator. Does it matter what type or RF generator that I should buy next?
Alan, can u comment on VHF/UHF monitoring? The scope probe impedance mismatch compared to the IF coil might cause a lot of reflection and interference? What would be the best way to monitor this process at say, 250Mhz or more?
+Ancel UnfetteredOne The scope probe capacitance can adversely load the circuit, so you are wise to be concerned. Most IF circuits aren't going to be that high in frequency, so that's good. Best practice is to use the lowest capacitance probe you can find (active probes are better). Another good technique is to probe one stage further downstream than the one you're adjusting.
+Ancel UnfetteredOne As Alan said, the normal procedure is to check an IF stage from the grid or base of the ampifier preceding the IF can, to the output of the amplifier following. This isolates the probes from the resonant circuit and is always the way an alignment is done.
So my signal generator has a VCF input that can be used to sweep the frequency, but it does not have a ramp generator in it to drive the sweep. I assume I can build a ramp generator myself to then have what I need. My question is around what if I want the x-axis to be logarithmic instead of linear-like what would be great to have to evaluate audio filters. If I want this, I assume I need an exponential “ramp” instead of linear, correct?
Yes, that is correct.
Is peaking the IF amps at their resonant frequencies all there is to aligning a receiver, or is there a lot more to it?
+Justmytake There's generally a lot more to it (adjustments of local oscillators, adjusting filters, etc.). It depends on the particular radio. For example, you can watch my video on aligning a Drake 2B receiver:
ua-cam.com/video/wfVJnIjxvHI/v-deo.html
Nice, u should be a teacher.Would like to suggest u do two using the scope n sweep signal generator. Aligning an old tube( cause they're very touchy)FM broadcast radio with a ratio detector and the second on a more HiFi type limiter/discriminator set.I had a lot of trouble with older tube based stereo stuff like H.H.Scott 340 early receiver not tripping into stereo.Turned out my alignment with just a v.t.v.m. had resulted in not enough pilot signal for the multiplex to work with. Only two very strong local stations would actuate the stereo function.After looking at the I.F. response with the sweep gen n scope discriminator was way off. I was picking audio up off the positive peak instead of the straight side of the slope as it should.I think it would be a very helpful set of bids. Thanks....N2VUW
I've been watching shango066's (you 'liked' this video) how-to on FM radio alignment using a BK sweep generator.In the absence of the BK sg, how would this be done using a signal gen only? I tried injecting a modulated 10.7Mhz signal from my SG to the FM radio's front end but could not get the same WF he's getting in his tests. Thanks for your help.
What brand and model sweep generator are you using here? Thanks for all your videos and time spent making them!
I used a Leader LG 1311 Function/Sweep generator.
Incredible video! Always informative, I learn something new with every one!
Can you do a video on how to produce an eye diagram or eye pattern on a DSO?
I have been watching this vidéo dozen of time and there is something I do not get; Is the frequency sweep and the ramp up the same or they are two different signal fed into X and Y?
In this video, I am not doing XY.
@@w2aew I'm sorry, I just a serious tinkerer in radio but definitely lack some knowledge and experience. Can you make a short video explaining a little more in depth the proceeding of sweeping the ''cans''? 73
@@w2aew Friend of mine showed me a way with X and Y. But it is different and I am all mixed up now...
What MHZ signal generator would I need for mostly aligning vintage transistor radios, the IF cans, and maybe a tube radio sometime..
Most AM radios use a 455kHz IF stage. A 10.8MHz IF is common in FM radios. Of course, you may also want to produce a signal at the receive frequency, which means up to 30MHz for most shortwave receivers, and up to 108MHz for FM radios (in the US).
@@w2aew How was it done when there was no sweep generator back in the day? How do I get that peak to look at..so I can adjust it on a scope...I have two, a Tektronix 2431L and a Hitachi V-302 30 MHz scope.
@@kennynvake4hve584 You would typically use a signal at the desired frequency and peak its amplitude. If is very common to use a simple modulated signal, disable the AGC circuit, and peak the output as measured by a meter on the audio output stage. Of course, if you have a scope, you can adjust the cans and watch for the peak response on the scope.
@@w2aew So I can hook the scope to the speaker terminals and watch it, and adjust it that way..thanks.for your help..
I don't know if I can use the same method and test points(front end and discriminator) that was used in shango066's FM alignment video. Based on my understanding from his reply, that method requires a BK415. He's making a vid response on how to align using signal gen and VM. Thanks for your guidance.
So on the frequency generator, would I need more than 10MHz? I am looking to tune a few 10 meter radios
I am just getting into it so I have much to learn but wanted to ask..
73 w5kgp
Hi nice video ...can you do this without the sweep generator?? I am trying to align my Halli...sx-71 if cans...and dont have a sweep generator...thanks...and by the way..thanks for all your good advise you give me...
The only way to get this "network analyzer" type of response is with a sweep generator or warbler.
A wobbulator, thats right..
Yes, a wobbulator - that's what I *meant* to say!
Can we also display frequency sweeps on digital O'scopes ?
Yes, you can.
Thanks..I need to replicate this to learn more about my scope. ...other than how much dust it can collect.
Excellent video :)
Would you be willing to peak a Hammarlund receiver's IF cans for a flat top and put it in video ?
thanks! BTW, what is that holder you are using for holding the can, looks very handy!
It's a Panavise model 350.
***** thanks, it looks very handy!
Great video