Enjoyed this video and learnt things too, thank-you. There are a lot of good constructional videos available but few explain in depth WHY things are done in a particular way and how that affects the outcome. As a lay person to electronics and a returning ham (after 33yrs!) this is immensely useful.
Glad it was helpful. Please note that I am not an expert, and the videos and blog are just a video log of what I am up to and not tutorials. I know I makes mistakes!
Thanks Charlie, I love when you have a new video! One thing I would be interested in is a comparison of your new diode ring mixer to the old one. maybe you're holding out till it's in a radio, that's probably where we may see a difference. I am expecting a bit of improvement with the new diodes. we will see. have a good weekend.
Will do Curt. My initial comparison did not show any significant improvement, which was interesting. I assumed it was my measurement technique so elected to leave it out of the video.
@@CharlieMorrisZL2CTM That is interesting, maybe it will make more of a difference in the frequencies it can handle or something else bizarre that we're not thinking of.
The most relieble RF mixer is a double balanced diode mixer.In compare to simple bjt active mixer - the double balanced diode mixer has been working more stable: there isn`t any parasitic oscillation.
Nice, you can also make up a test rig which doesn't rely on recording numbers, you make up two of the same circuit, common the Vin and GND, swap the 10R down to the cathode/earth side and then plug in two diodes, connect your meter from anode to anode and select for minimum reading. The reading you get indicates the 'quality' of the diode match.
If you want to select four diodes for such a mixer, a much better comparison criterion is uniformity of the detected voltage at the operating frequency.
That was an excellent demonstration. As it turns out, I just bought 100 5711s that I need to sort in exactly this way. I was going to use the built-in "diode" function in my meter which displays the Vf, but I don't know at what current. That may not matter too much, but I'd prefer to know what it is. So I think I'll use the constant-current setup you did, and I'll use the same 1mA. I've never blown a fuse in my Fluke measuring current, but maybe because I dislike using a DMM for current measurements. I'll use the same 10Ω sense resistor you did. If I'm feeling ambitious, I might experiment a little to see if diodes that match at 1mA still match at 5 or 10mA. I don't know what it might mean if they don't (except, of course, that their Vf curves don't match), but I'm curious. I also recall seeing mention somewhere (some obscure IEEE paper I probably misunderstood) about also matching diodes for junction capacitance. That may not apply to (or matter for) Schottkys since they don't have a regular PN junction. That's just as well since I don't know just how to measure the capacitance of a diode in forward bias.
Sounds good Todd. Keep us posted. As for blowing fuses, it's mainly been during bias adjustments. Not all the time, but really annoying when it happens! Nearly always FETs.
I've never seen a trimpot used in a diode ring mixer. Probably because a trifilar wound transformer should have decent balance all by itself. The pot might help balance out difference between the diodes, but just hand selecting 4 diodes with the same forward voltage should be good enough. I've used my fluke DMM on the 'diode' scale to measure the diodes, your method is probably more accurate. Could also select the diodes using a semiconductor curve tracer, good excuse for me to brush the dust of my Heathkit curve tracer scope adapter! You should also consider adding a diplexer to the IF output of the mixers to present a constant 50 ohm termination (since you are concerned with good balance). This involves a pair of toroids and trimmer caps to resonate at the IF frequency, plus a pair of 50 ohm resistors. One series tuned and one parallel tuned circuit.
The potentiometer thing is actually quite a common technique. Although in my experience it allows only to suppress the LO leakage for given LO frequency. Has little to do with DC passing or spurious products. The difference is best seen with SDR or a spectrum analyzer.
@@R2AUK Might be useful when using the mixer as a balanced modulator to get maximum carrier suppression. Probably not so much when used as a receiver front end as the IF filters will knock out the LO.
@@scharkalvin The last two superhets I've built using a DBM have used a diplexor on the IF port. The two tuned circuits are easy enough to resonate and the diplexor itself can easily be swept with a VNA. However I lack the expertise and test equipment to demonstrate the difference made by the diplexor. A simple test method and demonstration of the benefit would be good to know about.
Thanks Brian. I was about to take it back down as i didn't it added much to the topic. I'm trying to keep the overall length down, which makes it a bit harder.
@@CharlieMorrisZL2CTM I rather like it when you ramble -- it helps me understand more of your thought process, and get into your mindset as you're going through things. Please don't remove content!
@@CharlieMorrisZL2CTM I think the video length is about right, 10 to 20 min is good. As I'm 13 hours behind you I tend to get the new videos first thing in the morning and it's just right to sit down with my first cup of coffee and watch before I have to head off out to work. Really gets the old grey matter going for the day ahead..
Thanks for the video. I was hoping, though, for an explanation of how this works. The diodes aren't quite a bridge arrangement? The transformers are trifiler because?
Thanks for the feedback. The videos are essentially a video log of what I am getting up to with my homebrew. Their aim is to encourage others to give it a go. On purpose I try not to make them a tutorial as I am not an expert in this field. I understand there are some good videos on TH-cam on the theory of DBMs, which may be of interest. As for the diodes, I explain in the next video why I chose to arrange them as I did. They are per the schematic. Thanks again.
Me too. I've just put up another video with some more experiments with the mixer. I'm really pleased with how it turned out. Spoiler alert, the 100 ohm pot is being removed.
Charlie, just out of curiosity, did you happen to measure the resistance of the trim pot when you got the desired wave form on your scope from the mixer? Is that trim pot necessary? Thanks for posting your video and helping me learn the theory!
Hi Charlie, excellent video as usual. I have a couple of questions. How useful is the diode function on most multimeters for doing the diode matching? I notice you have removed large chunks of the vero tracks and kept only the parts that actually link the components, rather than just breaking the tracks where necessary. Was this because of something like capacitative effects between tracks apparent at the operating frequency? I take it that was a 50ohm resistor on the output port for the two mixers for the correct load. Briefly, how would you achieve port isolation here? Sorry more than a couple of questions…. You and Pete Juliano are a real inspiration to get moving and build something. Tnx Tim.
Hi Tim. I find the diode function on my meter works well enough. I have also used the forward voltage drop method, which also worked well. As for removing/breaking tracks, yes, I do that to reduce any inter-track capacitance. Again, I find that works well for me for the freqs that I use in the rigs.
Very good video and information! Thank you for that Couldn't the difference be because you're using a trim potentiometer? if you just take it out for a second? Healthy and Friendly Greetings from the Netherlands! Rob
I did think of that, but didn't mention it in the video. I might short it out and see what happens. I need to do some more testing anyway with the FFT.
I was wondering do you have any type of donation system in place? I would love to help with what I can. we can get you a few extra bucks at least for some parts or tools.
@@CharlieMorrisZL2CTM Don't get me wrong I wouldn't expect more out of you for a donation. I just want to try to make it easier for you to do all you do already. you do a tremendous job and have me hooked on a hobby I have wanted to do for so long and now I will probably do it for the rest of my life. Thank you!
STrange distribution of diode voltages, you would expect from same batches of production to have a gaussian distribution, so I guess you have a jumble of batches...note there is no balance on the SBL version. Actually I have found there are two version of the SBL one with a split winding (pins 3&4) one with no split... I think you have used the SBL+ which has no split. Anyway you mixer works very well and I think to have the adjustment is a better option
I think so. They didn't come as a strip, so I suspect they were not from the same batch. It certainly pays (for me at least) to take the time and measure them. That interesting about the SBL-1s. I have several of those and did not realise there are a couple of configuration. I always ground 3&4 so I guess it's never been an issue.
Certainly Mikhail. My aim with the radio is to only use readily available parts. The 1N5711 met that requirement. I acknowledge there are more suitable options out there.
Thanks and agreed. For me both are hard to come by easily. I've been burnt several times with bogus parts from overseas. The shipping costs for authentic parts is prohibitively expensive down under.
I have to be honest, I really really mean no offense or nore do i wish to make you feel bad or hurt anyones feelings, your content is great and your explanations and how you go about things is perfect, even for non-technical guys like myself, your channel should by all account have many many more followers, However, and here comes the "I have to be honest part" Again im sorry, There is nothing wrong with how you talk or the way you speak, when you pause or end a sentence you have a very distinct slapping mouth sound, you are not alone to have it, Again please do not take it as in insult or in any form of disrespect , Just, that slapping mouth sound drives me up the wall kind of like someones scratching their nails on a chalkboard or someone dragging their teeth on a fork when eating, I only say it because I want you to know it makes it very difficult to watch an entire video at once, maybe others feel like that too perhaps its why your channel is not getting the attention it deserves, Again I dont want to hurt your feelings in anyway way shape or form.
No offense taken at all. I'm not sure what I can do about that. I'm certainly not going to take speech allocution classes. I'm not keen to spend a whole lot of money either on filming equipment. Again, not sure what i can do. Pity.
@@CharlieMorrisZL2CTM It was really more along the line of constructive criticism than anything else, I do feel horrible saying it, out of respect for you I felt I needed to say it, and like I said before There is nothing wrong with how you talk or the way you speak, you most certainly do not have a speech problem IDK I'm sorry, perhaps it's just me and my little pet peeves.
![ค้าง (STILL) - GEMINI [ OFFICIAL MV ]](http://i.ytimg.com/vi/Ftxx3hk5vkU/mqdefault.jpg)
Enjoyed this video and learnt things too, thank-you. There are a lot of good constructional videos available but few explain in depth WHY things are done in a particular way and how that affects the outcome. As a lay person to electronics and a returning ham (after 33yrs!) this is immensely useful.
Glad it was helpful. Please note that I am not an expert, and the videos and blog are just a video log of what I am up to and not tutorials. I know I makes mistakes!
Charlie, I have used your mixer in my home brew tube transceiver with excellent results.
Thanks Charlie, I love when you have a new video! One thing I would be interested in is a comparison of your new diode ring mixer to the old one. maybe you're holding out till it's in a radio, that's probably where we may see a difference. I am expecting a bit of improvement with the new diodes. we will see. have a good weekend.
Will do Curt. My initial comparison did not show any significant improvement, which was interesting. I assumed it was my measurement technique so elected to leave it out of the video.
@@CharlieMorrisZL2CTM That is interesting, maybe it will make more of a difference in the frequencies it can handle or something else bizarre that we're not thinking of.
The most relieble RF mixer is a double balanced diode mixer.In compare to simple bjt active mixer - the double balanced diode mixer has been working more stable: there isn`t any parasitic oscillation.
Nice, you can also make up a test rig which doesn't rely on recording numbers, you make up two of the same circuit, common the Vin and GND, swap the 10R down to the cathode/earth side and then plug in two diodes, connect your meter from anode to anode and select for minimum reading.
The reading you get indicates the 'quality' of the diode match.
That's certainly a good idea. I'll keep that in mind. 50 diodes wasn't too band, but-say-200...!
Good one there Charlie, I like the time you put in tothe component selection and the comparison with the SBL 1..keep it up!!
Thanks. Just about to put up another video with some more mixer experiments.
If you want to select four diodes for such a mixer, a much better comparison criterion is uniformity of the detected voltage at the operating frequency.
That was an excellent demonstration. As it turns out, I just bought 100 5711s that I need to sort in exactly this way. I was going to use the built-in "diode" function in my meter which displays the Vf, but I don't know at what current. That may not matter too much, but I'd prefer to know what it is. So I think I'll use the constant-current setup you did, and I'll use the same 1mA. I've never blown a fuse in my Fluke measuring current, but maybe because I dislike using a DMM for current measurements. I'll use the same 10Ω sense resistor you did.
If I'm feeling ambitious, I might experiment a little to see if diodes that match at 1mA still match at 5 or 10mA. I don't know what it might mean if they don't (except, of course, that their Vf curves don't match), but I'm curious. I also recall seeing mention somewhere (some obscure IEEE paper I probably misunderstood) about also matching diodes for junction capacitance. That may not apply to (or matter for) Schottkys since they don't have a regular PN junction. That's just as well since I don't know just how to measure the capacitance of a diode in forward bias.
Sounds good Todd. Keep us posted. As for blowing fuses, it's mainly been during bias adjustments. Not all the time, but really annoying when it happens! Nearly always FETs.
I've never seen a trimpot used in a diode ring mixer. Probably because a trifilar wound transformer should have decent balance all by itself. The pot might help balance out difference between the diodes, but just hand selecting 4 diodes with the same forward voltage should be good enough. I've used my fluke DMM on the 'diode' scale to measure the diodes, your method is probably more accurate. Could also select the diodes using a semiconductor curve tracer, good excuse for me to brush the dust of my Heathkit curve tracer scope adapter!
You should also consider adding a diplexer to the IF output of the mixers to present a constant 50 ohm termination (since you are concerned with good balance). This involves a pair of toroids and trimmer caps to resonate at the IF frequency, plus a pair of 50 ohm resistors. One series tuned and one parallel tuned circuit.
Thanks. I might bypass one of the pots during transmit and see what happens.
The potentiometer thing is actually quite a common technique. Although in my experience it allows only to suppress the LO leakage for given LO frequency. Has little to do with DC passing or spurious products. The difference is best seen with SDR or a spectrum analyzer.
@@R2AUK Might be useful when using the mixer as a balanced modulator to get maximum carrier suppression. Probably not so much when used as a receiver front end as the IF filters will knock out the LO.
@@scharkalvin The last two superhets I've built using a DBM have used a diplexor on the IF port. The two tuned circuits are easy enough to resonate and the diplexor itself can easily be swept with a VNA. However I lack the expertise and test equipment to demonstrate the difference made by the diplexor. A simple test method and demonstration of the benefit would be good to know about.
Well that was one of the most interesting ramblings I've heard in quite a while. Lol......
Thanks Brian. I was about to take it back down as i didn't it added much to the topic. I'm trying to keep the overall length down, which makes it a bit harder.
@@CharlieMorrisZL2CTM I rather like it when you ramble -- it helps me understand more of your thought process, and get into your mindset as you're going through things. Please don't remove content!
@@CharlieMorrisZL2CTM I think the video length is about right, 10 to 20 min is good. As I'm 13 hours behind you I tend to get the new videos first thing in the morning and it's just right to sit down with my first cup of coffee and watch before I have to head off out to work. Really gets the old grey matter going for the day ahead..
Thanks for the video. I was hoping, though, for an explanation of how this works. The diodes aren't quite a bridge arrangement? The transformers are trifiler because?
Thanks for the feedback. The videos are essentially a video log of what I am getting up to with my homebrew. Their aim is to encourage others to give it a go. On purpose I try not to make them a tutorial as I am not an expert in this field. I understand there are some good videos on TH-cam on the theory of DBMs, which may be of interest. As for the diodes, I explain in the next video why I chose to arrange them as I did. They are per the schematic. Thanks again.
@@CharlieMorrisZL2CTM Thanks, Charlie.
Check out @W2AEW for very good explanations about many things like mixers.
Hi Charlie. Your DBM mixer is little different. You added 100 ohm variable resistor. This variable resistor for balance and supression LO signals?
OHH EXCELLENT MI FRIEND THANKS,GOOD LUCK...
Cheers.
SO GLAD THE DIODES SHOWEWD UP
73
Me too. I've just put up another video with some more experiments with the mixer. I'm really pleased with how it turned out. Spoiler alert, the 100 ohm pot is being removed.
@@CharlieMorrisZL2CTM I'm finishing a build on a regen with some bells and whistle then I'll follow n build ur rig cheers mate
Charlie, just out of curiosity, did you happen to measure the resistance of the trim pot when you got the desired wave form on your scope from the mixer? Is that trim pot necessary? Thanks for posting your video and helping me learn the theory!
Amazing man. Your construction style is beautiful! I just uploaded a video showing a prototype of an 80m BPSK transceiver, take a look! 😃
Thanks, will do.
Hi Charlie, excellent video as usual. I have a couple of questions. How useful is the diode function on most multimeters for doing the diode matching? I notice you have removed large chunks of the vero tracks and kept only the parts that actually link the components, rather than just breaking the tracks where necessary. Was this because of something like capacitative effects between tracks apparent at the operating frequency? I take it that was a 50ohm resistor on the output port for the two mixers for the correct load. Briefly, how would you achieve port isolation here? Sorry more than a couple of questions…. You and Pete Juliano are a real inspiration to get moving and build something. Tnx Tim.
Hi Tim. I find the diode function on my meter works well enough. I have also used the forward voltage drop method, which also worked well. As for removing/breaking tracks, yes, I do that to reduce any inter-track capacitance. Again, I find that works well for me for the freqs that I use in the rigs.
Very good video and information!
Thank you for that
Couldn't the difference be because you're using a trim potentiometer?
if you just take it out for a second?
Healthy and Friendly Greetings from the Netherlands!
Rob
I did think of that, but didn't mention it in the video. I might short it out and see what happens. I need to do some more testing anyway with the FFT.
I'm not sure why the 10 ohm resistor is necessary.
Couldn't you just measure across the 4.7k resistor?
Hi ,,,,,,,Excellent
👍👍
Very nice, good job. Question, do you think using good old fashion germanium diodes would result in lower insertion loss?
Not sure Michael. From what I have read Schottky diodes (aka hot-carrier diodes) are what is needed. I'd have to look at the differences.
I was wondering do you have any type of donation system in place? I would love to help with what I can. we can get you a few extra bucks at least for some parts or tools.
That's very thoughtful thanks. At this stage I'm happy to keep plodding along and putting up videos when I can.
@@CharlieMorrisZL2CTM Don't get me wrong I wouldn't expect more out of you for a donation. I just want to try to make it easier for you to do all you do already. you do a tremendous job and have me hooked on a hobby I have wanted to do for so long and now I will probably do it for the rest of my life. Thank you!
is there plan in future to build an SDR Rx circuit nfm am fm ?
I have in the past using the Teensy. I am looking to revisit that at some stage.
STrange distribution of diode voltages, you would expect from same batches of production to have a gaussian distribution, so I guess you have a jumble of batches...note there is no balance on the SBL version. Actually I have found there are two version of the SBL one with a split winding (pins 3&4) one with no split... I think you have used the SBL+ which has no split. Anyway you mixer works very well and I think to have the adjustment is a better option
I think so. They didn't come as a strip, so I suspect they were not from the same batch. It certainly pays (for me at least) to take the time and measure them. That interesting about the SBL-1s. I have several of those and did not realise there are a couple of configuration. I always ground 3&4 so I guess it's never been an issue.
I just bought a 50 pack of 1N5711s two weeks ago to see if i could make a vhf level mixer...
Excellent. Let us know how you get on.
thanks for a video ..
Most welcome.
bav99? bat54? 😉
Certainly Mikhail. My aim with the radio is to only use readily available parts. The 1N5711 met that requirement. I acknowledge there are more suitable options out there.
SBL1 is no that exotic only expensive but ADE-1 is 10$ for 5 pieces from china ;)
Thanks and agreed. For me both are hard to come by easily. I've been burnt several times with bogus parts from overseas. The shipping costs for authentic parts is prohibitively expensive down under.
I have to be honest, I really really mean no offense or nore do i wish to make you feel bad or hurt anyones feelings, your content is great and your explanations and how you go about things is perfect, even for non-technical guys like myself, your channel should by all account have many many more followers, However, and here comes the "I have to be honest part" Again im sorry, There is nothing wrong with how you talk or the way you speak, when you pause or end a sentence you have a very distinct slapping mouth sound, you are not alone to have it, Again please do not take it as in insult or in any form of disrespect , Just, that slapping mouth sound drives me up the wall kind of like someones scratching their nails on a chalkboard or someone dragging their teeth on a fork when eating, I only say it because I want you to know it makes it very difficult to watch an entire video at once, maybe others feel like that too perhaps its why your channel is not getting the attention it deserves, Again I dont want to hurt your feelings in anyway way shape or form.
No offense taken at all. I'm not sure what I can do about that. I'm certainly not going to take speech allocution classes. I'm not keen to spend a whole lot of money either on filming equipment. Again, not sure what i can do. Pity.
@@CharlieMorrisZL2CTM It was really more along the line of constructive criticism than anything else, I do feel horrible saying it, out of respect for you I felt I needed to say it, and like I said before There is nothing wrong with how you talk or the way you speak, you most certainly do not have a speech problem IDK I'm sorry, perhaps it's just me and my little pet peeves.
@@MrDacorp Apparently so