A deeper look into how the Diode Ring detector works: "the particular go of it."
Here I rely on a wonderful diagram from the RSGB. This diagram clearly shows how
in this circuit, the switching action of the diodes -- controlled by the VFO -- results in sum and difference frequencies at the output. This is amazingly illuminating.
I then tried to build this actual circuit. It works, but I am also getting a lot of AM breakthrough from a local AM station (WFAX) and Radio Marti at 7335 kHz. I will try again.
In any case, the diagram shows how the diode ring does its thing!
I need to beef up the Band Pass Filter.
I tuned around a bit on 40 meters -- you can listen.
Students at a local high school have been trying to get the DC receiver I loaned to them going -- they may be confused by the intricacies of SSB tuning. I will see them next week.
Here is the RSGB diagram that reveals the secrets of the Diode Ring. (Now that could be the title of a book or movie. I claim the rights to that!) Click on the image for a better view.
Maybe try a (say) 0.01uF to ground on the output of the RSGB??
ReplyDeleteThanks -- I tried that but it didn't seem to help much. I think the problem is the lack of ground return for the diodes. To be fair, RSGB never intended this to be an actual circuit -- they were just using it to illustrate multiplcation by 1 and -1. 73 Bill
DeleteNice video, thanks for posting it. I got a lot out of the mixer explanation.
ReplyDeleteI know the rig is still under development, but it might be less tiring to listen to with a 3.5kHz low pass filter around the RX audio amp. There seems to be a bit of high frequency hiss coming through.
I had the same problem with one of my amps that was running a bit hot. It self oscillated at 5kHz, with harmonics consistenly right out somewhere beyond 30kHz.
I didn't find it until I was mucking around with the frequensee app, then took a closer look in the frequency domain.
Well, I may be benefitting from some high frequency hearing loss! I just don't hear the high frequency hiss. But let's see how it sounds after I get my hearing aids. Seriously. 73 Bill
DeleteMine's coming along fast - another year or two and I'm sure I wont hear it anymore.
DeleteHi Bill. Good video !
ReplyDeleteI can’t really see the schematics, however, as mentioned during ½ cycle of the LO AC waveform, 1 pair of diodes is switched off while the other pair is turned off. This flips during the other ½ cycle of the LO waveform. The diodes do need a DC path to ground to ensure they’re optimally biased either on or off.
Wes is a mixer specialist (Triquint days and beyond) and thus he knows how to properly wire a diode ring topology mixer.
The output should theoretically not contain LO or RF or any of their even-order harmonics --- nor any intermodulation products arising from any even-order harmonics of either input signal (for example 2FLO + 2FRF). How well these theoretical possibilities occur depends on factors including the degree of balance provided by the transformers, diode quad matching to both the RF and LO input signals, ensuring proper phase relationships across the bandwidth, the input to output port isolation afforded by the layout and also the level of the RF signal.
Also, having a DC return path for the diode pairs. Further, wide band matching at the ports may also affect port to port isolation; hence port pads and AF/IF diplexers may help optimize this.
Not being critical --- I do hear piercing high AF signals and noise in your speaker output.
Incidentally, I posted a related topic --- a culmination of all my Gilbert cell mixer IC notes
https://qrp-popcorn.blogspot.com/2022/10/some-analog-ic-gilbert-cell-mixer-notes.html
Best to you!
Yikes -- correction --
ReplyDeleteI meant to write:
I can’t really see the schematics, however, as mentioned during ½ cycle of the LO AC waveform, 1 pair of diodes is switched OFF while the other pair is turned ON..........
I'm not so good at YouTube and blog messages while typing on my phone as a passenger in a moving vehicle!
Thanks Vasily for the wonderful Gilbert Cell info. My struggle to understand this circuit was at a much more basic level, but in the end I think I figured out how he built a DBM on an IC with no coils. 73 Bill
ReplyDelete