Want to get on phone? Let's make a simple and low cost Double Sideband Transceiver for the popular 10 Meter Foundational and Novice Section of the Band.
Mike: I've built at least three DSB transceivers. On the receive side, the way to go is to assume that the other station WILL be on SSB, not DSB. Once you make this assumption, you can get away with just building a Direct Conversion receiver to accompany your DSB transmitter. It works great. I NEVER met another DSB station, and most of the SSB stations never realized I was transmitting on both sidebands. Simplicity is a virtue! I hope you keep the receiver simple: Direct Conversion. 73 Bill N2CQR
This is great encouragement Bill! This is also a time machine it seems. Stuck some gain ahead of the mixer and tacked on my LM386 utility amp and signals blasted out of the cobbed up receiver immediately. Its the 10-10 Contest weekend!
I had heard of double sideband but knew next to nothing about it. This tutorial was just the job for me and I'm sure many others. I'm looking forward to the project!
Hi Mike, I have built a DSB transceiver some years ago for 40m and had a great deal of fun with it. Most stations didn't realise I was using DSB and had some great contacts and reports. A few even failed to find the other sideband. I would have loved this video series back then. I also have an old 10m DSB TX failed project still sitting on the bench. Made several QSO`s but kept breaking into oscillation. 73...David M0DAD
@@stephenwalters9891 Yes quite possibly, I was thinking it may be harmonic related. It worked great into a dummy load but would howl into the antenna. I found when I detuned the antenna with an ATU the howl disappeared and was able to make several contacts. It was one of those projects I couldn't get sorted and didn't want to give up so it has remained in the unfinished draw of my shack...David M0DAD
@@stephenwalters9891 That`s right I remember it. It was Bill Meara who helped me with some advice when I was building my 1st DSB TX. I think it was when he first moved to London. A very helpful chap and he was even kind enough to send me one of his trifilar wound torrid transformers so I could compare to my own.
I'm lazy and just go with the Mini-Circuits double-balanced diode ring mixer modules - LOL. Thanks for the video, it brings me back to my communication systems class.
Cheap is even better than lazy. For fun a took a choke from an ATX power supply with a solid ferrite inside and took the tiny 1/16 Dia. by 3/4 inch long ferrite rod and wound 7 turns of #28 trifilar on it and configured the transformer solenoid style. Then I replaced the two Schottky's with unmatched 1N914s. Everything was pretty maxed over to get a null, (the pot and the variable trimmer); but it worked just as well as the fancy toroid and the Schottky's!!
I love this theory stuff. Even when modulation happens in an SDR using IQ etc....an understanding of these basics is essential. Love this content. I am a huge "fan boy". I used your videos to neutralise the tubes in my Kenwood TS520. I also watched your tips for CW on the Kenwood. When I decide to valve homebrew ....I'll be back! I'm also about to build my first DSB rig...once I get my present channelised SOTA rig done 73 de VK2AOE greetings from OZ.
Ha SDR. Hey! Don't pop my balloon. Hee. Do you know my good mate Andrew VK3CV from Mel? He is the crazy guy who did the 122 GHz Transceiver module for QEX.
Great video really enjoyed it. One thing the Icom 706 (all versions) does transmit normal AM with both sidebands. It’s takes the SSB balanced modulator and applies a DC voltage to the audio input to unbalance it and transmits the carrier & both sidebands thru the AM receive 8khz wide filter. It’s 4 quadrant multiplier configuration. Also they use the FM audio limiter on the AM mode to limit the negative & positive, mainly so the modulator does not carrier invert at 100 percent negative. Works great, I used the same type of setup on my other radios for AM using a MC1496, UPC1037H or SN16913P which are double balance mixers or balance modulators depending how you have them configured. The best setup is a 2 quadrant multiplier, basically a single Gilbert cell. That gives you modulation that is identical to plate modulation and the carrier pitches off just like plate mod. Low distortion and sound super. All my radios have 455khz transmit IF, so thats were the modulator is inserted
@MIKROWAVE1 I would say just about all the older japanese analog SSB radios do it that way. Some Yaesu models have separate AM modulators like the FT-102 which uses a Gilbert cell and a few other Yaesu models use FET gate modulators. Icom radios have always unbalance the SSB modulator for AM. Same for Kenwood , except for the T-599 transmitter that use a Gilbert cell like the Yaesu FT-102. Those that have the Gilbert cell have extremely good modulation with low distortion and look exactly like plate mod on the scope. I know your using discrete parts for the creating the DSB which is fine , but a MC1496 or SN16913P would be much easier and will hold the carrier suppression spec better under all conditions. You don’t need any matching coils either and very low parts count, especially on the Texas instruments SN16913P
@@MIKROWAVE1 Wow thats so cool, His design using differential amps in a cross coupled configuration is the standard for mixing and IC balance modulators. I have a Yaesu FT-1000MP that is the only modern ham rig that has a Motorola synchronous AM detector, really works and sounds good. Looking forward to part 2 !!
Mike, I envy your 60dB. My first attempt is lacking, I'm using a Colpitts oscillator and even though I've tried to build nicely, it's bleeding. Will try harder. Steve M0KOV
Mike you just confused this old “G1” ( Nothing new LOL ) . When synchronous demodulation is used for double sideband suppressed carrier what's the PLL locking on to ? You shouldn't have a carrier unless it is BFO injection but that can move ( as can the RX signal ) . For synchronous demodulation I have used a IF limiter driving a mixer port with the normal IF signal on port 2 . It works but that's just for AM .
When you get to the build for the Final RF output could you explain how to achieve the 50 Ω output. Looking in the ARRL Handbook I see Tables for Low Pass Filters at 50 Ω. How do you get to the 50 Ω after the Transistor.
The easiest way is to force the final to be close to 50 Ohms and ignore it. RL roughly is Vcc^2/2P. So 12.5VDC and 1.5W = 52 Ohms. I know this sounds incredibly simplistic and ignores Xc, but simply making the first C in the PI filter a trimmer to absorb the C will get you started. But for more power, you can see that the impedance will fall to some number like 10-j5 and you have to convert up to 50 j0 Ohms. This is typical. This is where you use your formulas with a L (or T) Match, so you add an extra L in series before the Pi Filter. So the conversion up is done with a series L and the first Shunt C which is variable. Then a couple more stages of low pass PI and you are done. Assume a Q of 2 or 3 for a wideband match and maybe 4 or 5 for our 28 MHz narrowband case.
The only two channel AM (stereo) system was the old C-QUAM system that was never really a standard. It died out. DSB with a pilot tone was still being used here and there on the shortwave bands, but it's just one channel of AM and you needed a synchronous detector. Not sure if this is still out there.
@@MIKROWAVE1 Well well Mike! I am surprised you did not think of FM-Stereo L-R 38 khz signal, which is DSB, and the 19 khz pilot tone is then doubled to reinsert 38 khz carrier, for AM demodulation to reconstitute the two L & R audio channels. .
Wow! The magic of subcarriers and spectrum shifting! I used to work on FM Video transmitters that had two narrowband FM subcarriers for left and right audio added into the modulation. WE called this FM-FM. @@JCWise-sf9ww
