DSSC Double Sideband Supressed Carrier IC

I think I found a place to buy one of these
chips. Well, I might have to buy a whole
bunch of them...

I'll call the place on Monday. By the way,
the spec sheet says the chip is rated at
33 mW, although I'm not really sure what
that means.

I will have to do this very slowly, or I will
mess it up because of vision problems, but
here we go!

And, I will still be on the other thread
working on the 13 MHz AM transmitter.

Thanks again, Neil!

Bruce, MICRO1690/1700

Oops.

Gosh Neil, I guess I was wrong. I thought I had
found a supplier for the 1496, but I can't find it
again on the net.

Looks like I read something wrong.

That's OK, I'm still going to research this.

Best Wishes

Bruce, MICRO1690/1700

This thread brings up something I have thought for a long time. I noticed that using my ham radio in the car I could receive the carrier from my part 15 transmitter about 2 miles away when the am signal was only good for 3/4 mile. So as was discovered a long time ago in amatuer radio, ssb is way better!!

I would think that rather than re-inventing the wheel or using dsb, why not use an existing ssb generator (think old ham stransmitter or cb ssb radio) and hetrodyne down to the broadcast band? This would only require the designing of a local oscillator and mixer or use the first stage of an old shortwave receiver.

From there you can class C amplify the signal to 100mw input, filter the output and double or triple the range of your transmitter. As stated in the previous post the listener has to supply the bfo frequency to receive the intellegence.

This can be accomplished with a small stand alone oscillator next to your listeners receiver or even another receiver sitting next to the main receiver with it's local oscillator tuned to "beat" with your frequency. All a little difficult but not as hard as it seems. I certainly do not understand why anyone would build an am transmitter for the shortwave frequency when any receiver for that frequency would have bfo built in.

Hetrodyning down to the am band would be far easier than building a dsb generator/tx IMHO 🙂 Oh yea besides the the bfo problem the receiver needs to be very stable. One other advantage, The probable receiver for this would have the ability to have an outdoor antenna. There is no limit on the size of an outdoor antenna for receiving. This brings another outside the box idea. I bet a "system could be designed by a radio engineer where by 5ea part 15 transmitters could cover 100 square miles on ssb.

Part 15 fantasy system: 5 ssb transmitters ground mounted, 9' antenna each on a 120 radial 1/4 wave buried counterpoise, receivers using 500' end fed long wire ( or lacking longwire space, 90 degree tall tower with 120 1/4 wavelength radials ) with tuning system oriented towards strongest transmitter and sophisticated receiver with noise blanking. Any engineers think this is in any way possible by theory??? 🙂 Dave

While that would be a great setup. you have to remember SSB does not supply a High Quality audio signal. Its mainly limited to Voice.
If your Part 15 was a talk Station it would work great. Music on SSB would not sound that good.

Here's a brief overview of suppressed carrier systems:

Let's start with an AM signal. An AM signal consists of three parts, the carrier, upper sideband, and lower sideband. The information (intelligence) is contained in and duplicated in both sidebands thus the carrier and the other sideband are not needed. So in SSB the carrier and one of the sidebands is suppressed at the transmitter. This has two advantages. The bandwidth is now equal to the audio range (highest minus lowest audio frequency) rather than the bandwidth in AM which is twice the highest audio frequency so the bandwidth is about 1/2 that of an AM signal. The quality of the SSB audio in terms of frequency response can be as "hi fidelity" as wanted. Usually it is limited to 3 kHz maximum thus the telephone quality signals we normally hear but there is no inherent limit to the audio frequency response on SSB or DSB and good music fidelity can be had. The bandwidth of the DSB signal is the same as that for AM, twice the highest audio frequency.

Second, the power capability of the transmitter can now be devoted entirely to the one sideband rather than spreading it to the carrier and other sideband which carriy no additional information. Normally a 100 mW AM signal has 25 mW in each sideband and 50 mW in the carrier. SSB can put the 100 mW into the single sideband so the gain is 6 dB in signal strength for the same transmitter power over AM. The SSB signal gives the same results at the receiver as if it were a 400 mW AM transmitter.

DSB is somewhat easy to generate but SSB is not because it requires either a very good filter (usually a crystal array) or clever heterodyning and a filter to produce. DSB does not require such filtering but it also does not give the 6 dB advantage. It gives a 3 dB boost.

Amplification of the SSB or DSB signal requires a linear amplifier so Class C amplifiers are not used.

Dave's comments about reception are good, especially the "poor man's" method of using the LO (local oscillator) from a nearby receiver to supply the beat frequency for another receiver. I have done this and it works.

Bruce, I hope I didn't steer you into something bad about the availability of the 1496 IC. Try a web search on "obsolete ICs" and you might turn up something. Post back if you cannot find one.

While suppressed carrier transmitters are not as simple as AM types the DSB is doable and within reach for a hobbyist.

Neil

Good reply Neil except I believe linear amplifiers for ssb are operated class C. It's why you can generate the modulated signal in a low level stage and hetrodyne it to the operating frequency and hence amplify it whole and efficiently. The experimental setup I recommended would be only useful for voice as "borrowing" the signal from a cb that has it's bandwidth limited as Neil said would be low fidelity. I just suggested it as a quick experiment. Hetrodyning an existing ssb signal would be considerably easier than the dsb idea I think. When two signals are applied to a nonlinear device (a diode for example) the sum and difference of the two frequencies will be produced. Trust me on this, it can be produced in a rusty fence at a mountain top site and drive a certain technician crazy for a couple of weeks trying to find it. Producing the ssb signal maybe clever but hetrodyning is not. Anyway apply 10 mc and 100mc to a diode and you'll get 10mc, 90mc, 100mc, and 110 mc output. Or better yet set up a 26 mc oscillator beating with a 27 mc cb ssb signal and viola, 1 mc (am broadcast) ssb and 53 mc signal. Pretty easy to filter 26 mc, 27 mc and 53 mc. Of course you can get lesser outputs from the mixes you produce but if you filter and pass the one you want ( 1mc or 1000 khz if you must)you can then pass it on to the following stages.

Hi Neil and Dave and everybody else.

I had also thought of hetrodyning
(from another radio)
an SSB signal to the band of choice.
In my case the desired output frequency
is 13.560 MHz, but the desired output
frequency can be anything you want it
to be. I have several old klunky SSB
amateur radio transceivers that could be
used as the source. I just like to experiment.
Unfortunately
again, I am limited in what I can do with
my eyesight, so experiments go very slowly.
I need to go back and read all of your comments
again because they are very interesting.

Thanks!

Bruce, MICRO1690/1700

I started to suggest using two cb's, 1 am and 1 ssb rig to get into the bc band but unfortunatly when I checked the channel frequencies there is only 460 kc between ch 1 and channel 40 so that won't spread far enough to even getg to the low part of the am band. Dang I even had a suggestion as to how to "pick off" an attenuated signal to feed your diode. But alas it's not to be. Wait a minute. Isn't there a part 15 lowfer frequency?? :=)

Dave,

I believe linear amplifiers for ssb are operated class C

Are you sure it is class C? The one I have operates class B (biased at cutoff). It is hard to imagine operating class C (biased below cutoff) without some pretty high distortion as the input pulls it out of cutoff into the conducting region. Seems this would clip the lower amplitude parts of the signal.

Neil

OK now I have to go look. If you are talking AM yes you can't operate C because the amp only is on for a small part of the cycle in C and that would kill the modulation on the carrier. The old illegal CB linears were somewhat less than 30% efficient if my memory serves. Akk here I go into guess land cause I'm too lazy to go look for the real answer this time of the night. In SSB the intelligence is made up of many different frequencies in the sideband and each one is handled almost seperately by the amplifier. So I've given an answer and tomorrow I'll go see if I was right. Warning: don't even think about taking that explaination to the bank. I'll go look for my collins 30L1 manual.

You were right Neil. 🙁 Class B. Ahh. A litttle voice in my head was trying to tell me to shut up in that last post but nooo. I didn't find the Collins manual but a quick check of the handbook indicated either a or b is needed. I'll go to bed now . Dave

Hi Dave:

160 to 190 kHz is a Part 15 allocation. I think
there has been some SSB work down there.
But I think, besides cw beacons, most people
are using new sophisticated digital modes.

You could use two CB rigs to get a signal
generated down there. Then after that getting
the RF to the outside world is the really hard
part.

I believe years ago I saw a picture of a guy who
was trying to operate a 160 - 190 rig from his
car. The loading coil looked like it was the size
of a trash can. At one time there was a transceiver
for that band that somebody was selling. I can't
remember if it was a kit or already built.

Best Wishes

Bruce, MICRO1690/1700

Yes I did read about those bands a little and the digital techniques. It shows that where there is a will there is a way. Some amazing results with so little erp.

Hi Guys:

I am interested in all the approaches. The 13 MHz
AM transmitter was originally intended for a friend,
who tries to listen to my station a mile away. It
also comes in great through my trusty Hammarlund
HQ-140X, a radio which is now 55 years old. That
transmitter isn't perfected yet, but it does work,
and it is just plain fun.

I find the DSB approach to be a fun idea, again, just
for the experimentation aspect of the hobby. I would
just like to know how to build it.

I have a ten meter single band radio that is sitting
in the attic, and has been there since about 2002.
I had planned to use it when the sun and the F2 layer
cooperate. I think it would be great to hetrodyne
say, 29 MHz, with a 16 MHz oscillator and get
sideband on 13 MHz. Again, I just don't know
enough about the circuitry to mix the signals,
and also, the best way to attenuate the radio
that would be feeding the mixer.
That's the big problem for me, designing the
transverter circuitry. I have other HF radios
sitting around that might be used. Again, I
just wish I had the knowledge to just go and
build it myself. SSB on the top of the AM band
would be cool, too, just to try it.

Best Wishes
Bruce, MICRO1690/1700