Tuesday, March 17, 2020

New Technology for 2020 ~ A simple way to build a Phasing SSB Transmitter

PWKSCDS -- I just realized I made a very bad assumption. It came to me in a dream!

3-20-2020 ~ The emperor's buddies strike again!

[But 1st. Some people are saying that 3 Republican Senators got advanced notice of the CV-19 impact and sold huge chunks of stock BEFORE the market crash. Sounds like the swamp got a bit deeper. I sure would have liked to have been privy to that info so I could have sold  my few shares of stock and not taken a hit. Shame on them!]

[3/19/2020, 6:43 PM PST. California has essentially been shut down with most businesses to close by midnight. You are permitted limited travel (like taking a walk) and you can buy groceries; but that is about it. Aren't you glad that you now have a project to work on while you are holed up?]

A Phasing Rig must have struck a couple of nice chords. Today I got two  inputs from "down under". One VK ham (Thanks Greg!) has provided me a source for homebrewing your own audio phase shift network which is found at this link.  http://www.antennoloog.nl/polyphase-networks/  and the spreadsheet for the calculations at this location 

This work was done by PIM PA2PIM

The second input (Thanks Stephen!) made me aware that in the G-QRP Club SPRAT #120 someone did the heavy lifting and translated the 'toob" SSB jr. to an all Solid State version. Now that would be nice. That source also referred me to a project by   Fred Johnson ZL2AMJ called "The Tucker Tin #2". 

Lea Earnshaw, ZL1AAX, (founder of Southcom Intl and Kachina Radio) published a nice book called The Transistor Radio Handbook and in there is a very excellent simple Solid State Phasing Transmitter. So it can be done with little hardware!

March 19th, 2020 ~ More CVHI Projects.

Here is the bad assumption that I made: That hardware building skills still abound. Wrong! The hardware building skill level today, in our hobby, has been outstripped by those with software skills. Hardly anyone scratch builds stuff today and an even very smaller percentage builds "toob" gear

It would be a simple matter for me to go to my stock of aluminum chassis boxes, dig out the Greenlee Chassis punches, drill a few holes with my floor mounted drill press and I would have the chassis for the SSB Jr (below) . The total elapsed time --about 1 hour. Not many hams have those skills nor the tools to use a chassis punch today.

I also have several power supplies that would power a tube transmitter. Scratch that idea --no one would build it and most hams only have $1.95 Walwarts. Too hard!

Don't Give Up Just Yet!

But let us not give up on the quest to build a phasing SSB transmitter and ultimately a phasing transceiver. The "hard nut to crack" was the Audio Phase Shift Network. But then I discovered today that you can buy one from a very reputable supplier. Boom! Hans Summers and his QRP Labs sells the Polyphase Network  for an amazing price of $11. It is intended to be added to a receiver block so may require some modifications; but PWKSCDS.

So gang what if we undertake using two of the PSN Networks in a transceiver and brew our own phasing rig using these networks? We could actually take the SSB Jr schematic building blocks to create comparable solid state building blocks and at this stage I envision a low part count rig. I would start with the transmitter first as we could use the Web SDR receivers for the other end.

After I finished the block diagram it hit me -- quite possibly only a single PSN may be required and only the Mic Amp and Audio Amp are switched at a common port. That would make for a huge simplification. Sideband reversal would be done as normal by switching the outputs out of the PSN to get either USB or LSB. 

My intent would be to design the rig as we go along and some modules exist already. I have circuits for an excellent simple 2N3904 microphone amplifier as well as the Bi-Directional RF Amp stage (2N2219), plus RF Driver Stage (2N2219A) and IRF510 Final. 

Using the already proven RADIG Board would mean even less development required. We is on a roll!

The Audio Phase Shift Networks would be purchased. The Tough Nut is no longer as the RADIG takes care of the RF Phase Shift and the Balanced Modulators

Enter the Si5351 where one clock would supply the RF for a basic transmitter and a second clock could provide frequencies to heterodyne that signal to other bands. Sounds like I am designing the rig as I type. (I am!)

This may all be a bust; but a solid state rig with one of the critical components purchased at a reasonable price may result in more hams having an interest to build one while in CVHI. 

This might even encourage some hams who read this blog with circuit board experience to design boards that could be commercially manufactured. This is an option  for those hams who always start by saying where can I buy the PC Board?

Yes this could be done with Tayloe Detectors/Mixers; but what fun is that. We are starting on a journey to build a modern day 1950's Transmitter/Transceiver.

Pete N6QW

CVHI = Corona Virus Home Isolation

A Little Laughter is Good Medicine!

The GE SSB Jr. 3 Tube Transmitter

I suggest you visit the N4TRB Wesbsite where you can download the complete Article from the GE Ham News #205. Below is the Schematic for the SSB Jr.

I will see if I can find some substitutes for the audio transformers. Now think beyond what is possible and use the Web SDR receivers as a simple station. You can be heard on 40 Meters with just 5 watts. 

This is a great CVHI project and the parts are common (once I find you the transformer substitutes) Ebay and Antique Electronic Supply has everything else you need!

CRHI = Corona Virus Home Isolation.

We could start a whole new revolution of home brew Phasing Transmitters. We also need to think about a NET frequency so we can have our own exclusive net. I believe 7.285 MHz is the recognized 40m QRP Frequency -- so either find some crystals OR look to the AD9833 Oscillator Board as a source for VFO control. The AD9833 Board and Arduino Nano can be had for less than $10 and are available on Amazon. Couple that with a cheap LCD and we are uptown.

For those inclined to really tinker -- this could be transported to a solid state version. But having a tube rig would be a blast.

Let the parts hunt begin.

Pete N6QW

New Technology for 2020 ~ Improvise, Adapt and Overcome

What to do during the Pandemic? This is a chance to get back on the air or to take up an interest in homebrewing your own rig. You can bui...