Skip to main content

New Technology for 2020 ~ It ain't over until the Fat Lady Sings!

Tuesday June 2nd, 2020

I wish I could report that there has been some miracle happen that made the Phase Shift SSB Transmitter work properly. 

I even spent a small fortune for some 1% SMD capacitors to mate with the 0.1% resistors that would be employed in an 8 Pole filter. I didn't even open the box from Mouser. 

While one could easily be swayed to thinking this will finally do it. Realistically I just do not think I would see any different result other than poor opposite sideband suppression that I have been experiencing. 

I have become very skeptical of those who have reported amazing results with their phase shift networks and put those comments  in the same league as exaggerated gas mileage claims. 

We have a great word in Italian --Basta. Enough!

But I am happy to report that I have successfully built a 2nd ZL2CTM Teensy 3.5 SDR transceiver. the Hilbert Transforms Rule and indeed opposite sideband suppression! 

The why of the 2nd build is to have something presentable and not look like a bunch of wires hanging out all over the place and to eventually "harden" the build so there are no wires waiting to be shorted and no boards with cold solder joints. 

Yesterday I had a QSO with a station running a FLEX 6700 --try as he might he just could not denigrate the signal. His parting shot was that it was indeed a solid build and sounded really well --for a homebrew rig!

73's
Pete N6QW



Thursday May 28th, 2020

Here is a series of tests that only leave me totally baffled. 

I built a 6 Pole Audio Phase Shift Network using the Tonne Design Software but KK7B's Schematic. For a signal source I have a waveform generator and use this in the sine mode to cover frequencies in the range of 200 to 2800 Hertz at 200 Hertz intervals. The A and B channels were connected to my Rigol 100 MHz DSO set to read Lissajous figures.

There was a two fold purpose to the test the first of which to see if we got a circular pattern which is indicative of a 90 Degree Phase Shift. The second parameter was to see how that pattern held over the range 200 to 2800 Hz using a 200 Hz step evaluation. 

Assuming satisfactory results then this piece can be eliminated as an issue in poor opposite sideband suppression. By poor maybe only 5-10 dB. Below is the test setup.


In the initialization stage, the signal level from the source is critical so you don't overdrive the mic amp and the follow on circuitry. It takes very little signal level! Secondly on the APSN is an input balance pot and that was found to greatly affect the "roundness" of the plot. It is not at the center of the range as you would perhaps think.

The following are the test results...

   Reading at 200 Hz


 Reading at 400 Hz


Reading at 600 Hz


 Reading at 800 Hz


 Reading at 1kHz


 Reading at 1.2kHz


 Reading at 1.4 kHz


 Reading at 1.6 kHz

 Reading at 1.8 kHz


 Reading at 2.0 kHz


Reading at 2.2 kHz


 Reading at 2.4 kHz


 Reading at 2.6 kHz


 Reading at 2.8 kHz


General observations:

  1. At 200 Hz --a bit ragged but improving thereafter. No distortion, like at 200 Hz,  but higher in frequency a definite pattern shift
  2. Beyond 1500 Hz some shifting from circular to slightly elliptical 
  3. Very likely "not textbook" for 45 to 50 dB of opposite sideband suppression but I would venture certainly better than 5 to 10 Decibels.
  4. The front end with the DBM's has been tested with a 2nd ZL2CTM Teensy 3.5 and the opposite sideband suppression is very evident.
So now for the head scratching -- why such poor opposite sideband suppression?

Think about the emperor (with a nearly invisible e)  citing that there are only  100K deaths, 1.7M infected souls and 41 Million out of work and saying  "I have done an amazing job managing this pandemic."

73's
Pete N6QW


Memorial Day ~ 2020


For those who served, Thank You for your service. For those who made the ultimate sacrifice, we are deeply indebted. For those now serving may you be safe and know we stand behind you!

For those who golf during this pandemic crisis while the country suffers an unfathomable loss of life and dire economic impact ... (readers can finish this sentence)




TL084 Eight Pole Filter, two DCR's, Summer, 74AC74, Band Pass Filter  4X7" Board



Popular posts from this blog

January 26, 2024. A simple CW Transceiver/Transmitter

Cruise through the lower part of the ham bands bands and what do you hear? Well, FT-8 and CW. Often you will not hear any SSB stations yet go to the lower part of the bands, and it is a cacophony (I love that word) of bad sounding signals and some high-speed keying. Fast is not so much of the issue as is bad, run together and jerky keying. But none the less our hobby started there.    So, you could crank down your ICOM 7300 and watch the waterfall on CW or you could homebrew a radio. Actually, to do CW right you need more thought up front than you do with a SSB transceiver. Often, I will state that a CW Transceiver is much more difficult to build than a simple SSB rig. I published two articles in QRP Quarterly on CW transceivers and all I got was a yawn so maybe history will repeat itself.  Yawn!   30M CW Transceiver with RIT!   Of interest is that the LO is a Varactor tuned LC oscillator using a NE602. Look closely at the RIT circuit which is only activated on ...
Read more

March 31, 2024. Happy Easter to those who celebrate this day.

What a great day to Binge on Chocolate and experience the pain of that filling that has been leaking.  I would be in that category with the leaking filling(s) had I not just spent an amount equivalent to one of the fancy new uptown appliance box transceivers on two filling repairs. Well at least I can binge on the Chocolate bunnies without fear of pain. Regrettably everything appears to have jumped in price including the price of parts. Well not so much the parts as the shipping costs.  That notably is seen in the eBay treasures. I spotted a nice heathkit DX-20 for about $50 and the shipping was $65. Likely it is a twofer with part being a way to in effect charge a higher price by inflating the shipping and in part by increased shipping costs. Shipping with insurance across the US was about $150 for this jewel and that was three years ago. 6AM on the Left Coast ~ 20M Easter Sunday! My only hope is the cost of Chocolate Bunnies remains steady although a pound of See's Candies f...
Read more

August 30, 2024. A PNP 20M SSB Transceiver

Shown below is the Block Diagram for the 20M PNP SSB Transceiver steered in the  Transmit Mode . The components shown in the dotted block are relay steered so that the block module is single pass and amplifies in a single direction. The Block diagram show steered in Transmit.  Essentially the steering process works so that the IF Module input follows the Balanced Modulator on Transmit and then the input side follows the Receive Mixer on Receive. All done with some relays and a bit of RG174U coax. For those who count things in detail, this block diagram is not unlike what was used for the PSSST Transceiver which can be found on my website . Yes, a warmed over P3ST only using PNP devices. TYGNYBNT. 73's Pete N6QW
Read more