Left Coast Political Scene

Transceiver Architecture 2.24 Back to the Dual Conversion DifX Build   6/25/2017 ~ Working Field Day (at QRP level) with the 20M Shirt Pocket SSB Transceiver. At 16 cubic inches --smaller than a Bitx ! I actually made QSO's  with this transceiver and it is a testament to good things come in small packages. Definitely a DifX.     73's Pete N6QW            6/23/2017 ~ See video at the bottom for more MMIC Applications   Now that I was able to resolve the Crystal Filter that will be used in the second IF (it is not a Dishal nor any other form of homebrew filter) I have turned my attention to the issue of various amplifier stages that are used elsewhere in the rig. One such circuit is the bidirectional amplifier board I developed where there are two amplifier circuits comprised of a single 2N3904 in each leg. One leg is the receiver RF amplifier stage and the second leg is the Transmit Pre-driv...

Transceiver Architecture 2.23 Commercial and Surplus Crystal Filters   6/20/2017 ~ Short diversion -- OLED noise with a 128X32 OLED Blue Display       Believe it or not this test is important to an upcoming project that will soon be revealed.   73's Pete N6QW    6/18/2017 ~ In the original post I mentioned that I saw three German Filters on a board for sale from Israel but did not know much about them. Thanks to one of the regular blog readers (Thanks Jim), we now have info on these filters and from what I can see they appear to be symmetrical which is important if they are installed in a bilateral circuit such as the Termination Insensitive Amps and the Z in/out is 1 K which is a 20:1 match to 50 Ohms. A 9 turn to 2 turn matching transformer gets you close 9^2 = 81 and 2^2 = 4. 81/4 = 20.25.   The good news is that they are 8 pole filters which will really tighten up the skirts and resolve the "feathering" issue com...

Transceiver Architecture 2.22 Have You Ever Wondered?   Arduinos and Si5351 PLL Clock Generators are inexpensive (well depends where you live); but for around $20 (US) you can purchase a ProMini and a si5351 Clock Generator. I have not seen many designs where two Arduino's and two PLL clock generators are employed. So why not? Yes you will hear from the lurking illuminati that you don't need to use two but has any one really explored the possibilities opened up by such an approach.   Let us think "Out of the Box" for a minute. Suppose we take a device like the Pro-Mini and loaded that with code so that CLK2 would provide the injection frequency for a second mixer in a dual conversion transceiver (the 1st conversion would be an up conversion to say 45 MHz).Thus the second conversion would be to the IF frequency and CLK0 would provide the BFO injection frequencies. You got that OK?   Now think for a minute of a two position switch mounted on the fro...

Transceiver Architecture 2.21   We must look to the past often times to see the clarity of the way forward. I am reminded of something that Thomas Edison experienced. (Don't know if this is factual but may be more of an urban legend thrown in for good measure.)   It seems there was a major fire at his Menlo Park Laboratories and with that fire many of Edison's projects were burnt to a crisp. One of his assistants was lamenting to Edison about how terrible the situation was in that many of his projects were no more. Edison, ever the visionary, said this is actually good! The assistant could not believe what he heard --Edison chimed in -- "most of what burnt up didn't work and I just didn't have the heart to take it to the dump". The fire actually solved a problem for Edison --with the clutter removed he could focus on  more productive things.   So it is with all things Dishal! I had a ceremonial fire today and gone is all that wretched crap that...

Transceiver Architecture 2.20 6/10/2017~ More on Dishal Dyslexia  Part 2 There always has to be a reason why something as fundamental as 1 + 1 does not equal 2 and so it is with the results arising from building a Dishal Crystal Filter. So lets us take a few steps back and examine why 1 + 1 may not equal 2.   The Dishal software in large part requires the user to make some initial measurements outside of the software itself. Starting with the G3URR oscillator and my SDR receiver (capable of measuring to 1 Hz and verified by first locking on to WWV) I measured the crystals in the loaded and unloaded condition. Again the receiver is calibrated to be accurate to 1 Hz and the G3URR component values are 470 PF (NPO COG) in the Colpitts circuit and the load cap was 30 PF NPO COG. So the data was taken and crystals were found that were very close in frequency and thus were the basis for entering the data into the Dishal software. It is pretty automatic once you enter the da...

The LM373 Transceiver - What a Rig! The LM373 is a Real Gem! 6/7/2017 ~ New Video of the LM373 Transceiver!     6/6/2017 ~ Added >10 dB Attenuator to handle super strong signals. It is a "T Type" controlled by a small relay with the Series arms being 33 Ohms and the Parallel arm being 22 Ohms. A switch on the front panel controls the In/Out. Kind of amazing --with the pad Out of the circuit you can hear the noise on the signal and with it In --the noise drops like a rock. Good affirmation about RF amplifier stages and their contribution to noise. The Pad/Relay was mounted on a small circuit board which was soldered vertically to the main board.         The panel mounted toggle switch that selects Pad In/Out is located below the volume control and above the earphone jack. This is a solution to the strong signal overload.   73's Pete N6QW     Every so often the planets align and you end up with a r...

Transceiver Architecture 2.19 6/4/2017 ~ The Dishal Saga continues. Bob, N7SUR shared his Dishal experience (he was very successful) and in his configuration he has a TIA amp ahead and following the filter. He is also using a AD9850 signal source. I added a front end amplifier and the results improved somewhat. This added about 15 dB of improvement. The real test would be to add an amplifier on the back end and make another run. But NOT THERE yet but better than earlier. The theory about amplification is that the scope may not be detecting the lower signal levels (masked by noise) and with a boost this enable better readings. 73's Pete N6QW  6/3/2017 ~ More Listening Test with New BFO Frequencies (BTW only 1 kHz below/above the apparent Center Frequency --what does that tell you?)       The Dishal Filter must be on par with Fake News!   73's Pete N6QW   Four weeks of work and this is what you get --not very satisfied!!...