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Showing posts from June, 2017

A New Line of Transceivers ~ DifX

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Transceiver Architecture 2.26 07/03/2017 Yesterday we swapped out the 12.7 MHz filter pair for ones operating at 16 MHz as we suspected there was an issue with the 12.7 MHz USB filter (actually the LSB Filter --sideband inversion). I also opened up the tuning range so that the rig will tune from 300 kHz to 30. MHz which now lets me check out the performance across the HF ham bands. While tuning 15 Meters I ran across one of the Thirteen Colonies Special Event Stations. I made a short video of that station. The configuration is a the MMIC as the RF amp stage, no band pass filter and just the two Plessey amps. The Mixer and Product Detector are ADE-1's.  Houston we have ignition, the bird is flying! Today I wired up the Si5351 board plus the display and that worked well. Here are some snaps of the assembly and while I was at it I used the FFT function on my Rigol DSO to look at the outputs from the two clock generators. I was pleased.


A New Line of Transceivers ~ DifX

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Transceiver Architecture 2.25
A Hint and a Clue6/28/2017 ~ More on the Hint and Clue ---- Read ON

The above hint and clue is to show that I will be using a technique for USB/LSB selection where the BFO is at a fixed frequency and Upper and Lower Sideband filters are switched into the loop based on the mode selection of either Upper or Lower Sideband. R.L. Drake did this in the TR-4 transceivers and many commercial designs use this same approach. I actually had experience with a commercial Ten Tec transceiver which did this as well. It was the Model 100. In my second filter architecture I use a pair of filters that were liberated from a commercial Kachina Transceiver and operate at 12.7 MHz and thus only need one BFO frequency in the Arduino Sketch. This is a good frequency as the 1st IF will be at 45 MHz and the second mixer frequency will be at 57.7 MHz and with a double sideband frequency inversion there will be no sideband inversion. I looked at any unwanted mixing products or harmo…

A New Line of Transceivers ~ DifX

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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-driver stage. Relay switching is used to direct the signals in/out of the board -- a total of three relays. Whil…

A New Line of Transceivers ~ DifX

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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 complained about by one of the 40 Meter SDR police and cited in the post.…

A New Line of Transceivers ~ DifX

Transceiver Architecture 2.22Have 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 front panel so that one positi…

A New Line of Transceivers ~ DifX

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 didn't work and …

A New Line of Transceivers ~ DifX

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Transceiver Architecture 2.206/10/2017~ 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 data. The Dishal softwar…

The LM373 Transceiver ~ Three weeks on the air.

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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 really nice rig. No nice is not the right word but the correct terminology is that you e…

A New Line of Transceivers ~ DifX

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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!!!!  Several blog posts ago I mentioned about Method #1 which s…