Showing posts from November, 2015

Simpleceiver ~ Part 16

Hey? Nobody has asked about the Crystal Filters that are being used with the Simpleceiver Project!Addendum: 11/29/2015 Another on the air video of the Simpleceiver
Addendum #2: A view of the completed Simpleceiver "al fresco"
Addendum #3: 12/01/2015 Data for a 20M RF Amp
Addendum #4: Signal Output Data for the AD9850
Addendum #5: Band Pass Filter Data for 20 Meters

The following is the schematic for the RF Amplifier stage. Please note about the Resistor "R" and how that is made. Addendum #3: To use this RF Amp on 20 Meters (Query from WA7RHG) simply make L1 = 8 Turns on the FT-37-43 core and make C2 = 10NF. Addendum #4:Based on anearlier input regarding why I used the AD9850 straight into the SBL-1 without a "booster amp". I guess the simple answer is I hooked it up and it worked --so keeping thing simple. But to get full advantage of the SBL-1 it probably would be a good idea for a booster amp. Now when you measure the output of the AD9850 + Booster Amp make…

Simpleceiver ~ Part 15

We are nearly finished with the heterodyne receiver portion of the project! Hang in there.
Today I finished what I call the main board which is comprised of the Mixer stage (SBL-1) followed by the 1st IF Amplifier which is a 12 MHz design consisting of two J310 JFETS configured as a Dual Gate MOSFET. The board also contains the new 4 pole Crystal Filter followed by the 2nd IF AMP stage which is similar to the 1st IF Amp. Below is a photo of that board. I have tried to label the various sub-circuits so you can see the layout. The "squares" are 2/10 inch. The W1REX MePads would work ideal for this board.

Next here is a You Tube Video of the 3rd Generation. Close your mouth --yes that is a homebrew Simpleceiver that you can build!  The last stage to be built is the RF Amplifier stage. This stage is very similar to the IF amp stages in design and given with what I have seen with the IF Amp stage should work quite well. Given we are moving into the Holiday Season work will slow d…

Simpleceiver ~ Part 14

More of the Bits & Pieces This will be a short posting to provide more information and give rise to other possible configurations. Previously we mentioned about the hard core homebrewer's who did not consider this a homebrew project unless it was totally homebrew. To that end, today, I hooked a 5 MHz LC VFO I had that was left over from a prior project wherein it was replaced with a Si5351. In further response to the hard core group, in the future I will present a design for a crystal switched VXO so that segments of the 40 Meter band can be covered using the VXO. But for now here is the LC VFO video. Note how quiet the receiver is between stations and also note I prototyped a 4 pole crystal filter that is "haywired" into the circuit. In the most recent SolderSmoke Podcast #182 (11/20/2015) I mentioned to my friend and host Bill N2CQR about the power of the LT Spice simulations that were being used with this project and now I would like to expand a bit more on what w…

Simpleceiver ~ Part 13

Second Generation Simpleceiver This post is to let you hear how the Second Generation of the Simpleceiver sounds in operation. What I have done is to mate the front end of the 1st generation Simpleceiver consisting of the RF Amp Stage, homebrew Double Balanced Mixer, Post Mixer Amp and three pole Crystal Filter. Using this part it was "haywired" to the new J310 Product Detector, J310 BFO and the NE5534 + LM380 Audio Amp. Ahead of the 1st generation board sandwiched in between the RF Amp and the homebrew DBM, I installed the new Band Pass Filter. Take a listen how quiet it is between stations. I did make a modification of the interface between the J310 BFO and the J310's that are connected in Cascode. On Gate #2, I have added a 22K resistor to ground and connecting the two modules is a 100 NF cap. A revised schematic is shown below as well as the plot of the output. These changes were made to accomplish two things: 1) the BFO loading is improved and the BFO now reliably o…

Simpleceiver ~ Part 12

More Bits and Pieces In our last post we described the Band Pass Filter simulation with LT Spice and the measurement of the filter performance. There is no one more astonished than me that the O Scope plots seem to track very well what was shown in the simulation plots. Needless to say it is a lot more productive to spend time simulating the hardware and eventually honing the design to a point where one is satisfied and to only have to solder in the components --one time! I also want to highlight the use of the older publication SSDRA by W7ZOI in conjunction with the LT Spice. By way of review we have built the Audio Amp Stage, the Product Detector, the LO and the Band Pass Filter. This has resulted in a Direct Conversion Receiver. All of these pieces will be used in the Superhet version of the receiver albeit with a modification of the LO  frequency range and the addition of new modules. Items to be added include: Beat Frequency Oscillator, Intermediate Frequency Amplifier stages, a…

Simpleceiver ~ Part 11

Bits and Pieces Needed for the Transition from the Direct Conversion Receiver to the Super-heterodyne  Receiver version of the Project.Addendum: Oscilloscope plots of the BPF when driven by the Arduino + AD9850 and the filter connected to 50 Ohms. Amazingly what was theoretically shown in the simulation is in fact what is seen when connected to the real hardware. Let's hear it for SSDRA and LT Spice! If you have followed along this far by building the Audio Amplifier stage, the J310 DGM Product Detector and the Arduino/AD9850 LO then we are ready to proceed with the next bits and pieces. I struggled with having the prospective builder include the 40 Meter Band Pass Filter for the initial build and weighed carefully the balance between building yet another module or firing up the radio with a smoke test. In my initial testing I saw that the radio worked with just these three modules thus proving the design concept. But the Direct Conversion Receiver should have a Band Pass Filter…

Simpleceiver ~ Part 10

The Arduino Pro-Mini and the AD9850 Now we will explore the Arduino Pro-Mini driving the AD9850 DDS Board to provide the Local Oscillator injection frequency for the Direct Conversion Receiver and later with a one line code change will provide the required injection frequency when the Simpleceiver is converted to a full fledged Super-heterodyne. The Intermediate Frequency (IF) was chosen to be 12.096 MHz largely in part because I had a stock of 12.096 MHz crystals. But there is a method to the madness because with a 5.0 MHz VXO or standard LC 5.0 MHz VFO you can also operate the Super-het on 40 Meters. (Keep in mind 7 +5 =12 where the LO is now below the incoming frequency. In practice high side mixing is better because of harmonic issues but will work nonetheless on the low side). A separate crystal oscillator operating at 12.096 MHz will provide the BFO injection frequency. There is a lot of code floating around for driving the AD9850 with an Arduino; but one in particular I have f…

Simpleceiver ~ Part 9

More Investigation of the J310's configured as a Dual Gate MOSFETAddendum #1: Decoding the Suffixes. I am glad that every day I have a chance to learn something new and realize that being an "old dog" I can still learn some new tricks! A comment posted on Part 8 by Chris Horner made me realize that my old habits frequently trip me up. Having started soldering my fingers together early in 1950, many electronic conventions have changed (all for the good) but sometimes they can trip us up. Take for instance how capacitor values were named. A 470 PF cap today was called a 470 micromicrofarfad or 470 MMF. A 100 Microfarad today designated as 100 Ufd, was written back then 100 MFd.. This now leads me to C1 and C7 and their designation on the simulation presented in Parts 8. The values written on the earlier schematic were 100 mF and 10 mf (harkening back to 1950 where I would have said 100 Microfarad or 10 Microfarad). But that is not how LT Spice really recognizes values wher…

Simpleceiver Part 8

The Simpleceiver Direct Conversion Build is Working ~ Houston We Have Ignition! We now have the J310 "Dual Gate MOSFET" Product Detector working as a 40M Direct Conversion Receiver! All of the upfront analysis we prepared  has paid off in big dividends. The test configuration consists on the J310's as the Product Detector, an Arduino Pro-Mini driving an AD9850 in the range 7 to 7.3 MHz supplying the LO signal and the audio amplifier is the NE5534 driving an LM-380 . There is no additional amplification nor Band Pass Filter in line at this time. There is a short video to show "proof of life". Our basic J310 "Dual Gate MOSFET" schematic was used as shown below. There are but two additions: 1) A 3 turn primary to 20 turn secondary wound on a FT-37-43 core (#26 wire) is used to match the 50 Ohms on the antenna connected to Gate 1 (J2), where the match is forced to 2.2K. C3 is not used with the matching transformer. This is a 44:1 match and 2) A 10 NF is c…

Simpleceiver ~ Part 7

Back to the Simpleceiver ProjectAddendum: Graph Paper Layout of the Build
Addendum #2: Data for the J310 and new response plot
Addendum #3: Initial Construction photos PD Board 11/11/2015 I must apologize for the diversion to work on the Ten Tec Model 150A. Before picking back up with the Simpleceiver I leave you with this comment: "If you can find a Model 150A --grab it!". Much of the work I did on the Model 150A will find its way into the Simpleceiver project especially the LT Spice simulation work with band pass and low pass filter networks. So while the anxious readers may be grumbling about the diversion --it will benefit you in the end. Now back to the product detector circuit. We will use the circuit that was simulated earlier in LT Spice but convert this into actual hardware. The final step for the product detector is to mate it with the audio amplifier. The circuit below uses the 2N3819 JFETS but our final configuration is the J310. I do not have the spice simulation …