Showing posts from October, 2015

Hacking the Ten Tec Model 150A to extend its frequency range to 15 MHz

Be Amazed at the Wizardry of N6QW Hacking the Ten Tec 150A SSB/CW transceiver to extend its range to 15 MHz

Three actions:

Modify the Final Amp Low Pass FilterModify the RxTx Mixer Band Pass FilterModify the Low Level Driver Low Pass Filter All filter changes were simulated in LT Spice and I think it worked.

Pete N6QW

Errata ~ Part 4 Simpleceiver

Errata in the Part 4 Discrete Audio Amplifier One of the blog readers, W4JED contacted me regarding the "reversed  polarity" of the output capacitor on the discrete component audio amplifier that appeared in Part 4. The schematic error would have most like caused a smoking of the capacitor (or a very loud bang followed by the smoking). Thank you for bringing it to my attention. The corrected schematic is shown below, Pete N6QW  Soldering Surface mount can get a bit intense so what is needed is some loud music in the background to sort of calm the environment. For your listening pleasure some "Solderin Music"

Simpleceiver ~ Part 6

Dual Gate MOSFET Direct Conversion Receiver Based on inputs I have received either in direct comments on the blog or from email messages, there seems to be a desire to better know the "why" of various choices and actions. In this particular post we will look at the Dual Gate MOSFET being used in a Direct Conversion Receiver (DCR). We will also use an LT Spice simulation to demonstrate the "why". In the Part 5 we described the Direct Conversion signal frequencies and the resultant outputs. Essentially to receive an 800 Hz CW signal on the 7.030 MHz QRP frequency we would need to supply a local oscillator signal at either 7.0292 MHz or 7.0308. Again the Direct Conversion Receiver is simple to build and is quite sensitive; but does not give single signal reception. You will receive the same signal at TWO places on the dial! Below is a schematic representation of a Direct Conversion "detector" using JFET's configured as a Dual Gate MOSFET. We have chosen…

Simpleceiver ~ Part 5

The Product Detector ~ Dual Gate MOSFETSPlots added for the 2N3819 (10/19/2015)Data Plots for Additional JFETs Added 10/20/2015
Having covered the audio amplifier stage for the Simpleceiver (again the choice is yours) we will now move on to the Product Detector stage. As the name product detector implies, the output of this stage is a product of the mixing action of two signals. Think of the product detector as a "black box" where two signals are input to the box and the single output contains two products. One product is the sum of the two input signals and the other contains the difference. Filtering at the output port can remove one of the products. In its simplest form the "black box" can be the basis of a direct conversion receiver where a variable frequency oscillator (known as a Local Oscillator, LO) is connected to one of the ports and signal from the Antenna (after passing through a stage of RF amplification) is connected to the second port. The sum freq…

Belthorn (Bell Thorn) III Moved to 20 Meters

Belthorn III Moved to 20 Meters and Making QRP Contacts!
Several months ago I resurrected a project that was built some 12 years ago and updated the rig with a Si5351 + Arduino Controller, a color display and a new box. This radio had some innovations like using a Motorola Gain Block amplifier (CA2818C) which happens to be a 24 VDC device and led to embedding a DC to DC Convertor (MeanWell) into the project. It is a single conversion at 9.0 MHz and uses a GQRP Crystal Filter. The Arduino sketch includes a built in tone oscillator to provide a 988 Hz tone for tune up purposes. The RF AMP is an IRF510 but I wished I had used a real RF Transistor like a 2SC3133 as the output on 20 Meter is slightly less than on 40 Meters. I am seeing about 7 watts on 20 Meters where I got close to 10 Watts on 40 Meters. Now that I have a new beam antenna I decided to move the Belthorn III to 20 Meters and one of the first QRP contacts was with N0TUX/KH6. Thanks to Ron Taylor G4GXO for the original Belt…

Simpleceiver ~ Part 4

Audio Amplifier StageAddendum 10/13: You Tube Video of  a Test Amp. In our last posting we gave some advice about starting from the back end and working your way forward through the build. Not only does this chunk the project into manageable  pieces but also enables test as you go. Thus the completed assemblies in effect become part of the test system. You may argue with that approach; but it is a sound practice. Somehow soldering all of the project parts to a circuit board and hoping it works is only asking for trouble! We received an input in our last post about the LM386 audio amp IC and the issue of distortion when run at 200X gain. At this point it is uncertain that this excellent input, by the way, is based upon an individuals experience or just information floating around reflectors. But we did want to further explore the input and to give our response and take on the subject. By design the Simpleceiver is just that --a project with minimum part count and easy to replicate. Th…

Simpleceiver ~ Part 3

Secrets of Homebrewing Revealed How to build a project Heathkit had it right and much to their credit they had a very high success rate with their kit projects. Let us examine the difference between the Heathkit approach and today's kits. Much thought went into a Heathkit project so that there was a logical and progressive build concept that frequently is missing in today's kits. Typically a kit today, as received, is a bag of parts with an internet address and perhaps an link to a you tube video. Ben KK6FUT has called this solder smoke --you solder all of the parts and then watch it smoke when power is applied. The Heathkit approach was to chunk the overall build into logical and manageable small sized tasks and to test as you go. In effect the portions of completed work enable the builder to verify a circuit is working before proceeding to the next phase.  In essence the portions completed become a part of the overall test system. We strongly believe in this approach and Be…

Simpleceiver ~ Part 2 Continued

The Art of Homebrewing --- Continued In our previous post we outlined some "homebrewing get ready" actions such as setting up a filing systems and securing certain publications. We now want to continue that journey. The Hardware Part of Homebrewing Homebrewing tools and equipment can make or break project and so often even basic test instruments have not been secured and the question I frequently get "How do I know it is working?" You will only know if it is working is by testing and if it is not working then a troubleshooting  procedure needs to be in place. Basic tools include a good quality pair of needle nose pliers,  wire cutters (nipper), screwdrivers (various sizes of flat head and Phillips), a small adjustable wrench, flashlight, and exacto knife. Add to that a pair of forceps and tweezers. Also don't forget a suitable workspace with good lighting and last but not least a temperature controlled grounded soldering iron. Test equipment is a must! Some c…

Simpleceiver ~ Part 2

The Art of Homebrewing, A Disciplined Process!Addendum 10/2/2015~ Schematic Having spent most of my working life in the aerospace industry I can tell you first hand that having disciplined processes is paramount to producing high reliability products. It is only through disciplined processes that one can achieve consistent outcomes. That same logic applies to our wonderful hobby. Randomly  tack soldering a bunch of parts and wires could be successful but that most likely is a rare exception rather than a consistent outcome. Thus having a disciplined process for approaching homebrewing will move you way up the success curve. The very minute someone mentions a process there are all sorts or rigorous rules that are envisioned and that not is not what is meant. A disciplined process in our context is more so  an organizing effort that enables doing tasks in a logical, sequential and measured manner. We are lucky for today with just a few mouse clicks we have much of the information neede…