LTspice For Radio

04/25/2025

I updated this article with a Spice directive that you can use to measure the plotted output frequency more precisely than by measuring the wave cycles, using a directive that samples ten wave cycles in seconds terms (microseconds) and divides by 10 to derive the frequency. Which can read in the Spice Output Log of LTspice.

  In the featured photo above, we see a circuit diagram of the Franklyn VFO, as drawn by Michael J Murphy WU2D. Note the interesting way of controlling the VFO level by way of Q3.   …

04/22/2025

Temperature Compensated VFO Circuit Analysis Project

This past week I decided to venture into a topic I have in the past been interested in, which is the thermal control of a variable frequency oscillator or VFO. Which consist of designing circuits that are controlled by 10k ohm thermistors. In which I have been looking at two circuits, one of which makes a VFO oven much like a crystal oven, and the other is a frequency control compensation circuit that uses two 10k thermistors, with a Varactor (varicap) diode to make adjustment to a VFO based upon thermal changes.

The discussion of both might seem somewhat long, when using LTspice to analyze the circuits. However, the thing I decided to do, is to work with these controls relative to the common ranges of room temperature, so that in the case of the VFO oven, the range of difference between the VFO oven and room temperature would not be very large in terms of thermal losses from the VFO to the room. Hence, this idea would not work well outside in the cold or on a hot day in the sun, thus indoors where the room temperature is controlled by air conditioning or a furnace. And as for the VFO oven, I designed it to maintain an internal temperature of 77 degrees F.

In a few days I should have an article up and running on this, with two LTspice schematics. The LTspice circuit model performs an analysis on the circuit based upon changes in temperature and thus controls the VFO oven or the frequency compensation network based upon the target range of temperatures. Hence, these circuits will enable hobbyist to design and develop useful means to control VFO thermal drift. And both can be combined in a VFO for even more control.

04/09/2025

Over the years, I have often felt the need to comment or to propose rule making suggestions to the FCC. I must admit that comments and rulemaking at the FCC is highly competitive. And depending upon who all is in charge at the top, which consist of the main members of the Commission, they may not see the wisdom of your vision, and well, that is how it goes....

  Over the years, I have often felt the need to comment or to propose rule making suggestions to the FCC.  I must admit that comments and rulemaking at the FCC is highly competitive. …

03/27/2025

Part 2 of our transistor design and analysis series.

Part 1 | Part 2  Contents 1. Brief Review 2. Collector Load Study Circuit 3. What Controls What in a Transistor 4. Predicting AC Performance with Our Plots 5. Average …

03/26/2025

I have been currently writing and editing some articles devoted to examining transistor functions and operations, in terms of transistor performance plots and curves. These articles show how to use LTspice to explore all of the characteristic parameters of a transistor. And how to make your own data sheets from LTspice plots.

The plots that I produce go beyond what you find on a semiconductor data sheet and hence are about the more useful information you will need to design circuits. From plotting beta ß and input impedance to the saturation current level of a transistor. And lots more.

All of the information goes towards a later article about how to design amplifier circuits for audio and rf uses.

I have uploaded the first article and have the second in a draft ready to be published once I look over it for editing purposes.

I believe these articles will go beyond anything you find on the Internet currently regarding transistor design and analysis and will be most interesting for those who are into using LTspice, or any other SPICE software. I hope to take electronics hobbyist to where no man has gone before. Well at least in terms of fully understanding everything that is going on in a transistor at once, in one combined plot.

Hobby Radio Groups.

03/17/2025

The voice band sweet spot as defined by amateur radio operators, consist of the audio spectrum range of 100 Hz to 2900 Hz, where these two start and stop frequencies are the - 3 dB bandwidth specifications. In listening to AM and single sideband via an SDR radio, where the user can adjust the audio passband, it is noted that with weak AM signals that if you adjust the low frequency to 100 Hz and the high frequency to 2900 Hz in the audio passband filter feature, weak AM signals are more intelligible....

  The voice band sweet spot as defined by amateur radio operators, consist of the audio spectrum range of 100 Hz to 2900 Hz, where these two start and stop frequencies are the – 3 dB ban…

03/16/2025

In case you were not aware, we post articles from our Radio Wavelengths site on this page, and a few other pages. Our articles about LTspice circuit design appear at this website. Of course, Radio Wavelengths is devoted to various kinds of radio related content, so some articles will be about other radio related stuff, besides LTspice.

03/16/2025

Download LTspice | Analog Devices Here we want to look at how to use LTspice software to analyze a transistor model. In which, we can analyze the key specifics of operation based upon such things as the beta of the transistor, its input impedance, and its characteristic collector current curves versus input current and input signal level. Afterwards, using the data from these various parameter plots, we can design a transistor circuit for audio of rf use....

Download LTspice | Analog Devices   Here we want to look at how to use LTspice software to analyze a transistor model. In which, we can analyze the key specifics of operation based upon such t…

02/27/2025

This article is to notify RTLSDR users, that the latest extio_rtlsdr.dll which was a test version published Nov 22, 2023, does not contain the feature for Q mode of operation, which selects the built in HF downconverter in the latest RTLSDR dongles or rather hardware. The version ExtIO_RTL_x32_v2023-11-22_test.zip from Github, is using a new GUI interface to configure the RTLSDR device with software such as HDSDR and SDRuno etc, and hence does not provide for selecting the Q mode which is a disappointing development....

  This article is to notify RTLSDR users, that the latest extio_rtlsdr.dll which was a test version published Nov 22, 2023, does not contain the feature for Q mode of operation, which sel…

01/06/2025

Shortwave transmission to the Pacific is "more important now" than in 1990 when RNZ Pacific first broadcast into the region, New Zealand's Deputy Prime Minister says. RNZ Pacific Shortwave radio has updated its site's transmitters with a 100 kW Ampegon TSQ-2100 transmitter, with DRM capability. Since the world has lost the world service of Radio Australia, those nations in the regions of the Pacific have come to rely upon RNZ Pacific for their news and information, where the kinds of information include is information for times of crisis, such as a tsunami or cyclone....

  Shortwave transmission to the Pacific is “more important now” than in 1990 when RNZ Pacific first broadcast into the region, New Zealand’s Deputy Prime Minister says.  …