Universal Wideband Amp

Description: This kit is part of what is referred to as RF Tool Kits, specifically Electronic Building Blocks. A variety of these kits are available, with new ones being released periodically. The offerings can be explored and built in a homebrew style from the information provided online. Additionally, a large inventory of toroids and various components is maintained. The amplifier included in the kit is straightforward yet impressive, boasting a voltage gain of 7x or approximately 17 dBm power gain measured at 10 MHz with 50-ohm input and output, powered by 8 volts DC. This design is practical for minimal setups that may include NE602/612 and LM386 chips. Increasing the Vcc to 12 volts did not result in significant gain improvements. The amplifier's output remains consistent across 3.5 to 30 MHz, providing a power increase of approximately 22 to 23 dBm over the input signal level. Measurements taken at the 6-meter band showed a slight decrease compared to the 3 to 30 MHz range. A chart illustrating the power increase of the circuit, along with raw measurement data, has been created. The measurement setup included a Singer CSM-1 as the signal source, a Tek 2465 oscilloscope for verifying input signal levels (~200 mV peak-to-peak), an M3 Power/Frequency meter, and a 0 to 90 dBm attenuator to pad the input for the W7ZOI Spectrum Analyzer. The procedure for measuring the dBm increase between the amplifier's input and output was consistent across frequencies. An optional attenuator resistor was not installed; however, a 51-ohm resistor was placed across the output for termination, which helped shape the output waveform. A 51-ohm resistor across the input was tested but resulted in loading the signal generator, skewing output measurements by 2 to 3 dBm. The continuous wave (CW) portion of each band was selected for measurements, focusing on homebrew projects. Output from the signal generator was measured using the oscilloscope, aiming for ~200 mV peak-to-peak, and verified with the M3 meter. Switching the oscilloscope probe from 10:1 to 1:1 was necessary to obtain a sufficient signal level for accurate readings on the M3 meter. A tee connection was made from the oscilloscope probe cable to the M3 meter to avoid frequent cable changes during frequency adjustments. Once the frequency and input level were established, the output was measured with the M3 meter and verified with the spectrum analyzer. The variable attenuator was utilized to adjust the spectrum analyzer settings for accurate readings without changing scales to accommodate the -30 dBm input level. The frequency on the CSM-1 was selected, and the signal level set to ~200 mV peak-to-peak. After locking the frequency on the M3 meter by switching to 1:1 probe configuration, the probe was reverted to 10:1 to prevent skewing the power measurement. The probe could be moved from input to output on the amplifier circuit for waveform observation. Although using two probes was an option, the existing cable clutter was considerable. The M3 meter measurement mode was switched from frequency to power to record the readings, while the spectrum analyzer was monitored for data verification. The spectrum analyzer could detect levels below 2 dBm, ensuring any significant signal level changes were noticeable. After completing the measurements, preparations for the next frequency were made. Future measurements in the range of 1 to 60 MHz in either 1 MHz or 2 MHz increments may be conducted, although this would require substantial time due to other ongoing projects.

The RF Tool Kit amplifier circuit is designed for versatility and efficiency in electronic applications, particularly in homebrew projects. The circuit topology typically includes a transistor-based amplifier configuration, which allows for high gain and low noise performance. The choice of 8 volts DC as the supply voltage is strategic, ensuring compatibility with low-power RF components while maintaining a balance between performance and power consumption.

To facilitate accurate measurements, the circuit incorporates a well-defined input and output impedance of 50 ohms, standard in RF applications. This matching is crucial for maximizing power transfer and minimizing signal reflections. The amplifier's frequency response is optimized for the specified range, ensuring consistent performance across various operational frequencies.

In practical applications, the use of a 51-ohm resistor for output termination is a common practice to stabilize the output waveform and reduce distortion, enhancing the overall fidelity of the amplified signal. The careful selection of measurement equipment, such as the Tek 2465 oscilloscope and M3 Power/Frequency meter, underscores the importance of precision in evaluating amplifier performance.

Data collection methods described indicate a rigorous approach to testing, with attention to detail in signal conditioning and measurement accuracy. The documented power gain across the specified frequency range provides valuable insights for users seeking to implement this amplifier in their own RF projects.

In summary, this RF Tool Kit amplifier circuit exemplifies a robust solution for RF amplification needs, combining practical design considerations with thorough testing methodologies to ensure reliable and effective performance in homebrew applications.This kit is part of what Diz calls RF Tool Kits, Electronic Building Blocks. He has a number of these kits and more come out every so often. I like to look at what he has to offer and build some of them homebrew style from the data he has on-line. I also buy many kits from him which keeps him coming out with new items and ideas all the time. He al so has a large inventory of "roids" (toroids) as well as parts and odds-and-ends. His banner on the web page says it much better. The amp is straight forward and simple, yet remarkable. Diz boasts it has a7x voltage gain or about 17 dBm power gain measured at 10 MHz with 50 ohms I/O and powered with 8 volts DC. It is that and a tad more. The concept of Vcc being 8v-dc is a very practical approach if one were to use this circuit in a minimal rig that includes a NE602/612 and LM386 chips.

I found that raising the Vcc voltage up to 12 volts did not yield any appreciable gain. The amp circuit`s output is consistent when used for 3. 5 to 30 Mhz, providing about a 22 to 23 dBm increase over its input signal level. I looked at the output level for 6 meters and it was slightly down from the 3 to 30 Mhz range. I have graphed a chart (see below) that shows the power increase of the circuit. Also shown is the raw data from my measurements. I used a Singer CSM-1 for my signal source, a Tek 2465 o-scope for verifying input signal levels (~200mv pk-pk), the M3 Power/Frequency meter, and a 0 to 90 dBm attenuator to pad the input to my W7ZOI Spectrum Analyzer. The procedure for measuring the dBm increase between the in- and output of the amp circuit is repetitive in nature for each frequency.

The output of the amp circuit did not have the optional attenuator resistors installed. I did install a 51 OHM resistor across the output for termination purposes and it helped shape the output waveform. I tried using a 51 OHM resistor across the input, but this seemed to load down the sig gen and skewed the output measurement by two to three dBm.

I chose the CW portion of each band as that is where my interest normally lies with homebrew projects. I would measure the output of the sig gen using the o-scope, setting it as close to 200mv_pk-pk as possible, and verify using the M3 meter.

I found that I had to switch the scope probe from 10:1 to 1:1 to obtain enough signal level to get an accurate reading on the M3 meter to lock in the measurement frequency for the power measurement. this is unique to the M3 meter, but the extra effort is paid off with a very accurate and stable power measurement.

I Tee`d off the scope probe cable to the M3 meter so I did not have to change cables around between each frequency change. Once the frequency and input level were set, I would measure the output using the M3 meter and verify with my SA.

I used the variable attenuator to set up the SA so I could readout the power level reading without having to change scales to offset the -30 dBm input level requirement on the SA. I would select the freq on the CSM-1 (sig gen) and set-up the signal level for 200mv pk-pk. Then I lock the frequency in on the M3 meter by switching the scope probe to 1:1. Once the frequency was locked in, I changed the probe back to 10:1 so as not to skew the power measurement.

I could move the probe from input to output on the amp circuit if I wanted to view the waveform. I could have just used two probes, but there were enough cables scattered around as it was! I would switch the M3 meter measurement mode from frequency to power and record the reading. I also watched the SA to verify this recorded data. I can read to less than 2 dBm on the SA, so any radical signal level setting would be easily noticed. Once done, I would then set-up for the next frequency. I may go back sometime in the future and redo my measurements for a range of 1 to 60 Mhz in either 2 or 1 Mhz increments.

That series of measurements will take some time and I other projects