I tested three high-speed oscilloscopes regarding noise, speed, remote control and SCPI programming, handling and look and feel. This is no full product review, of course, but you can see quite some differences between the units.
The test candidates were:
- Keysight MSOS 8.4GHz
- Rohde & Schwarz RTO2000 6GHz
- Tek MSO4104
More details of the tests can be seen here:
Click here to see a High Speed Oscilloscope Comparison …
I now finished all three battery operated power supplies I needed for interference-free noise source testing.
We need a heater power supply (a few Volts max, up to 2A), an anode power supply (120V, max. 40mA in extreme cases), and a power supply for lamp, transistor, diode or small LED noise sources (15V very clean, 100mA).
After buying shares from Duracell, Eveready, Maxell and many others (not serious) I started off with a 15V 100mA design. This worked beautifully (using 20 x AA batteries), and so I also did a high current one (2A, 4V max, constant current, running off 4 x D Cells), and, last not least, a high voltage part for 120V at 40mA max (22 x 9V Block plus 10 x AA).
Spectrum measurements under load showed that the use of batteries can provide you with power so clean that I found no line-driven equipment that was able to match this.
Click here to see some Battery Operated Power Supplies I made …
After making some MiniWhip antennas I decided to make a small room antenna with a telescope. The main challenge here is large signal immunity; I used a Russian power MOSFET to get a very robust amplifier with 40dBm IP3.
Click here to see a High-IMD Antenna AmplifierUsing a High-Current RF MOSFET …
For the noise figure project with a budget spectrum analyzer I needed a USB powered preamp. Combining a USB to 15V converter with a lot of filtering plus a MMIC amp worked out into a nice preamp that only needs a USB connector as a power source.
Click here to see more Information about a USB Powered Low Noise Preamplifier …
Dedicated RF generators tend to be expensive. A budget generator from RIGOL costs ca. 2k€ and works up to 1.5GHz only. Pro generators like Keysight EXG cost a few k€ depending on maximum frequency and options. What if you mainly work in the shortwave bands or at 6m ? Could you use a much cheaper arbitrary function generator as an RF generator replacement and get away with it ?
The answer is YES. Up to 50MHz, a cheap RIGOL DG1062Z beats much more expensive RF signal generators in many aspects:
- analog modulation quality (a lot better)
- spectral purity (also quite as good or better)
- number of channels (2 instead of 1)
- flexibility (you can generate any waveform)
- price (3-4 times cheaper than a budget 1-channel RF signal generator).
I also tried a pro ARB with 240MHz maximum output frequency, with the result it could easily be used up to 200MHz with good results.
Click here to see an RF Signal Generator AM Modulation Quality Comparison, now including ARBs …
After building two tube based noise sources with 2D3B and 2D2S tubes, I wanted to try other tubes as well, having hopes to improve frequency limits and/or flatness. I tried the Sylvania 5722, the K81A and the 2D3B and 2D2S on redesigned tube mounts.
First results can be seen here:
Click here to see a Comparison of Vacuum Tube Noise Diodes …
Not satisfied with the 2D2S noise source frequency limit and flatness, I designed a better tube mount. This works very well, being flat within ca. +/-0.2dB up to 200MHz instead of 50MHz, having better matching and better shielding, too.
Click here too see a Tube Noise Source using the 2D2S Tube (Updated) …
Trying to make RF switches that do not “spike” (i.e., injecting switching pulses into the RF sigtnal), I created a transformer based PIN diode switch that can also be used as a mixer or modulator. Spikes are gone, but there are some other areas to get rid of.
Click here to see some info about RF Switches …
The next little project I wanted to make was an SWR sensor to protect power amplifiers. I chose the Bruene Bridge circuit because of frequency range and quite good accuracy.
Click here to see some SWR Bridges …