Swept Measurements
A simple way to be able to perform swept measurements is by using a noise source. Noise sources can cost a lot, especially for high frequencies. My Tektronix 2712 has inbuilt tracking generator to 1.8GHz. That covers the most frequencies I use. However, I have now also interest for 3 and 6 cm. My liteVNA can measure up to 9.3GHz (with some limitations of dynamic range). Still a very useful instrument, and does not cost much either.
I made a couple of simple filters for 6cm using common plumbing cups. And of course they need to be trimmed.
For 6cm I can use the VNA. It has a screen that works working with, not to small.
Quite fantastic that instruments like this can be available for under 200 Euro.
There is also free software for these devices available. Here a screenshot from the NanoVNA-App. (Note different scale).
My Anritsu MS710A spectrum analyzer can measure up to 23GHz. Sweep generators up to at least 12GHz are expensive, if you don’t luckily find one just laying around.
Cheap noise sources up to a couple of GHz can be found on different sources on internet. One I found can deliver 20dB noise up to 3.5GHz, then it drops. Not bad, however not enough.
There is also various of Chinese broad band LNA available. Here one rated range to 7GHz. This one has a quite flat response over its range.
The noise figure for the LNA is not bad. It could be used as a pre-amp with some filtering added. Plumbing cups filters are bigger than other filters available, however they are cheap to manufacture and easy to trim. These LNA’s cost a fraction of what other “Ham Band” custom pre-amplifiers do. If 0.8 to 1dB noise figure is ok for the application, try them.
Would be fun to mount the LNA on a Peltier cooler element and see how much lower the noise figure becomes. What I know can a single stage Peltier cooler cool a delta of 30°C.
My intention is to increase the noise source range to be able to use it up to at least 12GHz. However, I will start to see the performance at 5760MHz.
Here the noise source with LNA and the filter. Similar performance as with the VNA.
The filter loss difference between VNA and SA measurement was about 1dB. VNA -2.6bB and the SA jumping -1 to -2dB.
Everything working fine however, @ 10GHz the LNA has dropped the gain a lot. Another LNA is bought and it is rated 20dB gain up to 18GHz. Data from the manufacturer shows a quite flat response also for this amp.
How the setup will perform @ 10GHz is still unknown. When the LNA arrives more testing will be done.
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