Saturday, October 10, 2020

Comparison of tinySA and HP8563A

mcHF, tinySA, step attenuator
Although I had the tinySA on hand when I made the spectrum test yesterday on the mcHF transceiver, I hadn't yet used it enough to know whether or not to trust it. So I took the mcHF to work and used our recently calibrated HP-8563A to look at the mcHF's output on all bands.

With screenshots on the rig's spectral output on all nine bands now available I decided to make the same measurements with the tinySA to see how they compared.

I don't really like using either the tinySA or the nanoVNA as stand-alone units, preferring instead to run them from my laptop with the available programs. For the tinySA, this is tinySA-APP which is constantly being updated and improved.

Friday, October 9, 2020

Harmonic content of mcHF's output

From time to time I've read comments on various forums that mcHF transceivers should not be used with amplifiers because of the high harmonic content on the output.

I almost always use an amp with mine when operating from home so I decided to measure my  mcHF. My amp, a Hardrock-50, contains its own lowpass filters on the output so I was never concerned with whether or not the mcHF was "dirty".

Here are the results, made with a recently (July 2020) calibrated HP-8563A spectrum analyzer.

Each horizontal line represents 10dB. So the top line, where the fundamental is placed, is the reference or 0 dB. The next line down from that is -10dB, then -20dB, etc.

I've put a delta marker on the first harmonic and it's easy enough to count down from the top of the display to see the attenuation of subsequent harmonics, keeping the 10dB per line in mind.

Thursday, October 8, 2020

G0UPL discusses his kits - past, present and upcoming

 QCX-mini and QSX info begins at 56:00.





Monday, October 5, 2020

Dummy load with chemical impedance matching

Joe WB9SBD has come up with a unique way to build a dummy load.

Rather than a series of standard resistors made to present a 50-ohm load, Joe has mixed up the perfect concoction of household items to achieve a load that presents a perfect 1:1 SWR over a wide range of frequencies.

Those items are a glass jar, water and baking soda.

According to Joe's experiments, straight tap water yielded an SWR of 10:1 at HF frequencies.