I’ve been intrigued in the past from power measurements too. Started when I realized I couldn’t trust my ordinary power meter while calibrating an old radio. I’ve used the same principle except I didn’t have an SA. Used An oscilloscope and an rf millivoltemeter first. But there are other uncertainties there too. Then used an HP 437b power meter with a power sensor head running through a fixed high power attenuator directly into the sensor. At the end at HF all my measurements where all within a small window of uncertainty so I was happy with the results overall. Also I could check the accuracy over the entire scale of my Bird43 several slugs. Lab equipments and lab measurements are somehow fascinating. In the end I was kind of hoping to see how the results compare with the Bird. Congratulations for your videos and the effort you put into it. Best wishes Diego
It's hard to totally eliminate all of the uncertainty, for sure. I actually did measure each of the HTs' power outputs with the 50 Watt element as a kind of sanity check. The Baofeng read ~7.1 Watts (1.5 Watts high), the Yaesu read ~5.1 Watts (0.67 Watts high) and the ICOM read ~3 Watts (0.85 Watts high). Considering the measurement uncertainty of all of the measurement instruments, these were very much within the "ballpark".
You also could make your own RF sampler - lots of different ways - and characterize its loss at the desired frequency. You could also use your scope with a 50ohm input termination to measure the output of the sampler, assuming your scope BW is sufficient. (I won't talk about the elephant in the room - using a >$1000 spectrum analyzer instead of a
Maybe just slide a piece of wire underneath the shield of some coax(?) I suppose part of the challenge is maintaining the 50 Ohm impedance for the line being sampled as well. This especially once we start getting up into higher frequencies ... FAR less forgiving! 🙂
Hi, interesting method with the bucket of distilled water. I'm curious about the Rigol spectrum analyser you use and wondered if it can do power measurements over a specific bandwidth for noise and signal in order to calculate the SNR of a Wideband FM signal. Cheers
If you want these additional capabilities with this Rigol spectrum analyzer, you have to purchase the "Advanced Measurements" option ($577US). I chose not to drop that kind of cash on it because, well, the base unit does everything I need to do. With that said, I do encourage folks to get the model with the tracking generator output.
The bucket of water is in fact a caloriemeter. It seems an interesting experiment. (I never have used this to measure RF signals).You can also callibrate a calloriemeter with a known powersource to improve the measurement (as it also depends on the "bucket and the environment")
Great Video, I have a telewave 44A and don't need any additional elements. The none digital telewave is much cheaper then bird and you don't have to buy one element as it's all built in.
Very nice! Out of curiosity I took a look at the manual for the Telewave 44A. This is what I found ... Pg 2: Accuracy 6%F.S. plus, at frequencies below 150 MHz there is a correction factor chart (Fig 7-2). Pg 18: Figure 7-2, At 20 MHz it is a +40% correction factor. I, personally, didn't find this too attractive.
Thanks Ralph! Wondering if you can do a video on metal/ceramic vacuum tubes(4cx300a, 4cx800a, 3cx3000, etc.) for RF amplifiers, and what are reasons that one would select a triode over a tetrode. Any assistance is appreciated!
You are very welcome! Regarding vacuum tubes ... it has been a very, very long time since I last did much of anything with them. As I recall, the tetrode has certain advantages (e.g. lower input capacitance?) than the triode. I suppose the choice would come back to the specific characteristics of the specific tube. I'm sorry to say that I don't have much to offer on this level.
very good,,instead using bird,I have 2 birds,use a rf sampler,,,cheaper than a bird sampler,,I also have a Krytar rf power meter the head goes to 18 Ghz,using a attenuator
