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Thanks! 🙂

But, in its interaction with the common-base, it does approximate a gain of 1, in practice. This is how it was explained to us in engineering school and in the texts I reviewed to create this video. 🙂

@@eie_for_you With no emitter degeneration resistance, Rc=re for the top resistor and Re=re for the bottom resistor. In this case, the voltage gain is very close to 1, but the combined gain is not well-defined and varies greatly with signal level. Assuming gain=2 does consider the worst case for the Miller effect and is therefore not a bad strategy even when using emitter degeneration resistance to stabilize the gain..

@@byronwatkins2565 I hear ya! 🙂

You are very welcome! 🙂

You are very welcome! 🙂

I would that there is a LOT less inter-element capacitance with a vacuum tube. Thus the higher frequency capability. 🙂

True that! And I've done that many times. Also, I've provided time markers in the description if you need to jump to a specific place. just click on the marker and you are there. 🙂

@@eie_for_you Time markers are a great help, thank-you!👍

@@acestudioscouk-Ace-G0ACE You are very welcome! 🙂

I know the feeling! There are some things in electronics that take a bit of work to understand what is going on. 🙂

Thank you and you are very welcome! 🙂

You are very welcome, my friend! 🙂

Thanks, man! 🙂

You are very welcome! 🙂

Thank you so very much! I really appreciate the encouragement! 🙂

You are very welcome! 🙂

Well, the frequency limitations depend entirely on the specific transistor being used. It also depends on the gain you set it up for. You can control the overall gain by splitting the emitter resistor, the bottom one is bypassed. The top one works together with the collector resistor to set the overall gain. The lower the set gain, the broader the frequency response. All of this will be covered in the next video where I go through the design and then we will see the results of the design including the "limited gain" version. 🙂

Audio.

@@andymouse Actually ... the main purpose was to extend the frequency response out far enough to be used as video amplifiers. This puts it well up into the MHz range. But, the actual extent depends entirely on the specific transistor you are using and the amount of actual gain you design into the amplifier. 🙂

It is going to also depend on your signal source's impedance. Remember that "Miller capacitance" is the gain of the stage times the Collector-base capacitance. This capacitor works against you signal source's resistance in F=1/(2*pi*R*C) If you make a stage with a gain of 100 using a transistor with a 1pF collector to base, you get 101pF seen at the input from that. If your signal has a 200K impedance, the result will be good enough for voice but not hifi.

Now that is a very interesting analogy! Thank you for the encouragement! 🙂

You are very welcome, my friend! 🙂

Unfortunately, real validated standards are not cheap! However, for the kind of things we are doing, we can cheat a bit and get close enough. The short and open standards are easy enough to DIY. For the OPEN you can use an unpopulated connector. For the SHORT you can thoroughly short a connector. I used some braid from some stripped coax or a length of solder wick. Just make sure it is very substantial so as to avoid inductance and resistance. The LOAD is a bit more tricky. You *could* use 4x200 Ohm, 0.1% surface mount resistors with your connector --OR-- you could simply purchase a 50 Ohm terminating load (be careful to look closely at the specs for accuracy, frequency limits and SWR at the various frequencies). For a N-type, this one looks pretty good: www.mouser.com/ProductDetail/Amphenol-RF/202109-10?qs=%252Bm72Q7GxMuxG78p4FokgEg%3D%3D Hope all of this helps. 🙂

You are very welcome! and ... thank you! 🙂

Thanks, man! 🙂

Thanks! 🙂

This is why I measure the velocity factor for myself for these kinds of projects. 🙂

Very good question! In fact, that was one of the things I was thinking when I first started playing with this concept. Unfortunately, the Q of this filter is not high enough to accomplish this task especially if we are talking amateur radio 600 KHz, 2 meter band separation. If the transmit and receive frequencies are far enough apart, I do not know why not. I'd use the open stub with a variable capacitor termination so you could tune it easily. The only other issue I see might be the changes in tuning with temperature(??).🙂

You are welcome! 🙂

It depends on what you are trying to do. If you are looking to monitor the swr of your antenna while applying real transmitter power, then you are set. Be aware that, depending on the frequency and the make/model you may be introducing it's own SWR and loss into the transmission line. (see my video on the subject: th-cam.com/video/1fpoViuxn3c/w-d-xo.html) If you are doing antenna creation and characterization, then the nanoVNA is most definitely they way to go. Plus it will do a **LOT** of other jobs for you,too. 🙂

You are very welcome!🙂

If you are talking about locating the short on a known trace, I'm afraid that this won't do that for you. Finding shorts on traces is a tough job on a two layer board and **WAY** tough on a multilayer board. With the latter PCB companies often use special X-Ray machines. There are other devices that shoot signals down a trace and you use a special sensor-type instrument to find where the signal stops (short spot).🙂

Thanks so much! Small world!! Sorry, I do not remember Bill Forester. We lived in Moose Lake from 1992 to 2000. 🙂

Aaaah! How well does that work for you? I have a folded inverted vee for my 75/80 antenna. I created it because I was tired of the bandwidth limitations of the simple inverted vee (th-cam.com/video/McbDL1GxbqI/w-d-xo.html). I've heard of doing the termination thing, but I decided to keep it this way because I have the space for dedicated, single-band antennas. 🙂

Hello - I find the T2FD one really great antenna, with a very low VSWR from 80m to 10m. There are one or two spots where the VSWR goes above 2.5:1 but my ATU easily sorts that out. I've been on the air for 40+ years and I have to say that the T2FD is the best antenna for restricted places.

@@EI6DP That's cool! Thanks! 🙂

Ya know ... that is a good point! I've been thinking about that. Stay tuned for the second video on the CASCODE Amplifier for something new and different. 🙂

Thank you for the compliment! :-) Check out your manual, page 32 rigexpert.com/files/product_documentation/aa55zoom/AA-55-ZOOM_Antenna_Analyzer_User_Manual.EN.pdf 🙂

@@eie_for_you Thanks for the reply. I will check it out.

LOL!!!🤣🤣🤣🤣

Feel better now? You did not listen.

@@daveengstrom9250 I think you missed the meaning of my comment. Read it again. I made what I believe are several important points that make the explanation work better.

Yes, I believe that is exactly what I said in the video, though I didn't rope in the effects on hFE ... at least not directly. 🙂

@@eie_for_you My comment also put the points in a different order that I think works better. Getting the changing HFE up front explains the change in collector current as a change in HFE

@@kensmith5694 But, the change in hFE was not the point, but a side observation in the explanation of what it is all about.

A megger is a special, high resistance ohmmeter. The resistances are so large that the usual low voltage testing cannot be used because the resulting current is too small. The original models (eons ago - before my time) had a simple analog meter and a crank operated high voltage supply. Newer ones can be very, very sophisticated in setting controls and resistance ranges. These will have limits as they ramp up the voltage ... if they high the limit, they could shut down the supply and terminate the test. In the end, they simply provide a voltage that it applied across the high resistance and then measure the current flowing. A little math knowing both voltage and current and we know what the resistance is. We used to have to use this very kind of device to test conductivity of all of the "furniture" and the floors in the operating rooms at the hospital I worked at so that static couldn't be generated to cause a spark and ignite possible flammable gasses being used. This is much like the "conductive" mats used on electronics benches and the "conductive" bags used for static sensitive devices like transistors and ICs. 🙂

@@eie_for_you Thank you 😊

@@rtecha.m9648 You are very welcome, my friend! 🙂

Thanks! I'm so glad that you found this helpful. You are very welcome!

Thank you so much! I am so glad that you found this helpful. You are very welcome! 🙂

Yeah and neither have I. You rightly point out that by the time we add all of the tolerances of real life resistors and capacitors, precise calculations with transistor models are pretty much moot. Besides, even there ... the hFE possibilities of a particular transistor part number alone cover huge amounts of territory especially when we add in thermal considerations. It is a painfully imprecise world, my friend. 🙂

I thought for absolutely *sure* I already replied to this. :-/ Well, let me give it another try. Understanding the why behind the disparity between theory and practice is one of those mysterious semiconductor physics "rabbit holes." No one seems to want to admit the disparity in the first place. If they tipped their hand on this one back when I had to take 2 semesters of this in engineering school, I remember none of it (it was 43 years ago!). The good news is, in practical terms, we actually rarely need to know the Early Voltage or even use it if we knew it. :-)

Thanks! 🙂

You are right, the "plate and load" adjustment are a matching network of themselves. The difference is what they are actually matching in terms of impedances. The output impedance of the final amplifier is not naturally 50 Ohms or even close to it. It's output impedance is approximately the same as the plate load. At resonance, this is pretty high which is why we dip the place current. The purpose of the plate and load adjustments is designed to translate the high output impedance of the finals to a 50 Ohm environment. It has been a very, very long time since I owned a rig with plate and load adjustments to be made. If it were me ... I'd set them in the "starting position" as dictated by the radio's manual first. Then dip the plate. Now adjust the antenna tuner for best SWR. I would then go back and adjust the plate and load as per the radio's manual. And finally, I'd give the antenna tuner its last adjustment. 🙂

Thank you so much! I'm always looking to do it better. Never stop learning! 🙂

Thanks! I'd learned of all of this back when I was in engineering college, but had forgotten a lot of it through disuse. It is nice to have this stuff now coming back. I think vacuum tube have their own brand of things like this including the Miller Effect which affects semiconductors, too. (that is in the next video). Because of the nature of the Early Voltage, I think this is specific to semiconductor devices and, maybe, to BJTs in specific. 🙂

Now **THAT** is a good question! The problem we run into right out of the gate is amplifier drive. Like my little VHF amplifier will not switch into transmit mode until the input power reaches a certain level. So (just thinking out loud), I'd have to have an amplifier to bring the port 1 signal up to the required drive level of the target amplifier. Now comes the "fun" part ... calibration and measurement. I have a Bird inline wattmeter. It uses different plugins to configure it for frequency and power levels. It also has a plugin for an RF sampler which provides 50 dB of attenuation between the sampled power and the sample output. So, step 1 for me is to calibrate using all of this without the target amplifier in place. VNA Port1->Preamp->Bird->Dummy load. The -50 dB sampler output from the Bird-> VNA port 2. Calibrate as a through measurement. Remember, check the input level limitations of your VNA BEFORE doing anything. My Tektronix VNA is conservatively 0 dBm. According to the charts I have, +50 dBm is 100 Watts. So the output of my Bird sampler will be 0 dBm with 100 watts running through it to the dummy load. You *may* have to put an attenuator between the sampler output and VNA port 1 to make sure you are not exceeding the VNA's limits. Once everything is calibrated as a through measurement, then insert the target amplifier and make your through measurement as usual. Input impedance-wise ... for an amplifier like mine with the power sensitive transmit-receive switch, we can only measure the input impedance of the power amplifier if we can somehow trick it into thinking it needs to be in transmit mode. And don't forget to put a dummy load on the output of the amplifier. I hope this gives you some ideas. Always, always be careful. Attenuators are your friend to protect your VNA! 🙂

Thank you for your detailed explanation. Fortunaly, I also have a Coaxial Dynamics 87015 Directional Coupler (-50db 50 to 500 mHz and a Bird 50 ohm line section with above components, a hot S11 measurements should be possible with 5W, right? So I never understood the proper setup and calibration. A video would certainly make many happy. I,m sure several people encounter this. Regards, Marcel

@@MarcelGoedraad The problem is the VNA has to see the input of the amplifier directly to properly do an S11 measurement. In my mind, I'd be thinking about taking the cover off and figuring out how to "manually" put the amplifier in transmit mode. I am hoping you have what you need at this point. As far as a video goes, I'd have to either create or buy a 5 watt preamplifier to do this. I have nothing "in house". Worth thinking about, though because it sounds like fun! 🙂

You are welcome, my friend. 🙂