@Bordodynov I always like your solutions but now you chnaged the input signal wave form. I ask you to explain why and also I want to ask why the former one is no longer good to use. Because remember, the sine wave is, in fact, what I have in lab or at the DDS output! I can't change the hardware to fit your schematics.
You also changed R1 from 50Ω to 51Ω

Thanks

@MisterBill2 sure. I just wanted to make sure it was a mistake!

I just showed that you should not bother with two-way cable matching. So I added two 50-ohm cables (TLINE) to the circuit, about 1 meter long. The quality of the cable matching is easy to check with rectangular pulses, with steep fronts. Then the picture looks at the oscilloscope. If there is no ringing, then all is well. What I've shown is just for research on LTspice, but you can do it in reality, you just need to have a generator of rectangular pulses of the necessary amplitude. The frequency is not very important, gravely short fronts.
Regarding the denominations of the resistors. LTspice has a base of 1% resistors. I often use this when I need a resistive divider.

 

Yes, that one. That is the one that you asked about.

The signal generator from post#1 was claimed to output about 1 volt, and the output needed was 2 to 3 volts. For that you need a gain of two to three. Now the DC level of the input sum must keep the output signal from going beyond the linear range of the amplifier, which should not be so very difficult. But now I have a question, which is about the use of this amplified signal. What are you going to do with a signal set in the middle of the Citizens Band channels assignment? Nominally 27.0 to 27.405 Megahertz? It just popped into my head to wonder.

This is my final year project and the story goes more or less like this:

I saw the vswr basic circuit somewhere in the internet and it used a DDS to generate the signal. So I bought an AD9850 at ebay and started t work around it. My goal is to have this DDS module conencted to a VSWR bridge. And the output of the VSWR bridge will be processed by a uController and results will be shown in an LCD.
After many struggles and and don't even know what else, figured out that this ebay DDS module was not outputting enough power to the VSWR bridge. I got to this point because at home I don't have a function generator and I came to the lab to test the circuit and I increased the function generator sinewave amplitude and the results were kind of consistent with theory. For a matched impedance between the transmission line and the antenna, I got a VSWR close to 1. So, having this in mind, I started working on an RF signal amplifier to use between the DDS module and the VSWR bridge. That's where I'm at now!
But with the RF signal amplifier, new problems came. ATM, I'm looking to the scope and I'm observing quite a weird sine wave at the output of the amplifier using a dummy 50Ω load resistor. Meaning that I still haven't the VSWR bridge connected.

 

What happens is that amplifiers have both a small signal range and a large signal range, the difference is that in the large signal range the impedance changes as a result of the voltage or current level. So that will have an effect that is only explainable if you understand the circuit involved. But it will certainly caused "weird waveforms" that may or not be similar to the input signal. It may be useful to use another stage of amplification and distribute the gain between the stages. An alternative is to find an amplifier with a greater dynamic range.

ALSO, the package that you have described in post #122 sounds a whole lot like an SWR analyzer. There are quite a few of them on the market and it may be that you can gain some additional insight by studying their circuits. And it might possibly be that you do not really need a perfect sine wave for your system to perform adequately. My SWR analyzer certainly has a few harmonics.

WHEN I POSTED THIS, I got a message that I must wait at least 30 seconds befor performing this action. I do not understand that. @bertus