In the figure shown below, SWR Meter is using in two different
scenarios. First one for SWR measurement and second one for
dB measurement.

In SWR meter, same needle rolls on two scales simultaneously.
There is no any front panel controls to switch between dB and
SWR scales.

Then how can I confirm the first setup is for SWR and second
is for dB ?

In short, my doubt is that-Whether it indicates input VSWR or
feeding power of Horn antenna in the first case on SWR Meter ?

 

The question isn't all that clear to me. There are also a few unknowns here.

1. The attenuator & detector are probably well matched??
2. The horn antenna may or may not be well matched??
3. What adjustments are being made during the test - frequency sweep? Attenuation level? Slotted line location for the detector? .... ????

If the observation was only about what occurs as the slotted line location for the detector is changed then depending on the load (horn antenna) match quality one may observe signal level fluctuations along the line in the presence of any standing waves.

Also if you actually want the SWR rather than just signal dB, don't you have to make another connection to the indicating instrument? One normally uses a directional coupler for such purposes. What's the indicating instrument?

Your question needs some further clarification.

 

What's the indicating instrument?

Your question needs some further clarification.

Indicating Instrument is SWR Meter.

 

Hello,

Here is a link that will tell you more about the SWR meter:
http://users.cwnet.com/ysarc/swr.htm

Bertus

 

Indicating Instrument is SWR Meter.

You are being rather coy about this.

Perhaps I didn't ask the questions clearly enough.

I was thinking more along the lines of make and model. Is your question one with a practical purpose? If you are using an instrument with which you are unfamiliar, then more often than not you would refer to the operating manual to determine the function and use of the instrument.