[Premium-Rx] Receiver RF video questions

Sun Apr 22 03:25:03 EDT 2007

The "video" in the receiver context usually refers to the radar "video signal", which
is the envelope demodulated IF baseband signal. 

This concept has also been used to characterise signals that are not only from radar receivers,
but also to demodulated baseband signals that have wide information bandwidths (in the order of MHz)

Receiving systems that are intended for signal analysis in i.a. SIGINT applications usually connect specialised
measuring and analysis equipment to the "video" outputs, not to be restricted by the characteristics of any audio
stages "downstream" in the receiver.

1.) What types of applications would manipulate a video output signal?
(Other than TV, surveillance)

Signal quality measurements in broadcasting, analysis of analogue radio relay link loading, spectrum occupancy measurements, equipment signature analysis in SIGINT and related activities.

2.) Would raw analogue RF video be considered composite, with audio and
colours? (Compatible with composite video input to a video monitor, without
buffering / filtering?)

No. It would usually only be the envelope demodulated IF baseband signal. It may be shown properly on a 
B/W monitor having tolerant properties if the RF input signal happens to be a standard B/W analogue TV signal.

3.) What would be an application example of video signals used in
communications systems, e.g. DF signals processing?

A DF processor may be connected to a "video" output if the required information bandwidth is large enough.
Another example can be time or frequency multiplex multi-channel transmission systems.

4.) Radar systems use video signal processing.  Using a spectrum analyzer,
what type of information can be found by interpreting or interpolated by
studying / characterizing a video signal?  Is the video the result of rf
signal processing as a display of radar output? 

Traditional radar video signal processing usually takes place in the time domain.

The frequency domain pattern shown on the screen of a spectrum analyser therefore 
has little or no connection to the radar target information shown on a PPI, but can be of interest when analysing the
technical characteristics of radar transmitters for maintenance, interference analysis or SIGINT purposes.

Since a lot of interesting characteristics of a radar signal are lost by envelope demodulation, the preferred place
to connect a spectrum analyser would be to an IF output before the demodulator.

73/

Karl-Arne
SM0AOM

----- Original Message ----- 
From: "S. Schappertt" <scottsch at ix.netcom.com>
To: <premium-rx at mailman.qth.net>
Sent: Sunday, April 22, 2007 5:26 AM
Subject: [Premium-Rx] Receiver RF video questions

G'day to the list and members,

I have a few questions to pose to the list.  I do not have very much
experience with RF video and video applications, so I am interested to
understand some basic concepts of utilization of RF video signals in
communications applications.  Many premium receivers have provision for a
video output / input (either 50 or 75 Ohms), the product of integration of a
video amplifier into receiver functionality.  I have googled several
scenarios of "rf video" searches but find little usable information.
Sources of specific information on this subject seem elusive.  I did take
the opportunity to learn quite a bit about RF video amplifiers.

Here goes:  Video is video; picture images, from raw analogue TV to UWB
digital TV and all manner of video signals from wireless sources and
telemetry.  The wideband receiver has capability to tune and filter video,
based on BW filtering on the receiver itself.

Some questions:

1.) What types of applications would manipulate a video output signal?
(Other than TV, surveillance)
2.) Would raw analogue RF video be considered composite, with audio and
colours? (Compatible with composite video input to a video monitor, without
buffering / filtering?)
3.) What would be an application example of video signals used in
communications systems, e.g. DF signals processing?
4.) Radar systems use video signal processing.  Using a spectrum analyzer,
what type of information can be found by interpreting or interpolated by
studying / characterizing a video signal?  Is the video the result of rf
signal processing as a display of radar output? 

I hope I do not embarrass myself by asking what may seem like simple
questions, but I am very curious to find resources on the subject to better
understand applications concepts.  I also might guess that others have had
similar questions along the way to enlightenment.

Thanks very much in advance for some good first principles on the subject!

Best regards to all!

-Scott

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