Sensitivity - Maximum Input Levels; Frequency Response; Concept Of The Hm5510; Introduction To The Operation Of The Hm5510 - Hameg Instruments HM5510 Manual

Sensitivity – Maximum input levels
The specifi cation of spectrum analyzer sensitivity is not uni-
form. One method defi nes the sensitivity as the input level at
which the signal power is identical to the average noise power
of the analyzer. As an analyzer measures signal plus noise the
signal will appear 3 dB higher than the noise in case the above
defi nition holds.
The maximum input level of an analyzer is the level which is
safe for the input stage which does not mean that at such level
the instrument will still measure within spec. Customarily,
the level is considered maximum usable at which a compres-
sion of 1 dB takes place. The permissible level is dependent
upon the input attenuator setting. When using an analyzer it
is good practice to always start with maximum attenuation
switched in and then decreasing it. See the specifi cations for
the numbers.
The input stage may be overdriven without that this will
be clearly displayed in any case. HF energy outside the
instrument's useful band of 150 kHz to 1050 MHz may e.g.
cause input overdrive.
Due to nonlinearities in the input stage it is always advisable
to use the highest attenuation setting of the input attenuator
which is commensurate with a good display. The distortion
products generated by the HM5510 remain >75 dB if the input
level after the attenuator remains ≤30 dBm.

Frequency response

As with any system the frequency response should be fl at
over the useful band in order to assure that the accuracy of
the amplitudes displayed is independent of frequency. Filters
and amplifi ers must have reached steady state levels.
I n t r o d u c t i o n t o t h e o p e r a t i o n o f H M 5 5 1 0

Concept of the HM5510

The HM5510 is a spectrum analyzer for the range of 150 kHz
to 1050 MHz. The signal to be analyzed must repeat periodi-
cally.
The analyzer uses the superheterodyne principle. The 1
mixes the input with the local oscillator signal and converts the
st
signal to the 1 IF. There are 2 more mixer stages with different
rd
IFs. The 3 IF fi lter can be switched from 500 to 20 kHz.
Display (CRT)
Following the detector the signal passes a logarithmic am-
plifi er and is directly or via a video fi lter fed to the vertical
defl ection amplifi er. The X axis amplifi er receives a sawtooth
sweep signal. The lowest frequency corresponds to the 1st
(left) graticule line, the highest to the last (10
With zero span there is no sweep, the frequency
remains constant.
HINT

Introduction to the operation of the HM5510

Turn-on.
Please observe the following hints prior to fi rst-
time operation.
– Check whether the correct type of fuse is inserted.
– Mains outlet conforms to safety standards, i.e. it has a
safety earth pin.
– No visible damage
– Line cord undamaged
– No loose parts in the instrument.
Operation
The instrument is easy to operate, nevertheless please observe
the following precautions:
The most sensitive part of the instrument is the
input stage. It consists of an attenuator, a fi lter
st
and the 1
STOP
following input levels must not be exceeded:
+10 dBm (0.7 V
±25 V
DC
With the attenuator at 40 dB: max. 20 dBm (HF).
Higher levels may destroy the input stage.
th
).
mixer. With the attenuator at 0 dB the
) HF
rms
Subject to change without notice
st
mixer
33