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TELE-audiovision International — The World‘s Leading Digital TV Industry Publication

— 01-02/2015

terrestrial receiver antenna

terminal without adding any

additional coax cable.

Next ist the SLTE 60: it of-

fers very steep edge ampli-

tude response right above

790 MHz. However, it is not

a low pass filter but a band

stop filter. So, above about

850 MHz its attenuation be-

comes small again. It has

IEC connectors and due to

that it is well prepared to be

added to the TV receivers

equipped with this type of

antenna connector. Some-

times some of signal dis-

tribution components are

equipped with this type of

connector and then SLTE 60

is a very convenient choice.

Finally, the SLTE 90 is

a low pass filter with ex-

tremely steep character-

istics. According to SPAUN

specification, SLTE 90 per-

formance is really the best

among these three models.

It has female F connectors

on both ends, so in most

applications you will have

to add an additional short

coax cable with male F con-

nectors to hook it up.

In order to test the filters,

we created a setup consist-

ing of a wideband noise

generator and a terrestrial

TV spectrum analyzer. We

took a number of screen

shots. We maintained the

same frequency span set-

ting so that you could see

the difference in the steep-

ness of filter characteristics

among the filter models.

As expected, both SLTE 60

and SLTE 90 had very sharp

roll-off while the SLTE 30

filter had a moderate one

(Figure 1 through 7).

Then, we measured all

the filters at the frequen-

cies for which their attenu-

ation had been specified by

SPAUN. We got results very

close to the manufacturer’s

data. We must note here

that in some measurement

points filter attenuation was

so deep that our TV analyz-

er was not able to measure

it accurately. For example,

our analyzer measured at-

tenuation “> 41.2 dB” at the

point where SPAUN specifi-

cation read 45 dB. Simply

our general purpose TV sig-

nal analyzer was not able to

measure characteristics of

high quality filter at points

of high attenuation. In this

case, we left 41.2 dB as a

measurement result but we

had a good reason to be-

lieve that indeed those 45

dB were achieved for SLTE

90 at 823 MHz.

In the graph, we present

the measurement results of

all three filters at the fre-

quencies at which we com-

pared their performance

with the specification. Also

here you can easily see the

difference among the filter

models. Please note though

that straight line interpola-

tion between the measured

values does not reflect actu-

al filter characteristics. The

purpose of those straight

line segments is just to

make it easier to identify

which measurement point

belongs to which filter mod-

el. The actual character-

istics are presented in the

analyzer screenshots.

Finally, we took the ana-

lyzer screen shots showing

all three filters response

in the full analyzer band-

width: up to 1 GHz. In these

pictures, it is clearly vis-

ible that the SLTE 60 is a

band rejecting filter while

the other two are low pass

filters. If you take a clos-

er look, you will also no-

tice that the SLTE 30 has

smoother transition from

pass band to stop band