• Detección de señales débiles • Identificación de todos los satélites ...

xn..tele.satlite.ieb.es

• Detección de señales débiles • Identificación de todos los satélites ...

FEATURE

Actualización para los Medidores de Satélite 8dtek

Diagrama de

cascada para los

medidores de

• Detección de señales débiles

• Identificación de todos los

satélites activos

• Permite la alineación de la antena

muy precisa

• Medidas a largo plazo para el

descubrimiento fiable de enlaces

• Actualización ideal para los

medidores de satélite 8dtek

Satélite 8dtek

232 TELE-satellite International — The World‘s Largest Digital TV Trade Magazine — 12-01/2012 — www.TELE-satellite.com www.TELE-satellite.com — 12-01/2012 — TELE-satellite International — The World‘s Largest Digital TV Trade Magazine 233


FEATURE

Upgrade for 8dtek Satellite Meters

Unconventional thinking

turns 8dtek satellite

meters into genuinely

professional tools – without

costing a penny!

Vitor Martins Augusto

Satellite meters and satellite finders

are used to professionally align satellite

antennas and to identify flaws in an existing

setup. True satellite enthusiasts,

however, also have additional purposes

for meters: Satellite DXers are permanently

on the hunt for weak or rare

signals, while feed hunters are on the

lookout for undocumented transmissions

(feeds).

Both target groups prefer satellite

meters with spectrum analyzers, because

with the help of a satellite spectrum

it becomes possible to spot a satellite

long before a satellite receiver is

capable of locking a signal. In addition,

a spectrum display helps to identify and

analyze transponders. It is even possible

to find out whether new transponders

have become active at short notice,

which in many cases hints at new feeds.

Real-time spectrums are the display of

choice for those satellite enthusiasts,

as they have a refresh rate of way less

than one second.

Hence it’s no surprise that in recent

months a number of new satellite meters

with spectrum analyzer have been

launched. These analyzers are designed

to display the current signal situation

– but what do you do if you need

to monitor a specific signal for a certain

length of time This may be necessary

when you rotate a motorised antenna,

for manually aligning an antenna or for

performing a long-term measurement.

In ham radio circles a so-called waterfall

diagram is used for exactly those

purposes: It shows the spectrum over a

period of time using the three parameters

of frequency, signal level and time.

This would actually require a three-dimensional

diagram, something that can

only be achieved with great effort. In

order to display all required information

without having to do 3D calculations,

one parameter (signal level in our case)

is colour-coded.

So in a waterfall diagram the x-axis

refers to frequency and the y-axis

shows time as well as – in a gradual colour

scheme – signal level. A waterfall

diagram is drawn up line by line from

top to bottom, with each line describing

a full spectrum. Actually, this is how the

name was derived: Like in a waterfall,

information flows from top to bottom.

We wanted to provide proof that a

waterfall diagram can actually work for

satellite meters as well and to that end

we used three different 8dtek satellite

meters: Xtra-S, Gifted and Desired

(please refer to TELE-satellite issues

06-07/2011 and 08-09/2011 for test

reports about these devices). They are

absolute exceptions in their price segment

as all of them offer a functional

spectrum analyzer.

It’s rather striking to discover that the

manufacturer decided to focus on either

speed or display resolution: While

the 8dtek Xtra-S boasts a real-time

spectrum display – albeit at low resolution

– the Gifted and Desired models

impress with high-resolution displays at

the cost of display build-up time.

All three models feature a video out-


Image 1: The three satellite meters Desired, Xtra-S and Gifted from

manufacturer 8dtek were at our disposal for experimenting.

1

234 TELE-satellite International — The World‘s Largest Digital TV Trade Magazine — 12-01/2012 — www.TELE-satellite.com


2

6

3

4

put which creates a composite video

signal of the spectrum display.

We took advantage of that option to

save the video signal on our PC with

the help of a video card, and to extract

spectrum measurements using image

processing software in order to further

work with the data.

All you need for this is a so-called

video grabber, which is an adapter that

digitises the analog video signal and

creates a file for further software processing.

In theory, any TV card or USB

adapter should do – USB adapters are

frequently available in a bundle with

video editors to digitise VHS tapes. You

may even want to look for the ‘EasyCap’

adapter on eBay, which we were able to

obtain from Hong Kong for about EUR

5.00 including postage (see image 2).

For our experiment we proceeded

with programming software that converts,

analyses and extracts the spectrum

using a video grabber, so that

data can be displayed as a waterfall

diagram. TELE-satellite readers can

download the software free of charge

(www.TELE-satellite.com/waterfall-for-

8dtek.zip) so that users of any of the

three 8dtek meters can add waterfall

capability to their devices.

this is shown with a time element and

since it is always possible to compare

any current value with preceding values

finding the perfect alignment becomes

child’s play. In the lower image

segment you can easily see for yourself

how strong the signal is with perfect

antenna alignment.

For real-time measurement the 8dtek

Xtra-S turned out to be a perfect companion.

The spectrum builds up very

quickly on this meter, which is a huge

benefit. Unfortunately, however, the

display resolution is rather low, as can

be seen on images 3 and 4. 8dtek went

for higher resolutions with their Gifted

and Desired models, although at reduced

speed. This is why those two

models cannot be used for creating waterfall

diagrams to document antenna

alignment and rotation. For long-term

measurement, on the other hand, they

are perfect. Such measurements are

primarily performed to find out if or

why a signal has occasional errors.

Image 6 presents the result of a

long-term measurement focusing on

two transponders on HISPASAT. No errors

can be seen on this measurement,

since only a period of one minute was

analysed. With our software it is of

course possible to vastly extend that

period – all you need to do is select a

time between one second and ten minutes

instead of real-time. If you select

ten minutes, for example, every line

of the waterfall diagram corresponds

to a spectrum measurement after ten

minutes each. This allows documenting

the entire frequency range of a satellite

over a period of 24 hours. The individual

colours indicate any signal deviation

across the entire spectrum.

Looking at the Xtra-S, Gifted and Desired

satellite meters by manufacturer

8dtek from many different perspectives

our respect and admiration for those

neat devices was growing all the time.

It’s hard to believe how many features

and functions can be packed into such

small meters. Battery life also never

failed to impress: Three to four hours

Image 2: This EasyCAP video grabber was

bought on eBay for approximately 5 EUR.

Image 3: The waterfall diagram shows

changes during rotation of a motorised

antenna from 30.0W to 45.0E. All satellites

between these two stop positions are

clearly indicated.

Image 4: Fine-tuning of the antenna

alignment towards HISPASAT 30.0W.

Image 5: Long-term measurement of

ASTRA 19.2E using the Desired satellite

meter. This is where the device’s highresolution

display comes to the fore.

Image 6: Long-term monitoring of two

transponders.

Image 7: Set-up with small motorised

antenna. Due to lack of DiSEqC 1.2

support of the Xtra-S it was rotated using

the button on the motor itself.

5

Waterfall diagrams can be hugely

useful: After a short adjustment period

we discovered a number of scenarios in

which waterfalls diagrams can be put to

fruitful use. Have a look at image 3, for

example, to find out how our motorised

antenna moves from HIPASAT 30.0W to

INTELSAT12 45.0E. The waterfall diagram

shows all passed satellites, which

is an easy way of checking whether all

positions are already stored in the satellite

receiver.

Image 4 shows a rather different application

for a waterfall diagram. In this

scenario the antenna alignment (HIS-

PASAT 30.0W in our case) is optimised.

While a conventional spectrum display

can be used to perfectly align an antenna

using the peak level feature, a

waterfall diagram can achieve the same

result with much less hassle.

Seen from top to bottom the weak

red colours show somewhat mediocre

reception quality of HISPASAT. When

the antenna is moved slightly towards

the East the signal becomes weaker,

which is why the antenna is then rotated

in the opposite direction with the

signal becoming stronger, reaching its

peak level and decreasing again. All

7

236 TELE-satellite International — The World‘s Largest Digital TV Trade Magazine — 12-01/2012 — www.TELE-satellite.com www.TELE-satellite.com — 12-01/2012 — TELE-satellite International — The World‘s Largest Digital TV Trade Magazine 237


of continuous use was the rule rather

than the exception.

Have we raised your interest Simply

go to www.TELE-satellite.com/waterfall-for-8dtek.zip

to download our software

from the TELE-satellite server. Of

course you also need an 8dtek satellite

meter as well as a TV card or USB video

grabber.

Once the software is set up you first

need to select your video source (image

8). In the window that pops up you

choose your TV card or the video grabber.

Please bear in mind that many laptop

computers will also list the built-in

camera here.

Next, you select the video format

(image 9). Depending on the TV card

or video grabber various options may

be available; the only thing you need to

make sure is to select 720x576 pixels

(full PAL resolution). The software does

not support any other resolution! Some

8 9

video grabbers may not be set up for

PAL by default, but for NTSC or SECAM

instead – in such cases you need to

run the software that comes with your

video grabber and change to PAL video

mode. Finally, you select your 8dtek

model (image 10) and press START to

initiate the waterfall diagram. Due to

implementation of the video function

you need to press STOP if you want to

copy the image using PRTSC.

Happy experimenting!

10

Image 8: Selecting video

source.

Image 9: Selecting video

format.

Image 10: Selecting

8dtek model.

Image 11: Second test

set-up, this time using a

netbook and the Desired.

Long-term measurement

tests were carried out

with this equipment.

11

238 TELE-satellite International — The World‘s Largest Digital TV Trade Magazine — 12-01/2012 — www.TELE-satellite.com

More magazines by this user
Similar magazines