Rigol USB-GPIB Adapter Uživatelský manuál stáhnout pdf (Strana 3)

QST

– Devoted entirely to Amateur Radio www.arrl.org February 2013 57

Frequency (MHz)

80 Meter Band-pass Filter Test

Tracking Generator Level = -20 dBm

0 3.0 6.0 9.0

-100

-80

-60

-40

-20

Response (dB)

QS1302-Prodrev05

Figure 3 — Bob Allison, WB1GCM (in the white coat), checked the spectral purity of

handheld radios for visitors at the ARRL National Convention at Paciﬁcon last November.

Most radios met FCC requirements, but there were a few surprises.

Figure 4 — The

DSA815-TG’s built-in

sweep generator is

handy for testing ﬁlters.

Here is the frequency

response of an

80 meter band-

pass ﬁlter.

Figure 5 — This chart was made by saving the

data from the ﬁlter sweep shown in Figure 4 to

a CSV ﬁle, which was then imported into DPlot

graphing software to take a close look at the

ﬁlter’s response from 1 to 10 MHz.

In the Field

Our DSA815-TG was quickly pressed into

service at the ARRL National Convention at

Pacificon in Santa Clara, California, last

October. There, yours truly set up a booth

with the Rigol spectrum analyzer, power and

step attenuators, and a Bird 43 power meter

(Figure 3). I tested hundreds of VHF and

UHF handheld transceivers, each owned by

a ham eager to see if his or her unit met the

FCC spectral purity requirements (Part

97.307e). The Rigol never skipped a beat

during the entire event, unlike some of the

handhelds I tested that didn’t make the

grade. The LCD screen was easily seen by

all who visited my booth, despite the bright

overhead fluorescent lighting.

In the ARRL Lab

Back at the ARRL Lab, I put the

DSA815-TG through its paces, performing

some of the same tests I normally do

for transceiver testing. I also found the

DSA815-TG’s tracking generator very use-

ful while sweeping some of the band-pass

filters I use during amplifier tests. Figure 4

shows the response of a band-pass filter with

the tracking generator level set to –20 dBm,

with a start frequency of 0 MHz and a stop

frequency of 30 MHz. I was then able to use

the storage function to transfer a CSV file

(comma separated values with the X and Y

axes) of the band pass filter plot to a flash

drive. From that file, I used DPlot plotting

software to create the chart shown in Figure

5. Look closely: our filter has an attenu ation

smallest resolution bandwidth setting avail-

able versus the amount of swept frequency.

More Features

The DSA815-TG has the ability to search

and display the input signal of an unknown

frequency by pressing the AUTO button. I did

this repeatedly with a handheld transceiver

connected through an attenuator and sure

enough, the carrier would appear in the cen-

ter of the screen and with the signal level

auto scaled. I also connected a VHF/UHF

ground plane at the input and pressed the

AUTO button. Not surprisingly, the DSA815

showed local FM broadcast stations to be the

strongest received signals at our location.

Most spectrum analyzers have a headphone

jack, and the Rigol has one too. This allows

the user to hear AM or FM analog stations

via a headphone jack while using a demodu-

lator. After some adjustments, I got the Rigol

to play music from an FM broadcast station,

but the audio was disappointingly low.

I did encounter a problem when adjusting

resolution bandwidth, frequency span and

demodulation time in rapid succession

of 5 dB at 4 MHz and will attenuate a signal

at the high end of the 75 meter band (that’s

good to know!).Though our own HP 8563E

spectrum analyzer does not have the tracking

generator option, I used our analyzer and our

IFR 2040 signal generator to measure the

same band-pass filter at several frequencies;

the measurements were virtually the same as

those made with the Rigol DSA815-TG. For

basic measurements, it appears the Rigol

unit does just about everything a more ex-

pensive spectrum analyzer can do within its

frequency range. The more expensive instru-

ment will have a greater frequency range and

will have better resolution while looking at

chunks of spectrum spanning 1 MHz or less.

That translates to more data points along the

spectrum. Table 3 compares the capability of

the DSA815 and HP 8563E, showing the

1 2 3 4

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