Vertex Standard FT-2800M Spezifikationen PDF herunterladen (Seite 4)

42 September 2010

board as shown in the lead photo. The ex-

ternal connections include a BNC antenna

jack, an SMA jack for optional external

clock, a USB jack, audio output and a 5 V

power jack. An 8-pin DIN jack provides I/O

connections for planned additional devices,

to include a front end amplifier/pre-selector

and a transmitter module.

The QS1R board has only three major

ICs — a 16-bit 130 megasample per second

(MSPS) analog to digital converter (ADC),

a Cyclone III FPGA and a microcontroller.

Table 2

Software Radio Laboratory QS1R, Rev D,

serial number 100027

Manufacturer’s Speciﬁcations Measured in the ARRL Lab

Frequency coverage: 10 kHz-62.5 MHz As speciﬁed.

Power requirement: 5-6 V dc, 1A. At 6 V dc, 900 mA (minimum volume);

910 mA (maximum volume).*

Modes of operation: SSB, DSB, CW, AM, As speciﬁed.

SAM, FM, WFM.

Receiver Receiver Dynamic Testing

Sensitivity: 0.63 µV SSB at 10 dB (S+N)/N. Noise ﬂoor (MDS), 500 Hz ﬁlter:

0.137 MHz –114 dBm

0.505 MHz –117 dBm

1.0 MHz –117 dBm

3.5 MHz –118 dBm

14 MHz –118 dBm

50 MHz –118 dBm

Noise ﬁgure: Not speciﬁed. 14 MHz, 29 dB

AM sensitivity: Not speciﬁed. 10 dB (S+N)/N, 1 kHz tone,

30%modulation, 6 kHz bandwidth:

1.0 MHz 8.13 µV

3.8 MHz 7.08 µV

50 MHz 8.80 µV

FM sensitivity: Not speciﬁed. For 12 dB SINAD:

29 MHz 2.51 µV

52 MHz 3.09 µV

Spectral display sensitivity Not speciﬁed. –123 dBm.

Blocking gain compression: Not speciﬁed. Gain compression, 500 Hz bandwidth:**

20 kHz offset 5/2 kHz offset

3.5 MHz 122 dB 122/122 dB

14 MHz 122 dB 122/122 dB

50 MHz 122 dB 122/122 dB

Reciprocal mixing (500 Hz BW): Not speciﬁed. 20/5/2 kHz offset: better than 122 dBc.

†

FM two-tone, third-order IMD dynamic range: 20 kHz offset: 29 MHz, 56 dB;

Not speciﬁed. 52 MHz, 57 dB.

Spurious free dynamic range: 112 dB. 100 dB.

S-meter sensitivity: Not speciﬁed. S9 signal at 14.2 MHz: 50.1 µV.

Squelch sensitivity: Not speciﬁed. 29 and 52 MHz, 0.6 µV.

IF/audio response: Not speciﬁed. Range at –6 dB points (bandwidth):

‡

CW (500 Hz ﬁlter): 302-800 Hz (498 Hz).

Equivalent Rectangular BW: 481 Hz.

USB (2.4 kHz ﬁlter): 73-2384, 2311 Hz.

LSB (2.4 kHz ﬁlter): 73-2383, 2310 Hz.

AM: (6 kHz): 72-2809 (one sideband;

5474 Hz for both sidebands).

Size (height, width, depth): 2.0 × 4.1 × 6.4 inches; weight, 14.1 ounces.

Price: QS1R receiver, $999.99; power supply, $19.99.

*Depends on amount of processing in use; 1.5 A when used with Skimmer Server software.

**Blocking level exceeds the threshold of ADC clipping.

†

No reciprocal mixing occurred up to ADC clipping (+4 dBm).

‡

Adjustable with DSP.

The controller and FPGA are initialized at

power up by the QS1RServer program run-

ning on your PC.

At the board level, the QS1R has several

interesting features you can use to go beyond

basic ham applications. With a minor board

modification, you can clock the ADC, which

normally runs at 125 MHz, from an external

source at any frequency between 1 and

130 MHz. This lets you sync the receiver to

an external frequency standard if you need

high accuracy or stability. Even with the stan-

dard internal clock, a software adjustment

allows you to precisely zero beat WWV or

other frequency standard.

Frequency Aliasing

When an SDR samples the input at

125 MHz, you would want a low pass filter

at the radio’s input to reject any signal above

about 62.5 MHz, the Nyquist frequency.

Without the filter, any signal above

62.5 MHz will be aliased into the 0-

62.5 MHz “baseband.” The ADC operates

like a mixer with a local oscillator (LO) at

125 MHz and harmonics of 125 MHz.

The QS1R’s input low pass filter is rela-

tively flat up to 62 MHz and falls off by 20 dB

at about 75 MHz. The good news is that you

can receive signals up to 62.5 MHz with full

sensitivity. The bad news is that signals (and

noise) at a frequency, f, between 62.5 MHz

and 125 MHz, may be visible at an apparent

frequency 125 – f MHz. For example, the

FM broadcast band limits 88 and 108 MHz

alias to 37 and 17 MHz, respectively. At the

ARRL Lab, we verified that many strong

local FM stations were clearly received in

the 17 to 37 MHz range when we connected

to a GAP Titan vertical antenna. They were

attenuated but might cause you problems

above 18 MHz.

Frequency aliasing can be used to your

advantage, but you may have to provide your

own bandpass filter. You can make a small

board modification that bypasses the input

filter and lets you receive up to 300 MHz

or higher in segments of 62.5 MHz. The

SDRMAX-II software supports this “un-

dersampling” mode and provides the right

frequency scale readings.

This receiver provides the demodulated

audio on a stereo phone jack, suitable for

headphone listening or passing to your PC’s

soundcard input. Getting your audio this way

(instead of over the USB connection to your

PC) gives you flexibility and minimal time

delay, but it complicates the picture if you

want to use the receiver remotely over a LAN.

You would have to find a way to transmit the

audio separately from the data channel.

The QS1R always samples the entire band

from 10 kHz to 62 MHz, and you can display

a chunk of spectrum as small as 40 kHz or as

wide as 20 MHz. After filtering in the FPGA,

a digital output stream of up to 4 MSPS is

output from the receiver to your PC.

Software

Two separate programs run on your

PC to support the receiver. QS1RServer

talks with the receiver hardware, and loads

the receiver’s microcontroller and FPGA

The Nyquist frequency (half the sampling rate)

is the highest signal frequency that can be

accepted without aliasing. See en.wikipedia.

org/wiki/Nyquist_frequency.

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