Microbit RRC-1258 MkII(s) Bedienungsanleitung PDF herunterladen (Seite 7)

Datamodes

Whilst not supporting error detection or correction, PSK31 is self-

synchronising. It is very good at working through noise, indeed it is

copyable by a computer when it is too weak to detect by ear. It has a

high duty cycle though, which can easily lead to overheating if a trans-

ceiver is run at full power. Consequently it is advisable to run equipment

at a significantly lower power level than its maximum. 30 watts is consid-

ered by many to be more than sufficient on the HF bands.

On air, PSK31 sounds like a pulsating high-pitched whistle. Tuning

and frequency stability are critical for correct operation.

Olivia

This data mode was designed by Pawel Jalocha, SP9VRC, to work

effectively over difficult radio paths, i.e. those suffering from fading,

interference, auroral distortion, flutter, etc. It can work when the signal is

10-14dB below the noise level, which means that worldwide communica-

tion is possible using low power.

Olivia has 40 possible formats, this being brought about by the fact

that eight possible numbers of tones can be transmitted in five possible

bandwidths. There can be 2, 4, 8, 16, 32, 64, 128 and 256 tones, and

bandwidths of 125, 250, 500, 1000 and 2000kHz. All these combinations

result in differing characteristics and capabilities. The ‘standard’ formats

(bandwidth/tones) are 125/4, 250/8, 500/16, 1000/32, and 2000/64, while

the formats most commonly used (in order of use) are 500/16, 500/8,

1000/32, 250/8 and 1000/16. Data throughput is just under 60 words per

minute at 1000/8.

The basic code used is 7-bit ASCII and Olivia works by sending

characters in blocks of five over the course of two seconds. Multi

Frequency Shift Keying (MFSK) is employed, with Forward Error Cor-

rection (FEC).

Packet Radio

Packet Radio is a datamode used for sending text messages. It is a

time division multiplex system, so more than one contact can take

place on one frequency at a time. It also includes full error correction.

These two facets resulted in the creation of a worldwide network that

supports real-time QSOs and non-real-time contacts via mailboxes. The

former is akin to Instant Messaging used across the Internet, while the

latter is akin to e-mail, but they were both in widespread use by radio

amateurs before many members of the general public had Internet

access. On HF, Packet is transmitted at 300 Bauds, while on VHF the

rates used are 1200 and 9600 Bauds.

Data is transmitted in frames, which contain a start flag, an ad-

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Microbit RRC-1258 MkII(s) Bedienungsanleitung Seite 7