Re: ARLA/CLUSTER: Nova modalidade digital em 13 kHz obtém sucesso nas comunicações transatlânticas

[Carlos Pinheiro]

13 KHz ??? ou 136 ?

73 de CT1PT



No dia 6 de Janeiro de 2012 12:09, João Gonçalves Costa <joao.a.costa  ctt.pt
> escreveu:

> New data mode crosses Atlantic on 136Khz at the first attempt****
>
> ** **
>
> Running no more than 400 watts to a 12 meter top loaded vertical , with a
> carrier frequency of 137.5 Khz, estimated ERP of no more than 250 mW, Gary
> G4WGT using the new ‘OPERA’ data system successfully transmitted a signal
> to Joe VO1NA, at a range of 3500 Km . ****
>
> Joe completed Six decodes of Gary’s full call in a period of 2 hours, the
> first being at 21:43z, unexpectedly early in the night. ****
>
> ** **
>
> In contrast, using the established very slow cw QRSS and visual spectrum
> decoding, at QRSS 60, the call sign "G4WGT" will take 54 minutes to send,
> and would need to be visible on the plot. The 136KHz version of Opera
> taking only 8 ,or 31 minutes at enhanced s/n performance , the 500 Khz
> coding taking 2 or 15. Minutes****
>
> ** **
>
> The OPERA mode was envisaged by Graham G0NBD, as a way of providing data
> operations for stations who had only the capability of CW operation, to
> date, all data modes required the modulation of the transmitted carrier,
> either by frequency, phase or amplitude changes. This was to only use
> off/on keying.****
>
> ** **
>
> Outlining the idea to J Ros, EA5HVK author of the now established ROS Data
> mode, Jose Ros, after some email exchange’s, in turn took on the coding of
> the mode, using DSP techniques he had refined during the development of the
> ROS data mode and produced a complete windows compatible Tx/Rx package with
> internet spotting and chat facility, with com-port keying and audio tx
> drive. Far exceeding the original ‘idea’!****
>
> ** **
>
> Initial testing was conducted on the 500Khz experimental band, with G0NDB
> and G4WGT, later other stations joined the test group and Gus SM6BHZ made
> successful 136 transmissions using the then OP65 mode.****
>
> ** **
>
> Opera encodes the data and keys the transmitter with a sequence of
> variable length ‘dots and dashes’ extend out along a time line, with
> surprising results, the 2 minute version achieving a s/n performance
> similar to the established WSPR system and the longer versions are capable
> of many dB’s lower.****
>
> ** **
>
> Reception is facilitated in the normal ‘data’ way of taking audio from the
> receiver and decoding with software, decoding may take place with up to 33%
> data loss , development continues at a pace and the most up to date info
> can be found http://groups.yahoo.com/group/O_P_E_R_A_/, OPERA is now
> listed as a mode on the PSK-Reporting map****
>
> ** **
>
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>


-- 
Carlos Pinheiro
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