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FLARQ?

Discussion in 'General Technical Questions and Answers' started by KF6NFW, Aug 17, 2010.

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  1. KF6NFW

    KF6NFW Ham Member QRZ Page

    What is flarq and how do I use it?
    I recently started to get more involved with digi modes (MT63) and found this as a sub folder in the download. I opened it and started to lok at it, but it isnt making much sense to me. it almost looks like an email typeitem.
    Any help would be great though!
     
  2. K0RGR

    K0RGR Premium Subscriber QRZ Page

    I haven't played with it yet, myself, but FLARQ is a utlility for FLDIGI that gives it error-free capability for sending messages and data files. This is part of an EMCOMM system called NBEMS. http://www.w9tca.com/NBEMS
     
  3. N4UM

    N4UM Ham Member QRZ Page

    FLARQ, along with FLDIGI is part of the NBEMS suite of programs. Flarq is designed to be used in conjunction with Fldigi to send error-free messages. (It runs at the same time as Fldigi.) It is NOT a conversational keyboard mode. In fact, it is not a MODE at all. It can function running MFSK or PSK etc...any mode that does NOT have a long latency.

    Flarq is typically used to transmit a text file - such as a list of needed supplies, or a list of disaster survivors etc. - where 100 percent accuracy is needed. It does this by transmitting blocks of text along with a checksum. The receiving station computes a checksum on the received block and is thus able to verify whether or not it has been received without error. If an error has occured, the block is resent until it is received correctly. The art in using Flarq lies in selecting the best mode to use and the blocksize to use depending upon conditions.

    Under good condtions psk128 might be a good mode to employ with a block size of 256. Under very poor conditons MFSK 16 or MFSK 8 using a block size of 16 might be appropriate. Olivia, though it is an excellent weak signal mode, is not used with Flarq because of its long latency.

    I was involved in some of the early testing of Flarq in South Florida at the height of the QRN season on 80 meters. Using NVIS strategy I was able to use Flarq to exchange error-free text files using MFSK16 quite reliably over distances of 2-300 miles while running 5 watts or less.
     
  4. KF6NFW

    KF6NFW Ham Member QRZ Page

    I dont know that I would call Farq an Emcomm tool so much as I would call it just another tool available.
    I do emcomm work all over the country, and find it difficult to justify any mode or tool as being just an em comm item. I can see use for it outside of em-com work as well.
    My wife and I like to also storm chase, not exactly an em-comm thing, but certainly there is time when it would be nice for sending messages that dont need to go over the air in a recognizable format like voice! There is nothing good about announcing a tornado is heading for a particular community and have it over reacted to before the report is official. Besides there are times when we may have a side conversation that doesnt need to be put over the voice channels either as there are other users.

    However with all that said, I could see its use in a disaster as well. we just completed a state wide drill this last weekend, and though we used MT63 on FLDIGI I didnt see any problems other then I was accused of having low audio!
    So I guess this leaves me to conclude this is just another tool inside an already simple operation. Does it allow me to be user specific, or is this just as readable as the rest of the digi modes?
     
  5. AG3Y

    AG3Y Guest

    Think of the name flARQ with the ARQ being emphasized. My understanding of the mode is that it adds ARQ handshaking to some of the popular short turnaround programs such as have already been mentioned in the above posts.

    Back when AMTOR was popular, the protocol had two modes FEC ( forward error correction ) and ARQ ( ack request ) In ARQ mode, you link to one station, and set up a handshaking "dialog" between yourself and the linked station. As you send small packets of the text to the other station, you drop back to receive periodically to listen for the other station to send an "ack" ( I received that packet OK ) or a "nac" ( I did NOT receive that packet correctly ) . If the handshake is an "ack" you go ahead and send the next packet. If it is a "nac" you repeat the last packet until you get the "ack" for that packet. This goes on until the message is received correctly, or until the link drops, due to to many retries, or due to a loss of signal path between the two stations.

    That is pretty much how I remember it working.

    Hope this is right, and helps. 73, Jim
     
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