from K3UK's HF-APRS YahooGroup.
---------- Forwarded message ---------- From: oe3mzc <[EMAIL PROTECTED]> Date: Dec 18, 2007 4:22 AM Subject: [HF-APRS] Frequency accurracy tolerance tnc? main problem for HF-APRS shortwave ? To: [EMAIL PROTECTED] many tncs for 300baud FSk packet radio used for APRS on hf only decode within a very narrow frequency window of abt. +-30Hz. (KAM, MixW, AGWPE, PK232,SCS PTC-2,TNC-2 etc..) This is very difficult to adjust and represents the main reason for failure in decoding hf-aprs signals. To my knowledge there is only one hardware that could cope with frequency drift in a much better way: a DSP-TNC from SCS see: http://www.scs-ptc.com/datasheets/scs_datasheet_tracker_english.pdf This DSP modem can simultaneously decode multiple signals in a bandwith of up to plus/minus 400Hz around an adjustable center frequency, e.g. all signals with a 800Hz bandpass will be decoded. When connected in AX25 to two stations at same time, the tnc will even adjust its own transmitted qrgs according to the two partners and their individual offset automatically. The most helpful feature however is the frequency readout. the comand <ESC> %M <enter> will display a Mheard list with offset frequencies. This can be used to for tuning. example from 30m APRS channel in Europe: * %m * DIRECTLY RECEIVED HF-PR STATIONS: WIDE3 -15 Hz, DM5LW +25 Hz, OE3MZC-9 -25 Hz, OE3XMU -25 Hz DF5WXF-2 +25 Hz, F4CKT +25 Hz, F6KPH-4 +18 Hz, DF4FO -25 Hz DF4FO-3 -25 Hz, SR3NWY -25 Hz, DB0CHV +0 Hz, SL5ZL -25 Hz F5ZQC-4 +25 Hz, WIDE5 -25 Hz, G0JXN-10 -3 Hz, RA3IM -6 Hz F5LEB +0 Hz, TRACE3 +0 Hz, F6KCF-10 +0 Hz, TRACE2 +0 Hz EA6XQ -6 Hz, EA6XQ-5 +25 Hz, RELAY -6 Hz, UA1WCF -28 Hz HB9CGH-4 +0 Hz, UA1WCF-2 -25 Hz, WIDE7 +25 Hz, F5KCN-3 +25 Hz WIDE2 +0 Hz, G7EOB-7 +0 Hz, G0IQK-10 -25 Hz, MB7UJ +0 Hz * AA1XD -25 Hz, W1JMC -50 Hz *OZ4DX -43 Hz, W1ON -6 Hz, EA6AFM +0 Hz, OK2PEN -28 Hz, EC2A-1 +25 Hz, EB2EMZ-8 +25 Hz, 73 de Mike, OE3MZC
