> On 8/20/06, KV9U <[EMAIL PROTECTED]> wrote: > If you were to try and send an ALE call to several > different frequencies over a short span of time, how do you > insure you are not QRMing someone? > How are you able to listen for a frequency already being > in use
Hi Rick, ALE is a channel-based system, and receive-scanning the ALE channels is part of the basic foundation of it. ALE receivers scan through all the ham band ALE channels every 30 seconds or so, listening for less than one second per channel. Sometimes hams also use ALE on only one band, or on a few bands. It is compatible with any variety of multi-band, single band, or selected bands, including single-channel use. When initiating a call, it can take as little as a minute or as much as 20 minutes for the ALE to go through every ham band in an effort to link with any amateur station that is scanning all ALE channels. The actual time it takes depends upon a lot of different factors... and waiting for another QSO to finish is one of those factors that can delay the ALE call on any given channel that is busy. But, fortunately there are several ALE channels in each ham band, so that increases the likelyhood of a free channel to call on. Amateurs have developed a different ALE programming and operational method specifically tailored for QRM avoidance and compatibility with the wide variety of the amateur HF QSO environment, aimed at mitigation of both received and transmitted interference. While QRM avoidance is not perfect with any ham radio system, hams have evolved ALE operational methods for the past 5 years to a very good level. Currently, a combination of 5 "anti-QRM" methods are used in Amateur ALE: 1. Manual operator monitoring and initiatiation of ALE calls. Individual Calls or Net Calls can be made by operators while listening on any of the designated ALE channels. It is easy for operators to incrementally select a specific band and channel manually if they like, just by tapping through the channel list, and listening to the radio by ear. An ALE-assisted call, or a sequentially scanning call for the desired station can be made if it has not been heard within the past few hours on any channel. 2. Internationally coordinated channels. ALE channels are internationally coordinated, similar to the way SSTV, Digital Voice, and APRS are. Constant use of the same frequencies over the past 5 years, combined with "formal" frequency coordination with bandplanners of 3 IARU regions, various national organizations, and internet group and website listings. 3. Automated subband pilot channels. There are several amateur ALE channels on every band, but only one "pilot" channel per band, per IARU region (commonly called a "sounding" channel by ALE ham ops). The pilot channels are within the internationally recognized "automated station sub-bands" of national and regional bandplans, where available. 4. Short time duration of signals with low duty cycle per hour. The short ALE station identification bursts can be sent on the pilot channels, generally repeating about once every hour or so, and the bursts average less than 30 seconds for every 3600 seconds of channel time. 5. Busy detection with wait/re-check and postponed signalling. If the ALE detects the pilot channel or desired calling channel is busy when it wants to transmit a regular hourly station identification or a specific call, it can skip over that channel and come back to it 5 or 10 minutes later, and then transmits when clear. 73---Bonnie KQ6XA . Need a Digital mode QSO? Connect to Telnet://cluster.dynalias.org Other areas of interest: The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/ DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy discussion) Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
