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EchoLink @ PA3ABK
Echolink is a typical application which is not quite accepted within hamradio
world. Isn't confusing... no radio but still transmitting. Myself have still
my doubts but anyway I do run a so-called link, which connects the internet
user to the radiowaves. Using an old PYE MX294 for this purpose which has easy
access to several critical points inside. At least it gives others to do experiments
and decide for themselves whether is useless or not. Tendicy is that there are
more links and repeaters than users, which figures...
The interface is rather straight forward. Look
at the pdf-file here. Most of the diagrams are common. For long time I used
the vox option, but this had various disadvantages, the circuit delay can realy
build up! With the direct trigger from the squelch the QSO will be more interactive
than before. If you have a trx with a led indicating squelch open, just put
an optocoupler in series and you have the signal outside the transceiver. Adding
a 9V battery to give "high" on the DSR pin of the COM port and you're
in business. The battery will last for years and is cheap/quick solution for
galvanic separation. Note that the EchoLink volume indication will disappear
when using this option during "not qso" mode.
Echolink is also able to use a different soundcard. I purchased a cheap Sweex
soundcard. If you add an 2nd soundcard under Win 98 just try to have one with
a different soundchip. Cards with the same chip are sometimes not easy to get
going. XP can handle this well. SWEEX is using the CMI8738SX sound chip which
is rather deaf (everthing has it's price/value...). I had to put at least over
0,5V on the lineinput to get it full. A simple high gain three transistor amplifier
added some body to the sigs which I took just before the volumecontrol of the
isolating the
PC from the transceiver. I could have used an IC for it but I am one of those
who just use junkbox parts to get the job done. Circuitgain is rather high,
if you inject LF on the base of the 1st stage a 5mV will end up to at least
1V at the end. Due to the same junkbox I only had 1:4 transformers available
giving an additional boost. You can adjust it to your needs.
Other items, PTT control and line-in PC to input trx, are common, no comments.
Further I added some switches for my own convience, forced PTT, unable PTT,
which isn't taken up in the diagram.
JR6NJD has made a nice and simple if,
maybe I'll implement it too.
BTW diagram was made by a "free program" you will find at http://www.expresspcb.com/
When connecting PA3ABK-L you will NOT be announced on the frequency! You're ID will not be revealed until you do it by
yourself. In practice it proved that some collegues found it necessary to give test signals beyond any usefullness. So if you connect there is no announcement. Do note that there is a no-activity time out of 3 mins. There's no courtesytone, due this it will speed up the interact considerable
and locals don't even notice they are talking through the internet. Every
the 3 mins my call will be send out in morse at -18dB at a speed of 30 words/min. There is also no announcement if you disconnect. The system is only operational when I am around.
But do note I 'm not always listening in. Only when someone triggers the system from the frequency by DTMF it will interact with "ding" when connecting and "dong" when it disconnects. The connected station will be announced in speech.
The link in Dordrecht is fixed on 145.275. It's the local chat frequency, not
much of activity and in fact a good point to run EchoLink on. It will keep it
active. Antenna is SM7DVH homebrew at about 10m height, under normal circumstances
this will give a 10-15 km range for mobile
and over 40 km for fixed stations (pending
their height and antenna situation). Power is 10 Watts.
If don't have a charming voice you can get one from internet. http://www.cepstral.com/demos/ My favorite is Diane...
Type the text in, save it (.wav) and convert it to the format EchoLink likes. ( 8-bit, PCM, 8000 Hz, Mono format)