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Joe Della Barba wrote:
<blockquote cite="mid:28EB74E720B7491AAF207EC19F1D3023@UPSTAIRS"
type="cite">
<pre wrap="">I have a SSB on my boat set up for PSK31.
What do I need to do PSK83 APRS?
73 de N3HGB
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<br>
Full details here:<br>
<br>
<br>
<pre wrap=""> <a class="moz-txt-link-rfc2396E" href="http://wa8lmf.net/APRS_PSK63/index.htm"><http://wa8lmf.net/APRS_PSK63/index.htm></a>
</pre>
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<blockquote cite="mid:28EB74E720B7491AAF207EC19F1D3023@UPSTAIRS"
type="cite">
<pre wrap="">
[Posted from Iowa City, IA Motel 6 via WiFi from another motel about 1/3rd
mile away, using my "WiFi Super Blaster" DX antenna.]
Stephen H. Smith wrote:
</pre>
<blockquote type="cite">
<pre wrap="">I'm now on the fourth day of my cross-country trip, experimenting with
30-meters HF APRS over PSK63.
</pre>
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<pre wrap=""><!---->
Today I have noticed a number of STRONG PSK63 signals that simply
don't decode at all. These signals appear rather wide, and lack the
characteristic vertical double-line "railroad track" in the middle of the
waterfall spectrum display. They appear to be PSK transmissions with
excessive TX audio levels (or attempted RF power output), that creates
intermodulation distortion in the transmitter.
I have just added the paragraphs below to my PSK63 APRS page at:
<a class="moz-txt-link-rfc2396E" href="http://wa8lmf.net/APRS_PSK63"><http://wa8lmf.net/APRS_PSK63></a>
------------------------------------------------------------------------
IMPORTANT: PSK63 is a simultaneous two-frequency transmission, unlike
conventional FSK packet or RTTY which are single-tone-at-a-time constant
power transmissions similar to key-down CW.
*It is essential to keep the _average_ output power of the SSB transmitter
far below maximum in the PSK mode, to avoid severe inter-modulation
distortion (IMD) of the transmitted signal. *
High IMD will make your signal occupy excessive bandwidth on the air, and
worse make it unreadable to others, even if the RF level is strong.
If the transmit level is PROPERLY SET, the PSK63 signal will be received
without errors, even on signals too weak to move the S-meter.
1. Disable any speech processors, limiters or compressors in the
transmitter audio chain.
2. If you are reading transmitter output power on an averaging-type
wattmeter, you must adjust the soundcard audio level (or
transmitter mic gain) for an indicated power of about 1/3rd of the
keydown maximum power on CW or FM. You should NOT be showing any
ALC (automatic level control) voltage which would indicate that
you are at or trying to exceed maximum transmitter power output.
3. If you are reading power output on a PEAK reading wattmeter (or
monitoring the TX signal on a scope), gradually increase the
soundcard output level (or transmitter mic gain) until the power
output stops increasing. Then turn the level back down a bit
until the output drops about 20%. This will ensure that you are
not saturating the transmitter power stages.
------------------------------------------------------------------------
--
Stephen H. Smith wa8lmf (at) aol.com
EchoLink Node: WA8LMF or 14400 [Think bottom of the 2M band]
Skype: WA8LMF
Home Page: <a class="moz-txt-link-freetext" href="http://wa8lmf.net">http://wa8lmf.net</a>
NEW! *** HF APRS over PSK63 ***
<a class="moz-txt-link-freetext" href="http://wa8lmf.net/APRS_PSK63/index.htm">http://wa8lmf.net/APRS_PSK63/index.htm</a>
Universal HF/VHF/UHF Antenna Mounting System
<a class="moz-txt-link-freetext" href="http://wa8lmf.net/mobile/UniversalAntMountSystem.htm">http://wa8lmf.net/mobile/UniversalAntMountSystem.htm</a>
"APRS 101" Explanation of APRS Path Selection & Digipeating
<a class="moz-txt-link-freetext" href="http://wa8lmf.net/DigiPaths">http://wa8lmf.net/DigiPaths</a>
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</pre>
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