[WriteLog] codec performance, isolation transformers

[Barry N1EU]

I find the mpeg3 16kbps/11khz 16bit mono encoder under WinXP provides 
excellent playback with weak signals and very efficient file size 
compression (~7MB/hr ?).  I assume it was installed with the OS/Media Player 
but I also installed CoolEditPro and that might have provided the codec.

IMHO, RS isolation xfmrs are fine.  A while back I did frequency sweeps of a 
few xfmrs, and unless you're doing hifi ssb and need the very lowest 
frequencies, the RS xfmr does a good job.  I notice no distortion products 
with them.  If you want to take a step up, I recommend the xfmrs that W2IHY 
sells for $10.

73,

Barry N1EU
www.n1eu.com

>From: "Eric Scace  K3NA" <eric at k3na.org>
>Reply-To: eric at k3na.org
>To: "'WriteLog Reflector'" <writelog at contesting.com>
>Subject: [WriteLog] codec performance, isolation transformers
>Date: Tue, 18 Feb 2003 07:36:39 -0500
>
>CODECS:
>
>    There is a bewildering array of codec choices around.  As a HF/MF 
>contester and DXer (CW, SSB and RTTY), I would like to be able
>to listen to a contest or DXpedition recording and have a good chance of 
>hearing that extremely weak station who was responding to
>me while other nearby enormous signals were still calling.  This ability to 
>handle a large dynamic range seems pretty demanding...
>
>    Does anyone know of an authoritative site containing comparisons on the 
>technical performance of various codecs?
>
>ISOLATION TRANSFORMERS:
>
>    The WL help files suggest using the small Radio Shack isolation 
>transformers.  They work pretty well for RTTY signals at
>2125/2295, but others have pointed out that performance in the lower 
>frequency range is less than good with lots of distortion
>products.
>
>    A search of Mouser Electronic's catalog shows conventional audio 
>isolation transformers are in the $50/each level.  That adds up
>to serious money quickly.
>
>    Confessing now to the fact that I am not an audio engineer, could 
>someone more experienced in these matters suggest an approach
>to choosing audio isolation transformers that introduce a minimum of 
>impairments to receiver and transmitter audio?  My application
>is pretty typical for a WriteLog-equipped contest station:
>    -- computer with 2 soundcards.
>    -- W5XD Multi+ keyer for SO2R operation.
>    -- two transceivers, with ~1mW line-level audio input to the 
>transmitter... and separate line-level audio output, speaker, and
>headphone outputs.  For my particular transceiver of the moment, the 
>headphone and speaker audio are from the same source.
>
>    Thanks.
>
>-- Eric K3NA
>
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