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RE: Anybody can Help me????



Bob, if he is using the IFD board, he will not have widened the bandpass of the radio 
when used on normal 9k6 or FM voice operation.  The IFD board in just inserted in the 
1st IF circuit to "sniff off" a bit of the output of the first IF stage while still 
passing the same signal through a unity gain amplifier, on the IFD board, on to the 
normal xtal filter following the first IF stage.  The radio then can operate normally 
as though it had never been modified.  The "sniffed off" signal is passed through a 
completely different wide band IF on the IFD board, detected, producing the 38k4 
output audio to the 38k4 TNC.

-- 
73, Roy -- W0SL


Date: Tue, 20 Jul 2004 20:15:41 -0000
From: "Robert McGwier" <rwmcgwier@comcast.net>
Subject: RE: [amsat-bb] Anybody can Help me????

Enzo:

What you have done is to widen the bandwidth of the TS-790E to allow
38400 bps through the radio.  This is of course, four times wider than
that necessary for 9.6Kbps.  So you have four times the noise power
you had before and the total deviation of the 9.6Kbps signal as seen
by the TNC is now 1/4 what it was before.  I am afraid that without
a switching arrangement of some type, you will need a lot of signal
to noise ratio for the 9.6kbps to work with the 38.4kbps mods.

Google Italian translation (apologies in advance):

Che cosa avete fatto deve allargare la larghezza di banda del Ts-790e per
concedere 38400 bps attraverso la radio.  Ciò è naturalmente, quattro volte
più largamente di quella necessaria per 9.6Kbps.  Così avete quattro volte
l'alimentazione che di rumore avete avuti prima che e la deviazione totale
del segnale 9.6Kbps come vista dal TNC ora sia 1/4 che cosa era prima.  Sono
impaurito che senza una disposizione di commutazione di un certo tipo,
avrete bisogno del a.lot del rapporto di segnale/disturbo per il 9.6kbps a
lavoro con i mods 38.4kbps.

Bob McGwier
N4HY
----
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