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[TenTec] Trouble Tuning in CW Signals

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Subject: [TenTec] Trouble Tuning in CW Signals
From: w5yr@swbell.net (George T. Baker)
Date: Wed, 04 Aug 1999 17:09:17 -0500
Eric, I am unfamiliar with (but interested in!) TT radios. In most modern
rigs, the cw filters have their passbands placed, effectively, about a
frequency that is above or below the received/dial frequency by the
amount of the sidetone. If your dial says 14.060 MHz and you hear a
signal with a 700 Hz beatnote, then when you switch to a 500 Hz filter,
that filter passband is effectively centered about a frequency 700 Hz
above or below 14.060. 

Note the judicious use of "effectively" since there are many schemes for
placing filter passbands in modern multiple-conversion superhet

Now, the point of all this is that if you tune in a signal with the wide
filter and set the beatnote to the specified frequency, then switching to
a narrow filter should automatically place that signal in the center of
the narrow filter passband.

If it does not, then you will lose the signal as you describe.

What has happened?

The most likely thing is that that your rig has selectable-sideband
tuning for CW. That is, you can select which side of zero-beat you use to
receive a signal. If you choose one side and the filter is incompatible
with that choice, then you will not hear the desired sign. My ignorance
of TT rigs prevents me from going any further, but I suspect that either
TT rigs allow narrow filters to be used with only one sideband selection
(I really doubt this to be the case) or something is wrong within the
radio that prevents the narrow filter passband from being placed
electronically at the right frequency to work with your sideband

I am afraid that I speak from considerable ignorance re TT radios, but
maybe this confused explanation will be of some help.

72/73, George        AMA 98452          R/C since 1964                 
Amateur Radio W5YR, in the 53rd year and it just keeps getting better!  
AutoPOWER Systems, Fairview, TX (30 mi NE Dallas)  Collin County

Rosenberg.Eric@orbcomm.com wrote:
> I'm having troubles using the CW filters and am hoping someone can help.
> My question is whether the center frequency is different when the radio is 
> "wide
> open" vs when you put the filters in.

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