Re: [IRCA] Talking house on 1630 ruining DX on channel

["Bill Harms" <wharms@xxxxxxxxxxxxxx>]

Curt:

	Thanks for your observations and comments.  Yes, I know what is a 
Sub-audible Het (SAH).  If fact, I have been able to document SAHs of 
over 1 to 2 minutes in length using my audio graphing software.  

	In this case, it could be a SAH as you note, but the audio being 
produced is "dirty" and "sounds" almost like the infamous Cuban 
wobbler.  I have heard similar audio on other Part 15 transmitters.

http://philcobill.com/sounds/talkinghouse/01630-20060923-0820-
wobbling_talking_house.mp3

	I suspect there is something wrong with the carrier of the Talking 
House, but I have not been able to isolate the carrier on my screen 
shots (using Spec Lab) because there are too many TIS carriers. 
Although I suspect it is at about 1629.985.

	Check out the following: (add 1629.5 to the frequency at the top of 
the graph to get the exact frequency of the carrier)

http://philcobill.com/sounds/talkinghouse/capt0609241124.jpg

Bill Harms
Elkridge, Maryland

On 24 Sep 2006 at 2:31, W. Curt Deegan wrote:

> Bill,
> 
> You probably know all this, but just to be thorough I'll go through it 
> anyway.
> 
> What you might be hearing is what has been termed a Sub Audible Het
> (SAH).  Two carriers so close in frequency they don't produce a
> typical het with a high enough frequency for a human to hear, hence
> sub audible.  The result is a fluctuating signal strength as the two
> carriers interfere with each other, like the old dueling ripples on a
> pond routine.  Same thing as a normal het, except since you can't
> really hear the tone, what you do perceive is the varying audio level. 
> 
> The Wobbler is different in that it is the carrier of the Cuban
> station that is fluctuating in frequency, which accounts for the
> affect not being constant as you describe your local talking house. 
> As the wobbling station carrier fluctuates, it produces a varying het
> against any other stations or your receiver BFO. 
> 
> We have a local TIS/MIS which uses synchronized transmitters across
> town from each other to assure coverage.  Only problem is their off by
> nearly 30 Hz.  Where I am I hear both transmitters and the resulting
> rapidly chugging audio is infuriating.  At times the discrepancy has
> become bad enough the SAH turns into a very low AH -- Audible Het --
> when heard on an audio system with a sub-woofer. 
> 
> Curt
> -------
> W. Curt Deegan
> Boca Raton, (southeast) Florida
> 
> 

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