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Re: [TenTec] Audio Issues, revisited

To: tentec@contesting.com
Subject: Re: [TenTec] Audio Issues, revisited
From: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
Reply-to: geraldj@storm.weather.net, Discussion of Ten-Tec Equipment <tentec@contesting.com>
Date: Mon, 11 Feb 2008 13:34:54 -0600
List-post: <tentec@contesting.com">mailto:tentec@contesting.com>
On Mon, 2008-02-11 at 11:31 -0500, Joe Roberts wrote:
>  >>Is this behavior normal with the V?
> 
> Sadly, bad audio is "normal' with the V. Painful is more like it.
> 
> Yes, there is too much gain in the audio circuit, so you blow your head 
> off by even breathing on the AF gain knob. Taper of the AF pot probably 
> doesn't help either.

That can be improved by loading the output of the AF pot. Put a fixed
resistor between the wiper and ground, say 1/2 the value of the pot.
Less for even more taper.
> 
> The audible distortion in the V seems to come in earlier in the chain 
> due to overdriving the product detector. The W3TS Product Detector mods 
> discussed in recent posts address this issue and, in my mind, are a 
> major step toward making this radio fun listening. Less hiss and 
> clatter, smoother and more defined signal.

Overdriving the product detector would be nasty. Partly cured by
reducing the IF gain perhaps, more by increasing the AVC loop gain.
> 
> W3TS changed a resistor in the notch circuit to recapture some gain lost 
> in lowering product detector drive and I found that this value can be 
> adjusted or left stock to move the sweet spot on the volume control up 
> toward 11 or 12 o clock.
> 
> I am a big fan of the W3TS mods. Night and day difference in the 
> ergonomics of the operating experience.
> 
> See http://www3.telus.net/ve7tk/Omni%20V%20mods.pdf for the lowdown.
> 
> Joe N5KAT
> 
> 
73, Jerry, K0CQ

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