[TenTec] Corsair II sidetone mod

[Joe]

I agree Paul, if 2 or 3 bucks is important to you, then the Twin-T is the 
way to go. I agree, it is a more complex solution. The hardware might be 
slightly more complex, but I would venture a guess that the DDS solution has 
fewer parts once the keying and interface components are added to the 
Twin-T. The firmware is complex, but is available at not cost. If you want 
to hear the artifact of the Corsair II's QSK, just disable the sidetone and 
hit the key. You will hear the thump. It is not related to any sidetone 
implementation.

I think the DDS solution is better. While the Twin-T gives a nice sine wave, 
my observation of both on the oscilloscope shows less distortion in the DDS 
sine wave. It also has more output. The waveform is much better with the 
DDS. Why? 1) When keyed, the DDS always begins and ends at zero phase where 
as the Twin-T begins and ends at random phase. That makes for better keying 
waveform. 2) The audio envelope shape is much better also because amplitude 
weighting of the leading and trailing edges is accomplished in firmware by 
starting at -18 dB (relative to the max amplitude) on the leading edge and 
increased in 3db steps, each increase being applied at zero phase. The 
trailing edge is shaped in like manner.

I have the DDS circuit in my Corsair II and I am very pleased with it. I was 
not pleased with the Twin-T, but it was much better than the original. I 
also have the DDS circuit in a code practice oscillator. It is the best 
sounding one that I have ever heard.

Joe, N4YG
----- Original Message ----- 
From: "Paul Christensen" <w9ac at arrl.net>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Saturday, October 15, 2011 5:04 PM
Subject: Re: [TenTec] Corsair II sidetone mod


> Darn, for a small fraction of the circuit complexity and cost, the Twin-T
> oscillator can be used.  I noticed that Joe, N4YG tried the Twin-T on his
> Corsair II but stated that he "...could never get smooth keying..."
>
> Ten years ago, N4LQ suggested that I try a frequency-variable Twin-T, 
> stolen
> direct from the Omni V schematic diagram.
>
> http://www.qsl.net/tentec/mods/sidetone.pdf
>
> N4LQ applied it to one of his Omni D transceivers and I used it in a 
> Triton
> IV.  Neither of us heard the slightest trace of a QSK artifact.  Anyway, I
> would first try the Twin-T as implemented by Ten Tec in the Omni V, then
> explore the more complex alternative option if not satisfied.
>
> Paul, W9AC
>
> ----- Original Message ----- 
> From: "Steve Hunt" <steve at karinya.net>
> To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
> Sent: Saturday, October 15, 2011 5:45 PM
> Subject: Re: [TenTec] Corsair II sidetone mod
>
>
>> Jerry,
>>
>> You would certainly get two of those boards within ExpressPCB's
>> MiniBoardPro outline - maybe more. That option gives you 3 boards - and
>> therefore at least 6 sidetone boards - for $75 plus delivery.
>>
>> 73,
>> Steve G3TXQ
>>
>> On 15/10/2011 22:23, Jerry Haigwood wrote:
>>> Glenn,
>>>       I guess it would depend on how many people were interested.  To
>>> keep
>>> board prices down, you need to sell 50 or so PCBs.  The board would be
>>> small
>>> - maybe 1.5 inch x 1.5 inch and the cost of the parts should be low 
>>> also.
>>> Just depends on how many people would want a board or kit.
>>> Jerry W5JH
>>>
>>> -----Original Message-----
>>> From: tentec-bounces at contesting.com
>>> [mailto:tentec-bounces at contesting.com]
>>> On Behalf Of Glenn
>>> Sent: Saturday, October 15, 2011 3:34 PM
>>> To: tentec at contesting.com
>>> Subject: Re: [TenTec] Corsair II sidetone mod
>>>
>>> Wonder if Jerry would be interested in building some boards..Just a
>>> thought.
>>>
>>>
>>> Glenn WA4AOS
>>> DSM Labs
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: Barry N1EU<barry.n1eu at gmail.com>
>>> To: Discussion of Ten-Tec Equipment<tentec at contesting.com>
>>> Sent: Sat, Oct 15, 2011 11:54 am
>>> Subject: [TenTec] Corsair II sidetone mod
>>>
>>>
>>> N4YG developed a nifty and elegant sine wave sidetone mod for the
>>> Corsair II.  I posted all the info with Joe's approval at:
>>> http://corsair.wikidot.com/corsair-sidetone
>>>
>>> Joe is on this reflector, so any comments/questions can probably be
>>> directed here.
>>>
>>> 73,
>>> Barry N1EU
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>>>
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