[TenTec] Corsair II tuning

[Carlos]

Hi Gary,

I have never used the radio in 10 meters, so I wrongly assumed that it
was like in the rest of the bands. I'll find out later today (I just
bought a 1210 transverter)

Thanks for the note, very comprehensive.


cheers
Carlos VK1EA




On 8/27/18, MadScientist <dukeshifi at comcast.net> wrote:
>
>
>
> On 160 meters, the PTO (5.0 to 5.5 MHz) adds to the 5.8 MHz crystal to
> produce 10.8 to 11.3 MHz. The  the 9.0 MHz IF is subtracted from this signal
> to receive the incoming signal (2.3 to 1.8) MHz. On this band, as the PTO
> frequency goes up, the TX/RX frequency goes down.
>
> On 80 meters, the PTO (5.0 to 5.5 MHz) adds to the 7.5 MHz crystal to
> produce 13.0 to 12.5 MHz. The  the 9.0 MHz IF is subtracted from this signal
> to receive the incoming signal (4.0 to 3.5 MHz). On this band, as the PTO
> frequency goes up, the TX/RX frequency goes down.
>
> On 40 meters, the PTO (5.0 to 5.5 MHz) adds to the 11.0 MHz crystal to
> produce  16.0 to 16.5 MHz. The  the 9.0 MHz IF is subtracted from this
> signal to receive the incoming signal (7.5 to 7.0 MHz). On this band, as the
> PTO frequency goes up, the TX/RX frequency goes down.
>
> On 30 meters, the PTO (5.0 to 5.5 MHz) adds to the 13.99 MHz crystal to
> produce 18.99 to 18.49 MHz. The  the 9.0 MHz IF is subtracted from this
> signal to receive the incoming signal (9.99 to 9.49 MHz). On this band, as
> the PTO frequency goes up, the TX/RX frequency goes down.
>
> On 20 meters, the PTO (5.0 to 5.5 MHz) subtracts from the signal to convert
> the 14.0 to 14.5 MHz to the 9 MHz IF.  No band crystal is used.  On this
> band, as the PTO frequency goes up, the TX/RX frequency goes down.
>
> On 18 meters (incorrect marking for 17 meter band), the PTO (5.0 to 5.5 MHz)
> could go either way because the crystal frequency is incorrectly marked in
> schematic. I don’t know its frequency so cannot calculate its tuning
> direction on this band.
>
> On 15 meters, the PTO (5.0 to 5.5 MHz) adds to the 6.99 MHz crystal to
> produce  11.0 to 11.5 MHz. The  the 9.0 MHz IF is added to this signal to
> receive the incoming signal (20.99 to 21.49 MHz). On this band, as the PTO
> frequency goes up, the TX/RX frequency goes down.
>
> On 12 meters, the PTO (5.0 to 5.5 MHz) adds to the 10.5 MHz crystal to
> produce 15.5 to 16.5 MHz. The  the 9.0 MHz IF is added to this signal to
> receive the incoming signal (24.5 to 25.0 MHz). On this band, as the PTO
> frequency goes up, the TX/RX frequency goes down.
>
> On 10 meters position A, the PTO (5.0 to 5.5 MHz) adds to the 13.99 MHz
> crystal (the same crystal used on to produce 30 meters) to produce  19.99 to
> 21.49 MHz. The  the 9.0 MHz IF is added to this signal to receive the
> incoming signal (27.99 to 28.49 MHz). On this band, as the PTO frequency
> goes up, the TX/RX frequency goes up.
>
> On 10 meters position B, the PTO (5.0 to 5.5 MHz) adds to the 14.49 MHz
> crystal to produce  19.49 to 19.999 MHz. The  the 9.0 MHz IF is added to
> this signal to receive the incoming signal (28.49 to 28.999 MHz). On this
> band, as the PTO frequency goes up, the TX/RX frequency goes up.
>
> On 10 meters position C, the PTO (5.0 to 5.5 MHz) adds to the 14.99 MHz
> crystal to produce  19.99 to 20.49 MHz. The  the 9.0 MHz IF is added to this
> signal to receive the incoming signal (28.99 to 29.49 MHz). On this band, as
> the PTO frequency goes up, the TX/RX frequency goes up.
>
> On 10 meters position D, the PTO (5.0 to 5.5 MHz) adds to the 15.49 MHz
> crystal to produce  20.99 to 21.49 MHz. The  the 9.0 MHz IF is added to this
> signal to receive the incoming signal (29.49 to 29.999 MHz). On this band,
> as the PTO frequency goes up, the TX/RX frequency goes up.
>
> In all cases, the counter simply corrects its preset to give the correct
> readout. An analog dial would need a dual scale to work with this scheme.
> The only difference is that the knob goes the opposite direction on the
> higher bands than on the lower bands.
>
> 40 meters SHOULD tune the same direction as 160…
>
> One other error in the schematic is that the local oscillator is shown
> connected directly to the FET power supply line (regulated as well) and
> bypassed to ground via a 0.01 uF capacitor. This can’t work…
>
> Gary
> W0DVN
>
>
>> On Aug 26, 2018, at 2:07 PM, Duane - N9DG via TenTec
>> <tentec at contesting.com> wrote:
>>
>>
>>
>> A test that would be interesting to see is if the behavior of how the CW
>> signals tune behaves the same way when the mode switch is set to SB-N and
>> then SB-R. They should behave differently from each other, one should tune
>> like you expect CW to tune. And the other the way you now see CW tune.
>>
>> If SB-N and SB-R behave as expected then there's a very good chance that
>> one of the connections between the Mode switch and DSB board is not making
>> the needed connection when in CW mode. In any case it would be well worth
>> the time and effort to check the interconnection wire connections between
>> the Mode switch and the DSB board.
>>
>> After looking at the block diagrams and schematics it looks like that CW
>> should tune as if the radio is in CW-N, if the mode is set to CW-R it
>> should tune the opposite way, and the way you are describing.
>>
>> So the suggestion that the problem is in the Double Sideband Board (DSB),
>> or the wiring to it, I think is correct. But it should be noted that in
>> the Corsair II there is just one crystal that is placed above and below
>> the IF filter passband by capacitor that is switched into the BFO
>> oscillator circuit by the positions on the Mode switch. And in the case of
>> the CW tuning the wrong direction is because that crystal is not running
>> at the right frequency.
>>
>> So the issue is not related to the PTO or the LO oscillator mixer boards.
>>
>> Duane
>> N9DG
>>
>>> On Aug 25, 2018, at 12:17 PM, Paul DeWitte <k9ot at yousq.net> wrote:
>>>
>>> I am not sure how to explain my problem.
>>>
>>> I have 3 corsair IIs. recently I got one out to give it some air time. It
>>> had been a while since it had been used.
>>>
>>> When tuning in a signal on 40M I found that instead of turning the VFO
>>> CLOCKWISE to zero beat on a low pitch signal, I have to go down (counter
>>> clockwise) to get on frequencey. The offset tuning works the same way. I
>>> have to tune down to bring the signal up in pitch.
>>> That is exactly backwards of how TT radios work on 1.8 to 10 MHZ.
>>>
>>> Everything else seems to be correct. The frequency readout seems  to be
>>> correct as you tune up the band.It has good rcv audio, and this is the
>>> only
>>> thing that I find wrong.
>>>
>>> Is there  a wiring problem here? In looking at one of the others, I do
>>> not
>>> see any difference in wire routing.
>>> Can it be the PTO?
>>>
>>> Thanks for any replies,
>>> 73 Paul K9OT
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