51248Re: [softrock40] Softrock frequency for 10.680 MHz
- Jan 4, 2011Neil:
Much better to set it to 42.72 MHz. If you set it to 14,24m the receiver
will receive 3.56 MHz better than your IF frequency. The original reason for
the harmonic mixing was that 42 MHz crystals are either hard to find or are
Dave - WB6DHW
On 1/4/2011 1:24 AM, G3RIR wrote:
> I have just completed a Softrock Lite II and used the band specific
> components for 30m but I intend to use it on the IF of my TS2000. The IF is
> 10.695 MHz but an article I have found by K4DSP suggests setting the
> Softrock at 10.680 MHz to avoid a "DC hump".
> I have left one turn off the band-pass filter coil in the Softrock so that
> the band pass moves up a little from 10.1 MHz (30m band). I have also built
> a QRP2000 which has an Si570. I intend to disable the xtal oscillator in the
> Softrock and inject the QRP2000 signal into the divider of the Softrock.
> I understand that the way that the Softrock works "normally" for 30m is that
> the xtal is on 13.5 MHz which when divided by 4 in the divider is 3.375 MHz
> but this is rich in harmonics so the 3rd harmonic at 10.125 MHz is available
> which of course is in the 30m band and this is injected into the mixer.
> Now my question; the QRP2000 is capable of a very wide range of frequencies
> and before I go "chasing my tail" which frequency should I use?
> One possibility is to set it to 14.240 MHz so that dividing by 4 and
> multiplying by 3 gives me 10.68 and this would be very similar to the
> "basic" 30m setup. But it would seem to me better to set the QRP2000 to
> 42.72 MHz and this gives 10.68 from the divider and not relying on the
> presence of harmonics.
> One significant problem with the 14.24 MHz setting is that is well inside
> the 20m band and the divided by 4 frequency of 3.56 MHz is within the 80m
> band. I know that I will not use an antenna on the Softrock as it be
> connected (via a buffer) to the IF of the TS2000 but I still suspect big 20m
> signals to be picked up.
> So what do the gurus think?
> I have already built a Softrock for 80m and it is outstandingly good.
> HNY to Tony Parks and to all
> Neil, G3RIR
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