## Re: [softrock40] SI570 Question

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• Interesting to calculate permutations to see how those frequencies can be arrived at ... I cant look at it until Monday. Not difficult just time consuming.
Message 1 of 11 , Feb 16, 2013
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Interesting to calculate permutations to see how those frequencies can be arrived at ... I cant look at it until Monday.
Not difficult just time consuming.

John

From: Alan
Sent: Saturday, February 16, 2013 2:17 PM
Subject: Re: [softrock40] SI570 Question

----- Original Message -----
Subject: Re: [softrock40] SI570 Question

John,

I'm not sure if you understood.
To put it bluntly I'm saying you are wrong.
N9MS has not got a divide by 3 fault. I do not see how his figures confirm that.
The reception he gets at 7.02MHz when 2.34MHz tune is set is due to the 3rd harmonic of 2.34MHz = 7.02. The Si570 output will be
2.34 x 4 =9.36MHz.
Similarly 1.406666 x 5 = 7.033.

73 Alan G4ZFQ

>Interesting fault.
But this "fault" is multiply by 3. It happens because we are dealing with square waves and has been reffered to as "sub harmonic"
mixing. Used in crystal controlled Softrocks. As an example, using round figures, a 20MHz crystal is divided by 4 and the 3rd
harmonic of this division appears at the mixer and may be used for 15MHz reception.

I have presumed that N9MS could have heard the Si570 true fundamental and other harmonics? Unless CFGSR has been misconfigured the
Si570 will oscillate where CFGSR sets it.

Hello Alan,

Yes, looking at the divider outputs on a spectrum analyzer and varying the Si570 frequency reveals a lot.
At some frequencies the amplitude of harmonics is not far off the amplitude of the wanted frequency.

73 John G3UGY

• I ve been playing around with my Ensemble II a lot. Although the frequency range is specified to be 1.5 to 30 MHz, I find I can tune the AM band down to 800
Message 2 of 11 , Feb 16, 2013
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I've been playing around with my Ensemble II a lot. Although the
frequency range is specified to be 1.5 to 30 MHz, I find I can tune
the AM band down to 800 kHz. The filters are probably the limiting
factor here, but it seems they don't attenuate that much all the way
down to 800 kHz. I can still hear broadcast band stations and DX in
that band at night.

I can also tune up to 35 MHz or so with it, but there isn't anything
to hear up there. :-)

73, Zack W9SZ

On 2/16/13, Alan <alan4alan@...> wrote:
>
> ----- Original Message -----
> Subject: [softrock40] SI570 Question
>
>
>>I just got the receiver going on my 30/20/17 Ensemble RxTx.
>> The SI570 is driving me crazy.
>>
>> I couldn't find the 30m band so I started dialing around on the TUNE tab
>> of CFGSR. I finally found some signals on 40m by dialing
>> a Requested frequency of either 1.406666 or 2.34.
>>
>> I can hear the local oscillator on about 7.02 when I dial in 2.34 on the
>> tune tab. Like it's multiplying by 3.
>>
>> I can also hear the local oscillator on about 7.033 when I dial in
>> 1.406666 like it's multiplying by 5.
>>
>
> It seems as if what you see is normal.
> There will always be harmonics of the Si570 signal. So 3 x 2.34 = 7.02 and
> you will hear signals centred on 7.02.
> And Softrocks will hear outside their expected range.
>
> Why you do not hear signals on 30m IS possibly a problem. How about the
> other bands? Make sure they are open, sometimes signals are
> just not there.
>
> Have you put the DLL in HDSDR? You should be able to tune exactly the same
> as CFGSR.
>
> 73 Alan G4ZFQ
>
>
• ... Subject: Re: [softrock40] SI570 Question ... Zack, Yes, others have said the receivers work well down to the lowest frequency. You may find a few signals 3
Message 3 of 11 , Feb 16, 2013
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----- Original Message -----
Subject: Re: [softrock40] SI570 Question

> I've been playing around with my Ensemble II a lot. Although the
> frequency range is specified to be 1.5 to 30 MHz, I find I can tune
> the AM band down to 800 kHz. The filters are probably the limiting
> factor here, but it seems they don't attenuate that much all the way
> down to 800 kHz. I can still hear broadcast band stations and DX in
> that band at night.
>

Zack,

Yes, others have said the receivers work well down to the lowest frequency.
You may find a few signals 3 times or maybe 5 times the tuned frequency coming through but usually you have to look carefully.

But RXTXs should not be used on transmit outside their design frequency.

73 Alan G4ZFQ

> I can also tune up to 35 MHz or so with it, but there isn't anything
> to hear up there. :-)
>
• It s fixed. Too embarrassed to tell the group what I did wrong. Missed reading one paragraph of the Si570 setup. Starting to build the TX portion now. N9MS
Message 4 of 11 , Feb 16, 2013
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It's fixed. Too embarrassed to tell the group what I did wrong. Missed reading one paragraph of the Si570 setup.

Starting to build the TX portion now.

N9MS
• ... Subject: [softrock40] Re: SI570 Question ... Sorry Mike, you ll have to tell! John and I are both wrong, save us a lengthy discussion of what you might
Message 5 of 11 , Feb 17, 2013
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----- Original Message -----
Subject: [softrock40] Re: SI570 Question

> It's fixed. Too embarrassed to tell the group what I did wrong. Missed reading one paragraph of the Si570 setup.
>

Sorry Mike, you'll have to tell!
John and I are both wrong, save us a lengthy discussion of what you might have missed.
Private if you really are that embarrassed:)

73 Alan G4ZFQ
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