[DSP-10] Getting Started on First DSP-10

[Perry Ogletree]

Look at the NE602 or SA602 chips.  They are a neat chips with a Gilbert cell 
mixer and oscillator in the same 8-pin package.  For a quick test, you could 
just use a L/C tuned oscillator to generate the mixing frequency.  For real 
use, you would want to use a more stable source like a crystal.  Since you 
need a 436 KHz. (455-436=19) source, you might get a 4.36 MHz. crystal and 
divide it down to 436 KHz.  The biggest drawback of these chips is their 
lack of signal "ceiling".  They will overload on strong signals.  There is a 
later version of these chips with better specs but the part number escapes 
me!

----- Original Message ----- 
From: "Paul Black" <paulb at triode.net.au>
To: "Discussion of DSP-10 2-meter transceiver" <dsp-10 at mailman.qth.net>
Sent: Wednesday, November 10, 2004 2:23 PM
Subject: Re: [DSP-10] Getting Started on First DSP-10


> Thanks Perry,
> Do you know of any circuits for mixing the IF on an existing receiver down 
> to the lower IF frequency?
>
> Regards.  Paul
>
>
>
> Perry Ogletree wrote:
>
>> The "IF" they are talking about is a 19 KHz. or so IF created by mixing 
>> the receiver IF (455 KHz. in your example) down to the lower frequency. 
>> The DSP-10 is designed to produce the lower IF for the DSPx or EZKit 
>> Lite. Unfortunately, most affordable, commercially available, DSPs will 
>> only handle audio frequencies.  Sound cards suffer from the same 
>> limitation.
>>
>> ----- Original Message ----- From: "Paul Black" <paulb at triode.net.au>
>> To: <dsp-10 at mailman.qth.net>
>> Sent: Wednesday, November 10, 2004 1:27 AM
>> Subject: Re: [DSP-10] Getting Started on First DSP-10
>>
>>
>>> I've taken the plunge and ordered the DSPx and the adaptor board from 
>>> TAPR. More S/N is always a good thing. As I live in Sydney Australia it 
>>> will take about two weeeks to arrive. But hey I'm good at waiting (well 
>>> not really).
>>>
>>> I was reading that the DSPx could be used with the DSP-10 program 
>>> without all of the RF hardware. I also read that this could be done by 
>>> feeding in the audio out from your receiver. As I am basically a SWL 
>>> this seems to me to be a good way to get started. I could then use the 
>>> DSP-10 software as a programmable filter to improve the quality of my 
>>> received amateur transmissions.
>>>
>>> As I've been searching around the internet I've also read about a 
>>> program called LinRad which works using a sound card. Now here is where 
>>> I start to get confused. The LinRad docs talk about needing to feed the 
>>> IF output from my receiver into the LinRad program to perform signal 
>>> processing, but the DSP-10 program does much the same thing by feeding 
>>> in the audio out from my receiver.  How does a PC soundcard manage to 
>>> digitize a 455 KHz signal taken directly from the IF? What is gained by 
>>> directly processing the IF signal? Can the DSP-10 do the same sort of 
>>> thing and take an input directly from the IF out of a receiver?
>>>
>>> Cheers.   Paul
>>>
>>>
>>> Perry Ogletree wrote:
>>>
>>>> I have used the DSPx and it works better than the EZKit Lite board.  I 
>>>> have not used it with the DSP-10 yet as I am still building it, but I 
>>>> have played with the DSPx and the EZKit Lite.  The DSPx is based on a 
>>>> later DSP chip in the same family as the EZKit.  You will need the 
>>>> customized code from the DSPx site as it uses a different ADC/DAC chip 
>>>> (the one the EZKit used is on longer generally available).  Also, there 
>>>> was a mix-up of one of the output pins that requires a minor wiring 
>>>> change in the DSP-10 harness.  All this is detailed via links form the 
>>>> DSPx site.  The overall benefit of the DSPx is improved S/N and since 
>>>> it has more "horsepower" it would be possible to write your own code 
>>>> that includes advanced modes.
>>>>
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>>
>>
>>
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