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[Linrad] Re: Error: MAP65-IQ 4KHZ not MHZ
- Subject: [Linrad] Re: Error: MAP65-IQ 4KHZ not MHZ
- From: Joe Taylor <Princeton.EDU; joe@xxxxxxxxxxxxxxxx>
- Date: Wed, 11 Mar 2009 20:17:57 -0400
Thanks for your quick answer. I misinterpreted what you had written
earlier; I thought you had found a way to make Linrad account for an
error in the sample rate (nominally 66666667 Hz) of the SDR-IQ itself.
The SpectraVue software provides a way to do this. It's no big deal, I
can handle any necessary calibration issues in MAP65-IQ itself.
> There is a box in the lower left (until you move it) that lets you
> enter the center frequency of your hardware. Since I use the SDR-IQ on
> the 28 MHz IF of a DEMI transverter, I set the value to 28.125 to
> cover the digital EME passband. With that set, I use an fadd of 116000
> and I get pretty close to the right frequency on MAP65-IQ. I need to
> tweak the SDR-IQ setting through LINRAD around 200 Hz to be right on,
> but I don't know how to do that. The value in the box only allows 1
> KHz resolution. So, I just keep track of the offset and watch the
> value of DF in MAP65-IQ to decide which 1 KHz window to select for the
> focused decode.
> On Mar 10, 5:54 pm, Joe Taylor <j...@xxxxxxxxxxxxx> wrote:
>> Hi Ned,
>> You wrote something on the Linrad reflector that prompts me
>> to ask a question. Where does one set a frequency
>> correction for the SDR-IQ in Linrad? I haven't found this,
>> I guess.
>> -- Joe, K1JT
>>> You need to get it right in both apps. I used a signal generator and
>>> got the offset frequency in LINRAD right first by watching its
>>> display. And then I modified the fadd in MAP65-IQ to get its display
>>> right. There is a 3rd offset which I cannot figure out how to control
>>> My SDR-IQ is off around 200 Hz. There is not enough resolution in the
>>> frequency correction in LINRAD to correct for that...maybe I can get
>>> it right by adjusting fadd in MAP65-IQ. What happens with that SDR-IQ
>>> frequency error is that the station may be actually in the next 1 KHz
>>> increment than what my displays suggest. So, when I dial my TX
>>> frequency, I may be off by 1 KHz. To correct for that right now, I
>>> look at the DF and when it is a big number I known it is in the next 1
>>> KHz bin (which bin is determined by the sign of the DF).
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