Re: Spurs/Harmonics fixes for v4 based on v5 board design?

Bill Cromwell <wrcromwell@...>

Hi Jerry,

I read something in an ARRL publication about getting around that 40 dB dynamic range problem. Maybe by W7ZOI or W1FB. But it almost wants a spectrum analyzer to set it up. So it's a circular solution. Circular means chasing your own tail :) If you have a spectrum analyzer to set it up why do you need the toy analyzer?

It might be doable without a second SA.


Bill KU8H

On 1/21/19 10:53 AM, Jerry Gaffke via Groups.Io wrote:
If you want to pursue this, what you really need next is a step attenuator:
Kees is on the forum, he has a nice one here, kit #13 for $15:
And a whole bunch of other stuff you could spend that $165 on.
The RTL-SDR will be fine to learn with, a much better choice if you plan to
burn out the front end with that transmitter.  (I assume you also have an up-converter,
since those DVB-T dongles only down to around 30mhz.)
If you wind up with a $2000 spectrum analyzer someday, you will still need the step attenuator.
Yup, red flag that they say nothing about dynamic range on the RF Explorer, that's pretty basic info.
Manual is under Documents here, describes a bunch of different versions of the RF Explorer:
Page 46 of the manual has a table showing "Measurable Input Range" when using various
external attenuators, the figures they give are consistent with an 8 bit ADC (a 40dB dynamic range).
Get the vague impression elsewhere that it can see stuff between roughly -115dBm and 0dBm,
but that could be done with an 8 bit ADC and a variable gain amp.
So a very red flag.
But I could be wrong in this, look forward to hearing further from those that have one.
Jerry, KE7ER
bark less - wag more

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