[time-nuts] Weird Stuff WareHouse shutting down

Bob kb8tq kb8tq at n1k.org
Mon Apr 9 11:08:17 EDT 2018


Hi

> On Apr 9, 2018, at 9:30 AM, jimlux <jimlux at earthlink.net> wrote:
> 
> On 4/8/18 8:20 PM, Glenn Little WB4UIV wrote:
>> The USB stuff has no front end and stability and calibration is highly questionable..
> I'm thinking here of the $1K sort of device - traceable cal, quite stable, etc.
> 
> Not the $20 RTL-SDR
> 
> 
>> How can you discriminate between mixes within the USB device and the signal of interest?
> 
> The same way you can distinguish on a full up analyzer - you change the input attenuator and see if the relative heights of the peaks change.
> 
> 
> 
>> I will take my 141T or my 8566 over USB every time.
>> Rather lug a little weight around and know what I am seeing on the display is what is really out there.
> 
> A little?
> 
>> There is a reason that usable SAs have weight to them and USB devices do not.
> 
> Monolithic RF ICs have made it possible to get very good performance in a smaller package.
> Your 141T or 8566 have a fair bit of size and mass to run the CRT and user interface.
> 
> To be fair, one should take the size&mass of the computer you're running the USB pod with and add that.
> 
> One thing where the USB pods don't necessarily do as well is on the tunable preselector filters or on the number of attenuator steps.

The reason they can get away with that is their dynamic range. As number of real ADC bits goes up, the performance
improves. That was true back when RF ADC’s in spectrum analyzers cost thousands of dollars. It is still true today. You
still pay for performance. What you get for $2,000 is not what you get for $20. That said, if you are after a device that 
covers the HF to  VHF range, they just keep getting cheaper. There is more involved than just the ADC. To do well you
need things like a good clock system. If you happen to be … errr …. frequency oriented, the modern stuff locked up 
to a GPSDO can do some amazing things. 

Bob


> 
> 
> I'd have to go look at something like a Keysight/Agilent FieldFox or the Anritsu equivalent to see what sort of front end design they use - for all intents and purposes these are a tablet computer and 2 port VNA/Spectrum Analyzer in one (two)hand-held device.
> 
> 
> 
> 
> 
>> Glenn
>> On 4/8/2018 6:58 PM, Andy ZL3AG via time-nuts wrote:
>>> On 9/04/2018, at 3:52 AM, jimlux wrote:
>>> 
>>>> Test equipment tends to be aged - Unless you have a particular need for a HP 600 series microwave signal generator, there are probably better sources available much cheaper that use more modern components. In this day and age, I don't think people should suffer through 141T spectrum analyzers or even a 8568- Spend your money an a nice USB unit instead.
>>>> 
>>> Blasphemy!
>>> 
>>> 
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