[hpsdr] Spectrum Analyzer Software Feature for Mercury

[Joe Martin K5SO]

Hi Tom, 

Alright then, why not use the receiver in a narrow filter mode with the pass band of the filter on the region you wish to measure, then read the level directly on the main meter, as you suggest?   

Certainly you can use two receivers on a single Mercury board, or dual Mercury boards if you prefer, to monitor the main signal in one region (again, use a narrow passband filter) and another region of interest in the other, as  you suggest.  There is no limitation in that regard.  The two receivers can even look at exactly the same frequency with different (or identical) passbands, for that matter.  

The current RX2 PowerSDR program can do this, showing one level on the main RX1 meter and the other level on the RX2 meter.  

As you note, you will have to subtract the two levels to get the relative level.  

Alternatively, it is always possible (in theory at least)  to modify PowerSDR especially to your desires to create your very own personalized measuring instrument that performs whatever measurement you like.  Maybe the present PowerSDR capabilities are not what you seeking.

73,  Joe K5SO

On Dec 9, 2012, at 4:17 PM, Tom Cathey wrote:

> Hi Joe,
>  
> Thanks for the reply.
>  
> No, unfortunately, that would not do it.  The cursor reads the static position of where it is on the screen. 
>  
> I would like the reading to be dynamic and change with the two signal levels so that the side crud, 3khz away from the main signal, would be shown in  –db.    
>  
> I suppose a second receiver could do this, though we would have to mentally subtract the two levels to get an IMD figure.
> Some of the high end commercial spec analyzers will let us put a bug on the screen and it will calculate these difference levels.
>  
>  
> Hmmm... maybe one Merc receiver cannot monitor a second frequency – is this the limitation?
>  
> Tom
>  
>  
>  
>  
> From: Joe Martin K5SO
> Sent: Sunday, December 09, 2012 4:53 PM
> To: Tom Cathey
> Cc: hpsdr at openhpsdr.org
> Subject: Re: [hpsdr] Spectrum Analyzer Software Feature for Mercury
>  
> Tom, 
>  
> In PowerSDR, when the cursor is in the panadaptor window the position of the cursor is shown (in dBm) just below the panadaptor display on the left side.  Won't that do what you require? 
>  
> Just put the cursor on the point you want measured.  Yes?
>  
> 73, Joe K5SO
>  
> On Dec 9, 2012, at 2:46 PM, Tom Cathey wrote:
> 
>> ***** High Performance Software Defined Radio Discussion List *****
>> 
>> Hi All,
>>  
>> This may have been covered before, but here’s my idea for a software addition...
>>  
>> I use my Mercury receiver often as a spectrum analyzer to measure my final linear’s IMD.  (3-1000z, 8877, etc)  I sometimes like to compare one amplifier against the other to see the effects on drive, loading and other parameters. After some testing, we can usually find the sweet spot and then know where to run the amplifier for cleanest operation.
>>  
>> With the present PwrSDR software, it is difficult and time consuming on the fly to interpret the IMD without counting grid lines, etc.  A nice    feature to have would be to be able to set a distance from the main signal and see an ongoing numerical reading of how far down in db this level is.  For example, if your transmit signal is on  3700 using a two tone – and we punch in 3703 as the test point, a readout might show the side trash signal 3khz away is –35db.   By changing various amplifier parameters, we could see the best settings as this number changed.  Moving out farther, like 5kc, etc could start to show the rough 5th, 7th order, etc IMD numbers.
>>  
>> I understand that a Cyclops spec analyzer is coming out, but could this feature be considered for the PWRSDR software so that the Mercury could use it too?
>>  
>> Or is there a way to do this now that I am missing?   What do you think?
>>  
>> Thanks.
>>  
>> Tom, K1JJ
>>  
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