[hpsdr] Munin C25-C27 / IMD3

[Kjell Karlsen]

Hi Georg.

You are not the only one seeing this.

The power you are referring to, is that what you read on the Power Meter  
on PSDR? You will see that if the PA is in its very linear area, the  
indicated power is the PEP, twice of what you measure on a Bird or other  
normal Power Meters when running 2-tone test.

I have not seen any difference using the Drive level control or the GBB  
settings.

Do you use Alex or any other LPFs? Have you seen any difference with or  
without LPFs?

I have a new built Munin on my table so I´ll test through all the bands  
and settings with it.

73, Kjell




På Fri, 24 Jan 2014 15:26:30 +0100, skrev georg Prinz <getpri at t-online.de>:

> ***** High Performance Software Defined Radio Discussion List *****
>
> Hello,
>
> I was curious about the different behaviour between mica capacitors and  
> SMD ceramic capacitors C25 to C27. Therefore I replaced the mica through  
> 4x 220pf SMD.
> The result was marginal. But, what is interesting for both versions,  
> that the IMD3 differs strongly with the drive level. Actually, this is  
> not surprising at all, but I didn`t expect it with that amount and
> in some cases, IMD3 was better suppressed at higher output level:
>
> MHz    P [W]    IMD3 [dB]
>
> 1.85    118.0         -40.1
>                99.6         -25.5
>
> 3.7        99.9         -30.3
>
> 7.1        94.2         -21.2
>                94.2        -21.1
>                98.5        -16.4
>               85.6         -26.6
>               86.7         -34.8
>
> 14.2     90.1         -32.4
>             100.0        -19.8
>               92.2        -22.0
>
> 21.2    89.6         -22.1
>              87.8         -17.0
>              91.9         -20.2
>
> 28.6    81.2         -13.4
>
> 50.2    77.9         -24.1
>              86.2         -20.7
>
> Furthermore, I have the impression, that there is a difference if you  
> change the driver level through the PA-settings in the set-up window or  
> with the slider on the main window.
> Any idea why?
>
> As a conclusion of this test, I would say, that during normal operation,  
> you never succeed in an optimal IMD3 suppression. On one band I even  
> experienced, that the IMD5 was
> obviously stronger than IMD3.
>
> All measurements were taken with munin feeding a dummy load.
>
> Does anybody made similar measurements or is this a behaviour of my  
> munin set-up, only?
>
> Maybe, Kjell could comment on it comparing it with his measurements?
>
> 73, Georg, dl2kp
>
>
>
>


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