[1000mp] W8JI INRAD roofing filter measurements

[Garry Shapiro]

Lou:

The 7800 is arguably a different case, since it switches roofing filters 
and therefore may well have diode switches, which the INRAD does not. I 
suspect that what is referred to as "passive IMD" may really include the 
little amplifier, which is certainly not passive. It would be helpful to 
resolve this so we are all on the same page.

Garry, NI6T

Lou wrote:
> Hi Gary,
>
> Good point. I'm not familiar with a specific definition for passive IMD
> other than how you interpreted it.
>
> The INRAD roofing filter has has passive components (the filter), but also
> includes an amplifier "that compensates for the added insertion loss of the
> filter" so in entirety is not passive.  Without schematics for the IC-7800
> we don't know what components are getting switched in and out as the roofing
> filters are selected. So, is the IMD (3r order in this case) caused by
> passives or actives or both? Dunno...
>
> Lou W7HV
>
>
>
> -----Original Message-----
> From: 1000mp-bounces at mailman.qth.net [mailto:1000mp-bounces at mailman.qth.net]
> On Behalf Of Garry Shapiro
> Sent: Wednesday, April 25, 2007 2:58 PM
> To: All about Yaesu 1000mp
> Subject: Re: [1000mp] W8JI INRAD roofing filter measurements
>
> Lou:
>
> Of course--but the quote specifically says "passive IMD in the filter", 
> implying the nonlinearities are in the filter itself, rather than in the 
> mixer preceding the filter. If there are nonlinearities in the amplifier 
> section of the filter--and of course there will be to whatever 
> extent--these are not "passive". I am trying to resolve whether this is 
> semantics or an actual circuit phenomenon. Perhaps it did not translate 
> exactly from the German.
>
> Garry, NI6T
>
>
>
>
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