[1000mp] W8JI INRAD roofing filter measurements

[Adam Farson]

Hi Garry,

The possible reasons for the close-in IP3 degradation  are (1) IMD generated
in the filter, (2) IMD due to saturation of the IF amplifier driving the
filter resulting from mis-termination caused by sharp increase in filter
input impedance outside the filter passband or (3) both these effects in
combination.  

As mentioned in previous posts, the crystal resonator(s) and any
ferrite-cored inductors in the filter can be driven into saturation, at
which point they will behave as non-linear circuit elements and generate
IMD. This is the "passive IMD" referred to earlier.

Cheers for now, 73,
Adam VA7OJ/AB4OJ


-----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 17:45
To: All about Yaesu 1000mp
Subject: Re: [1000mp] W8JI INRAD roofing filter measurements

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