[Elecraft] Measuring performance of roofing filters

[Arie Kleingeld PA3A]

All,

Reading all info about the roofing filters...
Many opinions but I still miss a few things here to decide on which
roofing filters I'm going to buy.


I'm a guy who likes to see the figures. (In the Lord we trust, others
have to bring data...)

Here's an idea.


The following measurements for IMD would be nice.

- Determine the dynamic range at 10 kHz with the 2.7 roofing filter
switched in.

- Decrease signal levels by 3 dB or 6 dB or so (that's up to the person
that is measuring). The IMD-signal will then be well gone.

- Then decrease the spacing of the signal frequencies until the IMD
signals comes up again and write down the new spacing.

- Put in more narrow roofing filter and decrease the spacing of the
signals.

- Determine at what new spacing the Intermod comes up.

- Etc, do this for all roffing filters.


So we get the following table as an exampe:

Filter   spacing (kHz)  dynamic range

2700       10          103 dB

2700       3.2         97 dB (measuring the 103-6 = 97dB dynamic range
spacing)

2100       2.4         97 dB

1800       2.0         97 dB

Etc...

Etc...


So lets measure the spacing of the signals for a 97dB dynamic range
instead of the other way around.

If you really want to do this right, take several roofing filters of the
same width and take several K3's.

Cut the salestalk, bring me dataaaaaaaa.....

It will sur help me out.



Thanks in advance.

Arie PA3A