Its not always that the data matches up with the experience. I can show
you plenty of speakers with perfectly flat frequency response curves
that sound like complete crap. Read about some of the information that
Sherwood has talked about in the collection of data and actual use of a
product. At times many measurements just don't stack up to actual
use.
I think your best bet is to decide what modes are important to you and
where you're going to be contesting and the like and then figure out
what it is that is going to be important to you.
Personally I have a bad QRM problem in my area and don't have time to
make a loop antenna so I just switch in narrow filters to try and help
mitigate it. The NB in my K1 doesn't do all that great on the noise but
it helps. When this noise is present I find myself often operating
about about 250Hz. So I got that filter. During field day I like to
operate SSB as well so I got the 1.8Khz filter. If you're going to be
doing SSB contesting and you want a slight advantage the 1.8Khz filter
should be on the list. Then of course I'm going to be getting the
2.8Khz filter. My two remaining slots remain to be chosen but I'll make
that decision after spending a few months with the radio.
If you want data such as you mention the best way to get it is to do it
yourself. Then once you're done sell the filters you no longer want
before publishing it! ;) j/k
On Wed, 2008-04-02 at 08:27 +0200, Arie Kleingeld PA3A wrote:
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 dat.
It will sur help me out.
Thanks in advance.
Arie PA3A
___
Elecraft mailing list
Post to: Elecraft@mailman.qth.net
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
___
Elecraft mailing list
Post to: Elecraft@mailman.qth.net
You must be a subscriber to post to the list.
Subscriber Info (Addr. Change, sub, unsub etc.):
http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/subscribers.htm
Elecraft web page: http://www.elecraft.com
