I wrote:
Bottom line:
1. Narrower is not always better (Ten-Tec experience)
2. 8-poles is not always better than 5-poles (per Inrad)
3. Let IMD and BDR measurements be your guide
More evidence below to support waiting for IMD/BDR
measurements before ordering any roofing
Well done, Bill. This again shows the importance of real life
measurements... and why I didn't order any filters until more is known
about them.
Anybody interested in the subject of filter design must read the article
by list member Jack, K8ZOA in the current QEX. It gives a lot of
valuable
This I have noticed during my own IP3 measurements on my
FT-1000D, not as much as 16dB but around 3 dB.
This was with the INRAD roofing filter and 2 kHz offset.
in any case this was enough for me not to use the filter.
I´m eagerly waiting for measurement figures on the K3.
Beats me why they
Hat tip to Larry ... now all I need is a commission on every QEX sold ...
Crystals are non-linear and their motional parameters are, to some
degree or other, a function of drive voltage. Since a filter's loss is a
function of its motional parameters, the corollary to that is
intermodulation
The IMD contributed by inductor cores used in the front-end selective
circuits is often not taken into account either, or for that matter any core
within the signal path. They can bite.
73,
Geoff
GM4ESD
Larry Phipps wrote:
This is a subject which seems to be gaining in importance as
Adam (VA7OJ/AB4OJ) wrote:
It is highly significant that professional receivers manufactured by the
likes of RS, Rockwell-Collins, Racal and Harris have a single roofing
filter. This filter is typically 12 to 16 kHz wide, to pass multi-channel
ISB, VFT (multiplexed teletype) and high-speed
Dave G4AON wrote:
Adam
a friend has a
well maintained Racal RA1792 military receiver which is hopeless
compared to even moderately good amateur gear such as his Kenwood
TS-850, I appreciate the 1792 wasn't one of the better Racal receivers
but they weren't cheap.
If things in the Mother
W3FPR said:
The real facts are: 1) I will order my initial K3 with only the stock
2.7 kHz filter.
followed later by
My best recommendation at this time: Understand the consequences of
depending on a wide roofing filter while making your decisions - if
you choose only the wide filter, live with
It's deja vu all over again (from May 1).
73, Bill W4ZV
http://mailman.qth.net/pipermail/elecraft/2007-May/067147.html
K0WA:
How many roofing filters do you need in a K3?
I would suggest one for SSB and one for CW.
That's basically correct,
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