[1000mp] Which filter ? - and Diversity - Repost

[WD8ARZ]

Original Message:
-------------------------
From: Harald Garberg Gule <hagar@ekornes.no>
To  : 1000mp@jehosophat.com
Date: Fri, 24 Apr 1998 20:21:01 +0200
[1000MP] Which filter ?
I bought the 1000MP without any filters installed. I am thinking about
buying some soon, however as I do not have plans in the immediate future to
buy all of them, I would very much appreciate ideas from you guys on
which 2 (or 3) to buy first. Please note that the 2Khz SSB filter will be
one of them, which CW filter should I then go for ??

73 de LA6LHA, Harald

Hello Harald, and you have asked a very good and popular question concerning
filters for the FT-1000MP.
What I see in your request are two different questions. One is what
manufacture and type of filter should you get as regard to quality, and the
other is what bandwidth should you get.

As for quality, that does have a range and just because a manufacture of
filters had great quality at one time doesn't mean that they do today. I
have
heard of filters being bought from the major manufactures, and some third
party suppliers, that at times are great filters, but also that at times
some poor quality ones are released. Poor quality ones are not just a low
number of poles, or poor quality components, but the matching of those
components to each other and properly centered with the right bandwidth at
the center frequency.... and I am not getting into losses and impedance
matching. Make the manufacture that you buy the filters from provide you
with the technical specifications for the filters you want, and to make sure
that they supply the curves for those filters. Those that can not supply
that information are in the wrong line of work. Did I mention warranty and a
return policy?

The question about what bandwidth to go with is purely a personal choice.
That choice is directed mostly by the modes you operate, and what those
modes need for bandwidth to perform properly. Most digital modes would start
to get choked off if you use less than 500hz filters. Of course some rtty
modes would do just fine with 250hz. CW can be 200hz and less. If you are
not a hard core purist in some mode, the bandwidths as indicated on the
FT-1000MP filter panel would be great choices for the wide range of modes in
use today.

Some final observations: Don't forget the filter option for the sub
receiver.
Remember that each filter you add needs to be turned on in the menu for that
filter selection before they will work (page 100 in the owners manual).
Filters bandwidths don't have to match the labeling in the filter menu's,
the
front panel selection labels, or the manual. If you change the main receiver
Collins Mechanical Filter, you can use it in the subreceiver.
Remember that there are two IF's to put filters in for the best result for
each bandwidth. If only doing one, go with the one closest to the front end,
in this case the 8.2Mhz 2nd IF.

Most importantly be aware that filters from most manufactures come in two
styles. One is the filter housing all by itself and generally is a solder in
type. The other comes on a printed circuit module that plugs into the radio.
Your owners manual covers that detail, but the text and pictures confuse
some. The correct identification for the two types are: YF filters are on
the plugin printed circuit boards, and the XF filters are not. Most of the
filters in the FT-1000MP are the YF type, and probably what you need to
order. A couple of filter in the radio are the XF type, so just make sure as
to type needed before ordering.

You will find as a result of adding the additional filters, that not only do
you gain the bandwidth improvements for the modes you use them with, but
also that the If shift, width and shift controls are more effective as a
result.

Filters are the best way to go for improving any radio. DSP as it is used
today will not bring the effectiveness that filters in the early IF stages
bring. By filtering out signals and noise not needed for the operation at
hand, the system AGC lets you copy weak signals that would not be heard in
the presence of a strong signal. With out the right filters for the mode in
use, the AGC will reduce the radio sensitivity for strong signals in the
passband causing weak ones to be much tougher to imposable to pull out. DSP
filter is in later stages and will only treat the audio and maybe the last
if stage, so it has to work with all the crude that comes at it, and so does
your ears.

Last tidbit. Don't forget to use the Bandwidth Diversity Reception that you
can do with the dual receiver and filter options. Just make sure to use
stereo speakers or headphones and that the menu options for audio out is not
set to mono. You will be amazed at what your ear and brain can do to pull
out signals this way. I also use Mode Diversity to improve copy of AM
signals. USB on the sub receiver, and LSB on the main. Best results are when
using stereo headphones.....sometimes you can actually hear three aspects of
the audio this way. One in the left ear, one in the right, and the other in
center. Great way for pulling audio out of noise and fading conditions.
Other modes work this way too, and the extra filters go along way to make
the right choice for most situations.

Let us know what choices you make and who you order them from, and most
importantly, the results you have with them. Looking forward to your future
feedback.

73 from Bill - WD8ARZ
wd8arz@ix.netcom.com