The filters do become active when the DSP BW is at or less than the
prescribed filter BW. Remember these are roofing filters and it is the DSP
that determines the selectivity of receive. The roofing filters basically
protect the AGC from strong signals outside of the DSP passband.
Putting a narrow filter in a slot and telling the radio it is a wider filter
is more like trying to force a cherry through a soda straw.
73
Bob, K4TAX
----- Original Message -----
From: "Rick - DJ0IP / NJ0IP" <Rick@DJ0IP.de>
To: "'Discussion of Ten-Tec Equipment'" <tentec@contesting.com>
Sent: Wednesday, May 16, 2012 12:53 AM
Subject: Re: [TenTec] CW Filters ???
Barry, as I understand it, the 300 Hz filter doesn't kick in until the DSP
is tuned to 300Hz, so effectively its only active when you are down to 300
Hz anyway.
Just an idea, but maybe you could plug it into the 500 Hz slot or tell the
software that it is 500 Hz. That way it would be in the circuit as soon
as the DSP is adjusted to 500 Hz or below.
I must say that operating with just a 250 Hz in my Eagle, I rarely have it
down to 250 Hz unless there is a contest (and you need less than 250 Hz),
and I haven't seen any problems. It's just as Barry says, sufficient the
vast majority of the times. On the few occasions where you get QRM, just
crank it down to 250 Hz.
Of course the best solution is to have BOTH.
73
Rick
PS Yes, I too noticed that I first said 250 Hz, then I agreed with Carl
on 500 Hz, and now I'm with Barry, back to 250 Hz. Pretty wishy washy.
Perhaps I should run for some political office!
-----Original Message-----
From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
On Behalf Of Barry N1EU
Sent: Tuesday, May 15, 2012 10:24 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] CW Filters ???
The vast majority of the time, DSP filtering is sufficient. You need the
analog filter when there's very strong signals outside of the dsp filter
passband, strong enough that the analog to digital converter can't handle
them. When the going gets that tough, I'd opt for 300hz but it really is
a matter of personal preference.
My experience is that the Collins 500hz and 300hz filters used in the
Omni7 run a little wide - I think the 500hz is more like 600hz and the
300hz is more like 400hz. So the 300hz filter isn't as narrow as you
might think.
Barry N1EU
On Tue, May 15, 2012 at 8:05 PM, Rick - DJ0IP / NJ0IP <Rick@dj0ip.de>
wrote:
There you go James, as I predicted, you have now received all possible
answers.
As I said, it is a matter of taste.
We all have different preferences.
Perhaps Carl has the best suggestion for a beginner in CW.
Mine was more targeted for someone really seriously CW contesting.
So I will change my answer for now and say go with Carl's proposal,
buy the
500 Hz filter.
When you advance, you can always buy the 300 Hz filter later.
73
Rick
-----Original Message-----
From: tentec-bounces@contesting.com
[mailto:tentec-bounces@contesting.com]
On Behalf Of Carl Moreschi
Sent: Tuesday, May 15, 2012 9:46 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] CW Filters ???
I'm going to go against the grain here and say just buy the 500 hertz
filter. The 500 hertz filter adds badly needed skirts to the DSP
filters.
I find I almost always use 500 hertz on CW as the filter width.
The 300 hertz filter is rarely used by me. Only when the going gets
very tough do I find there is an improvement with this filter. I find
with the
500 hertz filter and a DSP setting of 200, things are close to the
best you can get.
Carl Moreschi N4PY
121 Little Bell Dr.
Hays, NC 28635
www.n4py.com
On 5/15/2012 2:53 PM, Richards wrote:
I am learning the Code and will soon try CW mode. I shall commence
with casual contacts, but eventually want to work CW contests with
the big boys at the contest station, with whom I now work phone
contacts.
I have a stock Omni VII transceiver.
QUERY:
Should I buy either or both additional 500 Hz and
or the 300 Hz mechanical filters?
Money is not a big object, but I don't wanna spend more than I must,
as that leaves me to buy other goodies for the shack.
[ Will this start a big fight ? ] ;-)
Thank you in advance.
---------------------------- K8JHR --------------------------
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