Jerry is correct on this one. The low frequency response is largely
determined by the position of the BFO frequency with respect to the passband
shape of the filter. It is a trade-off situation however. Move the BFO
more into the passband and gain more low end but loose some high end. Move
it further outside the passband and loose low end and gain high end.
Another way to look at it, take an example of a 2 KHz bandpass filter. You
will get any 2 KHz of the signal through it. For example: 100 Hz - 2100 Hz,
or 50 Hz - 2050 Hz, or to an extreme, 500 Hz - 2500 Hz. Just keep in mind,
if the audio isn't there, then a speaker won't restore what's not there.
Neither will EQ.
I used a 2.8 KHz filter with my Omni VI Plus with good results. The BFO was
positioned about the 150 Hz point down the slope of the filter. This gave
me a audio response of about 200 Hz to 3000 Hz.
To get best efficiency of any speaker, place it on a level surface,
preferably in a corner and at ear level directed toward the listening
position.
If you really want to know what comes out of your receiver and what
frequencies are associated with that receiver, download the Spectrum
Analyzer from this website. It's free and easy to use and quite accurate.
http://hotamateurprograms.com/downloads.htm Connect the line output from
the receiver to the line input on the computer, open the program and click
on the START button. What you see is what's coming out of your receiver.
You can adjust the lower limits and upper limits of the analyzer to expand
on what you see and it plots as well as do AVG and PEAK values. You'll be
surprised as to what's NOT coming out of your receiver.
73
Bob, K4TAX
----- Original Message -----
From: "Dr. Gerald N. Johnson" <geraldj@storm.weather.net>
To: <tentec@contesting.com>
Sent: Sunday, January 25, 2009 1:54 PM
Subject: Re: [TenTec] External Speaker Recommendations - Omni VI ?
> On Sun, 2009-01-25 at 11:59 -0600, Bruce Warner wrote:
>> Hi - I have the Inrad roofing filter installed in my Omni VI option 1,
>> but the SSB receive is 'trebly' (i.e., high end, but lacks bottom end and
>> fullness when in SSB receive). Is there an external speaker that others
>> have used with the Omni VI with good SSB sounding results? Thanks for
>> any recommendations/advice.
>
> So the real problem is that the roofing filter is narrower than the
> standard SSB filter which makes the carrier frequencies for USB and LSB
> too far from the filter pass band corners, or too far down the slope.
> What is needed is to always use the new roofing filter and to align the
> carrier/BFO frequencies to fit the narrower filter. A speaker won't
> solve the problem. Usually one wants the BFO to be set 300 Hz below the
> passband corner frequency.
>
> 73, Jerry, K0CQ
>
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