On Fri, 2006-04-07 at 12:19 -0500, Mike Gorniak wrote:
> Here is the frequency response data measured on my Orion (original) with
> both V1 (1.373b5) and V2 (2.056) software. The responses are
> significantly dissimilar and should be helpful to those trying to sort
> out the audio differences between the two software versions. The
> measurements were obtained by injecting the output of a Potomac
> Instruments AG-51 Audio Oscillator into the AUX input of the Orion.
> The Orion was connected through a Bird Model 43 Power Meter to a 50 ohm
> dummy load. Power Output reference was set to 50 watts. Special care was
> taken to ensure that no ALC action was occurring. The various
> frequencies measured were all adjusted to 50 watts output using the
> calibrated attenuator on the AG-51. No other adjustments were made. The
> transmit bandwidth was set to 50 - 3900 Hz, and the Speech Processor was
> set (of course!) to OFF. The Mode was LSB on 7.250 MHz.
>
>
> Freq (Hz) V1 Response (db) V2 Response (db)
>
> 40 - 10 < - 20
> 50 - 4 - 20
> 70 - 1.8 - 10.2
> 100 - 1.2 - 9.5
> 120 - 0.8 - 9.0
> 150 - 0.2 - 9.0
> 200 0 - 5.1
> 300 0 - 2.2
> 400 0 - 0.4
> 600 0 0
> 1000 0 0
> 1500 0 0
> 2000 - 0.5 0
> 2500 - 1.1 + 0.3
> 2800 - 1.4 + 0.5
> 3000 - 2.2 + 0.6
> 3500 - 3.3 0
> 3800 - 4.2 - 1.5
> 3900 - 9.6 - 6.5
> 4000 - 14.5 - 10.5
>
> It is also noted that the V2 version has an additional 5.5 db of gain
> (as measured through the AUX input), compared to version V1.
>
>
> Given these differences, it's little wonder that V1 and V2 software do
> not sound alike.
>
> 73,
>
> Mike Gorniak, NM7X
In my view, for COMMUNICATIONS, either response curve is too broad. The
guttural basso profundo sounds get filtered in MOST receiver filters and
just waste RF power and spectrum, while the voice screeches above 2500
Hz do the same, and neither helps understanding. Remember the PA is
limited by its peak power capability and any spectral components outside
what passes through the receiver filter just cut back on the useful part
of the spectrum.
The V2 low cutoff is reasonable, the high cutoff is too high. Though I
suppose the complaint is that the low cutoff was set for 50 but got
300... Maybe TT did that to protect the PA from those useless power
peaks.
--
73, Jerry, K0CQ,
All content copyright Dr. Gerald N. Johnson, electrical engineer
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