Sinisa: Great information! Was this on an O1 or O2? In AM, even with the
AGC settings you describe for low distortion, I still hear significant
distortion on the voice peaks on stable, ground-wave commercial broadcast
stations. Right now, I am hearing it on ABC's KGO, San Francisco. I
realize that broadcast stations use significant amounts of clipping in their
processing, but this is more than what I hear on my car radio or on my
TS-870.
The results of you test confirm my suspicion that the AGC is peak-detecting,
not RMS controlling, which would account for the S-meter varying with
modulation, which is not the case on any AM receiver I have seen before,
including the '870. But even with the AGC turned off, and the RF Gain
control turned to run the S-meter above the peak level of the station, I can
hear the distortion on the peaks. Must be a DSP thing.
Ron
N6AHA
----- Original Message -----
From: "Sinisa Hristov" <shristov@ptt.yu>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Saturday, March 18, 2006 8:37 AM
Subject: [TenTec] Orion AM RX Performance Measurements
>A fixed width font is recommended to view the data correctly.
>
>
>
> Part One - Total Harmonic Distortion
> ====================================
>
>
> Main RX, 3750 kHz, AM
> PREAMP OFF, ATTN OFF, RF GAIN 100
> ROOF 20 kHz, BW 6000 Hz, PBT 0 Hz
> modulation freq = 300 Hz, modulation depth = 50 %
> carrier level = -53 dBm (S9 + 20 dB)
> measured at speaker output with external 4 Ohm speaker connected
>
>
> Total Harmonic Distortion
> in Percent
>
> HANG dB/s 1.373b5 2.056
> -----------------------------
> 0.3 5 0.41 0.44
> 0 5 1.27 0.65
> 0 50 4.8 3.1
> 0 100 8.0 5.8
> 0 200 13.4 10.5
> 0 500 24.5 21.4
> 0 1000 35 35
>
> Orion can deliver up to 1.4 W into 4 Ohm load with
> less than 0.5 % THD, using HANG of 0.3 seconds and 5 dB/s.
>
> This is a static mesurement in laboratory conditions.
> On the air performance seems to be affected a lot by selective fading.
>
>
>
> Part Two - Frequency Response
> =============================
>
>
> Sub RX, V2.056, 900 kHz, AM 50 %, BW 6000 Hz.
> measured at speaker output with external 4 Ohm speaker connected
>
>
> Frequency Response in dB
>
> PBT setting
> freq 0 Hz 1200 Hz
> ----------------------
> 400 0.0 0.0
> 500 -0.1 -0.1
> 600 -0.2 -0.15
> 700 -0.35 -0.3
> 800 -0.5 -0.45
> 900 -0.7 -0.55
> 1000 -0.9 -0.75
> 1100 -1.0 -0.9
> 1200 -1.2 -1.05
> 1300 -1.4 -1.2
> 1400 -1.5 -1.35
> 1500 -1.7 -1.45
> 1600 -1.8 -1.55
> 1700 -1.9 -2.1
> 1800 -2.0 -5.9
> 1900 -2.05 -7.7
> 2000 -2.1 -7.6
> 2100 -2.2 -7.7
> 2200 -2.25 -7.7
> 2300 -2.3 -7.7
> 2400 -2.3 -7.7
> 2500 -2.3 -7.7
> 2600 -2.35 -7.7
> 2700 -2.35 -7.8
> 2800 -2.35 -7.8
> 2900 -3.15 -7.8
> 3000 -12.6 -7.8
> 3100 none -7.7
> 3200 none -7.7
> 3300 none -7.6
> 3400 none -7.5
> 3500 none -7.4
> 3600 none -7.3
> 3700 none -7.2
> 3800 none -7.05
> 3900 none -6.95
> 4000 none -6.9
> 4100 none -7.6
> 4200 none -17.1
>
>
> An attempt to shift PBT by 1200 Hz in order to obtain wider response,
> results in response being DOWN by almost 6 dB from 1850 Hz up.
> The weakened response continues up to 4.1 kHz.
>
>
>
> Part Three - Equipment used
> ===========================
>
> HP 33120A Function Generator
> R&S SME 03 Signal Generator
> Amber 3501A Distortion & Noise Measurement System (True RMS)
> TDS 3054 Oscilloscope
>
>
>
> 73,
>
> Sinisa YT1NT, VE3EA
>
> _______________________________________________
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> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>
>
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