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AOR AR500 S-Meter Measurement



The S-Meter can give exact values as long as you don't relate to the scale. I've measured dB values with a professional Rohde & Schwarz receiver. So here is what you may call a conversion table. The values depend on the IF filters used and the frequency.


reference frequency 1 MHZ, IF: 3 KHz

S-Meter S1 S2 S3 S4 S5 S6 S7 S8 S9 +5 +10 +15 +20 +25 +30 +35 +40 +43 +46 +48 +50 +52 +54 +56 +58
6 7 8 9 10 11.3 13 15.3 18 20.5 22 23.5 27.5 31.5 34 37.5 41.5 51 58 62 65.5 72 76 79 89


Wider IF-filters will lower the signal level. Values in dB:

3K 6K 15K 30K 110K 220K
0 -0.5 -1 -4.5 -8 -7



Frequency, pre-amplifiers and attenuators


There are at least four ranges with significant differences. The first one leads up to 230 MHz. There seems to be a pre-amplification centered on the 144 MHz amateur radio band, indicated by "AMP" in the display.



MHz 0.6 1 1.5 10 30 100 130 150 170 200 229.999
ATT 0 -1.3 0 +1 +0.5 +1.3 +6.7 +7.4 +12.8 +12.3 +10 +8.5
ATT 10 -10.3 -8.6 -10.2 -11.7 -13 -15
ATT 20 -21.3 -20 -20.7 -22.3 -26.2


example at 100 MHz with IF= 3 KHz:
S9 with ATT=off would be 19 dBµV - 6.7 dBµV = 12.3 dBµV
S9 with ATT="10dB" would be 19 dBµV + 10,2 dBµV = 29.2 dBµV

So ATT=10 at 100 MHz would result in a real attenuation of 29.2 dBµV - 12.3 dBµV. = 16.9 dBµV

The second area ranges from 230 MHz to 400 MHz. ATT20 does not make any difference to ATT10 anymore. The "AMP"- preamplifier can't be switched off. It seems like it's still the one that is focussed on 144 MHz because values decrease with higher frequencies.

MHz 230 300 399.999
ATT 0 +8.5 +5.6 +2
ATT 10 -5 -4.5 -7


From 400 to 1 GHz another pre-amplifier seems to be on. This one is centered at 600 MHz. ATT10 attenuates by around 9 dB in the whole range.

MHz 400 450 500 550 600 700 750 800 999
ATT 0 +5.5 +5 +5.5 +7 +9 +8.5 +5 +2 +0.5
ATT 10 -2.5 0 -12.5



Above 1 GHz the attenuators do not work. The AR5000 switches to another pre-amplifier. The signal at 1 GHz was +7 dB compared with the reference. As my professional oscillator stops at 1 GHz I could not measure anything above.


Questions? Corrections? Ideas? Comments?
Mail me: PeerAxel@aol.com

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