I managed to pick up a RE240A at a reasonable ham price.
I just wanted to verify the units performance using a signal generator. I don't
have access to the specs or sensitivity figures. Hopefully this data will be
useful for those who bought one up one of these units and need to verify the
units performance. This is the older Model not the current 242.
I used R&S SML01 signal generator with 1khz AM modulation for MDS. I used my
ears rather than a RMS meter/noise distortion meter to detect the MDS level. I
have good hearing and can typically hear -130dbm AM modulation in most receives
that can detect that level. I used the ARRL procedure methods.
I don't have a reference unit whose performance is known to be perfect, and my
figures might not be typical of a fully service and calibrated unit. I have
also not confirmed these figures with Radar Engineers and probably will not be
able to get access to any verification data.
These figures might not be correct since its just a quick bench test even
though my unit anecdotally appears to be working. My ears are certainly not
calibrated!
There is a +- 6db variation across the various frequency ranges.
MDS - HF -1.8 to 90mhz -100dbm average.MDS - VHF - 88 MHZ to 108 mhz -95 Dbm
average. Sensitivity drops in this range and there are other sensitivity
"holes" across the range.MDS - VHF - 100 MHZ TO 550 MHZ -105 DbmMDS - VHF -
550 MHZ TO 100 MHZ -105 Dbm
These figures above are using the standard filter bandwidth not using the
"narrow bandwidth" and I dont know the IF filter bandwidth. I will try and
measure it later.
To read "20" on the S-meter with the preamp off averages -85 Dbm with +- 6dbm
variation depending on frequency.
I used this level because this is basically the minimum signal level that you
can see on the scope, 1 division of 5 divisions.
The preamp gain gives about 10db of gain between on and off using 1 division
level as the reference level.
Full scale S-meter reading of "100" is typically -75Dbm +- 5 Dbm almost close
to S9 if -73Dbm is used as a reference level. This with the preamp on.
You can read higher levels if you turn off the pre-amp and vary the gain, which
typically has a 0 to 30db gain variation. At this level of "100" the unit will
read to 3 scope divisions.I did not want to blow the preamp since I dont know
what the units limits are. You can vary the gain and turn the preamp off. I
did not want to risk blowing the front end!
I did do 1 test on 144mhz and these are the figures.
Preamp on -78dbm full 5 divisions on the scope screen.Preamp off -70dbm full 5
divisions on the scope screen.
Again I dont know the history of this unit and if it represents typical
performance. A member of the reflector was kind enough to forward me a manual,
thanks.
Any discussions or suggestions on the units performance are welcome.
Has anyone changed the battery in one of these units? It looks like you have to
pull the whole unit apart to change the battery?
73VK3OD
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