Dan,
Tim just gave the exact explanation. This behavior seems weird the
first time because we all are used to the common S meter which is
really a bad implementation of a level meter in all "classical"
communications receivers that I know. The Flex radios really are also
measuring instruments and perform true signal level measurements at its
input terminals, like a Selective Level Meter or an Spectrum Analyzer.
73 de Ignacio, EB4APL
------------------------------------------------------------------------------------------
Tim Ellison wrote:
The purpose of the preamp is to improve the signal to noise ratio.
If you engage the preamp, the noise floor goes DOWN and the signal level stays
the same. Remember that when you engage the preamp, you have not changed the
signal level at the antenna terminal. You have, however; improved the signal to
noise ratio with the preamp and therefore the noise will go down in reference
to a fixed signal level. The previous statement holds true in all cases except
one. That is if the radio is antenna noise limited.
-Tim
-----Original Message-----
From: flexradio-boun...@flex-radio.biz
[mailto:flexradio-boun...@flex-radio.biz] On Behalf Of Dan Scott
Sent: Thursday, December 31, 2009 10:56 PM
To: EB4APL
Cc: flexradio@flex-radio.biz
Subject: Re: [Flexradio] High Noise Floor again using 1.18.3
Ignacio,
Wow! The Preamp was off for the bands causing issues. With the Preamp set to "High" the noise floor dropped to expected levels.
Now I'm only having an issue with the logic:
preamp "OFF" raises the Noise Floor
preamp "ON" lowers the noise floor
sounds backwards, so I assume there is some magic built into the preamp code.
No worries though, I can now use all the bands with 1.18.3. You solved my
mystery.
On to straight key night
Thanks, 73 and Happy New Year.,
Dan - W0RO
--------------
EB4APL wrote:
Since I also own a SDR-1000, I'll reproduce your tests with a dummy
load and will post here the results, but meanwhile you gave me a
clue: It seems to me that the switch noise is the preamp gain relay
and it is caused because you have selected different settings for
General band and ham bands. Look at the preamp settings change when
you move across band boundaries and you hear the click. If you use
different folders for each installation, as I do, your preamp settings
may be different on each version.
73 de Ignacio, EB4APL
---------------------------------------------------------
Dan Scott wrote:
I thought I had this issue resolved but I find that it was not. I'm
wondering if anyone else using (or that used) a SDR-1000 is
experiencing the same issue.
After install 1.18.3 the noise floor increased from less than S1
(dummy load) to S6.5 on 20-meters. The issue seems to be most
obvious on 17, 20, 30 and 40 (to some degree). I thought I had the
issue resolved a couple months ago by uninstalling 1.18.3 and
reinstalling it. But what I had was something that was better but
not resolved and after re-calibration it was obvious the problem
still existed.
Considering 1.18.2 as the baseline version and all testing into (or
from) a Dummy Load, the following comparison can be derived:
1.18.2 shows S1 (+/- .5) for the noise across all bands.
1.18.3 shows a noise floor of:
S1 on 10, 12, 15
S6.5 on 17
S7.5 on 20
S6.5 on 30
S2 on 40
S7 on 60
S6.5 on 80
S5.5 on 160
Once a fresh copy of 1.18.3 is installed I step through calibration
procedure starting with PA Settings. After each calibration step, I
would check the noise floor on all the band edges comparing the
in-band to out-of-band noise floor. Generally the noise floor on
20-meters would remain around S3 until doing the RX Image Reject
Calibration. Once the RX Image Reject Cal was complete, 20 should
show a S7 noise floor. I re-calibrated version 1.18.2 and each step
of the way the noise floor remained S1 +/- .5 all bands, so 1.18.2
reacts much better then 1.18.3 when doing an apples-to-apples
comparison.
After reloading the software and re-calibration, the band edges tests
for 17 through 40 would show S1 +/- .5 for out-of-band and a high
noise floor in-band. This condition could easily been seen when
looking at 13.999999 with a S0.5 noise floor and tuning to 14.000000
which shows a S7 noise floor. Also, tuning between in-band and
out-of-band would produce a switching sound in the SDR-1000 on all
bands except 15, 12, and 10 meters.
When using 1.18.2 the above condition does not exist. Therefore when
tuning from 13.999999 to 14.000000 the noise floor remains the same
and the SDR-1000 is not being switched. By "not being switched", I
mean there is no relay sound heard when tuning from out-of-band to
in-band and visa-versa.
The XP Pro system is a quad-core that has been running a couple years
with little change (other than Microsoft trying to mess with me from
time-to-time). It is dedicated to the radio plus one Video Editing
piece of software.
NOTE: Reload process for 1.18.3 is:
1. Uninstall 1.18.3
2. Delete the 1.18.3 directory from Program Files
3. Reboot
4. Install the software for 1.18.3
5. Reboot (I have reverted to 98 procedures... when Microsoft
systems were definitely com-booters)
6. Run pSDR/configure
7. (sometime an extra boot just because it is an MS OS)
Any ideas?
Thanks and 73,
Dan - W0RO
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