toggle quoted messageShow quoted text
It appears they require their own power supply with the gain
being controlled by the supply voltage.
On 20220709 12:01:14, Simon Brown
Please do a noise analysis for 88-108MHz. I think the S3 bias-t
is 5v, not sure what voltage these preamps require.
I have 25m RG6.
I could not agree more,
a step attenuator on the output is a good idea. You can of
course use the noise free bias tee on the S3 for the
supply. These are almost certainly PGA103+ LNAs. You can
use AppCAD and do a system noise analysis. If you like I
will do one and put it on here. In fact I may have already
done one and posted it some time ago. I’ll have a look.
The cheapest one would probably be good enough. The next
one up might be slightly better because you get a nice noisy
power supply and (possibly redundant) Bias-T tap for it. The
most expensive one would only be needed if you have some
exceptionally strong signals nearby.
18 dB gain may be a little high with only 2.5 dB of cable
loss. Something like one of the old HP 1 dB step variable
attenuators might be good on the receiver input. Adjust it
for a suitable compromise for dynamic range and signal
strength. I suspect you do not need this 10V version of the
(Did I just save you a bunch of money?)
On 20220709 11:12:30, Simon Brown
I'll start saving and buy a
masthead preamp (below). My income is way down now due
to COVID and other cost of living issues. Not a great
time to be relying on donations.
They have a bit of input filtering
already, don't know if it's enough.
According to the user manual
with the preamp and noise reduction on the MDS at
91.1MHz is -138dBm in 500Hz, which equates to
-165dBm/Hz. This is a 9dB noise figure and is probably
3-6dB worse because the NR makes things appear better
than they are. If you add 2.5dB to that noise figure
you can see that an LNA will be of great benefit.
I suggest that a system noise
figure of around 2-3dB is optimum for Band II DXing.
What's the S3 noise figure on
Band II ? I have maybe 2dB loss in the 25m RG6, so
am wondering what the total NF is.
BTW I put the BPF before
the LNA to help protect it from 144MHz EME high
power. I am not suggesting that a PGA103+ will
saturate from normal Band II situations. However,
it has a little bit too much gain, so a good
filter and an attenuator does no harm. The S3
really is excellent. Just like you said 😊
Hello Simon, I have done a
noise analysis and you WILL benefit from an LNA. I
have a PGA103+ preceded by a band pass filter and
it seems to work very well. However, I am still
waiting for a bigger antenna. I ordered an OPTDES
which never arrived. So, I will ask a few of the
local Band II DXers for an alternative.
The ELAD S3 is the best
Band II receiver I have. Am thinking about a
preamp on the mast for those very weak stations
- if I get close to receiving weak signals from
across the pond (USA, Canada).
I have attached 3
pictures all with Console running.
The RSPdx is the
only on of these three that has a decent
signal. Running uno is fine also.
It is the other two
that are causing problems. The native
software yields the same lousy signals.
There is a lot of noise on these two
receivers for the station in question. I
have fiddles with the R2 slide controls in
both Sharp and Console. The Elad appears
not to have any RF gain capability.
The frequency I am
using for this exercise is 98.9, 92 watts,
25 km away. I am using the same antenna
for all three radios. The antenna is
pictured in an attachment. Same feed line
to all three radios. My HF+ Discovery
works fine also.
As I said in a
previous message, the Elad S2 is the one
that really puzzles me. I would have
expected it to come out the best (based
only on price, that is).
Anyway, please let
me know if more information is needed.
Thanks for looking
On Friday, July 8,
2022 at 11:38:57 PM PDT, jdow <jdow@...>
14:47:30, George Stein - NJ3H via
92 watts not
Jul 8, 2022 at 2:24 PM, George
Stein - NJ3H via groups.io
to my last message. The
station in question is 25 km
away and running a mere 25
Using SDR Console:
With the Elad S2 and and the
Airspy R2, the reception was
With the Airspy HF+ Discovery
and the RSPdx, the signal was
full quieting. With the edge
going to the HF+ Discovery.
This was not a scientific
test, just a casual
observation. The only thing I
am surprised about was the
Elad S2 performance.
I then used the native
software for each device and
had the same results.
Regards and YMMV,
- + - + -