Thanks again for all the comments. Very interesting especially the
reasoning behind the designs.
The device I've picked for my design is the LTC6228. This is a new
device by Analog Devices that only came out late last year. The voltage
noise is 0.88 uV/sqrt Hz and the current noise is 3 pA/sqr
Lee,
I think you are confusing voltage and power. For incoherent sources like
amplifier noise, the voltages of multiple incoherent sources add in a
root-sum-squared (RSS) fashion. The voltage of the sum of eight incoherent
sources is square root of eight times a single noise source, assuming e
*JFET op amp vs bipolar op amps, *LTSpice simulations connected to a 3
meter monopole
A bipolar op amp doesn't always give the lowest noise with a short monopole
at 1.8 MHz because the op amp current noise creates noise voltage across
the antenna capacitive reactance. Additonally, op amps can be c
Chris,
Good choice.
Perhaps one note of caution. With a BJT input like this the input current
noise may be more dominant, unless the input impedance is kept low.
Would be great to see the final design.
GL and 73,
George,
AA7JV
On Thu, 12 Mar 2020 10:10:44 +
Chris Moulding wrote:
Th
ass a asa
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John,
Yes of course you are quite correct. I stand corrected. I should not have
used the word power. My thinking was along the line of what Mike W4EF posted.
Just did not say it right. Also, I have never disagreed with your choice of the
8055 as I was aware of why you made that decision. Fort
Hi Lee,
Yes, if you are combining coherent signals that are not in phase, then
the each of the voltage vectors is weighted by cos(phi-i) where phi-i is
the angle between the i-th voltage vector and the 1st vector. If phi=0,
then you have the case I described previously. I can see how this can
There are a lot of SMT to DIP adapter boards out there which would allow
newer SMD op-amps to be used in older through-hole PWB layouts.
https://www.digikey.com/product-detail/en/aries-electronics/LCQT-SOIC8-8/A880AR-ND/4754588
73, Mike W4EF.
On 3/12/2020 1:15 PM, Lee STRAHAN
On 3/12/2020 4:13 AM, John Kaufmann via Topband wrote:
I think you are confusing voltage and power. For incoherent sources like
amplifier noise, the voltages of multiple incoherent sources add in a
root-sum-squared (RSS) fashion. The voltage of the sum of eight incoherent
sources is square r
To assess the impact of amplifier circuit noise in "active" receive arrays,
we only need to be concerned with the contribution of amplifier circuit
noise relative to atmospheric noise. The details of how signals are phased
in any particular array do not matter. The objective is to keep the total
I'll stick my neck out and suggest Dallas Lankford's '2 FET amp'.
He designed it for phased loop antennas for the MW band.
I believe it will work to at least to 9 MHz and maybe to 30 MHz.
The specs High input Z, ~100 ohm output Z. He lists input intercepts:
IIP2 = ~ +88dbm and IIP3 = ~+41dbm i
Lankford's stuff works great.
I have used his antenna which does NOT use
a preamp.it's only suitable for situations
where match to the feedline isn't critical, but
it sure is great to not have any preamp outside.
de K8RYU
From: Topband on behalf
of Mikek
*Amp/antenna noise *-- is the AD8045 noise low enough for a 3-meter
monopole? *0.26 uV amp noise vs. 0.16 uV man-made rural noise and 2.3 uV
city with a 3-meter monopole. *
Feel free to review my method/math and make corrections as needed.
*Rural Noise*, ITU-R P.372-14 (link below)
Working thru f
On 3/12/2020 7:44 PM, Dave Cuthbert wrote:
Feel free to review my method/math and make corrections as needed.
Didn't review your math, but the more important question is, "how old is
your noise data?" In my experience trying to work EU on Topband now as
compared to c.a. 2007-8 is vastly more
Looks interesting. Does anybody has this system running (e.g. with two
mini-whip antennas) and can provide more experiences?
73, Harry, DH1NBE
Am 13.03.2020 um 00:29 schrieb Mikek:
I'll stick my neck out and suggest Dallas Lankford's '2 FET amp'.
He designed it for phased loop antennas for
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