*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
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 desig
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 n
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 t
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/LC
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
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 spe
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 an
*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 met
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 difficult thanks
The document was published last year so we might assume the noise graph is up to date. To put this in perspective, To put the ITU-R P.372-14 claimed noise in perspective here's the calculated antenna
<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 difficult tha
This is great advice, which I think a lot of folks are too quick to dismiss in this era of vanishing through-hole DIP ICs and transistors with wire leads. I successfully did just that with an SO-23 (
It's not clear to me. Wes N7WS limits on 160 band...and also 80+40. That or arrl legal remote RXs..... pick one. Jim VE7RF _________________ Searchable Archives: http://www.contesting.com/_topband -
More power to make up for my 10db excess noise = xxx Kw - whoopee! Need to get some 3 phase. Remote Rx, eg 100km makes a lot more sense. Clubs could put up shared facilities. With direct sampling syn