Re: 2N5109 amp directly biased with ZD
When regulating Vcc with a zener we automatically insert a simple cap-input Pi network in the Vcc line. I'd check with a scope to determine the before and after noise reduction and to establish the values.
The automatic go-to standard we use for sensitive front-end preamps is 1 to 3.3 uF and 30-100uH. The choke should be Hi-Q (80-100+), but in low current circuits the resistive loss will be minimal and 3.3V might end up being something like 3.25 at a low mA draw. But always build a test circuit on a punch board first to get a feeling of what's going on. I've done this on many WJ8711 and 8718 receivers along with a 500 Ohm trim pot on the output to establish the fixed gain ... usually 6 to 18 dB net. The WJs don't mind any impedance changes since they are never 50 Ohms (exactly) on the input anyhow. Actually, the receivers without the factory preselector act more like a constant voltage source and don't sag the source (antenna) voltage assuming your input signal is somewhere around 50 Ohms. I personally have used antenna input impedances of 25 to 150 Ohms (resistive) and cannot detect any problems. Additionally, having some kind of circuitry ahead of the WJ's front end (non-preselector types) is added protection from static discharges at the antenna. The WJs do not necessarily have much protection in that regard anyhow. We've done this with Racal, Harris, and ITT receivers as well.
Good signals to all in 2025, Bob, N1KPR
AmComm/Dynametrics(semi-retired)
-
- Youtube: N1KPR
- Youtube: Ham Radio Doctor
Engineering, where enigma meets paradox
On Monday, December 30, 2024 at 08:11:04 PM EST, W0LEV via groups.io <davearea51a@...> wrote:
Zeners are also good noise generators.? It could work well, but must be well filtered.
Dave - W?LEV
Hi All,
?
I saw an interesting article.
an amplifier using a 2N5109 at the bottom of this page.
It has a 3.3V zener diode and a 3.3k resistor to make a bias voltage.
It looks simple and stable, seems to work well in LTSPICE simulations.
I have a question.
I have never seen a direct bias style like this.
Is there any problems?
?
73, Hisami 7L4IOU
|
Re: 2N5109 amp directly biased with ZD
Zeners are also good noise generators.? It could work well, but must be well filtered.
Dave - W?LEV
Hi All,
?
I saw an interesting article.
an amplifier using a 2N5109 at the bottom of this page.
It has a 3.3V zener diode and a 3.3k resistor to make a bias voltage.
It looks simple and stable, seems to work well in LTSPICE simulations.
I have a question.
I have never seen a direct bias style like this.
Is there any problems?
?
73, Hisami 7L4IOU
|
2N5109 amp directly biased with ZD
Hi All,
?
I saw an interesting article.
an amplifier using a 2N5109 at the bottom of this page.
https://www.microchem.fr/ayet/atlas/hf_amplifier.html
It has a 3.3V zener diode and a 3.3k resistor to make a bias voltage.
It looks simple and stable, seems to work well in LTSPICE simulations.
I have a question.
I have never seen a direct bias style like this.
Is there any problems?
?
73, Hisami 7L4IOU
|
Re: "L Impedance Match" to 50 Ohm Coax
Agreed, and you need 3dB more noise with an actual antenna connected at any specific frequency, in order to ensure that your antenna is constrained by your local noise floor, so a 6dB rise in noise relative to a 50 ohm load should be aimed for.
?
Regards,
?
Martin
?
On Sun, Dec 29, 2024 at 04:11 PM, W0LEV wrote:
However, as stated in the original email, at HF frequencies and many times even 50-MHz, the real antenna noise exceeds this 3 dB of thermal noise.?
|
Re: "L Impedance Match" to 50 Ohm Coax
Just a quick gauge on thermal noise vs. antenna noise:
Define (ONLY for the purpose of simplicity) "antenna noise" as the increase in receiver noise experienced by connecting your combination antenna and feedline to your receiver regardless of frequency.? Again, this definition is ONLY for the sake of simplicity and keeping math out of the argument.
If your "antenna noise" is greater than a 50 ± j 0 load at room temperature attached instead of the feedline, don't bother with matching or worry about mismatches or preamps.? You are antenna noise limited and no preamp or other means of matching can or will improve that.? In reality, even a good preamp can and will degrade the noise performance and possibly also dynamic range.
A bit more:? A matched load produces 3 dB of thermal noise.? With a good receiver and a well designed and quiet front end, that 3 dB is just detectable.? However, as stated in the original email, at HF frequencies and many times even 50-MHz, the real antenna noise exceeds this 3 dB of thermal noise.?
Dave - W?LEV
"Fabricating Impedance Transformers for Receiving Antennas"? is available at IRCA Reprints, #A-155, index at? ?
? also still has a copy, I believe.
best wishes,
Nick
?
On Thu, 26 Dec 2024 10:11:46 -0800, "James Redding WA9VEZ via " <wa9vez=[email protected]> wrote:
?
There is a thermodynamic problem embedded in the design a broadband antenna matching network, named "entropy". The issue is well covered by:
?
?
or as an actual software based broadband automated calculation, here:
?
?
However, below 30 mhz, the ever present background noise is many times the universal thermal/Black-body noise, especially if you are living in an urbanized area.
?
Without playing with the math, if you need to change impedance of an electronic circuit (exempting transformers), you will get to the idea of "Q", which is roughly the ratio of reactance to resistance at a single frequency. "Q" also is the inverse of bandwidth in a network. . . That exchange occurs when you passively transfer between impedances, which also forces an exchange of bandwidth.
?
There is an transformer configuration network called a Brune network that creates a "negative inductance". (With apologies to every reader who has done a manual root extraction and wound up with the "beast".)
?
?
?
Here is a link to a Motorola app note from the early days of bipolar power RF transistors (like 2N3375):
?
?
I recall that someone implemented an internet site that automated the various equations in the AN721 app note but the page has morphed into a "404 error".
?
?
As for your transformer, the "Wayback machine" has a copy of the 2001 article:
"Fabricating Impedance Transformers for Receiving Antennas" which was on the web at:?
?
?
I had to go thru the "Wayback Machine" to see a copy of the original pdf.
?
Usually below 30 mhz, the background and man-made electrical noise is 20 db (or more!) above thermal noise and precise receiver impedance matching is a waste of time. A loss of capital and effort that could have been used tuning for signals. Above 50 mhz, the noise figure becomes more important as does the height of your antenna and time of year (E-skip!).
?
Anyway, for those that got to the bottom of the reply, the math used above is why you were taught "synthetic division" of polynomials back in junior high school. . .
?
Jim/VEZ
?
|
Re: "L Impedance Match" to 50 Ohm Coax
There is an updated version of John Bryants transformer paper:
?
?
regards, Fred
|
Re: "L Impedance Match" to 50 Ohm Coax
"Fabricating Impedance Transformers for Receiving Antennas"? is available at IRCA Reprints, #A-155, index at? https://dxer.ca/images/stories/2019/irca-reprint-index.pdf?
https://dxing.info/? also still has a copy, I believe.
best wishes,
Nick
?
On Thu, 26 Dec 2024 10:11:46 -0800, "James Redding WA9VEZ via groups.io" <wa9vez@...> wrote:
?
There is a thermodynamic problem embedded in the design a broadband antenna matching network, named "entropy". The issue is well covered by:
?
https://eng.libretexts.org/Bookshelves/Electrical_Engineering/Electronics/Microwave_and_RF_Design_III_-_Networks_(Steer)/07%3A_Chapter_7/7.2%3A_Fano-Bode_Limits
?
or as an actual software based broadband automated calculation, here:
?
?
However, below 30 mhz, the ever present background noise is many times the universal thermal/Black-body noise, especially if you are living in an urbanized area.
?
Without playing with the math, if you need to change impedance of an electronic circuit (exempting transformers), you will get to the idea of "Q", which is roughly the ratio of reactance to resistance at a single frequency. "Q" also is the inverse of bandwidth in a network. . . That exchange occurs when you passively transfer between impedances, which also forces an exchange of bandwidth.
?
There is an transformer configuration network called a Brune network that creates a "negative inductance". (With apologies to every reader who has done a manual root extraction and wound up with the "beast".)
?
?
?
Here is a link to a Motorola app note from the early days of bipolar power RF transistors (like 2N3375):
?
?
I recall that someone implemented an internet site that automated the various equations in the AN721 app note but the page has morphed into a "404 error".
?
?
As for your transformer, the "Wayback machine" has a copy of the 2001 article:
"Fabricating Impedance Transformers for Receiving Antennas" which was on the web at:?
?
?
I had to go thru the "Wayback Machine" to see a copy of the original pdf.
?
Usually below 30 mhz, the background and man-made electrical noise is 20 db (or more!) above thermal noise and precise receiver impedance matching is a waste of time. A loss of capital and effort that could have been used tuning for signals. Above 50 mhz, the noise figure becomes more important as does the height of your antenna and time of year (E-skip!).
?
Anyway, for those that got to the bottom of the reply, the math used above is why you were taught "synthetic division" of polynomials back in junior high school. . .
?
Jim/VEZ
?
|
Re: PA0FRI, Silent Key Loop info
?
?? Maybe try a different browser.
?
Henry
|
Re: Wellgood amp enclosure
If anyone is interested, I have several retrofit amps for the Wellbrook ALA1530 loop. They are in a PVC case, and potted. They are a match and fit perfectly on the ALA1530.?
?
Everett N4CY
In a message dated 12/27/2024 12:38:02 PM Central Standard Time, k2tl@... writes:
?
Thanks for all the suggestions, but I recently purchased an LZ1AQ type amp from Everett instead.? Local waterproof PVC electrical boxes fit the circuit board just right.? I use 1/2 inch Heliax for the loop material.? Little bit of modification and all is well.
|
Re: Wellgood amp enclosure
There is a
filament known as ASA that is really durable and offers much more
UV resistance but it requires a printer that can handle hotter
melting temps and has a heated bed.? I have some but have not
tried it out yet. Normal PLA barely works but I found it does not
hold up well outside here in the Midwest UV and rain, plus it
breaks and cracks easy.
Gedas, W8BYA EN70JT
Light travels faster than sound.....
This is why some people appear bright until you hear them speak.
On 12/27/2024 1:42 PM, W0LEV via
groups.io wrote:
toggle quoted message
Show quoted text
Diecast aluminum boxes are relatively
inexpensive, some can offer waterproofing with an inset
gasket, and offer good E-field shielding (if proper attention
is paid to ingress/egress of conductors).?
My first question on the 3-D printed
enclosure would be survival to solar UV radiation.
Dave - W?LEV ?
Dave - W?LEV
can you not find the dimensions online and make some
using a 3d printer? Just a though
?
Nick
G8SYE
--
|
Re: Wellgood amp enclosure
Diecast aluminum boxes are relatively inexpensive, some can offer waterproofing with an inset gasket, and offer good E-field shielding (if proper attention is paid to ingress/egress of conductors).?
My first question on the 3-D printed enclosure would be survival to solar UV radiation.
Dave - W?LEV ?
Dave - W?LEV
can you not find the dimensions online and make some using a 3d printer? Just a though
?
Nick
G8SYE
|
Re: Wellgood amp enclosure
Thanks for all the suggestions, but I recently purchased an LZ1AQ type amp from Everett instead.? Local waterproof PVC electrical boxes fit the circuit board just right.? I use 1/2 inch Heliax for the loop material.? Little bit of modification and all is well.
|
Re: Wellgood amp enclosure
Suggestion for KISS method completely DIY.? I thought it was rather difficult to make such a small PCB preamp DIY without a special PCB, so I am just using a 80x80x50mm waterproof electrical box with a LZ1AQ preamp constructed bug style on some double sided PCB 60x60mm.. The new box will be fixed by bolting it through the old potting compound of a blown Wellbrook loop given to me by a friend, after making new end connections.
73, John
|
Re: Wellgood amp enclosure
can you not find the dimensions online and make some using a 3d printer? Just a though
?
Nick
G8SYE
|
Re: "L Impedance Match" to 50 Ohm Coax
There is a thermodynamic problem embedded in the design a broadband antenna matching network, named "entropy". The issue is well covered by:
?
https://eng.libretexts.org/Bookshelves/Electrical_Engineering/Electronics/Microwave_and_RF_Design_III_-_Networks_(Steer)/07%3A_Chapter_7/7.2%3A_Fano-Bode_Limits
?
or as an actual software based broadband automated calculation, here:
?
?
However, below 30 mhz, the ever present background noise is many times the universal thermal/Black-body noise, especially if you are living in an urbanized area.
?
Without playing with the math, if you need to change impedance of an electronic circuit (exempting transformers), you will get to the idea of "Q", which is roughly the ratio of reactance to resistance at a single frequency. "Q" also is the inverse of bandwidth in a network. . . That exchange occurs when you passively transfer between impedances, which also forces an exchange of bandwidth.
?
There is an transformer configuration network called a Brune network that creates a "negative inductance". (With apologies to every reader who has done a manual root extraction and wound up with the "beast".)
?
?
?
Here is a link to a Motorola app note from the early days of bipolar power RF transistors (like 2N3375):
?
?
I recall that someone implemented an internet site that automated the various equations in the AN721 app note but the page has morphed into a "404 error".
?
?
As for your transformer, the "Wayback machine" has a copy of the 2001 article:
"Fabricating Impedance Transformers for Receiving Antennas" which was on the web at:?
?
?
I had to go thru the "Wayback Machine" to see a copy of the original pdf.
?
Usually below 30 mhz, the background and man-made electrical noise is 20 db (or more!) above thermal noise and precise receiver impedance matching is a waste of time. A loss of capital and effort that could have been used tuning for signals. Above 50 mhz, the noise figure becomes more important as does the height of your antenna and time of year (E-skip!).
?
Anyway, for those that got to the bottom of the reply, the math used above is why you were taught "synthetic division" of polynomials back in junior high school. . .
?
Jim/VEZ
?
|
Re: PA0FRI, Silent Key Loop info
Can't find the links for the ANT articles within there.
73 Horacio CX3BZ
El jue, 26 de dic de 2024, 09:10, Radioman ZeroZero via <radioman= [email protected]> escribió:
He was very friendly and I got a mention on his website for fd4 antennas.
Rest in peace.
--
Thanks Steve M0ZEH
|
Re: PA0FRI, Silent Key Loop info
He was very friendly and I got a mention on his website for fd4 antennas.
Rest in peace.
--
Thanks Steve M0ZEH
|
Re: "L Impedance Match" to 50 Ohm Coax
For a broadband transformer the “rule of thumb” is that the reactance of the low impedance winding should be 4x the impedance ?at the lowest frequency of operation. So for a 50 to 450 ohm transformer operating down to 4 MHz. you need a reactance of 200 ohms at this frequency. ?So you calculate the inductance required and the number of turns. ?If 5 turns are required then you need 15 for the other winding.?
|
Re: "L Impedance Match" to 50 Ohm Coax
I suggest you try The free program
TLW which can match using several different methods like L, T, and Pi.
?
|
Re: "L Impedance Match" to 50 Ohm Coax
Why not use SIMNEC 2.5, this versatile tool from AE6TY does the job, including the transmission line and much more. Lots of support and tutorials available.
?
?
If you want to do the calculations on your own, her are the formulas:
?
regards, Fred
|
Bob, N1KPR
Everett N4CY
James Redding WA9VEZ
Horacio A. Nigro, CX3BZ
Radioman ZeroZero
Roger Need