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junk box noise generator

 

I want to test filters and once again Santa stiffed me on all the fancy test gear I wanted.? It could be my fault as my chimney leads to the boiler.? Anyway, I have an rtl-sdr and an upconverter so all I needed was some clean noise.? Searching lead me to N5ESE's description of using a zener diode.? He references an earlier design by N0SS.? N0SS is now SK and his website is no longer but thanks to archive.org I found this
I breadboarded N0SS's circuit


and lo and behold it works great.? Below shows without and with the noise circuit.? The upconverter adds an offset of +125MHZ


if you are a Spielberg fan and live on a Native American burial ground you should probably skip this.

Doug
AC9RZ
 

Doug,

Do you have a sample circuit for a noise generator that goes an octave or two higher??

Would you be willing to speculate on stripline / SMD construction techniques to go up to or past 1 GHz?? My guess is -- duplicate the schematic with SMDs and use some common microwave transistors like MRF901.

73
Jim N6OTQ


On Thu, Jan 3, 2019 at 11:44 AM Doug W <dougwilner@...> wrote:
I want to test filters and once again Santa stiffed me on all the fancy test gear I wanted.? It could be my fault as my chimney leads to the boiler.? Anyway, I have an rtl-sdr and an upconverter so all I needed was some clean noise.? Searching lead me to N5ESE's description of using a zener diode.? He references an earlier design by N0SS.? N0SS is now SK and his website is no longer but thanks to I found this

dummyfile.0.part
dummyfile.1.part

 

Jim,
I do not have much more than what I posted.? As to a design for UHF, I am not the best to answer that.? You guess looks reasonable to me but that is like asking Ronald McDonald to check over your beef wellington recipe.? There are some pretty savvy UHF/VHF/microwave folks that pop in here from time to time, perhaps one of them will jump in and help.

Also, in case it wasn't apparent from my post, the receiver is actually tuned to 7.2MHz not 132.2MHz? due to the offset from the upconverter.
 

You can also use the base/emitter junction of a random transistor in place of the zener for the noise generator portion

Jim

On Thu, Jan 3, 2019 at 9:44 AM Doug W <dougwilner@...> wrote:
I want to test filters and once again Santa stiffed me on all the fancy test gear I wanted.? It could be my fault as my chimney leads to the boiler.? Anyway, I have an rtl-sdr and an upconverter so all I needed was some clean noise.? Searching lead me to N5ESE's description of using a zener diode.? He references an earlier design by N0SS.? N0SS is now SK and his website is no longer but thanks to I found this
I breadboarded N0SS's circuit


and lo and behold it works great.? Below shows without and with the noise circuit.? The upconverter adds an offset of +125MHZ


if you are a Spielberg fan and live on a Native American burial ground you should probably skip this.

Doug
AC9RZ
 

This morning it occurred to me -- an MMIC on micro-stripline will basically amplify ANYTHING from DC to daylight, so I googled on "MMIC noise source."? It led me to a site which showed a HB noise gen that used an emitter - base junction in an NPN transistor (thanks to Jim Tibbetts for reminding us of this) and three chained MMICs to deliver amplified noise.? But the builder mentioned creating more than 100 thru-board vias by hand.?? So ... look down the search results and -- voila!? A group discussion not unlike what we have here that referenced "you can buy this stuff on ebay."

One click later, and I saw that pre-built, MW-capable noise sources can be had from China for twelve bucks (and twelve weeks).

So I'll probably buy AND build, since I have MMICs and zeners in the junk box, and I am not in a hurry for this. A comparison might be interesting.

It's a nice day when I find that something I could imagine -- could be built, AND if I wanted one today I didn't have to invent or even re-invent it.

73
Jim N6OTQ

PS -- When you "google" something, be sure to use duckduckgo as well, because their search algorithms are different, and BOTH search engines come up with true gems that the other one missed.? Difference is -- you have to wade through all of google's paid placements and SEO-enhanced results.
 

I decided to use this little circuit as a chance to learn how to make PCB's.? The first picture of the transfer and drilling is not the one I actually used.? I got the process down better but didn't take a picture of the final one.? I was also playing with a new pair of magnifying loupes which I am not used to so the soldering is awful but it works.? I went back to the bench and touched some of it up.? I layed everything out in easyeda and did the transfer by printing onto magazines sheets from my laser printer and then running it through a cheap amazon laminator about 20 times.? I etched with vinegar and hydrogen peroxide plus table salt and drilled with a cheap dremel knock off, then transferred the "screen" to the top side.? I get the same results as the bread boarded circuit I posted earlier so I am calling this a reasonable first home brewed board.
Alan Jones
 

Doug,
Congratulations on making your homebrew pcb.
I have not used the vinegar-hydrogen peroxide-salt etchant yet.
What are the proportions you used for the etching solution?

Al, N8WQ

On Sun, 10 Feb 2019 19:15:34 -0500, Doug W <dougwilner@...> wrote:

I decided to use this little circuit as a chance to learn how to make PCB's.? The first picture of the transfer and drilling is not the one I actually used.? I got the process down better but didn't take a picture of the final one.? I was also playing with a new pair of magnifying loupes which I am not used to so the soldering is awful but it works.? I went back to the bench and touched some of it up.? I layed everything out in easyeda and did the transfer by printing onto magazines sheets from my laser printer and then running it through a cheap amazon laminator about 20 times.? I etched with vinegar and hydrogen peroxide plus table salt and drilled with a cheap dremel knock off, then transferred the "screen" to the top side.? I get the same results as the bread boarded circuit I posted earlier so I am calling this a reasonable first home brewed board.
 

1:1 on the vinegar to hydrogen peroxide.? The table salt is kind of trial and error, you want enough so you see bubbles coming off the copper.? With 120ml of solution this equates to the extremely scientific value of a few good shakes.? I found no discernible difference between cheap iodized table salt and fancy non iodized sea salt.? This method takes some time work.? I found it took 20-30 minutes to completely etch.? It helps if you agitate a little and wipe the sludge off the board with a foam brush.? The chemicals are cheap so use more than you think you need.? My first try I only used 60ml of total solution my little 50x50mm board.? It never completely etched and the mask failed.? I doubled it to 120ml total and it worked well.? I also found you can not reuse the solution but that my not be the case if you use a larger quantity per board.? I have never done this before so I can not compare it to using muriatic acid or commercial solutions.

I first found the method here ?
This is the lamintor I used for the transfer

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