Spectrometer

 Throughout the summer I had been recording some very high air quality readings on my weather station, This is a terrible situation for anyone with breathing issues. Personally, I do not have such issues (yet) but I like to know what is floating around in the air at any given time so that I may not develop such issues.

I had started to notice that whenever the air quality was particularly bad, that we would have some of the most amazing sunsets ever granted for human eyes to ever behold. This got me doing some research and I found out that the California wildfires were the cause. The smoke was literally working its way across the country and causing breathing problems thousands of miles away.

So it was all smoke that was making the sunsets so nice. Immediately I had thought about something I read some time ago about how astronomers use the light from a star passing through the atmosphere of a planet to determine what the atmosphere was made of. This begged the question, "Could I look at the light from one of these sunsets to see what was in the atmosphere between me and the horizon?" 

I would imagine that I would need something that could split light into its components, then I could take pictures and compare them with a clear day and see at very least the difference. I started mulling over a design in my head. I would need some sort of prism, and an adjustable aperture, and perhaps a plate to project the scattered light onto. A small hole with a camera could be fashioned to record things.

I took to the internet and quickly realized that other people have been collectively working on a DIY spectrometer for some time. As always I was late to the game but this allowed me the luxury of having most of the work done for me. Even the software was freely available.

The effort is called Theremino. If you scroll some way down on their page you can find the blog entry about the spectrometer. Or you can just go directly to this article and it will explain things,

In a nutshell, its really just a box with a slit in it to allow light to enter. The box has a webcam in it with a diffraction grating to split the light. Make sure the inside of the box is as dark as you can get it. That includes making the interior black. Software on your computer looks at this real-time picture and it allows calibration to associate where different bands of light are and maps then to a wavelength of light. Once calibrated I was astonished at its accuracy.

I won't speak too much of the particulars of how, why, & what does all of this. Just download the software and play with it. I will however outline my version of this DIY spectrometer.

A few things were needed before I could start playing. A webcam and a diffraction grating. 

I had considered using a prism that I have but in reality it is just too bulky and doesn't allow for the simplicity that a diffraction grating has. When selecting a diffraction grating you want to select anything that is at or above 1000 lines/mm. I  believe this one would work. 

As for the webcam. I had picked up 3 or 4 of them at Microcenter since they were only four dollars each. There is a Microcenter close to where I work so it was just the natural selection of place to purchase from.

One note about webcams is that if you want to read infra-red light you will either need a webcam that can see this or remove the filter from the webcam that cannot. You'll have to do your own research for this. Because I had so many webcams that I had purchased I sacrificed one to see if I could find the IR filter in the optics. I did not immediately see anything of the sort so I merely hoped for the best.

Here you can see my rough prototype, using a box I slapped together with some 2x4's and old Pergo flooring. The aperture is two razor blades I fastened over a hole using painter's tape. The Theremino software is running, although not calibrated. I had used the Infra-red light on my security camera to test if the webcam was sensitive to that light and as you can see there is a spike indicating that it is.

At this point things were loosely cobbled together. You couldn't even move the box lest you screw all the adjustments up. I needed a way to secure everything properly and make it in someway articulating to allow for pointing it at a light source.

This is when it is nice to have a 3D printer at your disposal. I used a pretty neat free online CAD site called TinketCAD That allows you to import and create 3D objects. I knew I wanted the aperture to be adjustable and have the precision of a razor's edge, so I found a 3D file for a razor scraper and modified it a bit and created a holder for it. Also I wanted something that I could mount the camera to that would also hold the diffraction grating. Below I have provided a link to my STL files. You might have to manipulate them to suite your own needs.

STL Files

Here you can see the assembled aperture in place. I had created screw holes but in the end I just ended up gluing them to the front of the scope. Things were a little loose so I jammed some folded cardboard behind the sliders. After all its not rocket science, I just want it to be able to roughly adjust how much light gets in.

Moving to the inside of the spectroscope, you can see my camera mount and diffraction grating holder. Just a note here that a lot of the literature I read says that you need about a 30 degree angle to the incoming light to get the proper spectrum on your webcam. I designed the mount with a screw hole so things an be adjusted. The black construction paper is there to cut down on any sort of glare. In my experience this doesn't do much. If the light is bright enough it will glare.

Since I was planning on pointing this at the sun, and shooting lasers at it, I anticipated that glare, and proper light alignment might be an issue. So I installed this diffuser. This is made from an old alcohol bottle that I cut up. I merely velcro'ed it to the aperture holder so I could remove it in darker conditions.

Finally I mounted the whole thing onto an old telescope mount I had picked up at the thrift store. This allows me to move the entire assembly around.

Calibration was a little tricky in the beginning, before I had installed the light diffuser. You can see the results before and after the diffuser was installed. There is nothing too complicated about calibrating it. The software has designated markers for a few different types of light. The best being a florescent CFL bulb. These bulbs have very specific wavelengths of light that you can place markers on. Ones that is done I have noted that my spectrometer is accurate within a nanometer. More on that in a bit.

Here you can clearly note how much glare there is. The spectrum repeats itself and falsely reports light in the infra-red range. The software allows you to "tighten" the view boxes that it looks at. This helps a little but would completely ignore upper and lower bands depending on how you have things adjusted.

 Once the diffuser was installed the spectrum looked a lot cleaner. And the CFL bulb had clearly defined peaks that I could place markers on. Now that it was properly calibrated, we can verify by shooting some lasers at it.

Every laser I have had the pleasure of playing with has always had power and wavelength clearly labeled on it. Using this information I could compare what what the manufacturer lists alongs with what I can read with my new spectroscope.

This is my green laser. It was dead-on at 532nm. There was some glare since it it an 80mw laser.

Next was a cheap red laser that had a "range" of what it emitted. Its escapes me as to what those numbers are but the peak was near the center of this range. I was satisfied with what I was reading and was confident that I could successfully identify the wavelength of the light entering the scope.

Now it was time to see how sensitive the scope was to infra-red light.

This is the IR spotlight from my security camera.

This is a UV LED

I was curious how close to the spec my grow light was. As you can see this is before I had the diffuser installed.

Things were VERY close to the manufacturer's spec.

Finally I took everything outside on a clear day to get some sunlight.

I believe that same day we had a full moon and I decided to capture the moonlight. The aperture was nearly full open to gather enough light to get a sample. I found it interesting that there seems to be less green light. I would have anticipated that the sample would look just like the full sun.

This was a very fun project with good intention. However, by the time I got everything built and calibrated properly the summer was long over and the wildfires were under control enough so as not to cause us ill effect here in New Jersey. We are just going to have to be happy with our own home grown pollution for now. That is until California catches fire again next year.

More to come on this next summer I hope.

The Great Decametric Dipole Experiment of 2022 has been canceled due to Fear and Loathing

 "What happened?", you say? Well, apparently the neighbors that live behind me, in particular the Man, his Wife, and Daughter have all been experiencing "headaches" since I put my RECEIVING antenna up a few weeks back. My guess is that these "headaches" are of the variety to inflict an individual whenever they look into my backyard and see something they don't like.

Now before I am judged as being uncaring, crass, or unsympathetic, especially when concerning a neighbor. I would ask of you, a few of your valuable moments to read through the events that led up to all of this and judge for yourself, if my annoyance is well placed.

First, let me say that these are not bad people. I have never had an issue with them up until a few years back. And even then it was something that rubbed me the wrong way in such a fashion that I am actually too embarrassed to speak of with anyone who is not a close friend, let a lone the entire internet.

Dateline, late October of last year. I managed to take a few pictures of Jupiter in the night sky that I was rather proud of. It was this event that inspired me to explore what radio emissions Jupiter might have to offer. I did quite a bit of reading and realized that I had a lot of the equipment necessary to receive a larger Jupiter emission. The only thing that was needed was an antenna. I researched smaller design antennas in the hopes that I could just construct something directional and small enough not to cause suspicion. To that end I failed and had to settle on a single dipole antenna cut to around 20.1Mhz.

This required at least 30 lateral ft with10 ft on each side of yard. Furthermore to get the antenna pattern I required, to encompass the low angel of sky that Jupiter occupied at this time of year, I had to get everything at least 15 ft above ground. I was able to accomplish this with some Romex house wire and four 10ft lengths of PVC.

I don't know, I rather like the way it looks with the backdrop of a nice sunset.

Setup proved to be way faster and easier than I had expected. I only needed to adjust the guy wires (strings) to insure that the antenna did not sag in the middle or lean towards one side or the other. It was actually a beautiful day with many people going about their outside business. No one seemed to notice or care what I was doing in my backyard. They never do, as I try to keep a low profile.

While adjusting one of the guy wires, my neighbor, who we will call Mr. F. in the interest of annominity, called out my name. I was a little surprised since I haven't talked to this person in literally years. We don't even wave to one another. Still not really sure why. Anyway, I said hello and asked how he was doing. He was looking at the antenna. Before he could speak I said, "Its ugly isn't it? You don't like it?" 

He seemed surprised that I said that and offered back "No, no its beautiful, I like it."

"Really?, I think its ugly, but looks don't matter. So what's going on? I haven't spoken to you in a long time.", I said.

One thing I think I should mention about Mr. F is that he is Ecuadorian and has a VERY heavy accent. The kind that I have trouble understanding most times. So from this point forward I will be paraphrasing what I THINK  he said to me. At very least my interpterion is how I will illustrate it here.

Mr. F starting talking about how he was worried about the pandemic and how nobody in his household wears masks or takes things seriously. Especially his mother-in-law. He also started talking about keeping his yard clean and how hard that was because he is always working.

Then as sure as shifting gears without a clutch, he grinded over to the question, "So what is this thing for?" I was all too happy to explain everything to him, not so much to leave the dreary line of small talk conversation that I felt roped into, but to honestly share my enthusiasm for radio astronomy with another human being.

I tried my best to explain what I was doing and why I was doing it, but alas I got a "deer in the headlights" stare from him. Sensing that he really didn't want to connect about anything other than a big strange thing being erected in my yard I kept it simple and said, "Its ok I am just testing something and I won't have it up too long." That kind of satisfied him and I bid him a good day and didn't think much of it.

Fast-forward a week later. I finished up my development work for the day and decided to indulge a bit by reading my book. "The Big Ear" by John Kraus, awesome book by a true radio pioneer. Anyway, the doorbell started me, because it is so seldom rung. "No Soliciting" signs are well worth the money. I checked the front door camera and seen that it was Mr. F.

"What?, Really? <sigh> Why?", I thought to myself. I reluctantly answer the door.

"Hello Mr. F., won't you come in", I extended while locking eyes with him. I continued, "Wat can I do for you?"

He feverishly shook his hands and blew in them to scare away the cold. "It's my daughter, she is upset. She says there is something in your window."

"My window?"

"Your window."

"MY........win...dow?"

"Yes, she is very scared."

"Fine lets go take a look", I said while heading towards the stairs.

"No wait!, Let me take off my shoes on your nice floor", Mr. F barked. I have to admit that I did feel nice that he noticed our new floor, but this was quickly replaced by a feeling of annoyance that I was being interrupted for what I had predicted would be an exercise in futility.

As I watched him fumble with his double tied laces to get his shoes off, I exhaled through my nose probably louder than I should have. 

It took a moment but we got past that eternal wait. "Come on let me show you", I said.

I led him into my office/station/studio or rather my "man-cave". 

Upon entering the doorway his eyes grew very wide, and I heard a little gasp from Mr. F.. There presented for Mr. F's review was a variety of blinking things. The three screens from my work computer invited him first. Then a slight hiss from my HF rig listening to static on 20.1Mhz drew his gaze over to another laptop with a selective voltmeter and large power supply. I could see that he was slowly taking it all in and had not expected to see all of this.

"So you see? There is nothing in the window!" I snapped as if I pulled Mr. F. out of trance. I then pointed to a third laptop that had an active line plot. "You see, that antenna outside listens to the Sun and other things and sends it to this computer where I can analyze it and compare it with..." I clicked an icon and brought up the NOAA Geophysical & Solar Daily Report. "this report that tells me all of the confirmed things the Sun is doing."

He truly seemed astonished. But he kept insisting that his daughter was getting upset about something in my window. So again I asked him, "Is it the antenna outside, does that bother her, or perhaps YOU?"

He shook his head immediately. "No, no ,no I like it.", he assured me.

"Riiight. well ok, then I am not sure what problem your 'daughter' has with anything, would it help if I visited and talked to her?" I offered.

"No, no ,no that's ok." He firmly stated.

At this point I attempted to show him the particulars of what I was trying to observe, but that lead into the same dead end stare I had received earlier.

"Well ok then, my wife will be coming home soon and I need to get dinner ready so thanks for dropping by."  I said while opening the front door. As he pasted me I added, "If there is a problem you have with my antenna in the yard, just let me know and we will address it."

"No, no ,no everything is fine, thank you.", he muttered while waving his hand as he made his way down my walkway.

Not a word from these people in like five years, and now all of a sudden this guy is telling me about  his "problems". It was clear that SOMEONE in that house had an issue with my antenna, but honestly I wasn't going to take anything down yet since I was experimenting and was expecting to see some solar activity within the next week. So if anyone had an issue they would need to speak up loud and clear.

So apparently yesterday they did.

Because of the pandemic I have been fortunate enough to be able to work exclusively from home, until things even out a bit. I won't lie, I have enjoyed it. It allows me a great deal of freedom. The kind of freedom that allows me to roll out of my bed and into my computer chair.

So here I am, sitting in my chair at around 8:30am. Outside was cold and wet. I do believe that ice was actually falling from the sky at that time. I had just put my slippers on that had been sitting on the heating vent for a spell to toast them up for my receiving feet. I sipped mildly at my warm cup of coffee. Ahh the serenity, I thought. There was no doubt about it, I was more than ready to take charge in our weekly developer's meeting. Business as usual. Work, and schedules peppered with light humor to keep things positive. Then the doorbell rings and I look at the camera.

"Oh you have GOT to be kidding me?"

What do I see? A frail Mr. F. standing at my doorstep in only a hoodie, hands clasped around his upper arms shivering in the the cold, icy rain., What could I do? I was running a meeting talking about important stuff. So I left him there to ring the bell a total of two times, driving the dog absolutely insane.

It was at this moment that I decided that this had to stop.

After my meeting I bundled up proper and went to knock at his door. It took him a moment but he finally answered. Before he could even offer a "hello", I looked him straight in the eye and asked directly, "What do you need to talk about? I could not answer my door because I was in a meeting working."

He broke eye contact with me and shook his head, then said "Please, please come in"

"No, I will not come in, this is my work day, I have errands to run and then immediately go back to work", I replied while simultaneously taking a large step back from his doorway,

"Now what is it that you need to discuss with me?", I added.

Mr. F. took a moment to compose his thoughts. He noticed that I was glaring right at him. Some folks are intimidated by this and I hope he wasn't one of them. I glared at him because I wanted to be sure I understood EXACTLY what he wanted, because this would be the last time I would give him audience.

"My family, wife and daughter, we have been having headaches", he attempted to say in his most convincing voice.

"Really? That's terrible, have you been to a doctor? Because those are all symptoms of the pandemic, and I seem to remember a few weeks back that you were concerned about that.", I put firmly.

"No, no I haven't been to the doctor. We all started getting headaches after I talked to you that day in the yard", he added.

"So you mean that day I had put up the antenna in my yard? " I snapped. Mr F. was about to say "yes", but then I quickly added, "The same day that you said it was beautiful and you liked it and had no issue with it? RIGHT?"

He then sheepishly said, "Yes".

At this point I was a little angry, and I became more firm. "LOOK AT ME!", I barked. Surprised he locked eyes with me. "DO YOU WANT ME TO TAKE THE ANTENNA DOWN?" I added very firmly.

"no, no your a good guy I like you", he said. He was about to say more but I interrupted him.

Again I barked, "LOOK AT ME! DO YOU WANT ME TO TAKE THE ANTENNA DOWN?"

Still he persisted that he was ok with it being up but that he didn't know what to do because it gave him headaches.

At this point I could take two courses of action. I could either loose my patience and literally berate this poor guy on his own door step(That's not the guy Mom raised), or just give him an easy out because he was clearly being manipulated by someone in that house to take care of what they deemed of as a problem. So with that I regained my composure, exhaled the rage and asked him this simple question.

"Let me ask you this. Would you feel better if the antenna had never been put up", I asked calmly.

"Yes", he replied.

I extended my hand to shake his. I shook it quickly and then handed him a piece of paper.

"That is my phone number, if I do not answer, leave a message, I am not available between 8am to 6pm because I am working. Please do not knock up at my door. The antenna will be down today"

He thanked me a few dozen times, as I walked away. I then used my lunch break to dismantle the antenna I so carefully erected. After that I played with the dog some and that cheered me up.

At this point I am just kind of over it (says the guy who just wrote ten pages about it). But in the end it was always a temporary fixture and I just wanted to learn with it. And I did just that. However,  Mr. F didn't make it easy. Mr. F did teach me a valuable lesson though. And that lesson is that although my burning curiosity about the cosmos above might inspire me to build large and strange things to listen to it, it indeed inspires fear and loathing in others who have to witness it.

And with that in mind I think a hydrogen line telescope would arouse much less suspicious to those who are commonly afflicted with headaches of this sort.

Thanks for allowing me to bend your ear.

The moment of truth

 After a lot of testing and reading on baluns, I ended up removing an additional two winds on each of the coils of my 1:1 balun. The performance was not MUCH better but was something I could settle with. 

Yesterday the temperature did not venture very far above 24 degrees. This did not make the lowering of my current dipole an enjoyable experience. Furthermore I had to heat the garage for about an hour before I could stop seeing my breath whenever I exhaled. Once the garage was at a semi-comfortable environment I removed the one wavelength RG58 coax that was feeding the antenna and replaced it with my 1:1 balun. The new feedline was 50ft of LMR-400 low loss coax. This ran into the barrel connector into my office window and finally another 6ft of LMR-400 that would go to my transceiver. 

Once again, confusion ensued. I hooked the antenna analyzer up and got ridiculous readings. I am not really sure why or how I was getting these reading, But, by using the process of elimination I removed the barrel connector and additional length of 6ft or LMR-400. Another tested proved to be much better. This made me wonder if my earlier setup was plagued by the same issue. None the less I pushed forward and installed everything. Below is a table of SWR for the balun alone, the old version of the antenna with one wavelength feedline, and then finally my new setup with balun and LMR-400 feedline.

As you can see its not of monumental improvement. I even gained SWR on the upper end above 20Mhz and gained a BUNCH below 15Mhz. This doesn't really concern me as of yet. I really want to see if this reduces the amount of noise I receive and if this will still be able to pick up solar events. I would also like to try and transmit on this antenna at some point.

Another thing that bothers me a little is that the feedline and balun put a lot of weight on the center of the antenna and as a result is sags a bit. Perhaps if I move to a single antenna mast and hang the feed point from that in an inverted V fashion I could get better results.

At this point I still feel as if I am poking around in the dark to see if I can get things to work. Normally I don't mind this too much, but with the temperatures being so low and the time it takes to get everything down and up the antenna masts it really does prove to be a frustrating experience when I realize I had forgotten something before I put it all back together, Such is life I suppose.

More to come.

Baluns

I'm not going to sit here and pretend I know anything about BALUNs. In fact, the majority of what little I know has only been recently accumulated in the past month. That being the case, I recently took it upon myself to try and construct one with little to no knowledge of what I was doing. Amazon is full of "balun" kits, that provide boxes, connectors, wires, toroid's, and loosely translated to English instructions. I snagged one for a little over twenty dollars.

My need was simple. I had been reading about antennas used to detect emissions from Jupiter and the Sun.  I recognized that more than a few people were using folded dipoles. These are antennas that are a lot like a normal dipole but has both ends folded on each other and connected.  This provides a wider bandwidth and allows wider tuning. To facilitate this a balun is requires that matches 4:1. To put it in terms that I think I understand, the antennas resistive component is 4 times more than that of a standard ham transceiver. 

Once the kit came in the mail I followed the instructions as best as I could, assembled the folded dipole, and installed everything. I turned everything on and nothing was heard. A simple random length of wire provided better reception. I took everything down and tossed the balun on my workbench.

About a week later I picked things back up. In the time leading up to this I had a read a little on baluns at the following page.  I assumed that I wound the toroid wrong and decided to rewind it. However this time I would try to wind a 1:1 balun and just use it with a regular dipole Also rather than hooking everything back up to an antenna I decided to use an antenna analyzer with one side of the toroid hooked into a precise 50 ohm load and the other the analyzer. The instructions had the following diagram for how things should be wired and wound.

I wound six turns around the toroid and ran a test. The following table shows the results.

As can be seen the performance was horrible. I really didn't know what was wrong. I made sure that I wound things properly and in the right direction.. I just could not get good results. I decided to go back to the drawing board. I watched a few videos of other hams winding their own baluns and it appeared that no one used the method described in the instructions I had. They actually wound a total of four coils. Two on each side and respective colors twisted together at each end. I decided to try this out and use ten turns on each side of the toroid. As you can see in the following table the results were VERY good. I was under an SWR of 1.5 across all the ham bands.

I quickly assembled everything in the provided box with all connectors and ran the test again. This time the results were a little different.

At this point I can only assume that the hardware, such as the connectors, is some how detuning things a bit. I might try to remove a few turns on the toroid and see if that helps things  a bit.

More to come.

UPDATE: I removed two turns on each coil bringing it down to eight instead of ten and got mildly better results. At this point I think I am done with this. I closed it up and will attached it to the dipole I currently have up which tunes roughly around 20Mhz.

First detection

After many days of capturing data with a receiver in a noisy environment tuned to 20100Khz. I was able to compare another observer's report of solar activity with the data I had recorded. Unfortunately there was no NOAA information to compare this to. The observation was on 01/09/2022 at around 18:18:00 UTC. Below is the observer's report followed by my plot.  I hope to improve the antenna system and see if I can possibly reduce the noise. This is the first of many (I hope) successful observations of the Sun.

Observer's Report

Observation at my QTH

UPDATE:

I have to admit that I did not feel as elated as I had hoped about my first detection. A few things didn't feel right to me. Although I was confirming the observation of a long time and trusted observer I felt that I needed further confirmation from another reliable source. When I checked the NOAA GOES X-Ray data I did not see anything that would indicate an X-ray solar event. I resigned to take the win of first detection 'as-is', no matter how small it might have been.

Last night, I was laying awake in bed. My wife inquired if I was ok. I seemed troubled. I took this as an opportunity to explain to her exactly what I was feeling about this detection. Needless to say she didn't understand a word I was saying. This is nothing new, however one of the many beauties of my wife is that she is a perfect sounding board for me to talk to. 

Shortly after my nocturnal rant, I realized that I never checked the Solar & Geophysical Event Report for that day. Maybe this was no X-ray burst. Sure enough, when I checked the report for that day there was a minor fast drift burst also know as a Type III emission. FINALLY CONFIRMATION!

1130       1818   ////      1824  SAG  C   RSP  025-150   III/1          

I think its evident at this point that I need to learn and read A LOT more to even scratch the surface of "knowing what I am talking about".

I am a little more satisfied with my setup now. I can see minor bursts and hopefully when a Class C X-Ray burst happens there will be no mistaking it.

More to come.....

Decametric Radio Astronomy

 

Dipole Sunset

          This is my latest creation. A dipole antenna tuned for 20000Khz. Hanging from adjustable posts that can be configured between 10-20ft. My goal is to use this antenna for monitoring solar activity and other events that might occur in and around the spectrum of 20000Khz.

Below are some of the antennas performance characteristics at various lengths above ground, As you can see I am still working on it,

More to come at a later date.