Friday, August 21, 2020

RTL-SDR Weather Satellite Preamplifier

I have been playing with the SATNOGS earth observation satellite system for a few years, but since I am still living in the desert, the climate is against outdoor activities, so its been a bit low key. To work on an antenna on the roof, requires a hat, black sunglasses, a wet T-shirt, a wet towel, a litre of water and a big black umbrella and after that I'm broiled for the day...

The few times I tried to download a weather picture, it actually worked, despite having seemingly more noise than signal.  An RTL-SDR or HackRF One receiver really needs to have a low noise RF preamplifier for best results.  There are several solid state, one transistor preamp kits available that one can buy and build in an evening and stick on the antenna cable, but why do something the easy way, if one can do it the hard way?

I recently made a 'simple' (!?) power supply for a Magic Eye cathode ray tube VU meter and the same power supply circuit can be used for a one valve RF receive amplifier.

Small Sovtek 6CW4 Nuvistor
(Whatever you see on your screen is about life size!)

A problem with garden variety glass thermionic valve amplifiers is that they do not work at VHF or UHF frequencies.  The big glass tubes are good for an electric guitar at baseband and shortwave radio, but not much beyond 50 MHz.  However, there are special, low noise metal and ceramic valves, that were designed for this purpose and one can get small triodes that work up to 3 GHz.

Although these parts were in common use for about 30 years in TV receivers, most people don't know about them, because they are small and don't look like a vacuum tube. They look just like a metal can transistor, but with too many leads and instead of a silicon crystal, there is a vacuum inside!

VHF Nuvistor RF Preamplifier

The above circuit should work for a 146 MHz weather satellite, using a 6CW4 Nuvistor triode.  I got a handful from my favourite Electronics Junque Store in Russia.  

Since these tubes are very small, the internal parasitic capacitances and leakages are small.  Therefore, they can be used with either Grid leak biassing, or with Cathode biassing.  They behave almost like a NPN transistor, or a N-channel FET.

Electron tubes are very forgiving - just feed it some lecce and see what happens.  I have never managed to blow up a tube. It would require very special skillz to smoke a vacuum tube.

Circuit design for Audio is different from design for RF.  Audio circuits need to be linear and wide band over multiple octaves at base band.  RF circuits need to be narrow band and reject signals both lower and higher, to reduce the noise and improve the SNR.  For this reason, audio circuits are biassed with resistors only.  Capacitors are used to stabilize the power and provide a slow roll-off to high frequencies to prevent oscillations.  In RF circuits such as for the weather satellites at 136 to 137 MHz, the biassing and feedback are done with tuned circuits, to increase the Q and make the circuit narrow band.

Therefore, there are little coils that you should wind from magnet wire, but don't be scared of that, the designs are not critical.  However, don't put them right next to each other.  Try to keep them a little apart and at 90 degrees to each other, to minimize coupling.

Any RF circuit should be built as small as possible, to avoid problems with parasitic capacitance, inductance and coupling, but there is a limit to what one can do.  This circuit is about the highest frequency that one can still build successfully on a tag strip, but use a single ground point and use as few tags as possible.  A Christmas tree circuit with most parts soldered directly to the nuvistor is the best way to do it.  You will need some thin heat shrink tubing to prevent shorts.

Another way to do it, is to cut some squares in the copper of a single sided PCB with a Dremel cutting wheel and build a blob circuit. Use a square in the middle as the ground, with some smaller lands around it.  Drill some holes for the nuvistor leads and put it on the other side.  It would be best to sketch the physical circuitry on paper before you start.

Wind the RF Coils from magnet wire around a 1/4 inch drill bit and slide it off.  The input transformer matches a low impedance antenna to the high impedance Grid.  Wind the negative feedback RF Coil on top of the 1M resistor - the 500p capacitor  only blocks the high voltge DC.  The output transformer 40T:10T can drive a low impedance antenna cable. If the tube oscillates - remove one turn at a time from the 28T coil on the resistor, till it stabilizes (Less turns = more negative feedback = lower gain).

Be sure to use large 2 W resistors and high voltage capacitors, else you may get smoke signals.

These little triodes were widely used in television sets in the 1960s and 70s, so there are millions of them still available.  The thimble size triodes are good up to about 1 GHz and they are not really any more difficult to use than a transistor - they just need a higher supply voltage and building the PSU keeps things interesting. 

So, instead of the ubiquitous 2N2222 NPN transistor, you can use Nuvistors and amaze and confuse your fellow geeks when you hook a vacuum tube running at hundreds of volts to a Raspberry Pi or Arduino.

Well, now I don't have an excuse anymore and should grab the soldering iron and find a traditional old tobacco tin to house it in...

La voila!

Herman

Saturday, August 15, 2020

GI-7b Microwave Triode

I recently obtained an ancient Rusky GI-7b microwave C-band triode.  Packed in an innocent looking styrofoam container (I didn't know they had styrofoam in the bronze age - maybe that is how they floated the pyramid stones down the Nile!), it is quite a monster:

GI-7b Radar Amplifier Triode

This is a radar amplifier tube designed to operate while pulsing at up to 9 kV and 3 GHz.

To digress a bit, contrary to common perception, there are still lots of microwave electron tubes in use,  for example microwave ovens, radars, medical diagnostic equipment and satellites.  Travelling Wave Tubes are popular in satellite transmitters, because they are very efficient, very rugged and small. TWT amplifiers have been manufactured by the likes of Honeywell, Thales and others for over half a century - the frequency band just keeps going up and they now operate in the Ka bandhttps://aerospace.honeywell.com/en/learn/products/satellite-communications/traveling-wave-tube-amplifiers

What I would like to do one day, is build a Thermionic Valve satcom UHF preamplifier for use with a SATNOGS  Raspberry Pi earth observation ground station - just for fun.  I got some small Nuvistor tubes for that.

Really BIG electron tubes and oscillators are made in China by the Bejing Jenerator Co:  https://jenerator.en.ecplaza.net

There is also still a manufacturor of new electron tubes for audio amplifiers, the Xpo-Pul (Reflektor) factory in Saratov, Russia:   http://rutubes.com/category/reflector-tube-saratov-russia/

The big GI-7 tube is supposed to have a vacuum inside - I hope it is still in there and that it didn't crawl out through a crack in the casing - it was designed for use in a battle tank, so it should be OK!

Serious Data Sheet

The Heater and Cathode are at the bottom, the Gate in the middle and the Anode at the top.  It is wired like a simpe Triode - no confusing extra grids as in a Pentode.  I frequently wondered whether the extra grids of a Pentode really do anything useful, or are just there for marketing purposes.  Hey, five are better than three right?

Electron Tubes tend to be very forgiving things and like a little kitten, will usually try their best to please you, if you warm them up nice and cozy and feed them some lecce.  Therefore I'm wondering how it will do at a more pedestrian 335 VDC at 10 kHz baseband, in an audio amplifier output stage.  The biggest problem will likely be the 12 V, 2 A heater current - 24 Watt to do mostly nothing - maybe it will work at half that.

One should not run a tube at kilovolts in your living room anyway, since you can get X-rays and Ozone, which are both not very nice.

Some Audiophile amplifiers have a random tube or two on display and wired such that if you remove the tube, the amp stops working, while it actually doesn't do anything at all, but since I grew up with tube fired radars in the Army, I'll find a way to make it work for real!


Crazy Socket

The socket for this valve is total overkill, so I'll have to make something more aesthetically pleasing.

UHF and Microwave Ceramic Valves are usually quite easy to solder to, since the contacts are silver plated.  So I can run some copper steam tubes around the valve just for show: 

RG405/U - https://www.pasternack.com/semirigid-0.085-rg405-50-ohm-coax-cable-copper-rg405-u-p.aspx

Semi-rigid coax make nice looking steam tubes and shield the signals from 5G Audiophile interference, so you don't need a double layer tin-foil hat when you listen to my amps. https://www.aeronetworks.ca/2015/02/cool-amplifier.html

Here is the complete thermionic valve data sheet:




GI-7b Triode

Microamp per kilovolt - Hmmm...  Keep yer kotton picken fingers in yer pokkets!

What I want to do is far off the left-hand bottom end of all the curves, but it should work anyway.


For now, it will have to rest some more in my Junque Bochs.  

Maybe I'll get to it next year. 

No rush.

The tube patiently waited 50 years already, so it can wait some more!


La voila,

H


Saturday, August 1, 2020

Covid19 in Alberta Reality Check

The Ultimate Question
How many people actually have a problem with Covid 19 and how scared do we really need to be of this disease?


Internet Statistics
A popular statistic bandied about, is that up to 80% of people are asymptomatic and 6% of patients need intensive care.


That sounds very scary, but the 6% only applies to the 20% that actually get sick, so that makes it 1% of the population, which means that 99% of the population need not be worried, but some folks are still worried that they will be the 1% - fair enough.

So much for (probably bogus) statistics off the internet and social networks.


Reality Check
Let's look at the cold, hard, real numbers, of my home state Alberta Canada, straight from the official government web sites:
  • Population: 4,428,247
  • Cases: 10,843
  • Deaths: 196 
  • Percentage of deaths: 196 * 100 / 4428247 = 0.004%
Percentage of Albertans who don't need to worry about Covid19 = 99.996%

To make that number clearer, I made a graph of the Death Rate due to Covid19 in Alberta:


Death Rate Due To Covid19 in Alberta

You cannot see it?  Maybe you need reading glasses...  

I even used a pink sticky note for emphasis, but the result is still decidedly non-scary to me.


Reality Check Against Influenza
Lets compare Covid19 to everybody's favourite, last year's Influenza, again using the official government web site data:

Population: 4,428,247
Cases: 6082
Deaths: 30
Percentage of deaths: 30 * 100 / 4428247 = 0.0007%

Percentage of Albertans who don't need to worry about Influenza: 99.9993%
(Provided that you got your flu vaccine!)


Vaccines
Covid19 in Alberta, is about 6.5 times more deadly than Influenza, but Influenza has widely administered vaccines, which make the number better.

The flu vaccine reduces hospitalizations by about 80%  https://www.cdc.gov/flu/vaccines-work/vaccineeffect.htm

Therefore, Covid19 (without vaccine) and Influenza (without vaccine) really are about equally bad.

However, Covid19 is worse for old people (80%), while Influenza is worse for young people (children and pregnant women).  For young people, the risk of Covid19 (without a vaccine) is about the same, or less than flu (with a vaccine).  

It is only old people who need to worry about Covid19 and for them, a vaccine probably won't work, because old people's immune systems likely will not react to the vaccine, and for young people it won't make much difference.

So, the question about Covid19 vaccines is: Why bother, if it won't help either way?

We need to find different treatments and there already are some, for example Antibody treatments:


Masks
Now, after six months, now that it is all over, some people want to make masks mandatory in public:

I'm not actually against masks, since I suffer from pollen/dust allergies and it may reduce the prevalence of Influenza, TB and common colds slightly, but don't expect masks to be much use against Covid19, because it is over already.


It Is Over
In the England and Wales, the Covid19 deaths have gone down for the 20th consecutive week and all deaths, are below the 5 year average:

It is hard to fathom what more proof people need that it is over and that it is time to get back to more important things.

In the USA, after the very vulnerable people sadly passed away, the illness continues to burn through the healthy population, the majority of whom will not get seriously sick, the death rate keeps going down and is now around 1000 per day, which is very low compared to the peak:

In Canada, the death rate is down to about 1 per day (mostly Quebec):



The 'second wave'? There will only be a second wave if there is a second 'new' virus.  This one already had multiple 'waves' and has burned out.  


Bogus Case Numbers
Ignore the bogus 'case numbers' - they do not reflect reality at all.  The PCR test is effectively a negative test.  If it finds that you are negative, then you can be pretty sure that you are negative.   
 
However, if you test positive, then you are only 5% to 15% sure that you are positive!
 
Testing can show any number anyone wants to see, since the vast majority of positive cases, 85% to 95%, are false positives.  Therefore, if you want a worse number of cases, just test more people, as seen in the below graphs.

No correlation between Cases and Deaths in Canada

It is abundantly clear that there is no correlation between cases and deaths in Canada, unless you think that rising cases means less deaths.  
 
The testing system clearly doesn't work, produces very large numbers of False Positive results and is therefore mostly a waste of time and money:

As a comedian put it:
If you do more IQ tests, the moron number will also go up.

The only hard number that is difficult to bodge, is the death rate, since we don't usually test people multiple times to make sure...


BS Detectors Needed
A problem that I see is that the good Doctors in charge of the epidemic response are not Farmers, Mathematicians or Engineers and are udderly unable to detect BS projections.  

Budding Epidemiologists should please read this book:
Calling Bullshit
The Art of Scepticism in a Data-Driven World
Jevin D. West (author), Carl T. Bergstrom (author)

BS Example: BC Scary Statistics
Look at this scary graph!  The lines are going up!  We are all going to die!

BS Line Graph:
  • The top two lines are cumulative totals - they cannot go down.
  • The third line is the difference between them.  It is just as useless.
  • The Deaths line is also a cumulative total, designed to scare.
  • The only lines that are somewhat useful, are the bottom two - the deaths and the new cases.
If you look at the bottom line, you will see that there never was much of a peak anywhere - just a little noise ripple barely above zero. 

BC doesn't even publish a graph for daily deaths, because it is mostly zero and currently there are only 3 people in Intensive care.

The new cases number is not really useful, since it depends on the testing strategy and is not the real new cases at all.  In addition, most people never actually get sick (Asymptomatic means that you are not sick!) and most of those that do fall ill, recover in about 7 to 10 days, without going to a hospital, same as with Influenza.

Despite the very scary graphs, the real impact of the disease in BC is very minor, same as in AB.  You just need to ignore all the BS, which is almost everything they publish.


Covid Mathematics
It appears that Covid Mathematics is a branch of Bistro Mathematics, the science behind the Infinite Improbability Drive invented by the late Douglas Adams in his Hitch Hiker's Guide To The Galaxy series.  

O'l Douglas postulated that: 
When it is infinitely improbable that something will ever happen, 
it will happen almost immediately.

Here is a good refutation of the predictions of doom:

Dear Lord, please save us from the Crazy Doomers.


Vaccines

However, an old stalwart, the BCG vaccine, seems to be almost as good (about 80% of deaths are prevented) and it is available right now.   A specific vaccine may not be any better that this one, percentage wise, but for individuals where the one fails, the other may help - so get all immunizations.

Luis E. Escobar,  View ORCID ProfileAlvaro Molina-Cruz, and Carolina Barillas-Mury
PNAS July 28, 2020 117 (30) 17720-17726; first published July 9, 2020 https://doi.org/10.1073/pnas.2008410117

The analysis shows that the Covid19 disease mainly affects South Western Europe and the Americas.  The impact on the rest of the world is very minor, probably thanks to the BCG and other immunizations bolstering the immunity of most everybody. https://www.bbc.com/future/article/20200915-the-mystery-of-why-some-vaccines-are-doubly-beneficial

For example, I had these immunizations:
Smallpox, Yellow Fever, Typhoid, Hepatitis B, Tuberculosis, Polio, Measles, Mumps, Rubella, Pertussis, Diphtera, Varicella Zoster, Tetanus, many Influenzas and possibly one or two more that I can't remember.  West Europeans and Americans would never have heard of most of these illnesses and were never immunized against them.  Bear in mind that all organisms on earth share a whole lot of genes - the horrible single cellular ones also, with the result that some vaccines can provide wide protection.

The above graphs indicate that the Covid19 disease is a failure of primary health care in a part of the world where states under invested in immunizations for the past 100 years and are now reaping the fruits.  Et tu Quebec!

So if you don't have the TB vaccine marks on your left shoulder, maybe you should get it - if you are too old already, then it won't help though: https://www.sciencedaily.com/releases/2020/07/200708121433.htm  

A little googling will find more results, since several BCG evaluations are now drawing to an end.

Stop worrying and get a BCG vaccine.


It Really Is Over
With the death rate due to Covid19 down to around 1 per day, Canadians need to get on with their lives.

Ignore the false positive BS case numbers and unscientific exaggerated projections.

Covid19 was only a problem in about 10 countries in the world, which doth not a pandemic make.  It shows that there is a problem with Primary Health Care in these 10 countries, the rest of the world is doing OK.

Type this into Google: "covid deaths slovakia" (or any other European country), then you will get a graph like this one:

That number 6, is really six, not six thousand, or six hundred, just six.  Slovakia is in the exact centre of Europe and is a good example.  Most of the European graphs look the same.
 
 
The Second Coming of Covid
The amazingly bad Covid19 PCR tests are now causing a false positive Second Coming of Covid - which is all hype and no substance.
 
Look at these scary BS Graphs with vast numbers of false cases.  No matter how hard the hysterical Doomers are crying, the hospitalizations and deaths in the UK, France and elsewhere, stubbornly refuse to go up.
 
Blighty:

 
 
Froggy:


There is no correlation between the test results and reality, unless you believe that more cases lead to fewer deaths - if that was true, then please bring on some more.
 
Clearly, the PCR test results are quite useless, but you will not see the above graphs in a newspaper, since it will give the game away.
 

Post Mortem
What really happened?
 
A horrible Common Cold virus wrecked the world economy.  That is what happened.
 
Initially, everyone was scared, since it was an unknown killer disease which spread very rapidly.  Inappropriate tests and false statistics made it look much worse.  A disproportionately huge amount of money and resources was invested in combating the spread and finding a cure.  Now, we need to recoup that investment and the only face saving way to do that, is to convince everyone on the planet to pay for the immunization.
 
There is no need to suspect conspiracy, 
when collective stupidity provides a sufficient answer.

The new Corona virus immunization is not a bad thing - it may help against other Corona viruses as well; and anything that helps against the Common Cold, is good by me!

--oOo--

Ignore the exaggerated predictions of the Doomers.

Don't make a mountain out of a mole hill.

Get all available immunizations.

Enjoy life.  

H.