Measurements Are Only As Good As Your Tools

Today I got a mic connected to the uBitx and a key and was able to test that its making RF and doing its thing. My home antenna is resonant on 40m, so i do not need to check the swr or anything, but i thought i would use the power meter in the swr meter to check what the power output of the uBitx is. Trouble was, it was making about 5w cw and 3w ssb.

So i got to scratching my head and wondering about the radio itself. I was about to put it in the cannot be bothered for today pile when i grabbed down the scope probe, put it across the antenna port and keyed up cw, 22v rms or 10 watts out, so i grabbed the mic and spoke in my normal voice, 21v rms or about 10w out.

Obviously the power side of this swr meter is kind of crap and not giving an accurate measure of power out. Anyway, i know the uBitx is working now and making enough power to be useful, now all i gotta do is get out portable and use it.


LED Bezels

So months ago i bought 100 LED Bezels, it seemed like a good idea at the time and something i would later find use for. So today when i actually need one for a project, i go looking for them and cannot find them. It is not like my shit is a mess, its rather neat and tidy and somewhat organised with like things with like things. But can i find the LED Bezels, nope. No fucking idea at all and I have been through each and every tray looking for them.


TX On 40m Takes Out NBN

So, for no apparent reason, lately transmitting on 40m has been causing the NBN to disconnect. It never done this before, nothing has changed with settings, the radio is in the same spot, using the same antenna and all that. So tonight while listening to the 7.130 dx net, i decided to do something about it. I got into the settings and changed the channel that the WIFI is operating on just in case that was the vector for RF overload, no change, so for stage 2, i grabbed a couple of 12mm clip on ferrites and wound as many turns of the power and telephone cable i could around them, problem solved. I can talk and internet again at the same time. For now 🙂


When Your Opinions Do Not Matter

In a discussion of ideas, a range of opinions is probably a good thing to have, to find common ground see the pro’s and con’s of various idea and hopefully get the best outcome possible for the greatest amount of people. And this is a good thing, if you are talking about social issues or how to spend money etc. However, when it comes to scientific debate, like on climate change, your opinion is worth SHIT and what matters is the scientific evidence. And here is why:

When you get into an aeroplane you expect that the boffins at Boeing have used their slide rules, tape measures and calculators and Science’d the living shit out of the design, don’t you. If the CEO of Boeing came out and made an announcement like; This is Bill, Bill designed the wing on our new mega jet using his opinions, emotions and feelings, you would shit and never get into one of their planes ever again. Because that giant flying turd is more than likely going to kill someone.

The same going with Climate Change, your opinions, feelings and emotions mean absolutely nothing at all and if you think your opinion matters you are being wilfully ignorant to the extreme. Get the Actual Factual, you know, Science. And if you are too stupid, inbred or dumb to find and read the science, do what you do with everything else in your life you do not understand, defer to the bloody experts. And those experts are not the retards on Fox News or The Guardian, they are the actual scientists doing the work.

Every aspect of our modern society is built on science and you don’t impose your stupid opinions on those things do you. Its not like you have an opinion on how NASA should get get a rocket into space, or your doctor when he gives you antibiotics, and try putting opinions in your car rather than petrol and see how bloody far that gets you. Science, gives you all the things you take for granted in our modern society like that phone, tablet or computer you are reading this post on, your opinions did not build the internet or create the computer science did and yet you think you know so much more than actual scientists doing climate science, through experimentation and observation that you think it is your right to question and impose your opinions on Climate Change. That is wilful ignorance, arrogance and extreme stupidity.

Try shitting in your fridge and see how long that works for you. You know, before you get food poisoning or cholera and die because guess what, your opinions did not create our modern sanitation systems science did. Well, ignoring the science of climate change is exactly the same as that, shitting in your fridge. All because your ignorance and arrogance led you to believe that you know more than science does. And here is the place where you can exercise your opinions, what do we do about climate change? because the science is clear and real and has been that way for over 30 years.


When The Image Matters

Sometimes you find out what you thought to knew about a subject is just utterly wrong. When it comes to image frequency for a long time I have believed that the Image_F = Desired_F + or – 2 * LO_F. Which is essentially true, the image can be plus or minus but I was ignoring one critical piece of information and that is the position of the Local Oscillator in respect to the desired frequency.

So there is only 1 image frequency, not 2, if the LO is below the Desired frequency then the image frequency is Image_F = Desired_F – 2 * LO_F and if the LO is above the Desired frequency then Image_F = Desired_F + 2 * LO_F. Which now means that using a 455Khz IF for AM Broadcast Receiver actually makes sense if using a high side LO to do the mixing in a superhet design.


New Computer

So i finally got the shits with the computer I was using, so grabbed out my gaming PC and installed the nessessary evil of Windows 10, then put all the regular software I use back on and am making sure everything is working as it shoud. The whole exercise has ben rather smooth and I now also have some power again, with a quad core, 16gig ram and SSD for the OS and software.


Ok, I Am Not Dead

It has been quiet a while since I have updated this. Yes I am not dead but I have been dealing with some health issues. Nothing all that serious just arthritus in my right hand, which has made doing anything more or less imposible and so I have taken a break from homebrewing as even cutting the leads off a resistor has been all but imposible. And while things are certainly not great currently, I do have some movement now and should be able to get back to doing some radio. I even started to clean up my work space in anticipation.


Taking Off The Training Wheels

Its interesting when you actually start designing for yourself and not just follow someone elses potential blunders, how many small things you have to overcome once you start prototyping your designs that you never considered would be an issue at all.

In my latest project i figured I would use a relay for the Tx Rx switching along with a micro controller and a push button that might one day become rf sensing. It works a treat does exactly what its meant to do and I am happy. And then i got to thinking, how much isolation is there between the 2 output poles of the relay. Its not an RF relay just the cheep 5v relay using in arduino projects, so i dont expect it to be great.

So i injected a 27dbm signal into the common of the relay, that about 0.5 watts and measured what was being seen on the isolated pole, 2dbm or about 1.5mw. So i have about 25dbm of isolation and enough power floating on the isolated port to burn your retinas out if you are a double balanced mixer, let alone the 25mw of Rf that’s going to be there when 5W is put thought it, assuming the isolation remains constant with power and im not sure it does, I do not have 5w to stick in there to see atm.

So i looked at the specs of a number of RF Relays, and they are only sporting 40 to 50dbm of isolation, much better but still soul destroying if you are the receiver DBM. So either way I have to find a way to protect the mixer and so im thinking either bidirectional amplifiers or just muting the rf preamp by cutting the power to the transistor. Hooray for me, I now have more thinking to do.

Thanks for reading an hombrewers lament 🙂