So I thought I would tidy up and test a few things out before putting them away, then this happened. SHIT EVERYWHERE.
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.
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.
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.
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 🙂
So i got to thinking about my own homebrewing , after reading this post by Pete Juliano, http://n6qw.blogspot.com.au/2017/02/gum-on-your-shoe-bitx40.html
Now i am certainly no expert on all things homebrew, i am nothing but a total noob with some passion for self learning. Key point here, homebrewing is not all monkey see, monkey do, it is about self learning. Asking someone, hey your widget does not work, fix it for me is not doing homebrewing at all. there comes a point where everyone has to bite the bullet and start to understand what is going on, this is especially so with Arduino.
I do not provide schematics for my Arduino projects, the simple reason why is you the individual needs to learn for themselves how to find the right way to connect things to the board you are using. I have seen plenty of people complain this code does not work, that guys project never works and when you did a little deeper you find almost 100% of the time END USER FAILURE.
What pins you use to connect something to the I2C bus as an example is different between NANO, UNO and MEGA, and then if you use one of the spinoff boards from another 3rd party it might be different again. So, the point here is, you the end user needs to learn some basics about how things connect to a micro controller, how to read the pinouts for your board so you can find the I2C, Interupts pins etc, you then need to learn to read the code ENOUGH to find the lines of code that set the pins, so that you can change them to suit your board.
None of this is terribly difficult to learn, but it does take some effort to get off your own butt and learn something more than monkey see, monkey do. Trouble shooting is something everyone of us needs to learn. Going though some basic trouble shooting should be something we all do before we ask for help. So give trouble shooting a go, give learning a go. Get a basic understanding of how micro controllers work, buy a book, have a read, google even, the truth is all out there if you actually look for it. And in electronics, there are no Trump ALTERNATE FACTS, only end user failure and lack of understanding.
You realize the yellow inductors you bought off ebay are not iron cores but probably ferite because 40 turns is equal to + 70uH. Or when you realize your LCR meter is a giant pile of gimp shit and will not measure a value of inductance lower than 10uH. It has been one of THOSE days in homebrewing and so now I am making a test jig to use with the signal generator and oscilloscope to measure the value of the inductors I am winding with some level of accuracy and then getting confused about how accurate the measures will be because inductance changes with frequency and and all that. HIHI. The life of the unwitting, the unknowing and the down right confused.
EDIT: the yellow inductors are most likely type 26, yellow and white. The inductance values I am getting for a given number of turns would suggest this is the case. Type 26 is not much use in RF, good to 1mhz.
So i am getting some boards made with PCBway they are a board manufacturer in China that offer a whole lot of professional services, but also cater for the home brewer. So I thought i would document my experience with them from start to finish.
They offer 10 boards upto 100mm x 100mm in size for $10 US. Which is great for me as most of the projects I build will fit on that size board really easily. The project i was getting build is the board I designed for the Arduno VFO with SI5351a Synth. I designed up the board in Sprint Layout, exported the gerber and excellion files, put them in a zip file and uploaded them to PCBway.
Once a day they have someone check the uploaded files meet with their specifications for track size, drill sizes, board dimensions etc and that you have the correct amount of gerber files etc. About 20mins after uploading i checked and they came back that I was missing the soldermask files. Well the files were in the zip but for some reason I stuffed up something and they contained no data, no big deal, i re-did the files, this time checking for myself that the soldermask contained data by loading them up in Flatcam, and then resubmitted. About an hour later, I got confirmation my files were OK, I could then pay for the job and have it put in the process cue.
This is one really good thing about PCBway, they do not take your money until they have confirmed and checked that they can process your job. Unlike some of the other places that want money without even checking your job is appropriate.
So the rest of this is really just a timeline of how quickly they process the job.
My order date and time was Order time & date: 11/20/2016 6:28:30 PM, from there the job was put in the process and It proceeded as follows.
|MI (Manufacture Instruction)||11/21/2016 9:55:02 PM|
|Board Cutting||11/21/2016 10:25:30 PM|
|Drill||11/22/2016 4:01:02 AM|
|Plated Through Hole||11/22/2016 5:39:16 AM|
|Circuit||11/22/2016 8:25:54 AM|
|Etching||11/22/2016 10:04:25 AM|
|AOI||11/22/2016 2:42:58 PM|
|Solder Mask||11/22/2016 7:16:54 PM|
|Silkscreen||11/23/2016 12:30:48 AM|
|Surface Treatment||11/23/2016 1:58:30 AM|
|Double Drilling||11/23/2016 5:58:25 AM|
|Routing||11/23/2016 5:58:35 AM|
|Testing||11/23/2016 7:18:08 AM|
|Package||11/23/2016 8:41:50 AM|
|Delivery Ready||11/23/2016 11:48:54 AM|
You can follow online on the website the process of your job as it proceeds through each manufacturing process. All up, from when I booked the job to when it was put in the post, 4 days. Super fast, and when you take DHL as the postage method, a few more days and you will have the boards in your hand. So after receiving the email confirmation that my job has been posted, I checked the tracking number on the DHL website and it shows the job has been picked up, so i expect i will have boards in my hand some Friday this week. So I am estimating, a total of 7 days from order to receipt of the boards. One cannot complain at that.
I will upload this post with pictures of the boards and my thoughts on the quality once I have them in my hands. So far, so good though. Cant wait to see the boards.
Quality of the boards is certainly high. I cannot find any flaw other than the once I made in the design. Its not like PCBway can read my mind, understand my project and fix those things for me HAHAHA.
The board kind of assembled.
And thats the final assembled board. I am one happy customer, and will be going back to PCBway very soon to have more boards made, for some other projects i have in the works. 10 boards, 100mm x 100mm for $10. WIN.