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Using the Raspberry Pi Wobbulator to test the G6LBQ Multiband Bandpass Filter
The problem in using a Digital IO pin on the pi to generate RF signal would mean it will generate a squire wave signal witch has lots of harmonics. To solve the harmonic problem you will need to build a low pass filter. This harmonic would not be in regulation with rf transmission and would therefore need to create a low pass filter to remove the harmonics. Here is the Low pass filter spectrum analyzer curve on my LWT, The Harmonic level should be about 25 db below good rookidee nicknames carrier.
Source link. Harmonic about 25 db down with now filter. Here is a filter I build to get rid of the harmonics. RFSim99 application.
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Still need to replace the two wires with Free code correct cable.All of them use the DPLL and a digital output which produces a square wave. However, a square wave would not meet the FCC regulations on spurious emissions because of the odd harmonics that turn the fundamental sine wave into a square wave. A sharp filter is necessary to reduce the unwanted harmonics that make up a square wave.
Paragraph That requirement jumps to 60 dB below the fundamental emission for frequencies between 30 and MHz. Any acceptable filter must reduce the the 3d harmonic, at Since the expected power output from the RPi will be small 10mW the insertion loss of the filter should be low. The first step will be to evaluate the filters with the nominal values specified in the design.
I will check:. Then for the BPF I will look at what happens as the adjustable capacitors are tuned. In order to determine the inductances needed for the circuit model I used the Turns-Length calculatorat the bottom of the Specs for T RF Toroids page. Most of the schematic is clearly from the specifications. Addition bits are added as required for an S parameter simulation and to calculate values of interest:.
The BPF provides adjustable capacitors that can be used tune the filter. The parts list does not provide a part number for the capacitor, but the vendor only sells two adjustable capacitorsso we can guess that it is the Sprague GKG with a range of pF. The key difference between this schematic and the one used for the nominal analysis, above, is the Parameter sweep simulation. Parameter sweep repeats another simulation, SP1 in this case, using a different value each time SP1 is run.
Another important difference in the schematic is that equations using the xvalue and yvalue functions have been eliminated. Those functions will not work with the data produced a Parameter sweep simulation, so we will have to read the values we are interested in from a graph, or use an external program to process the data.
For this exercise I am just going to use the graph. The values for C4 and C5 the variable capacitors in the design are replaced with a variable. The variable value is simple and it's sweep can be specified directly using settings in the Parameter sweep simulation block. I don't know how characterize the variation due to winding, so ignore it for now and look at just the material variation.
The material variation is specified as a percentage of Alinductance per turns-squared. My assumption is that all three toroid cores will be from the same batch and the Al values will therefore match. The variation in Al inductance per turns-squared yields an inductance variation of approximately 0.If you have children at your home, you might have felt the need to block certain undesirable websites. Another common problem area are social media websites — you might feel that children and adults waste too much time on Facebook, Twitter etc.
This appliance also intercepts the websites that these devices access, and blocks them if they try to access a blacklisted website. There are commercial, ready-to-use content filters available in the market, but for us DIY types, there is no fun in that. Thus, we will get our hands dirty, and set up a Raspberry Pi for the job. We chose the Raspberry Pi for this project because of its tiny size and negligible power consumption.
However, these instructions will work nearly unmodified with almost any computer running Debian Linux or a derivative Ubuntu, Mint etc.
How to Use Raspberry Pi as Router and Content Filter
Disclaimer : This guide assumes an intermediate level of experience with Linux, and a willingness to troubleshoot problems if and when they arise. Prior experience with command lines and firewalls is a bonus. For this, we will need two network interfaces on it — one to connect to the internet, and the other to act as a WiFi hotspot for our other devices to connect to.
So in this scenario, we can use an Ethernet cable eth0 to connect to the internet, while the WiFi module wlan0 will act as a hotspot.
In this case, you will need a compatible USB WiFi dongle wlan1 to connect to the internet, while the built-in WiFi module wlan0 will act as a hotspot.
This is the configuration that we will use in this guide. Do keep in mind that while a Raspberry Pi 3 is mostly adequate for a home setup with a few laptops and smartphones, it will not provide the performance needed for a big office setup.
Look into more capable hardware if a lot of clients will be connecting to your content filter. Software We will use the excellent E2guardian to intercept and filter our web requests. Since content filtering can have a performance impact depending on the size of the blocklistwe will use Squid cache to offset this performance hit.
Prerequisites 1. Raspberry Pi 3 with the latest version of Raspbian OS installed, and access to the internet. If you are only getting started with the Raspberry Pi, we recommend reading our guide on how to get started with Raspberry Pi 3.
If you are planning to use WiFi for both connecting to the internet and as a hotspot, this is required. Physical Access to the Raspberry Pi — Due to the nature this article, a single mistake in the firewall configuration can lock you out of your Pi if you use it in headless mode.
Therefore, it is recommended that you connect a monitor, keyboard and mouse while configuring it until everything is set up. Connect your Pi to the internet using Ethernet eth0. Leave the built-in WiFi module wlan0 as it is for now.All that extra cruft slows down your browsing.
But with a bit of tinkering, you can program a tiny and cheap Raspberry Pi computer to block this noisome dross. Follow these instructions to install the free program Pi-hole, which checks all incoming data against blacklists of your choosing before deciding whether the packets should be passed on to your devices.
It's more efficient than a standard ad blocker; the filtering works across every device on your network, banishing ads, trackers, and malicious code from phones, iPads, PCs, game consoles, Rokus, and even smart TVs.
The secure protocol sends commands from one computer to another; find instructions at Raspberrypi. Close the terminal window; we're done with the command line. See, that wasn't so bad. This is where you'll control Pi-hole and decide what to block and what to allow. You'll see some default options to block the most egregious trackers on the internet, but you can always fine-tune things to suit your needs by adding the web addresses where specific services live.
Try nuking ads in Twitch or blocking Alexa requests so your kids can't summon pizzas or Ubers. Keep your Pi-hole powered on and connected to your network; plug it directly to your router if you can. You wrote it down earlier, right? This will force all inbound data to go through the Pi and get checked against your lists before going out to your devices. Now restart your networked devices one by one; this forces them to reconnect to the internet through the Pi-hole. If Firefox is your browser of choice, there's one extra step.
There are some additional settings you'll need to tweak; find those instructions in the official Pi-hole documentation. That's it. You're up and running with Pi-hole. Want to see how much gunk you're now blocking? Check out the dashboard at pi. If you buy something using links in our stories, we may earn a commission. Learn more. This article appears in the October issue. Subscribe now.
Get more tech news with our Gadget Lab podcastavailable on iTunes and Spotify. He studied at the University of Georgia. Writer and Reviewer Twitter. Featured Video. Thanks to an assist from Congress, your cable company has the legal right to sell your web-browsing data without your consent. This is how to protect your data from preying eyes. Topics magazineFinally, I decided to use the Raspberry Pi Wobbulator to test the frequency response characteristics of the G6LBQ multiband bandpass filter which I had built as part of a homebrew transceiver project.
A screen shot of the results obtained from testing the m bandpass filter is shown below. The wobbulator performed a sweep from 1. A screenshot of the results obtained from testing the 80m bandpass filter is shown below, using channel 1 on the ADC Pi module with PGA gain of 8x.
The wobbulator performed a sweep from 3 MHz to 4 MHz in increments of 10 KHz, and the response shows a nice peak around 3. A screenshot of the results obtained from testing the 40m bandpass filter is shown below, using channel 1 on the ADC Pi module with PGA gain of 8x. The wobbulator performed a sweep from 6. Although the response of the filter peaks around 7. Those in the x86 processor ecosystem Latest Feeds.
Share 0. Share this:. A screenshot of the results obtained from testing the 30m bandpass filter is shown below, using channel 1 on the ADC Pi module with PGA gain of 8x. The response shows a peak around A screenshot of the results obtained from testing the 20m bandpass filter is shown below, using channel 1 on the ADC Pi module with PGA gain of 8x.
A screenshot of the results obtained from testing the 17m bandpass filter is shown below, using channel 1 on the ADC Pi module with PGA gain of 8x. The wobbulator performed a sweep from Tags: bandpass filter g6lbq multiband wobbulator.
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Build Your Own Raspberry Pi Home Network Content Filter
CNC Machines Projects. Development Board — Kits Projects. Game — Entertainment Projects. GPS Based Projects.This ensures that outdoor photos look more natural. However, some nature photography can be enhanced with the removal of this filter; the colours of sky, plants, and water can be affected by its removal.
The camera can also be used without the filter for night vision in a location that is illuminated with infrared light. This procedure cannot be reversed: the adhesive that attaches the filter will not survive being lifted and replaced, and the IR filter may crack when it is removed.
Removing it will void the warranty on the product. Nevertheless, removing the filter will be desirable to some users.
To remove the filter: Work in a clean and dust-free environment, as the sensor will be exposed to the air. Unscrew the two 1. Be careful not to let the washers roll away. Lift up the board and place it down on a very clean surface. Make sure the sensor does not touch the surface. Before completing the next step, read through all of the steps and decide whether you are willing to void your warranty.
Low pass filter 146Mhz ideal for Raspberry Pi
Do not proceed unless you are sure that you are willing to void your warranty. Turn the lens around so that it is "looking" upwards and place it on a table. Using a pen top or similar soft plastic item, push down on the filter.
The glue will break and the filter will detach from the lens mount. Replace the main housing over the circuit board. Be sure to realign the housing with the gasket, which remains on the circuit board. The nylon washer prevents damage to the circuit board; apply this washer first. Next, fit the steel washer, which prevents damage to the nylon washer. Screw down the two hex lock keys. As long as the washers have been fitted in the correct order, they do not need to be screwed very tightly.
Note that it is likely to be difficult or impossible to glue the filter back in place and return the device to functioning as a normal optical camera.Hi Tom, fine job and nice project, have you published some schematics and parts?
Hi Jacques, If you have a look back through my last few posts all the details are there. I'm hoping to develop a PCB for the Wobbulator with everything on one board, but that may take a little while to sort out. Finally, I decided to use the Raspberry Pi Wobbulator to test the frequency response characteristics of the G6LBQ multiband bandpass filter which I had built as part of a homebrew transceiver project.
The fully assembled filter board is shown below it is part of a Bitx Transceiver project I'm working on and it covers the whole HF spectrum in 9 bands, all the way from the m band 1. Each bandpass filter uses a 3rd order Butterworth design and built using the "redeveloped" component kit from Spectrum Communications.
A screenshot of the results obtained from testing the 30m bandpass filter is shown below, using channel 1 on the ADC Pi module with PGA gain of 8x. The response shows a peak around A screenshot of the results obtained from testing the 20m bandpass filter is shown below, using channel 1 on the ADC Pi module with PGA gain of 8x. A screenshot of the results obtained from testing the 17m bandpass filter is shown below, using channel 1 on the ADC Pi module with PGA gain of 8x.
The wobbulator performed a sweep from A screenshot of the results obtained from testing the 15m bandpass filter is shown below, using channel 1 on the ADC Pi module with PGA gain of 8x.
A screenshot of the results obtained from testing the 12m bandpass filter is shown below, using channel 1 on the ADC Pi module with PGA gain of 8x. The response shows a broad peak around A screenshot of the results obtained from testing the 10m bandpass filter is shown below, using channel 1 on the ADC Pi module with PGA gain of 8x. The response has a peak around 29 MHz, and a secondary peak around 28 MHz, indicating possible misalignment of the filter. Unknown 1 November at Newer Post Older Post Home.
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