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KD6W

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  1. Are you near anybody with a frequency counter? What is the impedance of the probe? What type of coupling does the probe have? How fast is the sweep on your scope, 10nSec? Does the oscillator look like this? - https://www.digikey.com/product-detail/en/txc-corporation/9C-28.800MBBK-T/887-2449-2-ND/4475367 --- 28.8 MHz??? To read the exact frequency, find a 10 pF (smaller is better) capacitor and "hook" one end of the capacitor with your o-scope probe. Set the channel and trigger to AC coupled. Now look at the PC board and next the crystal "Y1" find capacitors "C3" and "C2" near the edge of the board. Each capacitor has one pin tied to ground (the one towards the middle). Move the capacitor on the scope probe to touch the one end of the C3 but don't touch the metal on the crystal can. Start by touching C3 the side away from capacitor C2 and adjust the trigger till you get a lock and measure the distance between peaks. Now try to back the probe away so the capacitor probe doesn't touch the pin but can still couple and try to read the peaks again. The act of touching the crystal pin will actually shift the frequency a little bit. I speculate the peaks will be slightly less than 35 nSec apart. Good luck, Joel - KD6W
  2. How much is a YSO? $130. Ok, so what is your time worth? Me, I'm fricken priceless so $130 is a few less starbucks so BFD dude. Buy the thing already and get on with the hacking and help the rest of us Linux noob/dweebs! If you are developing a link system, remember, it takes two to tango... Got a license? 300-348 MHz (talk to the door/gate openers and make friends with the military!), 391-464 MHz, (talk to weather balloons, weather stations or piss off some hams in this band) and 782-928 (jam your friends cell phone or eaves drop on your favorite baby monitor in this band) Cool tool... I wish I had LYNUCKS skills so I knew what 2 do wif it... 73
  3. @quicksilver123, for just goofing around on a bench, which antenna you pick doesn't really matter, a paper clip would suffice. For making something that looks a little more polished, in a 3D printed case with nice connectors, either one antenna will do the job. The ghetto antenna relates to the goofy connector and I agree, it's not as slick as the other one but it still works. 50 ohms is relative to the frequency of interest but at those low power levels, again, a paper clip would work all day and you can't blow a YSO up, albeit short of a direct short at the connector but then what's the point? The speed of light is your friend so make your own antenna (468/Freq in MHz = length of dipole in ft). You, wire, a connector and some soldering skills and bingo. Impress your friends and make new ones. The big question is what are you trying to achieve, short term, long term, etc? Stay frosty. 73
  4. Provided below is a link to the amateur radio "band plan" which provides more details by breaking down the amateur allocations into their sub bands to organize who is transmitting what signals where... http://www.arrl.org/band-plan 73
  5. You must have heard the saying, "you get what you pay for", haven't you? How about, buyer beware? How much do you like YOUR money? I don't know anybody who doesn't like it when you give YOUR money to THEM. What you hope to get in return is up to YOU to decide if it was what you wanted and does what you need. Most here are not interested in a copy which may be cheaper but rather choose to respect Michael's work. If you can't afford the one you want today, then save your money, otherwise you get to take the risk. Let us know how that works out for you. Good luck. - 73
  6. Dude, i know! I am so into asian prons, they are sooo tasty!
  7. GNU SDR expert I am not, I know enough to get into trouble. But as the name of two objects implies, 1. The rational resampler is just that, the "Low Pass" filter also has a decimation process as a function to create a filter to make a cut off hence, a low pass filter. 2. AM demod can be swamped with alias energy coming from above the desired tuning range so a low pass in front of the highest tuneable range (pass-band) is applied to knock down unwanted signals from above the area of interest. Signal energy from below doesn't matter since it won't introduce an alias and a low pass filter is much easier to design and have sharper slopes than a pass-band filter. 3. Just like you i have those SAME questions and wait for soul to appear on this planet to write the book and teach the courses on GNU radio! HNY - 73
  8. Electronic Engineering Degree - I get it. Starting with top level product requirements - what is the start frequency? what is stop frequency? what is the max sample size (in MHz)? OR what is the total data throughput? What is the front end sensitivity requirement? What is the noise floor requirement? What is the near field carrier rejection requirement? More refinements - what bit accuracy is required? {8, 10, 12, 16, etc.} (may be limited by the throughput rate) what peripheral interfaces are allowed/needed? What are the environmental requirements? What are the power requirements? IF the design includes the ability to transmit there are a whole bunch of different requirements. 73
  9. Which frequency are you looking to measure? The lower the cheaper...
  10. Way over priced for what it can do. Hack a Baofeng to do this... they cost 35 dollars and come with a nice lithium battery.
  11. I can think of another option but not with an analog GSM radio. Use a single HackRF1 and set it to time division multiplex once a carrier is detected (46 mS receive or transmit and 4 mS idle) on a single frequency to sync with another HackRF1 on the opposite cycle. It's like having two, two stroke engines exactly operating exactly 180 degrees out of phase. The antenna ports (RX/TX) can either have their own antenna but will have better performance with a circulator in between them to feed a single antenna. DMR radios do a form of this today, albiet on two different frequencies to offer two voice paths. But a simplex DMR repeater sits in the receive mode and will sync with the first carrier to come up when an operator accesses it. The repeater starts cycling and listens for DMR packets on the receive cycle. Once a payload is recovered it is then fed to the input buffer of the transmitter output cycle and wraps the output in the repeater output protocol to announce the output to the other receivers, all on the same frequency.
  12. Path prediction is based on the sum of all gains and losses in dB. This assumes you have access or measurements of all the gains and losses of the system. First add up the gain of the transmitter output and receiving amplification and then subtract out all the attenuation and losses in the desired path. The trick in calculating is not mess up the terms when converting dBmW to dBi where mW is based on the milliwatt and the I is based on the gain of an isotropic antenna when compared with a dipole at the resonant frequency. Having said all that, I use tool based on a web site called "radiomobile" where you plug in all those variables mentioned above and the output is a map with the predicted results. And then there is nothing better than to develop your own empirical results, hams do this everyday. KD6W
  13. Get Pentoo to boot up in your PC and attach the hackRF to a USB and build up the flow graph to make a "narrow" band FM demodulator using the FM demod tutorial. Set the frequency to your favorite dispatch freq and use a squelch object to mute the static. The audio output block sink shows up in the audio mixer and then pipe the PC audio to your streaming server.
  14. You should be able to run python on any host including raspian and link the modules to the sinks and sources in the hardware, (no modules to support the pineapple as far as I know), then use the generate button to generate the "file.py" code and execute. The trick will be to get the hackrf to mount onto the USB port on the raspberryPi. If the raspberry can boot into Pentoo then are we done yet?
  15. Guess what dude, YOU are in luck... http://hackrfblue.com/
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