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  1. searsjames

    Garage door opener antenna problem.

    Would it not just make sense to match the existing length of the hanging wire? I.E. Strip the coax back this far at each end. Dont forget to ground the coax shield to the opener case.
  2. searsjames

    Propagation characteristics of horizontally polarized RF

    My cow antenna my be easiest to configure if it radiates with horizontal polarization. I am interested in the 433 Mhz band as well as 900 Mhz meaning that blocking vertical polarized interference is a Plus. My Questions: Compared with vertical, 1) How well does horizontal propagate over...
  3. searsjames

    Countries allowing 433 MHz telemetry

    Merry Christmas! This relates to the cow questions. What countries allow 433 Mhz telemetry with low duty cycle? I already 433 usage is harmonized in Europe and the US. How about Canada, Austrailia, Brazil, Japan, and Argentina? Much thanks jim
  4. searsjames

    Loop antenna glued on back of cow-Gain question

    OK I am intrigued. It is really unwise to get a cow and a $7000 network analyser within pissing distance. How do you know that a watermellon is a viable substitute? BTW I was on my hands and knees saying moo yesterday. Jim
  5. searsjames

    Loop antenna glued on back of cow-Gain question

    The cow will have an intrinsic impedance of about 50 ohms though I dont know what that means as far as minimizing coverage. I would love to get a diagram of any suggestions. The cow skin does need to breath. W1VT of the ARRL has graciously turned be on to EZNET so now I can analyze simple...
  6. searsjames

    Loop antenna glued on back of cow-Gain question

    64khz FSK modulation, TX=0dbm, there is no coax loss, and -103dbm at the reciever. Hope to get 0 to -5 dbi at the TX antenna, am analysing now...that is the main question I have for this forun.... The propagation models i have checked say things should work. Antenna is the question... What...
  7. searsjames

    Radio propagation programs

    www.ecommwireless.com has several simple point to point calculators for free.
  8. searsjames

    Loop antenna glued on back of cow-Gain question

    >= 1 mile over varied range conditions to 30 foot receiver height, 10-15 mw, .005% Emperical testing is always the best way to be sure. I plan on it. Just getting a head start. Jim
  9. searsjames

    Loop antenna glued on back of cow-Gain question

    Thanks, Collars snag in ranch environments and do not place the transmitter in the physical position we need it. GPS is not used for cost and coin battery life issues. ANOTHER QUESTION. How will the beam pattern change? Will the horizontal donut flare upward or downward? Will nulling of...
  10. searsjames

    Loop antenna glued to the back of a cow - Gain Question

    Gentlemen, I have also submitted this in antennas forun. I am developing a tracking system operating at 433 MHz that utilizes a loop antenna glued in the horizontal plane to the back side of a cow. The diameter is 1/4 wave and it will be spaced 1/4 inch from the skin. The height above...
  11. searsjames

    Loop antenna glued on back of cow-Gain question

    Gentlemen, I am developing a tracking system operating at 433 MHz that utilizes a loop antenna glued in the horizontal plane to the back side of a cow. The diameter is 1/4 wave and it will be spaced 1/4 inch from the skin. The height above ground will be 4.5 feet. According to...
  12. searsjames

    Fastest Counter around?

    I am starting to answer my own question. The fastest counters seem to be in FPGAs from Xilina, AMD, and Actel. SO far I have seen referance of up to 400 MHz.
  13. searsjames

    Fastest Counter around?

    I have a question along these lines. Are there binary counter chips that work up to 250 MHz. If not what is the fasest logic family that actually includes either toggeling flip-flops or counters?
  14. searsjames

    Ranging using radio

    Oh my goodness, PRS encoding relies on Shannon theory and everything else acording to Google. I think I have to hit the hay at that. Im going to get back to this tommorow. Thank you guys for your help.
  15. searsjames

    Ranging using radio

    I plan to send a time calibration signal to each receiver about once per second and oven stabilization of their clocks will be used if needed. I am only ranging up to 500 meters so weather is less of a problem and yes I will have fixed, known position transmitters to perform periodic range...
  16. searsjames

    Ranging using radio

    One of my constraints is that I will have hundreds of transmitters to track from each pod of three recievers. Each transmitter needs to cost <$10 @50K quantity and so will only send its ID # and a few more bits. The recievers can cost several hundres dollars or more and can be constantly time...
  17. searsjames

    Ranging using radio

    First I am confined to a plane and so 3 receivers work. The relative time of reception at these 3 receivers is all i need. The first problem is the detection circuit for triggering a 4 ns resolution time tag repeatably after the 433 MHz hits each receiver. The second problem is the counters...
  18. searsjames

    Ranging using radio

    I have a very similar problem. I need to distance range using 3 recievers in a fixed grid and a 433 MHz pulse transmitter moving around. The objective is for the recievers to each time stamp their reception of the transmitter pulse to within a repeatability of 4 nanoseconds. Accuracy will be...

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