We seek to understand and document all radio transmissions, legal and otherwise, as part of the radio listening hobby. We do not encourage any radio operations contrary to regulations. Always consult with the appropriate authorities if you have questions concerning what is permissible in your locale.

Author Topic: Sawtooth hifer beacon 13554.40 KHz  (Read 2173 times)

Offline Dag

  • Full Member
  • ***
  • Posts: 100
    • View Profile
Sawtooth hifer beacon 13554.40 KHz
« on: June 27, 2015, 2321 UTC »
I've constructed a sawtooth hifer beacon on a dial frequency of USB 13554.40 KHz running a few milliwatts into a homebrew multiband ladderline-fed-MFJ-tuner tuned zig-zaggin' attic dipole up about 15 feet/3 meters. The signal should show somewhere between 725 Hz  and  750 Hz on the spectrum display at the aforementioned dial frequency: the drift is due to ambient air temperature changes.   

The circuit is an NE555 in astable mode and an EPSON SG 8002 oscillator and some old junk box parts on a prototype breadboard with a lot of alligator clips.

The calculated time constant of the NE555 with resistor/capacitor that I'm using show a completed cycle each 343.78 seconds or 5 min 43 seconds, but I  suspect the capacitors/resistors I have are not of tight tolerance. Hence the time it takes to complete one cycle may be off a little, but it looks pretty much in agreement on my spectrum display.

The frequency shift of the sawtooth is about 3 Hertz and with the narrow frequency shift and slow oscillation of the sawtooth, it takes a slow waterfall to see it.

It runs 24 hours/day using a 7 volt wall wart.

I would appreciate some reports and screen shots to test the consistency of copy before I rebuild it Manhattan-style on copper clad pc board in an insulated enclosure to minimize drift.

Should I move the frequency? Are there other ISM signals on the same frequency that may interfere? Codar?

I intend to construct a new dipole or vertical for this signal, and possibly get it solar powered with a night-time battery voltage source if it proves relatively copyable.

This beacon looks nearly like a straight line on a spectrum display of 3 seconds/dot and 10 seconds/dot. It clearly shows it's sawtooth character at 30 seconds/dot and 60 seconds/dot.

Thank you.

Dag
« Last Edit: June 28, 2015, 1629 UTC by Dag »
Seminole county, Florida, USA, Earth, Solar System, Universe.Icom 7610 + attic dipole. Black coffee. Ketosis.

 

HFUnderground Mug
HFUnderground Mug
by MitchellTimeDesigns