HFU HF Underground
Technical Topics => Equipment => Topic started by: Under30 on September 06, 2020, 0130 UTC
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I am interested in setting up a beacon in the 22 metre band :)
Are these transmitters home brew?
What else do I need to get started?
Thanks,
Jeff
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https://www.blackcatsystems.com/rf-products/22_meter_band_part_15_beacon_kit.html (https://www.blackcatsystems.com/rf-products/22_meter_band_part_15_beacon_kit.html)
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Thanks :)
What's involved in choosing a call sign and frequency?
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Calls signs are up to the operator. Often related to location, their name/initials/whatever. Ideally unique from any others on the air, to avoid confusion.
Most operators avoid the center of the band (13560 itself) as there is more RFI there, and hang out near either end of the band, but within the legal limits. Stations tend to fade in and out (and are actually rarely heard at all due to the low power levels) so you don't need to worry too much about interference from/to another legal Part 15 beacon.
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Thanks for the info :)
Sounds like something I would like to do ;)
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When I picked my call, it was both an oblique reference to location, and to the construction materials (PVC) used to build the antenna.
It also makes sense to choose an ident that is easy(er) to read as a weak signal. This involves care in the choice of letters to get a sensible ratio and juxtaposition of dots and dashes. For example HI would be a pretty poor choice (.... ..) , whereas XO (-..- ---) might work quite well, if one is using simple keyed CW. For FSK, things are a bit easier, because the carrier is always on.
Choosing a frequency has a number of aspects. The first is doing one's best to stay away from the centre of the band at 13,560 kHz. There is a lot of commercial interference here, so it is much harder for a mW power beacon to be heard in the QRM. The second factor is the adjustment range available with the setup, especially if trying to "pull" a crystal oscillator. This could determine whether the transmitter is above or below the band centre. Lastly, of course, it is polite not to land on top of another beacon, but one can afford to think really narrow, and 100 Hz, perhaps less, is a decent margin. Listening is often via spectrum analyser, so as long as traces don't overlap, they can be picked out. There are a couple of beacons that are well known for drifting up and down in frequency as the local temperature changes. There are no hard and fast rules, aside from working within the band limits, and not exceeding the maximum allowable field strength, but there are some good tactics to enhance one's chance of getting some reports.
Cheers
Ed
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Thanks Ed :)
I'm still in my planning stage and need all the advice I can get :)