Discussion in 'Amateur Radio News' started by KD4HSO, Jan 31, 2010.
that is just a really cool article! I wish they had included some details on radios and freqs they are using, but still, good work kid!
This is a better article and has a nice pic of the antenna!
It is wonderful to see this article carried widely, with the excellent work of the young cave radio enthusiast Alexander Kendrick.
Low Frequency (LF) or Very Low Frequency (VLF) in the audio range is often used for cave radio, especially for RDF/radiolocation using the loop null method. Efficient small size loop antennas at these frequencies have very narrow bandwidth... from a few hertz at VLF up to about 2kHz at LF.
But MF and HF also works great for communications, and coil-loaded whip antennas or wire antennas on the ground, can be used for SSB HTs on HF. For those who are interested in Cave Radio, please see "Speleonics", the journal of the Communications and Electronics Section of the National Speleological Society (NSS).
Here is an issue of Speleonics with an article on SSB and CW on both LF and HF in caves: 185kHz Radiolocation and 7MHz Communication Experiments in Bigfoot Cave
One of my homebrew 185kHz SSB/CW/beacon cave radios
185kHz Pedestrian Mobile cave radio RDF loop antenna and 7MHz whip antenna in use above the passages of Bigfoot Cave in California.
Hams who are also cave radio operators often use the ham bands for cave radio. But there are also several areas of spectrum that allow unlicensed operation, such as the LoFER bands. Typically, SSB is often used for voice, above 70 kHz. CW or beep beacons are used for radiolocation below 200kHz. PSK or FSK is used for text/data. The frequencies below 500kHz typically use either earth dipole or loop antennas for communications. Loop antennas work well for RDF survey work. For HF communications, wire antennas, guide wires, or portable whip antennas are used for communications. Here are some of the common frequencies used for cave radio.
100-4000Hz (Audio band) direct voice audio amplifier to antennas or guide wire
715Hz (Audio band) CW beacons for RDF/Radiolocation
3496Hz (Audio band) CW beacons for RDF/Radiolocation
136kHz (135.7kHz -137.8 kHz Amateur Band) International
185kHz (160 kHz - 190 kHz LowFER band) USA/Canada
3885kHz (75m Amateur Band) for ham cave radio operators
3996kHz (75m Amateur Band) for ham cave radio operators
7095kHz (40m Amateur Band) for ham cave radio operators
7240kHz (40m Amateur Band) for ham cave radio operators
27MHz (CB Band, SSB, AM, FM) direct or with guide wire
VHF (various bands) direct in lava caves or with guide wire in other rock
UHF (various bands) with guide wire
Funny, I just read this on one of my Abandoned Mine websites and was trying to do a search for more info and found QRZ.
I think it's awesome and it sounds like that kid is pretty bright. I think it's impressive! So would this require a license? Didn't see his name in the FCC database...
So Bonnie, would this be pretty similar? Or identical?
(We were posting at the same time)
So there may finally be something that can provide limited communications to coal miners as mandated (by people with absolutely no comprehension of RF communications) following the Sago Mine Disaster.
There's been a system around for years, called "The Mine Radio" Works on a highly inductive loop system. The UK National Coal Board pioneered it and spent millions developing it in the late 60's through to the end of UK nationalised coal industry.
Many mines around the world are using the system.
Coal mines are unique when it comes to RF propagation, they tend to be deep, they tend to have lots of steelwork in them as supports etc. To overcome that, a "guide wire" grounded at one end is run along a main travelling road, useful range is a max 1.5KMs . (Repeaters are used after that and at every 1KM intervals.)
There is another system being developed here in the US, it's already being used, it is certified for hazardous locations, but is more of a paging system and automatic tracking system for miners underground. Again, it requires a "guide wire" along roadways to work successfully.
Here's a link
He might have 'set a record' but there appears to be a fair amount of literature on the subject.
Obviously, he had to make the antennas and 'radio' equipment, probably VLF.....
New?? not sure.....might be first time keyboard was use for texting.....
Spread the word
It would be nice to see an article in QST, QEX or CQ on this topic. I don't think it is "common" knowledge with most hams.
Seems like a very active community and it is very interesting reading.
Congrats on the science fair victory Alexander.
Thanks for your links Bonnie, will definitely read them.