= wrote: >=20 > Is my reading of the UK frequency allocation chart right?=20 >=20 > One can operate without a licence in the old 73kHz band using = licence-exempt inductive devices rules as long as the output is less = than 72dBuA at 10m? Not sure what sort of ERP this equates to. A few uW = I assume? >=20 > Perhaps someone can advise/confirm. >=20 > 73s > Roger G3XBM >=20 > --=20 > http://g3xbm-qrp.blogspot.com/ > http://www.g3xbm.co.uk > https://sites.google.com/site/sub9khz/ > http://qss2.blogspot.com/ > http://www.youtube.com/user/g3xbm >=20 >=20 > __._,_.___ > Reply to sender | Reply to group | Reply via web post | Start a new = topic > Messages in this topic (1) > RECENT ACTIVITY:=20 > =95 New Members 1 >=20 > Visit Your Group > Switch to: Text-Only, Daily Digest =95 Unsubscribe =95 Terms of Use > . > =20 > __,_._,___ --Apple-Mail=_AE46EB55-92B2-4CD1-A85A-F13A7713BABD Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=windows-1252 Some years ago David Gibson of = CREG estimated the ERP of a Heyphone feeding 4W into a 2 m diameter loop = (as sometimes used in cave radio) as of the order of a few microwatts. = He also examined the case of a Heyphone feeding a couple of Earth = electrodes a few tens of metres apart. In practice the latter gave a = range of up to 1.5 km in the French Alps.

I don=92t = have details to hand for other places, nor of David=92s calculations but = it all seemed to take place more or less within the near field. David = also pointed out that, because of the restricted range in terms of = wavelength, one should not speak of cave =93radio=94 =96 it is in effect = an induction system.

The Heyphone and similar = technologies have been used for many years in cave rescue and = exploration. In the UK, the authorities are well aware of what we do and = have been known to issue NoVs allowing the surface end of a cave radio = link on 87 kHz to be connected to an HF transceiver. One example of this = was to allow cave to cave communications between locations in the North = of England and South Wales. As far as I=92m aware, the authorities never = mentioned licensing the cave = equipment.

There is still a requirement, = regardless of frequency, for such equipment not to cause undue = interference to scheduled services. There was a case where NoVs issued = for experiments around 9 kHz included a requirement in some = circumstances to liaise with the Met = office.

John = F5VLF

On 28 Jan 2014, at 12:27CET, = Roger Lapthorn <rogerlapthorn@gmail.com> = wrote:

Is my reading of the UK = frequency allocation chart right?

One can = operate without a licence in the old 73kHz band using = licence-exempt inductive devices rules as long as the output is less = than 72dBuA at 10m? Not sure what sort of ERP this equates to. A few uW = I assume?

Perhaps someone can advise/confirm.

73s
Roger = G3XBM

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