[Lowfer] multiple transmitters allowed?

[John Davis]

>Are we allowed to have multiple transmitters, each running the full legal
>limit (1 watt)? I would think this is ok, as long as we have separate
>antennas for each transmitter. Since lowfer transmitters are not licensed,
>I wonder if they could object to this?


To take the last part first, just as a matter of interest, yes they could.
Under the Communications Act, all intentional radiators require either
licensing under some radio service, or else certification as compliant with
Part 15.  The use of unlicensed transmitters is by grace rather than
birthright.  :>)  And as Lyle cited, there are limits on the number of user
certified home-built devices one can build before getting into the harder
(i.e., more expensive) requirements for commercially produced devices.

There is another factor to take into account.  Multiple radiators that are
part of a single system connected by wire or cable have to be regarded as a
composite device [Sec. 15.31(h)], which in total has to meet the limits of
the relevant sections of Part 15 under which it is intended to operate.  So,
depending what a person is trying to do with multiple transmitters, you
could end up with (say) five of them, each with input of no more than 0.2W
and antennas of 10 feet.  I once operated three MedFER transmitters in sync
as a directional array, but eventually I realized that the way I was driving
them with a common exciter formed a composite device under these provisions
and discontinued it.

>I've tried receiving via a 40 meter dipole and a random wire-it doesn't
>work. I hope to put up a loop in the Spring. I can barely hear the 2 DGPS
>stations in Maine (and they are within 50 miles of my qth). I'm not sure
>whether the receiver or the antenna is the problem, maybe a bit of both:>:


Could be either, although a sufficiently long random wire in an area of
minimal electrical noise can be pretty effective.  That suggests perhaps the
receiver is not as sensitive as it could be.  Many that tune down to
longwave are half deaf by design.  What kind do you have?  You may be able
to improve its performance with a preamp, by internal modifications to the
receiver itself, or by addition of an upconverter.

John D