[SOC] Unlicensed FM or AM brodcasting to my yard...

[JMcAulay]

At 10:01 PM 04/13/2002 -0500, Rob, W=D8JRM wrote:

>Ah HA!  That's perfect for what I'm wanting to do... OTR shows sound better
>on the AM band anyway :^)  Plus the 1/4 mile range is great, that will
>allow me to take a little handheld radio up to the neighbor's pond when I
>go fishing.  Of course you say that's a poorly designed and installed
>transmitter... how far could I get with a good one??? :^)

I know of one installation which has drawn fire to the FCC more than once
because some people complain about it, because they are convinced it's not
legal -- but it is.  You can hear the thing for a mile or better.  It's
installed on top of an advertising sign on a tall pole, with a
helically-wound vertical antenna (sort of like a great-big "doorstop" AKA
"rubber duckie" vhf hand-held antenna).

>What would you use for an antenna that's only 9 foot long at that
>wavelength?  If you were to wind a massive coil, would the length of the
>finished coil be what you measure or would you measure the length of the
>wire that you used to wind the coil?

There's been a lot of argument on that for a long time, and some people
swear you just better measure all of the wire.  I think they are just
trying way too hard.  As far as I know, the FCC has never gone after anyone
because they measured overall length.  The rule says the *antenna* plus
transmission line and ground lead can't be more than three meters long, not
the *antenna wire*.  So I would use a helically-wound antenna and measure
just the overall length.  What I would do, however, is not legal advice.
If you have any concerns about it, I suggest you consult your lawyer.

>Maybe a massive pi network in the box with the transmitter, and then attach
>a couple 4.5 foot lengths of wire to each side of the box?

Don't think so.  Horizontal polarization in the BC band works lousy for
almost anything.

>(Yes, I know a meter isn't exactly 3 foot, I'm rounding :^))

Yeah, but you're rounding way down.  Three meters is less than two inches
short of ten feet.

><---
>>There is also Sec. 15.225, "Operation within the band 13.553-13.567 MHz."
>>This allows you to radiate 10,000 microvolts per meter at 30 meters.  This
>>means in any or all directions.  This obviously equals 100 microvolts per
>>meter at 300 meters.  It's not bad.  Of course, you'd require a short-wave
>>receiver, but I'll bet you have one or two of those lyinmg around.
>>--->
>
>Yeah, but it doesn't go above 13 unfortunately...  Aren't there
>experimenters there like there are in the 1750 band?  I've thought about
>whipping up a little rig to operate there, but never have got around to it
>:^))

So, tweak the radio.  :)  Yep, lots of people operate there.  And, by the
way, how second class of me:  "obviously equals 100 microvolts per meter at
300 meters"???  Obviously?  No way.  That's 100 microvolts per meter at *3
kM*, not 300M.  It would be one millivolt per meter at 300M.

Rob, I have a couple of neat little transmitters put out by "Realty Radio,"
or something like that.  They are tunable across most of the AM BC band and
are certified for Part 15 with a three meter wire antenna.  They have
built-in endless cassette players, but I've gone into the tape head
connections on one of them with low-level audio and it worked fine.  If you
want one and would like to trade something I just can't live without, I'll
shoot one out to you (as soon as I find it).

73
John WA6QPL