[BC] Part 15 radio station

[Tom]

No, it's supposed to be impossible to use a Part 15 TX to get more than 
about 100 meters' range, maximum - and that's for Carrier Current operation.

The expected range for free antenna systems is about 30 meters. Note the 
Rules vary either the distance (15.221) to a specified field (15 µV/m) 
or the allowed fields (15.209) at 30 meters based on frequency. Both 
Rules actually favor the LOW end of the band, except... it's a LOT 
harder to MAKE those levels with an antenna, due to the limited physical 
length, at the low end. It's a lot easier to tune a 9-foot whip at 1700 
kHz than at 540 kHz. Which is why many Carrier Current boxes are at the 
LOW end (and the power restriction also disappears for Carrier Current, 
BTW), where the distance from the conductor is further out, but most 
antenna-intended units are at the UPPER end of the band, because the 
tuning components are smaller and easier to fabricate, and the antenna 
itself is somewhat closer to resonance (not by much, but every inch counts!)

In fact, at one point, LPB made mention of this on their website when 
advising colleges about installing AM systems - and noting the fact that 
CC and Radiated systems are two different animals, and trying to get one 
frequency to do both would be difficult-to-impossible.

Of course, with no limit on conducted RF on-campus for all intents and 
purposes...

OTOH, RadioXTZ-AM complies with 15.221 (a), as of the last time I 
measured it - with a new final.
Not being on a Campus, I HAVE to be in compliance with subparagraph a; 
none of the other regulations would apply.

Quoth:

"(a) Carrier current systems and transmitters employing a leaky coaxial 
cable as the radiating antenna may operate in
the band 525–1705 kHz provided the field strength levels of the radiated 
emissions do not exceed 15 uV/m,
as measured at a distance of 47,715/(frequency in kHz) meters 
(equivalent to Lambda/2Pi) from the electric power line...."

At 640 kHz, that's just over 74.5 meters, or just over 240 feet... from 
the closest point of the power line being fed RF. I've established 
monitoring points and can provide same if the RI ever come knocking. 
Extasy AM complies as far as practical with what would be Part 73 
compliance, substituting the Part 15 values where appropriate (radiator 
efficiency, etc.)


Dana Puopolo wrote:
> So, it's impossible to use a part 15 device anywhere but on the 
> ground? That's
> whacked.
>
> -D
>
>
> ------ Original Message ------
> Received: Fri, 16 May 2008 01:22:14 PM EDT
> From: <chrysafis74 at comcast.net>
>
> Mr. John A. Reed of the FCC Office of Engineering and Technology wrote 
> the following comment in response to a query: "If the installer/user 
> places the transmitter atop a metal pole or other conducting structure 
> and grounds the transmitter to that structure, the height of that 
> structure also is counted toward the three meters maximum length."
>
>
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-- 
Tom Spencer
PG-18-25453 (nee' P1-18-48841)
http://radioxtz.com/
Part 15 transmitters on AM 640 and FM 100.1