• Get involved.
    We want your input!
    Apply for Membership and join the conversations about everything related to broadcasting.

    After we receive your registration, a moderator will review it. After your registration is approved, you will be permitted to post.
    If you use a disposable or false email address, your registration will be rejected.

    After your membership is approved, please take a minute to tell us a little bit about yourself.
    https://www.radiodiscussions.com/forums/introduce-yourself.1088/

    Thanks in advance and have fun!
    RadioDiscussions Administrators

A Recent Part 15 AM NOUO

R

rfry

A thread on another website referred to the recent NOUO at this link http://transition.fcc.gov/eb/FieldNotices/2003/DOC-309211A1.html , which includes the following quote: Your operation on frequency 1620 kHz was measured at 900 microvolt per meter (uV/m) at 1132 meters.

A popular belief in this situation might be that this operator was using a greatly overpowered transmitter in order to produce that field at that distance.

In reality, that field at that distance could be produced by many combinations of antenna input power and antenna gain with an applied antenna power of less than 100 milliwatts.

Below from a NEC-2D study is one example of a practical and unremarkable combination that could produce the 900 µV/m field, 1132 m from the transmit antenna that was measured by the FCC.

  • a 10-ohm r-f loss in the loading coil needed to resonate a 2.9 meter whip
  • the 2.9 meter vertical whip attached to the r-f output terminal of the transmitter
  • the transmitter with attached 2.9-m whip installed on an elevated mount 10 meters above the earth
  • a 10-m, unfiltered conducting path including a short "ground lead" connecting to an assumed "lightning ground" such as a massive wire, tower, flagpole, billboard etc, which connects to a functional lightning/r-f ground (something buried in the earth)
  • a 20 ohm r-f loss in the functional ground connection (example: several buried ground rods in parallel)
  • about 65 milliwatts of Z-matched transmitter output power applied to the input of the loading coil

... just for a heads-up to those that may be interested.

RF
 
Would you consider the above described system to be compliant with Part 15 rules?
 
BobOnTheJob said:
Would you consider the above described system to be compliant with Part 15 rules?
Click to expand...

No, because the radiating length of the antenna system exceeds the 3-meter length permitted by Section 15.219(b) -- even though the 65 mW of applied power could be produced by a transmitter compliant with Section 15.219(a).

My post above was made to illustrate that it wouldn't necessarily take a transmitter running much more than 100 mW input power to produce the field measured by the FCC that was shown in the NOUO. That can also be done with a transmitter FCC-certified for Part 15 AM, connected to a non-compliant antenna system.

This link gives another example of this: http://i62.photobucket.com/albums/h85/rfry-100/AM_System_Comparison.gif
 
Status
This thread has been closed due to inactivity. You can create a new thread to discuss this topic.


Back
Top Bottom