AM1
•
16
“On the Air” Etiquette
1. Do not use “made up” call signs to identify your transmissions. Only the
FCC has the authority to grant such callsigns. Use some other way to
identify your transmitting activity, such as “ This is radio 550, Pittsford
School Student Radio,” and so forth.
2. Identify the location and purpose of your transmissions from time to time.
This is a common courtesy toward other persons who may hear your
transmission. The FCC is toughest about clandestine transmission which
costs time and money to track down.
3. If you are contacted by the FCC regarding the use of this device,
cooperate fully and promptly.
4. If you receive any complaint about your transmissions interfering with
broadcast reception, stop or change your operation immediately.
You also have the option of writing a clear and polite letter to the FCC
Engineer in Charge of your local district, describing your intended operation.
Mention the operating frequency and planned hours of operation. This could
be a good step to take if your project is on behalf of a school, scout or
community group.
ANTENNA EXPERIMENTING
Since one wavelength (
λ
) at AM broadcast frequencies is over 950 feet, and
the distance of only ten feet is allowed between the transmitter and antenna,
including the antenna, you may want to experiment with a “loaded”
antenna for better performance.
An easy way to describe what happens when you “load” the antenna is that
we electrically increase the “length” of the antenna without increasing the
mechanical “length” of the antenna. Our goal is to approximate a functional
portion of the full wavelength (i.e.
λ
/4 or
λ
/8)
Using an 8 foot whip antenna, a series inductance of about 350 µH is
required to properly load the circuit. Older CB radios and car stereos usually
use a large inductor in series with the power lead, typically 100 to 150 µH.
Two or three of these coils placed in series and connected to a whip can do
the job.
As long as you’re at it , you can try to “roll your own” loading coil using a
common paper tube from your paper towel dispenser.
Start by shellacking or otherwise clear coating a cardboard tube to “stiffen”
the cardboard. Then, using wire from an old transformer or other type of
“magnet” wire (available at a local electronics supply shop or Radio Shack)
Summary of Contents for AM1
Page 6: ...AM1 6 PARTS LAYOUT DIAGRAM...