- October 19, 2004 at 6:15 pm #6262matthParticipant
Total posts : 7
Base Loading.. legal?
Is it really legal to base load an AM station? I ask because you’ve definately got more then 8-9 feet of wire wrapped around there.
Unless I’m not understanding how this works… do you just wrap the wire around the PVC and then run a wire through the middle of the PVC? Or is that 62 wraps of wire on the PVC part of the antenna connected to the transmitter?October 21, 2004 at 8:34 am #11935tregonseeGuest
Total posts : 45366
From my understanding, the FCC has not counted loading coils against the 3-meter limit, as the purpose of a loading coil is for impedance matching and not radiating.
In a base-loaded antenna, the coil (wound on the PVC form) is the bottom of the antenna. The “top” end of the coil is connected to the antenna element. You can do this on the outside, which will leave the connection exposed. You can also drill a hole in the PVC form near the top end of the coil wire, run the coil wire inside the PVC form, make the connection to the antenna on the inside, then join the form to the antenna element.
If you’re making an antenna to a prescribed single-frequency design (like the Base-Loaded 3-Meter Antenna in the Library), the end of the coil is connected (by a short lead) to the transmitter. This can be exposed, or you could drill a hole in the form, run the end of the coil wire inside the form, and make the connection inside the form (this generally assumes your transmitter is mounted below the loading coil).
If you’re making a tunable antenna like the SSTRAN antenna in the Library, the transmitter lead will attach to a “tap” point on the outside of the coil. The instructions should tell you where to make the initial tap. You start with an alligator clip attached to the transmitter lead, so you can move the coil tap point. When you find the best tap point, you remove the clip and solder the lead to that point. The transmitter lead should be insulated so it can’t brush up against the coil, which changes the tap.
Hope this helps.
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