-
You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.
Medium Wave
- Thread starter Se7en
- Start date
Hmm, well how are they transmitting their signal that causes listeners to use a bar horizontal antenna?
I'm not quite sure what you're asking. The AM Broadcast (AMBC) station is using a vertically-polarized antenna and the receiver is using a ferrite rod sitting horizontally in the radio case and you're wondering how a horizontally- polarized receiving antenna can receive a vertically-polarized signal...is what I think the question is.
The answer is that, for a local AMBC station, the RF field is so strong that just about ANYTHING would work as an antenna. True, there's about a 20dB "loss" because of cross-polarization, but your radio won't even notice that until you're several hundred miles away from the transmitting antenna.
What happens if you turn the receiving radio on its side so that the ferrite rod is aimed vertically? I'm guessing you won't notice much change.
From my home town (Las Vegas NV) I used to listen to KOMO radio (1000 KHz in Seattle) with a little shirt pocket radio. At that distance - ~1200 miles - I had to be careful to keep the radio sitting in the horizontal plane correctly. If the ferrite rod was vertical, it didn't matter.
The answer is that, for a local AMBC station, the RF field is so strong that just about ANYTHING would work as an antenna. True, there's about a 20dB "loss" because of cross-polarization, but your radio won't even notice that until you're several hundred miles away from the transmitting antenna.
What happens if you turn the receiving radio on its side so that the ferrite rod is aimed vertically? I'm guessing you won't notice much change.
From my home town (Las Vegas NV) I used to listen to KOMO radio (1000 KHz in Seattle) with a little shirt pocket radio. At that distance - ~1200 miles - I had to be careful to keep the radio sitting in the horizontal plane correctly. If the ferrite rod was vertical, it didn't matter.
If i turn the radios with the bar antenna facing vertical I'll loose reception quiet a bit ! All the stations i listen to are with in one hundred fifty miles or less.
While it is true MW stations transmit a vertically polarized signal, the towers ARE the antennas rather than a support for antennas, the issue with a ferrite rod antenna is not so much polarity as it is pattern. The response pattern of a ferrite rod antenna is like two balls that just touch. Imagine the rod running between the two balls. In the horizontal plane the response is good all around but next to nothing straight up and down. Turn that antenna on it's end and now you have good pickup straight up and down but next to nothing in a horizontal plane all around. That's the reason for the difference, not so much polarity.