Elsewhere I have blogged my plan to abandon FM as a part 15 vehicle for distributing audio to AM transmitter relays, because of the unsatisfactory nano-pea field strength provided by 15.239. However, while that changeover is engineered we are continuing to seek solutions to an ongoing problem with our FM relay system.
Testing has shown that the signal transmitted from our certified FM transmitter is free of artifacts from the nearby high power stations, but one FM receiver is reproducing artifacts from both full power adjacencies which are clearly heard in the background of our audio as relayed on AM.
We prefer to perfect the existing equipment rather than bear the expense of a more selective FM receiver.
The receiving antenna at this time is simply a random length of wire connected to the antenna terminal at the receiver, and we will be trying more carefully designed antenna methods to reject the unwanted interference from the other stations.
For curiosities sake the antenna variations and results will be shared.
Suggestions are welcome.
Carl Blare says
Step Taken
I looked at the Panasonic Tuner on the lower shelf out by the AMT5000 transmitter, and realized that disconnecting it to get access to the antenna terminals would be more fuss than a lazy person cared to mess with, so I looked at the wire that goes up the wall from the radio.
Once I was done looking at the wire I measured it and found it was just about dead on the half-wave length of the offending high power signal that can be heard in the background of all my AM broadcasts. I cut the antenna down slightly below my half-wave length, and the unwanted signal did attenuate enough that during most program material it is not noticeable.
I proudly declared it a good night’s work and will return to refine the job once the trees bloom.
censoredship says
I’d start hard wiring those
I’d start hard wiring those transmitters Carl 🙂 Easy to eliminate the hum and interference that way.
Any projects in your world to get the transmitter or at least antennas outside?
Carl Blare says
Moving Out
Yes sir censoredship, have big plans for outdoor antennas.
Will be putting a 3-meter vertical with radials way back in the back in a cleared area. It will be about 60-feet from the building, and it will be fun to go the the front room indoors and hear the signal from “far away”.
Also plan to erect a 3-leg bamboo tower in the front for another AM frequency, sharing space with flowering vines that will give the tower a “purpose” in the watchful eyes of the landscape police. It will be interesting to observe how much the vines reduce the signal strength. In the winter the tower will hold 3 blue lights in a vertical array as both a holiday display and aviation help for owls.
The 2 existing Wintenna sites will be maintained as backups, all of the transmitters controlled from a Remote Control Panel at my world desk.
Also, there will need to be something for the 1-Watt 184 kHz long wave transmitter, but a 50-foot vertical might not be possible, so we may end up with a sloping wire.