- November 25, 2008 at 12:28 am #72021710thetopParticipant
Total posts : 7
I have some good news, after modifying my loading coil a bit, and moving my antenna higher, and selecting the best tap, I can recieve the signal of my AM25 all over my house. I am on the frequency 1480 and I can actually pick up my signal crystal clear in my yard and my car radio on my street. It finally seemed like I made it work.
Then, the bandwidth issue. I recieve the signal perfectly clear in my house on 1480 kHz, but I also recieve it crystal clear on 1560 kHz on my radio a few feet from the radiating antenna. AND in between, it is scattered, my problem is that there is a station on 1550 kHz in Scranton which I do not want to interfere with. When I am downstairs, I can get it perfectly on 1480 kHz and broken up on 1560 kHz. Outside, I can hear it clear on 1480 kHz and very faintly on 1560 kHz. Does anyone know why this is happening? How can I fix it so I do not interfere with the 1550 station?
ThanksNovember 25, 2008 at 5:28 am #16919RADIOBRANDYGuest
Total posts : 45366
Some transmitters will create a spur, it might also be overload or mixing of a strong local station. As long as it is as weak as you say it is I would not worry about it. We have a 1550 that is legally free to interfere with the station on 1560. Its inference covers a much bigger area around 100 SQ miles.
Radio BrandyNovember 25, 2008 at 8:08 am #16921radio8zGuest
Total posts : 45366
It is not unusual to hear your signal on other frequencies when very close to the transmitter. This could be due to receiver overload or other artifacts which may not be an actual signal. But, since you hear it farther away it may indeed be a “spur” from the transmitter.
A few things can cause this. Without being able to put my hands on it all I can do is offer some suggestions. The first thing I would suspect is the power supply. A supply which is “soft” to RF could be a problem even though there is a good bit of bypass capacitance in the transmitter from power in to ground. I have seen problems such as this with VHF amplifiers, especially when used with a regulated supply. Try another power source.
It could also be that the loading coil/antenna is not actually resonant at your operating frequency an it is preferentially passing this artifact from the transmitter or providing another resonance for the output circuit. Try changing taps and see what happens.
Also, thanks for reporting on your loading coil success (despite this minor problem).
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