Part 15 AM Broadcast Frequency

[WCWalker]

In the event that I stay in the Kansas City area I am trying to figure out a way to avoid having to use 1610 for my frequency because of the IBOC digital hash that is present at night. I may be able to use a frequency below 1500 here because I've found a couple that are clean during the day and have minimal skip at night.

Has anyone tried using a Part 15 AM transmitter in the frequencies above 1300 but below 1500? If so, how much did the range diminish when comparing to the frequencies above 1600?

 

[Neil E.]

I have not done any scientific experiments re this but I did play with it for a while. Using a Ramsey AM-25 I tried some clear frequencies around 1200 to 1500 kHz and from my drive around the neighborhood assessment I observed no meaningful change in range compared to my tests in the 1600 to 1700 kHz band.

I did note that there was more daytime background noise (from broadcasters) in the low band vs. the high band but this is probably due mostly to station density.

This is all anecdotal and not based on science or real measurements, just casual observations.

The real range killer here is electrical noise from our "modern" home devices. I cannot listen to AM on a line powered receiver in my home. Battery operated equipment is OK and my "big ear" comm. grade receiver (line powered) works well with an outdoor antenna and coax feed of about 100 feet. I once clearly hear a Talking House type transmitter 2.7 miles away with this receiver and antenna. But all my other line powered receivers with built in antennas fail to produce a quiet signal from commercial broadcasters. One thing you might look into is how the electrical noise varies in you home vs. frequency.

Since many factors affect range and reception, most specific to a particular environment, you may just have to try it and see what works for you. I believe electrical noise will be a bigger factor affecting range than the frequency you use. Just an opinion.

Neil

 

[carlvenorden]

We've done it William, up to 1200kHz with a very long coil, and the same small antenna/sstran tx.
As you know we are tricking the antenna into thinking it is longer, and with a much longer and more tapped coil, we have had a great signal on 1200am.
Now, getting lower on the dial is a little trickier, I"m thinking we can go to about 1000 (It's been done, but really required a more involved coil) but it is safe to say it can be done up to 1200, all other factors the same (clear frequencies, etc)
Carl

 

[Tom Wells]

I operate on 1620, but in the past used 1550. My oscillator is not designed to operate that low and I had to use some lumped capacity
to get enough feedback to run there...it was right at the critical level for enough feedback to oscillate.

I noticed no meaningful increase going up to 1620. The difference is incremental. In other words, you'd notice if you tried to run at 530 khz, but +/- 2 or 3 hundred khz from the upper end of AM dial, you'll never notice the difference, even though there absolutely IS
a difference. It may be measurable, but not noticable. The daily variance and other factors are smaller than the "mismatch" of the fractional-size antenna, which at ANY AM broadcast band frequency is so large as to be the major limiting factor.