Isn’t that one of the first questions we always ask when we go on the air? Well recently I purchased a Hamilton Rangemaster to add to my stable of transmitters (which includes the SSTran, the Ramsey AM25C, the Vectronics AM-1, and the venerable Knight Wireless Broadcaster). Of course, I was excited to find out how far it would go. And, I’ve developed an interesting technique for DXing that I want to share with you.
But first, the Rangemaster is awesome! I like it very much. I also like my SSTRan very much (but for somewhat different reasons). I bought the Rangemaster because I wanted to be able to operate it withough worrying about complaints about unlicensed operation.
So what did I find? Well, first of all, a little background. I am operating on a cluttered frequency (aren’t they all?) in a major metropolitan area, from out in the suburbs. I don’t have an ideal site. I have a small yard with a lot of trees. I wish I lived on a farm with hundreds of acres to put up experimental antennas… alas, that is not the case. Temporarily, I’m just using the CB whip antenna. The transmitter is grounded to a single 6′ ground rod. I’m watering the ground rod with a garden hose at a slow trickle. I plan to add additional ground rods over time.
When I first put the Rangemaster on the air, I didn’t pay close enough attention to the power adjustment instructions, and the range was very poor. Then I re-read the instructions and brought the power up to 100 mW, and the range improved markedly. I don’t own a field strength meter (I wish I had bought that Potomac FIM-41 I wanted when I was a kid)… So here is what I can tell you… my signal is really strong for about 200-300 feet, such that you can comfortably listen to it in a neighbor’s house on a reasonably good quality portable radio with little noise in the background. In my neighborhood, that’s about 2-3 houses away. The signal is intelligible for about .25 mile (2 blocks). At night, when the QRM is bad, you can just about listen to it a block away.
Now for the interesting part. I decided to see how far it was really going… despite the QRM. So I used the tone oscillator on my Shure M267 mixer, which is driving the transmitter, to generate a 1 kHz tone. Now, that tone is REALLY annoying to listen to at close range, but as the signal starts to get weak, it’s not as bad. You will find, if you try this, that the tone will stand out even if your signal is buried under 3 or 4 other stations in the muck, and you will be able to hear it for a long way. The ear is very sensitive in the 1 kHz range. So I put on the tone and drove off to work. In the morning, local sunrise is around 7 a.m. and it didn’t go far… about a mile was the farthest that I could hear it. But on the way home around 4:30, I was shocked to discover that as I was about 2 miles from my home, I started to hear it! And today, after I made some improvements to the ground system, I actually heard it several miles away. But the useful “broadcasting” range remains only a couple of blocks at most.
Now, what conclusions can be drawn about this? First, don’t try this experiment unless you are not afraid to be noticed. A 1 kHz tone on the AM dial left on all day stands out like a sore thumb. (So maybe don’t leave it on all day like I did). Second, the useful range of a Part 15 transmitter is a LOT less than the distance it actually can be be detected. On an area basis, if two blocks is equal to 1/4 mile, then the useful coverage area of my station is very roughly 0.2 square miles. But the absolute limit of reception is considerably farther. Now I will say, if you wanted to key the tone with Morse code, you could probably communicate at some distance… (yes, I am a ham radio operator). But that’s not why we get into LPAM, is it?
I noticed some interesting things while driving around. As you drive away, the signal rapidly drops off to a low level, such that you would think it would fade out entirely… but it “hangs in there” for a long, long distance (with occasional fade-outs). It’s amazing to me that after the signal gets weak, I can drive quite a bit farther before it actually disappears.
In any case, I would be interested to hear from people that try this experiment. How far can YOU go?!
Nice Description of a Range Check
Thanks, WEAK, for your report.
My experience is similar to yours. A few years ago, when I was using a Ramsey AM-25 with an antenna in my basement, I did a drive around range check.
My results seem to be similar to yours. I used a 1000 Hz tone since it was distinctive. It also puts a lot of power into the sidebands compared to the usual voice or music programming.
It was noteworthy that as I drove along the highway in my humble city that my signal faded in and out. I live next to a river, and when I approached the bridge to cross the river about 1.8 miles away from my tx., the signal faded. At the other side, it was back. Hmmmm….why would a river attenuate my signal. Then I reaized that there were no power lines on the bridge.
OK, now what? I listen to an AM station on 820 here and there is one in Dallas on 820. Driving home from work after sunset there was no problem hearing the local station untill……(suspense builds)….I traversed the same highway I had used for my station tests. The Dallas station came in loud and clear on top of the local station. So, I conclude, right or wrong, that the power lines parallel to the road somehow are acting as a receive antenna and are coupling to my mobile receiver.
Though I had good range with the Ramsey AM-25 ,and some of it might have been due to the power lines, it is now retired. I found out that the input power of my unit greatly exceeded the 100 mW limit and the modulation was not good.
Love my SSTRAN.
Neil
Power Lines
Neil,
I found the same thing. Power lines can carry electrical noise, but they can also affect your coverage– in some cases, extending your range and in other cases, attenuating it.
Interesting comment about the Ramsey AM-25. I found the same thing, but I also can provide recommendations on how to simply and easily correct the problems you noted. I will post that information separately for those that might be interested.
Thanks for posting your comment! I hope we get some additional comments on this topic.
WEAK-AM
Classical Music and More!
Re-Radiating
by MRAM 1500 kHz
Among others, my main transmitter is a Talking House. My usable area coverage is about a .4 mile radius. But, this is greatly affected by weather, time of day, season, etc.
I do believe that within my neighborhood, the power lines are re-radiating my signal providing great near field coverage. The signal is very strong where I’m near the power line secondary feeder or neutral. The end of the line on my street is .4 miles from my site and the signal drops abruptly at that point. As you had stated, the signal is much weaker but remains fairly constant for some distance from that point.
Propagation is a funny thing. There are “hot spots” around town where my signal suddenly jumps up from nowhere. I’m talking maybe 3 miles away. Since the trees have begun their Fall change, and it’s been a little drier, areas that previously had coverage are now dead.
I guess during this “dead” time would be a good time to tweak the antenna and ground system.
Range test update!
I turned off the programming and put the tone back on the air again today for another test. Believe it or not, this time I first heard the tone from my station at a distance of 4.7 miles (driving toward home). That’s almost a mile farther than the last time! As before, the tone is very weak at first, and hardly changes amplitude for a long distance. The first point at which it became perceptibly stronger was 2.3 miles after I first hear it, or about 2.4 miles from home. It remained at about the same level until 3.8 miles from first hearing, or about 0.9 miles from home. And it became strong enough to exceed the audio level of the other muck on the channel about 0.5 mile from home.
That is sure interesting to me! I can’t wait to try this test again after I get the frequency moved over to the X band, where it’s a little quieter.
WEAK-AM
Classical Music and More!
Weak signal range
Although I haven’t bothered with using a tone, I have noticed that in some areas of town, I can hear my station up to four miles away. However, the signal is really in the mud and would not be normally listenable. I would equate it to a very difficult to catch SW DX station. Also this type of reception is very spotty.
Re: Range
Well it’s been a couple of years since my only post but this topic caught my attention and revived a thought I had a while back about a possible way of drastically improving range “”possibly””??. I used to come home and listen to my station with my mobile amatuer transceiver (alinco dx60) on 1610 am and since there was a 15 mile distant highway transmitter I would listen to the beat note between the two transmitters. I could tell when I first could detect my station by the flutter on the carrier signal and this started about 4 miles away. I could not actually hear any audio until 1/2 mile out. These things confirmed what I new from 47 years as a ham operator ranging from AM to SSB. Now I got to wondering how far SSB would extend the range. If my ham experience is any indication it would at least double the range. I have not tried it but my idea would work something like this: 4ea 100mw tx’s placed about 3/4 mile from each other on a square and a 100 mw ssb tx for program material in the middle of the square. Adjust the transmitters distance out on the square for best reception at the receivers. The 4 outer transmitters provide carrier only to compensate for the lack of a bfo in the receivers. No audio or carrier synchronization or stl needed. It would probably quack like a duck in some areas and of course it would be mainly for voice but what do yo’all think about range potential? I chose 5 transmitters because of the part 15 rule limiting homemade to 5. I did not find any restrictions under part 15 against SSB (single side band) modulation. Anyone think this might work. It was only a thought on my part and thoughts have not led to any critical technical thinking… Cheers.
Hot spots
MRAM said: “There are “hot spots” around town where my signal suddenly jumps up from nowhere.”
Yes, I have noticed this with my SSTRAN, also. There are several places around town where this happens. The best one of these is about two miles from me, behind a Lowe’s (like a Home Depot). The funny thing is, the hot spot is on the far side, with the building between me and it.
If I could figure out what causes this and spread it all around town, I’d be set 🙂
Interesting idea!
Hi Dave,
That is an interesting idea! One of the most novel approaches I have read on this board, without doubt. My sense is that it would be difficult to synchronize the carrier frequencies of the four carrier generation transmitters to ensure that they are precisely on the same frequency. I think they would have a tendency to beat with one another. Also, as you know, you have to be very precise about the frequency between a SSB signal and the carrier frequency to recover it using exalted carrier reception.
I do know that some Rangemaster owners have set up systems with multiple transmitters that are phase locked. Visit the Rangemaster web site for more details about that.
SSB to increase range
Yes the locking of the oscillators together is needed but compared to some of the other problems associated with AM simulcast I have read about on this board it would be a minor problem. When I had my Motorola business I remember working with FM and if I remember correctly we always adjusted the carriers to be in phase in the “overlap area” not necessarily on excactly the same frequency. This was because of the benefit of “FM capture effect” I don’t remember exactly what the db difference was for capture on narrowband fm but 3-6 db sticks in my mind. In the capture area it didn’t matter how far off frequency the simulcast transmitters were the system worked fine. In the overlap area distortion would rais H— with the paging tones if the phase of the audio was off. A couple of other ideas for using SSB on the broadcast band would be to operate outside a broadcast stations legal coverage area but still within the useful area of the carrier. The part15 station could even survive at night. Is it considered interference outside of the licensed ststions coverage area?? Still another idea would be to make small (5-6 dollars or less) oscillators to give to your listeners for the IF frequency of their receivers. With that idea you could probably spread out five SSB simulcast transmitters to cover a whole town. My guess is that SSB mode would have a solid 2 mile range from each Tx and audio phasing problems should be much easier to deal with. Or how about using SSB on the part 15 shortwave channel to reach your other 4 AM BC transmitters as a cheap stl.. No audio phasing problems. So many ideas …so little ambition..Hi Hi..