I've always opted for 1700 to take advantage of the increased range, but it had first occurred to me about 20 years ago that can be disadvantages to that. At the time the transmitter was tied into the elaborate grounding system of the islands pier and pavilion which resulted in achieving good reception about 7 miles away on the next island over. We'll Anyway every year a caravan of vintage car owners visit the island and meet at a local convention center.. and that's when it occurred to me nonemmm their radios ...Dammit that's the second time I've accidentally closed the window.. I hated posting using a smartphone..
I'll come back to this, I think you know where I'm going with it.
So.. these guys with their classic cars have only AM radios in them - which tune up to 1600, or 1610 max. It just seems wrong to be broadcasting on a frequency they couldn't tune in.
More recently came across "Retro Radio" in Montana, a part 15 station who broadcast on 1490AM, why? As he explained:
".. We found an estate...We bought over 200 radios from his family, so that was the basis for creating the Retro Radio Part 15 station here. Since older radios only go up to a dial position of 1500, we chose the available 1490 so that you can easily run the knob up to the top and back it down just a bit to find our signal quickly..."
It's something to consider, the antique radios that is.
Which begs the question: Presuming you have a letter to the law compliant 10ft antenna system, in say with a ground conductivity area of 8, broadcasting 1700.. Then how much range capability would you lose at 1600?... How about 1500? What about way low, like 830?
I've always operated on 1500 kHz and had pretty good performance. I use the Talking House with the range extender antenna.
Currently, the antenna is mounted on a 10 foot mast on a 4'X4' satellite dish sled in the backyard. No ground radials other than the sled which simply sets on the ground.
I don't have any predictive software to model a system but I'm sure someone on here probably does and will chime in.
In my case, it's cut and try. Just put it on and see how it does...
By the way, nice to see you here. Found your old password?
@end 80...I know about this stuff and here's the answer.
The lower part of the band is better by far! This the facts. The lower the frequency with sound or electromatic radiation the less energy needed to create the wave and keep it going. Lower frequencies travel farther. The higher the frequency the the more energy behind it and needed to keep it moving. On commercial radio the stations at the 530klz to, say, 900klz range carry way better than the high end of the band. All being equal transmit power and antenna location. When I was up at the cottage in Ontario around 120 miles north of Toronto there was 50,000 watt stations at 1050 and 1430 and then at 680, 610 etc and the lower ones came in like locals and the others were weak and barely heard on an average radio.
At night the lower band stations can be heard all over N America even if not clear channel.
Now with us here's why we go at the top. Because the 3 meter antenna works better with the higher frequencies and more important in the Procaster and Rangemaster examples where the loading coil is used to make the peaking and the short antenna work like a longer one, the manufacturers chose to work at the high end of the band. If they designed it for the low end of the band with the same 3 meter antenna and the correct value of loading coil which would be larger for the value to be correct we would have better range in the 530-900klz part of the band than at the top as the same 100mW would work better with the lower frequencies than higher ones.
As for wondering about how much you loose if you go from say 1630 down to 1560 for example so every radio would get it, I tried with my Procaster and all other things being equal, the lower I go the signal strength decreases. The tuning meter which directly corresponds to what comes off the antenna peaks lower as you decrease frequency. If I went to 1200 from 1630 the loss is about 30 to 40%. From 1630 to 1560 which is the next best spot here in the Toronto area the loss is about 10%....the meter doesn't peak as high.
As for the radios that can't get that like any made before 1989 or so most analog ones even though they say frequency range to 1605 or 1620 typical will still get to about 1650, even the older tube ones. A little tweek on the oscillator trim will also work.
But I thought like you and if I want listeners and they have an older radio it will not get the expanded band but yes there will be a little sacrifice in range just going from 1630 or 50 and then going down to even just 1590 or 70. How much? if there are other stations there and you have to go down to 1550, lets say, then about a 10 to 15% drop in signal coming off the antenna. You have to stay as high as you can.
I am on 1630 and the few listeners I have get it so it's good and 1630 is better at night with less skywave but if I have to I can go to 1560 with the small reduction in range. I can't just go to 1590 or 1600 as here there's stations at 1650, 1610, 1580, 1540, so the next best place going lower is 1560.
Yeah Bob, but I actually had my password right, it was my user name that was wrong (I thought my username was "end80" but it apparently my name) inally figured that out.
It would be cool to have a simple software that would provide a potential range capability just by entering frequency and ground conductivity.
By the way Mark, I recall Keith Halminton mentioning that the Rangemaster does not employ a loading coil.. He said that during a discussion with R Fry over at the RadioDiscuss forum about 10 years or so ago
Richard Fry demonstrated that a compliant install with a ground conductivity of 5 (average), broadcasting on 1650 had the potential of 84uv at a one mile distance, which evidently indicates that a usable signal could be achieved at that distance.
But if broadcasting on 570 under the same conditions it could only produce 34uv at one mile..... To which he concluded: "The reduced, groundwave propagation losses at 570 kHz are not able to compensate for the lower ERP that system produces."
However, I presume that with a long ground lead that loss could be compensated for (in a non-compliant manner), thus a listenable signal could be achieved a mile away on a frequency as low as 570.. but of course it wouldn't really be part 15 anymore.
I've never heard of any part 15 broadcaster utilizing such a low frequency.
I just realized I'm basically repeating my earlier post above but ending with a question. In an old post titled "Part 15 AM Coverage - High vs. Low Carrier Frequency" at www.radiodiscussions.com/threads/part-15-am-coverage-high-vs-low-carrier-frequency.701750/ Richard Fry calculated that a compliant install in an area with a ground conductivity of 5 broadcasting on 1650 can produce a signal of 84 µV/m at 1 mile, but if broadcasting on 570 it can produce only 34 µV/m at mile.. which evidently would be unusable..
Curious to know what the minimum µV/m field intensity is required for reliable reception to a receiver.
... Curious to know what the minimum µV/m field intensity is required for reliable reception to a receiver.
Highly variable, with the three biggest contributor categories probably being:
Sensitivity and r-f/i-f bandwidth(s) of the receiver itself
Gain, pattern, polarization, and physical orientation of the receive antenna
Field intensity of ambient r-f noise on/near the receive frequency at the receive location, including atmospheric noise and the radiation from nearby sources such as "switch mode" power supplies, lamp dimmers, arcing insulators, etc
