|
Post by jimhenry2000 on Apr 7, 2017 4:35:36 GMT
|
|
|
Post by jimhenry2000 on Apr 11, 2017 5:05:21 GMT
Yesterday I installed (7) 30 ft radials in my backyard and moved the antenna over directly above them. I was disappointed in how little the improvement was. It was a little better but not much. So today I re-tuned the transmitter and found that performance was pretty much doubled! So now I think my next effort will be installing more radials, at least 20 if not more. If I find the time I will add 40-50 more radials. It seems to make a key difference. Radial LengthCENTINEL asks: " About how long are these radials?" You are probably asking about my radials so the answer is... I've never made a precise measurement but ABOUT 100-feet to the north and 100-feet to the south. Might only be 60-feet. They are matched length.
|
|
|
Post by Druid Hills Radio on Apr 11, 2017 12:30:42 GMT
The radials ONLY need to be as long as the antenna is high.
|
|
|
Post by jimhenry2000 on Apr 12, 2017 2:23:35 GMT
The top of my antenna is about 30 ft. high and each of my radialks are 30 ft. long. The radials ONLY need to be as long as the antenna is high.
|
|
|
Post by Boomer on Apr 13, 2017 1:37:01 GMT
I notice that the professional Traveler's Info Service (TIS) installers use ground radials that are shorter than the antenna.
TIS antennas are allowed to be 50 feet high, but the ground plane systems used with them use 20 foot radials, sometimes longer at the low end of the broadcast band.
Within that 20 feet, the density is high though, somewhere around 60 radials, and more radials should improve efficiency somewhat, from what I understand.
For another twist, there are some TIS installations with NO ground radials, and instead they use a large diameter pipe sunk deep into the earth. The pipe seems to be the mast itself, it's something like 4" inches in diameter for a large amount of contact with the earth ground. The hole is drilled down with an auger bit to 6 feet, and the mast pipe placed in it, with a center loaded antenna at the top.
That system is for places where they can't lay a ground plane, such as in paved areas. The picture shown was a narrow strip of dirt between a sidewalk and a stone wall, that's where the radial-free antenna was installed.
That might be an idea for some Part-15 folk who live in the city and have no allowance for radials.
Another factor is that TIS stations aren't that efficient, transmitter output versus radiated power, according to my calculations. The transmitter is 10 watts output, and the Effective Radiated Power (ERP) was around 130 milliwatts.
I did my ciphering before I was as interested in P-15 radio, and don't have the formulas I used any more. Does someone on the board know what the real ERP is supposed to be, have you done calculations yourself, I'd like to compare notes.
Boomer
|
|
|
Post by Boomer on Apr 13, 2017 1:39:23 GMT
Jimhenry2000, I looked at your coverage maps, and can see why you need good range where you are, to reach those Northern subdivisions.
Also, what kind of operating system is that, with the shell on the Start button, some kind of Linux?
|
|
|
Post by jimhenry2000 on Apr 13, 2017 4:00:08 GMT
Jimhenry2000, I looked at your coverage maps, and can see why you need good range where you are, to reach those Northern subdivisions. Also, what kind of operating system is that, with the shell on the Start button, some kiwindownd of Linux? No it's the Windows Classic shell interface, added to Win 10 to make it behave more like Win7.
|
|
|
Post by Druid Hills Radio on Apr 13, 2017 13:08:30 GMT
Guys, we are not taking about the height above ground, but the length of the antenna. If a vertical is ground mounted and is 3 meters in length, the the radials do not need to be any longer than 3 meters. There is NO advantage to placing an AM transmitter on a pole aside from theft mitigation, getting buried by snow, etc. How many AM radio stations have you seen? The antennas are ground mounted. Also, radials only need to be an exact length when they are elevated.
|
|
|
Post by jimhenry2000 on Apr 15, 2017 4:02:41 GMT
My 20 radials are 30ft. long each. Now I am debating on whether or not I should add more. Yesterday I installed (7) 30 ft radials in my backyard and moved the antenna over directly above them. I was disappointed in how little the improvement was. It was a little better but not much. So today I re-tuned the transmitter and found that performance was pretty much doubled! So now I think my next effort will be installing more radials, at least 20 if not more. If I find the time I will add 40-50 more radials. It seems to make a key difference. Radial LengthCENTINEL asks: " About how long are these radials?" You are probably asking about my radials so the answer is... I've never made a precise measurement but ABOUT 100-feet to the north and 100-feet to the south. Might only be 60-feet. They are matched length.
|
|
|
Post by jimhenry2000 on Apr 16, 2017 7:38:14 GMT
I am wondering if I should not have stopped at 20 radials and continued on to 30-40.
|
|
|
Post by Boomer on Apr 16, 2017 9:51:51 GMT
I've never done real extensive testing on radials, I'm kind of new to the Part-15 antenna game myself, and I haven't done a formal radial install yet. In my tests I've just laid out radials on the ground temporarily, bits of wire I had around, with at most 6 radials up to 50 feet long. It seemed to work okay, but my installs are close to other objects and trees.
One of the better tries was using rolls of chicken screen, 25 feet in a cross pattern under the antenna, the transmitter was sitting on it, I used clip leads to assure the two pieces were electrically connected to each other and the transmitter ground. The good thing about it was it was cheap and easy to unroll and roll up again. I got a stronger signal with that rather than long ground leads, I probably had 4 of those before the chicken screen.
Boomer
|
|
|
Post by jimhenry2000 on Apr 17, 2017 4:26:07 GMT
Boomer, Chicken wire does sound like something very interesting to pursue. I've never done real extensive testing on radials, I'm kind of new to the Part-15 antenna game myself, and I haven't done a formal radial install yet. In my tests I've just laid out radials on the ground temporarily, bits of wire I had around, with at most 6 radials up to 50 feet long. It seemed to work okay, but my installs are close to other objects and trees. One of the better tries was using rolls of chicken screen, 25 feet in a cross pattern under the antenna, the transmitter was sitting on it, I used clip leads to assure the two pieces were electrically connected to each other and the transmitter ground. The good thing about it was it was cheap and easy to unroll and roll up again. I got a stronger signal with that rather than long ground leads, I probably had 4 of those before the chicken screen. Boomer
|
|
|
Post by jimhenry2000 on Apr 17, 2017 4:46:00 GMT
Boomer I think I answered this but in case not it is called Classic Shell. Install it on Win 8, 8.1, or Win 10 and your menu interface will look much more like Win 7 or Win XP which I strongly prefer. Jim Also, what kind of operating system is that, with the shell on the Start button, some kind of Linux?
|
|
|
Post by Druid Hills Radio on Apr 17, 2017 11:59:02 GMT
If you can afford it, use 1/2 inch hardware cloth.
|
|
|
Post by Boomer on Apr 17, 2017 21:37:36 GMT
Hardware cloth would be tougher, and I guess have thicker galvanize on it to last longer with ground contact. That's the thing about chicken screen, wire or poultry netting, it will rust in a handful of years, faster if on the ground.
I can't see chicken wire being as good as copper ground leads set up radially, which is more ideal, with the high concentration of metal at the antenna's base, right where it's needed. Crossing the chicken wire pieces must have helped though, making higher density at the cross.
For me it was better than 4 really long wire radial ground leads, and it was a good test, and cheap, a trip to a local hardware store. There's also other kinds of galvanized wire in big rolls that's dirt cheap that might make good radials. Copper clad steel wire might be the best, cost to performance ratio, if you can find some.
The classic shell looks good, getting a desktop look back, where newer Windows looks like it was made for tablets with touch screens, using the tiles.
Boomer
|
|