This time, the chicken finally gave up the tower and escaped to the safety of a Real Chicken Shed with an even taller tower, through a hole in the fence.
However, the fox stealthily followed the chicken through the very same hole, threatening all the other chickens in The Shed.
But a cow who liked chickens, came with bags of hay, chased out the fox, and stood guard while the chickens stuffed hey into the hole to repair the fence.
The fox, who wasn't interested in cows, decided to go on his way, looking for other prey, and the chicken was safe and happy to be able to crow to many, many more chickens and cows ..... THE END?
Epilog: We think some other farm animals may have recycled the parts left behind, moving them to smaller Sheds with no towers and perhaps fewer foxes.
So, was the fence grounded?
I guess so ... I dunno. You'l have to call in to the program and ask ... that is, if you understand chicken ...
I think they should get a new station call letter ID ... KLUX 😀
How does the chicken get the Part 15
signal to get across the road?
He drags a Collins R-390A with an extension
cord attached onto the side of the road.
(This is one strong chicken.)
He plugs the extension cord into an outside
AC outlet on a nearby house. He attaches
a Quantum QX Loop and tunes in the
Part 15 station on the R-390A. It's S3.
Chickens aren't good at making transmitter
antenna loading coils.
Bruce, MICRO1690/1700
P.S. Ken and Rich, thank you very very
much for the test to speech info. I haven't
tried it yet. But, I will very soon!
Thinking of how chickens are always attracted to roads, it is significant the chicken never follows the road to see where it goes. Instead, it crosses the road until it's over on the opposite side. I would say it imagines there are chicks over there, in the sense of girl chickens.
Girl chickens are swayed by portable radios tuned to a nearby part 15 station.
Egg breakfast, tomorrow.
I liked the other chicken stories, too.
Bruce, MICRO1690/1700
First, I was pointed to this thread from one on the ALPB. I know it's a few years old but I believe I have read the entire thread before posting. Also I am going to rely on the old adage that the only stupiud question is the one un-asked, so please cut me a break if possible. My background - I am a degreed electrical engineer who received his degree 45 years ago but have worked very little in that field. Instead I've been an optical network engineer, later telcom executive, much more familiar with lasers, optical link budgets, fiber characterization (Polarization mode dispersion, chromatic dispersion, optical return loss, etc.). I can say that I was building elecronic kits and other circuits since I was about 10-12, off and on, in my younger years. I still have my working KnightKit VOM I built in 8th grade which was 50 years ago, and for a couple years I was involved in evaluating various wireless solutions such as wireless DOCSIS channel extensions and strand mounted WIFI access points for my employer. So that is a little of my background, but designing, building, operating a Part 15 broadcast station is all new to me. I now have a working SSTRAN AMT-5000. Just running it un-modified from my 2nd floor workshop I've been getting a decent range of about 1500-1800ft. I should mention that my home is about 200ft above street level which I'm sure must help. In the northern direction, which is the direction most of my potential audience resides, I have line of site visibility to the next town which is about 14 miles as the crow flies. No I don't expect my signal to ever reach that far, just trying to describe the lay of the land. Currently, for testing purposes, and I know I must change this to become compliant, I have a 102" whip antenna mounted on a 25ft telescopic fiberglass mast on my 2nd floor deck, fed from the transmitter via 50ft of coax. I am getting no better range with this setup than with the original one with everything inside. I am told this is due to the losses caused by the 50ft of coax. Makes sense to me and my plan is to house the transmitter on the antenna and reduce the transmission line from 50 ft to about 6 inches.That should help tremendously, right? NOW, as to grounding. Currently I have a AWG#12 stranded copper ground run from the xmtrs ground terminal to an 8 ft ground rod that also grounds my home backup generator. It's about 30 ft long.
GOING FORWARD, I know I should create a system of ground radials. I have a bunch of AWG#8 solid copper I can use for this. I have the property but not just directly under where the current antenna is located. I am thinking of just daisy chaining a new 8ft ground rod off the existing ground rod about 20 ft away, and then laying about a bunch of 20 ft. radials around the new 8ft ground rod. My property continues to slope upward here so they would not be horizontal on the ground. However the angle they would be at would also be more aimed in the direction of the vast majority of my potential listeners. I figured I would lay them out on the ground and hold them in place with 8" landscape staples so the landscaper would not accidentally hit them with his mower. So far, this would keep the transmitter and antenna mounted on my 2nd floor deck. Does this seem appropriate? If better, I could move the transmitter and antenna to a ground mount right above the ground radials, although of course I would then have to fabricate extended cables to feed both audio signal and power to the transmitter at the new locations and the antenna would not be as elevated.However I COULD move everything up the hill farther and still have a ground mounted install that is just as elevated as if it was mounted on my 2nd floor deck and 25ft. mast. So far now, I am talking about strictly a 102" whip for the antenna. I should mention that I ALSO own an ISOTRON 200B broadcast antenna that I also might try, but my intention was always to get some kind of performance baseline before I introduced the ISOTRON 200B. The ISOTRON 200B does also seem to use a base loaded coil. All of your advice, comments, criticisms, suggestions, etc., are most welcome.
Jim
The trick you're going to run into, is that to be legal, an AM Part 15 installation can have a TOTAL COMBINED LENGTH of antenna, feedline, and ground lead, not to exceed three meters. Basically, ten feet.
So if you're going to ground your transmitter it will, for all practical purposes need to be ground mounted over your radials. If you're running an elevated transmitter, you won't be grounding it (legally). So if you have a three foot antenna, and three feet of feed line, you've got just enough to get your transmitter a bit more than 3 feet off the ground.
Basically, add the length of your antenna, the length of your antenna feedline, and the length of your ground lead from the transmitter to the ground attachment, be it a ground rod, water pipe, etc. If it all adds up to under 10 feet you're good to go. If it adds up to more than that, you're not legal.
It's the one fact of Part 15 AM that makes it a real puzzle to come up with what works best for you and meets the rules. Your 30' ground and 50' feedline are not legal.
Hate to be the one to tell you that, but I guess I got here first this morning
TIB
A few added comments ...
The loading coil for a Part 15 AM transmitter system is needed/used to offset the capacitive reactance of the ~ 3-meter monopole antenna. Otherwise the SWR of the antenna system is so high that almost all of the transmitter power arriving at the base of the monopole is reflected back to the transmitter, and dissipated as heat in its output circuits.
Using a 50-ft length of 50 Ω coaxial cable between the antenna output connector of a Part 15 AM transmitter and the base of a 3-m monopole makes it more difficult to resonate the antenna system using a loading coil included in the transmitter. It would reduce the r-f bandwidth of the antenna system -- making such adjustment more difficult, and less stable. Also the length of that coax cable (or "transmission line") must be included in the 3-meter length limit shown in FCC §15.219(b).
The length of conductors used between the transmitter chassis and the point where those conductors connect to buried conductors such as ground rods or buried radials has a great affect on system performance.
This can be seen in the graphic below, for the conditions shown there.
A sensitive AM receive system located in an area of low r-f noise and no co-channel interference might need an arriving field intensity of 100 µV/m or better for reasonably useful reception.
I'm amazed you are getting out at all, there is some serious loss for part 15 AM with coax that long and a ground that long is near useless for the transmitter. Above all the setup is exceptionally illegal, you'd be better off ground mounting the thing.
1. The attenuation of RG-58/U, 1/4" OD coaxial cable operating in the AM broadcast band is less than 0.3 dB per 50 feet (1:1 SWR).
This means that about 93% of the power applied at one end of that length of cable is available at the other end of that length.
That amount of power loss is negligible in this application.
2. The graphic included in my previous post here shows that the longer the "ground" conductor between the transmitter chassis and the earth, the greater the field intensity that system will produce (other things equal).
This is the reason why that length is included in FCC §15.219(b).
a transmitter challenge involving the various 50 ohm capable transmitters feeding a ground mounted isotron 200 over a suitable ground plane and see how it compares to a rangemaster and procaster under the same scenario. i want to see how the filed strength compares between the setups. my own rudimentary tests on the Isotron using a Chez TS-100 were dismal in performance compared to my procaster but i don't have the area to lay out 32 x 20ft ground radials to get any kind of good performance.
Thanks for the information Rich, would a long lead effect the tuning at all?
... would a long lead effect the tuning at all?
Yes, it would. The radiation resistance of the antenna system increases as the length of the "ground" conductor increases -- see the green curve and green vertical scale on my chart.
Radiation resistance is a contributor to the load impedance match that must be optimized in order for that system to radiate the highest possible fields for that configuration.
Jim, as Rich stated above the loss in 50 feet of coax at AM frequencies is negligible but there is another characteristic of coax which could be affecting the range. A length of coax acts as an impedance transformer so the Z presented by the antenna is not what is seen at the transmitter end of the coax, the exception being when there is a perfect match to the antenna.
In the extreme, a 1/4 wave length of coax open on the end will present a short at the other end, conversely, a shorted 1/4 wave coax will present an open at the other end.
The best change I made which greatly affected my range was to place 12 10 foot radials at the base of my transmitter/antenna system. A ground rod makes many folks feel good re lightning but does little as a RF ground for an antenna.
Neil
EDIT TO ADD Here's a writeup plus pictures of my experiments with radials which will give you some idea of what I did.
http://www.part15.us/forum/part15-forums/antennas/antenna-field-test-results-updated
Since the test was a success I permanently installed the system at another location in my back yard with the radials buried and the wine bottle replaced with an isulator.