Hi guys been very busy testing my 4 new antenna design out., all it consist is the hot element and a ground element and with NO GROUND ATTACHED works great with the rangemaster transmitter test and has better coverage then the original antenna and fill in dead spots and goes farther ( I had the system about 10 feet in air and had a solid clean signal 2 miles away, did not have to adjust truck radio volume at all ) even pick up good with a hand held radio 1 mile away that run on 3vdc inside truck. ) Now working with a procaster transmitter have to find out what the output impedance is it’s not a 50 ohm output!. I will be getting the sstran 3000 & 5000 and will do testing as well to find out how they both work out as well. Good luck on all antenna design and have fun. Station 8
Antenna Construction
Hi The reason i’m trying to design a better antenna do to most or all part 15 am transmitters really dont have a good antenna gain what i would like to see is more gain., Some use a 102 inch whip 17-7 stainless steel 1/4 wave antenna at 50 ohm input really has no gain at all so my purpose is to make an antenna design that has gain and keep the hot element and a ground element within the 3 meter length i’m still building & testing. I used my antenna design and the original antenna on a rangemaster, procaster & Graymark 533 kit and found during testing the transmitter at ground level using a national panasonic DR49 as my receiver 50 feet away from transmitter i have found my antenna has a 3db gain over the original ( factory ) antenna that comes with eack transmitter and saw a significant gain increase. i’m trying to shrink the antenna just a little more and i should be done then comes the retesting and driving around test in truck.That is why i’m trying to make the hot antenna and ground antenna to be on it’s own without a ground do to fcc doesnt give you much for a antenna and ground length.
What you can do for lighting protection !
What you could do where you mount your tranmitter on the pole put a fiberglass pole up higher then the antenna ( so The metal dosent detune antenna ) and have a copper rod on top of the pole and run a ground wire from that to your ground and make sure pole is grounded to.
the other thing you can do is take a small piece of wire go from ground on transmitter and place real close to grounded pipe ( but dont touch the pipe ) so lighting can jump and go to ground.
Just thinking outloud
Antenna Stuff
Looking forward to the details of your design, especially if it significantly improves performance.
For lightning protection keep in mind the objectives:
1. Preserve life and safety.
2. Protect property.
3. Protect equipment from damage.
Methods used:
1. Divert the lightning current and energy harmlessly to ground.
2. Isolate the antenna from people and property.
3. Prevent a lightning strike (wishful thinking.)
A common way to provide some protection is to provide an intentional path to ground for a strike and to disconnect the antenna during storms. The old saying that “lightning follows the path of least resistance to ground” is WRONG. Lightning follows ALL paths to ground.
Here, I have spark gap shunts between the outside connections and the building ground at the point of entry. At the outdoor transmitter I use a gas discharge tube between the antenna and transmitter ground connections. The installation has been in place for over a year with no lightning damage but I expect a direct or nearby hit will take out the transmitter and hope that the energy doesn’t enter the building.
Neil
Being Real
I’ve operated on the notion that if lightning is expected I can go about the house disconnecting all the transmitters, antennas, grounds, power connections, etc.
But all too often the storm is way ahead of me and lightning happens before I disarm the place.
This is even more so if I’m away and not available to take defensive action.
Therefore I believe we must build systems that are safe all by themselves, even if we are not.
lighting strikes storys
When i had 2 antenna up the first one was 6 foot high off the ground the second was 40 feet in the air and was 10 feet away from a maple tree which was 60 feet in the air and guess which one got hit the most, the 6 foot antenna got hit more by lighting and the wire had to be replace do to it was brttle & charcoal , The 6 foot & 40 foot antennas were up for the same time frame. the only difference between the two was the height that all. So keep in mind lighting doesn’t always hit tall objects.
Here another story you will like, our house sat back from the road 250 feet i saw lighting hit across the road my sister came up to me and ask if i could look at her radio which wasnt plug in at the time i check it out would not work so i took apart and it was Black & fried like you would not believe i told her it was not fixable. see what lighting can do even taking precautions.
Personally i have had lighting do more damage to my radios unplugged from wall outlets and antennas, then have it plug in.
knock on wood .
Replies
station 8 wrote:
“The reason i’m trying to design a better antenna do to most or all part 15 am transmitters really dont have a good antenna gain what i would like to see is more gain., Some use a 102 inch whip 17-7 stainless steel 1/4 wave antenna at 50 ohm input really has no gain at all…”
Suggest that this point of view reveals a need for more research.
A 102 inch whip is 1/4-wavelength long at some frequency, but that frequency is FAR above those in the medium-wave AM broadcast band.
A 102 inch whip is less than 5.3 degrees in length at the top of the AM broadcast band (1700 kHz), and even less than this for lower frequencies in that band.
That ~5.3 degree length (max) is much shorter than 1/4-wavelength (i.e., 90 degrees) at frequencies in the AM broadcast band.
“What can you do for lightning protection?”
One rather practical/economic approach is to turn off your transmitter whenever lightning is present or expected, and re-connect its antenna system input to a conducting path having very low impedance to the earth.
Licensed AM broadcast stations largely avoid lightning damage to their hardware without doing so, through their use of spark gaps and static drain chokes across the feedpoints of their radiators, and transmitters that sense lightning disturbances in their load impedances so as to inhibit their r-f ouput for a long enough time interval to prevent such damage (usually less than a few milliseconds).
This May Have Been Missed…
… from my add-on edit of my last post in this thread.
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Licensed AM broadcast stations largely avoid lightning damage to their hardware without doing so, through their use of spark gaps and static drain chokes across the feedpoints of their radiators, and transmitters that sense lightning disturbances in their load impedances so as to inhibit their r-f ouput for a long enough time interval to prevent such damage (usually less than a few milliseconds).