Been mentally thinking about the many observations about radials and grounding recently and ideas about soil.
Most people live in and probably install on homes that are mainly wood in composition.
Has anyone dealt with multiple Part15 installs in, on or adjacent to both wood structures are well as masonry (brick and/or block)? Has anyone noticed different effects outside of masonry structures?
Imagining the masonry creates a signal block if transmitter and antenna is within the structure. Certainly would reduce the signal. Deal with that all the time with Wifi and as an AM radio listener.
Signal deflection (where antenna was external) I'd expect to be higher than with wood exterior.
Relative here since contemplating effects created by exterior buildings. A ground level install with antenna installed in back yard would mean the signal running into a massive amount of bricks that form an L on two sides some 15ft on one side and 25ft+ on the other. Even placing antenna ground level in front of house means same L but on other brick faces.
Placing transmitter in detached lot means signal would get about 100 feet away from the brick pile, but the lot is filled multiple feet deep with gravel which stinks for grounding, is quick to dry out and generally rather useless (folks used it as a parking lot for decades). I've worked for a year with hand tools and tillers to undo the damage and salvage the land.
Most attenuating effects in masonry walls will come from wiring or conductive plumbing within them, or other conductive things like re-enforcement rods.
Putting the setup in the center of it all sounds like the best ground mount option even with the gravel laden ground it will sit on. Clearing out that gravel, or at least moving it to lay down a radial system onto the dirt and then put the gravel back will work.
I can see the interest now in an elevated setup. But you have options your exploring which is always at the core of setting up a Part 15 AM system in any location. And like I have said like a broken record around here what seems a million times, every location will have it's own unique challenges...219 or 221.
RFB
Absolutely true, as RFB indicates, the metal work located within walls minces RF radiation into a weaker, jumbled mess.
Also to count window screens, metal window frames, metal storm doors, metal siding and metal stucco netting in some walls.
However, stone, concrete, cinder blocks, bricks, plasters and lumber have their own attenuations, in my opinion. Glass and roofing tile may also reflect and absorb some RF energy.
Very early testing of our new outdoor transmitter is very strange.
We are getting an alright signal in east and west direction. Walked roughly 1/4 mile and signal went to nothing (this was with portable radio walking the middle of the street with power lines all over the place). The south direction is basically little to no signal. Haven't walked north to test yet.
What is odd is east direction is literally blocked by 25ft of brick wall and transmitter and antenna is 5ft away from that wall.
1/4 mile is a good start considering no ground yet and sub optimal placement. But, signal appears to be so far directional with east direction most so.
Topography here is flat plane except to the west which goes downward and eventually to river 1/2-3/4 of mile away. Each block is double boxed by power and other interference wires. There are runs along the main street and also in the alleys. Typical urban wire jungle.
What do folks think?
Power and utility lines can act as antennas both by capturing and carrying the signal and by coupling the signal to the receiver. Maybe this has an effect. One thing you can try is to place the receiver near the poles and note what happens.
Since you were walking in the street I assume you are using a portable receiver. 1/4 mile is not bad for the typical portable.
Neil
I don't think the power lines are capturing and "rebroadcasting" later down the line.
Seems to the south direction that the power lines are actually blocking signal. I say that because saw same effect when transmitter was indoors using the wire antenna.
There is a hum interference when crossing under the power lines.
Power line on the south side runs length of property, actually runs entire street. Those lines are approximately 15-20 ft from the transmitter and are overhead, oh 30ft up I'd say.
In the direction of the least signal, is there something beyond that point from your property that could be causing the signal to be so directional..say a neighbor's metal shed or pile of stuff or large metal trash bins etc?
RFB
Well the south direction is the weakest side tested so far. It is extremely weak.
Where the transmitter is, within the greenhouse is in the rear of the property behind the building. The only obvious obstructions heading south in the rear of the property are the overhead power lines.
In the southwest direction is a few hundred feet of empty lots. Probably 300ft x 125ft. Signal in that direction should be phenomenal. It's just as bad as in front of the building. Can't even find the signal at the next street which is < 200 feet from the transmitter and totally unobstructed.
The front of the building heading south gives a maximum signal of about 5 houses before the signal can't be found. That's under 200 feet.
I need to go look at building coverings. Can't think of anything off hand that should be creating a problem. Our building are brick, block and wood siding. Neighbors mainly are wood.
Our lots are large and open and the at a corner, so not boxed in by other structures.
Interesting. Well MW loves to hug the ground as it propagates. You may want to try running a few ground radials in the direction of the weak areas from the greenhouse. Perhaps that might pull the signal more into that direction..of course this may reduce the range currently in the other directions.
Though a slightly different issue, Carl had a problem where his signal would not travel in one direction up a hill. He discovered that by running a ground radial wire in the direction of the hill (null), the signal followed it and now that null area has a signal.
As I have said many times like a broken record, every site is going to have it's own unique difficulties regardless of the pile of experience of others in their particular location where some common things may work for them, but not for all situations. It's good to try those common approaches to find out things. But when you tried them all, the next step is to go beyond the text book approach and begin to experiment and discover. That is the nature of Part 15 and regardless of others level of experience, unless they have experience with your particular location directly, all that experience they bring won't mean a hill of beans. So with that in mind, and taking into account of all the things you have tried up to date, begin now by expanding and going beyond the basics and begin experimentation to find the solution.
There is something unique on your site that is causing this highly directional signal where it should be uniform, especially off the simple wire antenna. Now you got the same results with a whip directly attached to that wire antenna stub. Take the giant leap for all mankind and begin exploring beyond the realm of simplicity or common approach and you will find that solution.
RFB
My TH5 with the external loading coil is receivable as much as 1.5 miles on the downhill side but peters out after 1/4 mile on the uphill side.
Just a question - what kind of portable radio are you using for your tests? Most portables have horrible sensitivity and even worse selectivity; it's the latter that causes the worst problems,as strong signals in adjacent channels cut into yours and overpower it.
Have you tried your listening tests with a car radio, which generally has much better sensitivity and usually awesome adjacent channel interference. It would be interesting to see if you got similar results (once, I isolated my problems down to the testing radio, as opposed to any issues in my signal per say).
"Most portables have horrible sensitivity and even worse selectivity; it's the latter that causes the worst problems,as strong signals in adjacent channels cut into yours and overpower it."
Very good point. However if that were the case, then the effect would be in all directions from his TX point and not choose one area over another. Given the testing zone is within 1/4 mile, in all directions, and the result is a directional issue and not an overall range issue, I would say it isn't the radio receiver being used that's being selective and making the results run in circles....eh...pun or no pun...that's the question. 😉
RFB
To add, OP did not mention that in the areas where the signal nulls he is picking up co-channel blanketing. Neither did OP specify if there is a licensed high powered station in the direction of the null, just an overhead utility grid and a 25 foot high brick fence.
It's a weird situation, one very well worth studying and finding out what's making the signal so directional. Being 5 foot from the fence, that signal should be gang busting over past that overhead power line into the next lot with ease..but it is not.
RFB
I skipped working on the transmitter today.
Going to draw up a diagram or a map with overlay of the environment here and see if collectively intelligence can comment on what they would do.
My next step, along with moving the transmitter is to assemble a ground radial collar along with wiring the runs of wire and make it so can be packed up and moved easily for above soil testing or roof.
Planning on making a radial collar in the shape of a square 12 inches on each side with screw terminals drilled through every 2 inches. That would be 6 radial screw downs per side or 24 collectively on the 4 sides. Radials will be coated 16 gauge wire intended for speaker wiring since I have an unused spool sitting here.
Need to find metal and someone to punch the metal for me. Alternatively thinking about easily doing this with steel angle materials people use for shelving in garages.
Does this sound prudent? Will the steel create the intended effect or harm the concept? Is a ground radial square of this size too big and distance from the whip antenna itself?
As far as my testing radios go, I have two:
1. Eton FR-250. Nice little radio that does AM/FM/SW. Does pretty good just on tuning and has two different tuning dials for additional selectivity.
2. Sony ICF-SW7600GR. This radio is arguably the best portable receiver on the market still. First or second on nearly every list.
Car radio testing is nice, but listeners have non car radio mainly and are indoors. So testing the car radio route is minimally useful in my opinion. Will do the car radio test over the weekend though in addition.
Did one test with car (van actually) to our problematic south side and that yielded the distance of five whole houses < 200 ft range.