I added another tap giving the coil 4-more-turns of length, and added 1-dBm to the gain shown on the SA.
The Signal Analyzer is still on my desk, but I moved its 13" telescopic antenna to a spot 7-feet away from the Wintenna (previously 3-feet).
The AMT3000 is on the floor below the window, the triangular coil is laid horizontally rather than vertically, based on a mention that this can improve transmitting antennas (ARRL Handbook).
By the way RFB, the loading problems we talked about in e-mail were solved by changing a jumper in the AMT3000 (S7).
There is another significant addition to the mix, a baseboard dipole running 24-feet in both directions, total of 48-feet, tapped in the center and connected to transmitter ground. This creates an indoor ground plane. I have yet to analyze how that is affecting or effecting the overall result. In addition to doing this, I need to figure out how to use Team Speak.
Pity about Pussy Riot.
I don't really know what that means, but they say it in television production. Strange, because I worked in television and ran a video service. We never said, "It's a wrap", but I think it means, "That shot is fine let's use it."
Now I need to circle back to the subject of indoor antennas, and we have achieved our first success ready for publication. The key to the final solution to this particular antenna experiment was found in this publication, NOT part of the AMT3000 Manual, but linked at sstran.com
http://www.sstran.com/pages/COMMON/sstran_buildant.html
I'll start at the end of this story, then fill in detail until there is a beginning.
When I thought I had "succeeded", I was hearing modulation distortion, and that's never a good sign. But the sub-conscious mind remembered something I had read about adjusting the output of the AMT3000 using a quality voltmeter.
First I read the Manual, but didn't find what I was looking for. So I dug into the file folder and retrieved my copy of the Construction Instructions for Building a Base Loaded Vertical, back on Page 10...
Item 9. If the voltage reading at the tuning peak is greater than 13 volts DC, increase the trimmer, C5, capacitance by rotating the trimmer clockwise until the voltage drops to 13 volts DC. If the voltage is not reduced to 13 volts DC, your RF signal output may be distorted resulting in distortion of the received signal. When the meter reads 13 volts DC, the antenna is perfectly matched to the transmitter.
Before making this final adjustment I was seeing a meter reading of 15 volts DC, higher than I've ever seen before using the AMT3000.
Since tuning to 13 volts DC there is no more audio distortion.
The artificial ground method described by Radio8Z, rich, and anticipated by myself, works wonderfully and is dramatically better than expected.
It is a 48-foot length of wire strung horizontally along the baseboard, center-tapped, with the RF ground feeding the center of the wire, putting 24-feet of wire extending to the left and right of the transmitter. The choice of 48-feet is arbitrary in any electrical sense, and is based on the length of the available baseboard space.
With the artificial ground removed the Signal Analyzer shows a 30 dBm drop in signal level.
The loading coil is wound on a triangular form, which previous discussion predicted would work the same as a circular form, is laid horizontally, wound with insulated hookup wire for a distance of 7 3/4-inches (late some night I'll count the number of turns).
A vertical antenna wire rises from the coil and attached to the bottom of the metal window frame. Out on the porch an additional length of wire is connected at the top of the window frame and extends straight up to the porch ceiling. The sum total vertical height is about 10-feet.
A permanent documenting of this experiment will be posted on the project page, linked at the beginning of this thread.
According to all measurements at my disposal, the antenna output from the AMT3000 transmitter at 1550kHz with loading coil and grounding dipole is better than previous, the actual performance in the field is poor, compared to previous results.
My guess is that the ultra-dry ground is playing a role, given our long drought condition.
As a comparison, our carrier current system picked up dramatically when I wet the ground at the ground rod, and fell off completely a few weeks later when the ground dried out.
The Mars conversion going on here on earth is changing radio behavior.
While testing the AMT3000/triangular loading coil/Wintenna, I spotted some out-of-band peaks showing up in the LW band between 204 and 217kHz, about 30dB below the main carrier at 1550kHz.
These "spikes" followed the bandwidth, appearing every time a strong sibilance or high-frequency sound modulated the carrier.
RFB advised that this might be SW (standing wave), energy being reflected back to the transmitter and causing the out-of-band action.
Knowing from previous work with the AMT5000 on the other Wintenna, the capacitance of these antennas is much higher than an antenna located away from obstructions, and that transmitter was brought to a proper load be feeding the RF through a 20pF capacitor between the loading coil and antenna.
The AMT3000 being a different transmitter, with a different loading coil, I found that a .01uF capacitor between loading coil and Wintenna completely prevents the LW spikes without sacrificing any signal strength.
The baseboard is the wooden strip that intersects every wall in a house with the floor.
For indoor antenna installations a HAM operator once suggested stringing wire along the baseboard to create an artificial ground.
I think it was Radio8Z, but it could have been MRAM, who talked about a two-element radial built by center-tapping a long baseboard wire and attaching the transmitter ground.
I have installed such a baseboard 2-element radial and also call it a shunted dipole, since it is electrically joined at the center point.
As I described already, this greatly improved the loading of my coil/antenna and gave a higher peak reading on the Signal Analyzer.
I want to seek a few opinions on further describing such a ground system.
One issue I wonder about is the fact that a baseboard is not one long straight distance, but makes left turns and right turns to shape itself to the rooms and doors.
If a bi-polar ground radial makes so many sharp turns to follow the baseboard, what does that do to its RF performance?
If the transmitter ground were dropped down into the basement a more elaborate system of ground radials could be installed on the basement overhead, but it would be ultimately shaped by the basement space available.
In some cases a few radials could be projected outdoors and continue under the earth.
Interesting. If it were me in such a situation, ie apartment or other condition where no access to Earth ground were around, and if possible, lay down steel or copper mesh and put throw rugs over that meshing which would be your ground plane.
I would think that with just single wires ran along the baseboards on the floor, the curves, turns etc would alter that ground's effectiveness since those curves and turns would change the layout pattern of your ground system. Instead of nice straight runs of wire, they go zig zag back and forth hugging the baseboard along the floor.
Hopefully no one trips on one!
RFB
Appreciated your remarks about the baseboard ground plane.
I thought the turns and corners of the baseboard layout might pose a problem.
The copper mesh idea would work for some, but would probably be an off-center ground plane, because the antenna cannot be centered in the room... it'll have to be along a wall.
I won't do the mesh with throw rug because I hate rugs.
People trip on throw rugs everyday. Some of them hit their head on the coffee table and the rest of the family inherits their radio equipment.
By the way, and I hope you'll get back to me on this, I think that water pipe grounds and electric service grounds introduce a lot of noise into the antenna path, picked up from all the junk that's attached through the neutral and ground leads from all over.
Am I right about that?
"I think that water pipe grounds and electric service grounds introduce a lot of noise into the antenna path, picked up from all the junk that's attached through the neutral and ground leads from all over. Am I right about that?"
Yep. Considering the fact that ground is the place where noise and junk gets dumped by design in many devices used daily everywhere.
As more devices from household stuff to industrial get tied together via power or control communication, wired or wireless, all of it eventually has to take a dump somewhere!
Best place to put the stink is in the ground! 😀
Isolating certain segments of the EM spectrum where the junk is a problem can be filtered out, like for a receiver equipped with tight IF bandwidth notch filtering etc. Simpler examples are a loop antenna rotated to maximize signal vs the noise.
RFB
I may have to do an indoor Part 15 AM
system, eventually. This is of great
interest to me.
Specking of RF noise - I've got a doozy
of a problem right now. Last night
I was getting "spark gap" noise from the
AM BCB up through 30 MHz. It would run
for about 20 seconds, then it would stop
for about 80 seconds, and repeat.
It rained a little bit this morning, and the
noise stopped. I have reason to believe it's
the power lines around here somewhere on the
street.
Tonight, it's back. I haven't measured the
time intervals yet. This has been an intermittent
problem for years, but this time it's really
pretty bad.
Oh well. It's time to catch up on those
Low Power Hours. I've been listening to the
meetings. You guys are doing a great job.
I guess I'll do that now.
Best Wishes,
Bruce, GNATs, SLUGs, etc.
Anyone remember where that line comes from, what famous robot TV series back in the day?
Sounds like somewhere on the grid is a bad connection buckle along the HV high tension lines or static buildup on them discharging through the spark gaps.
Electricity is a neat phenomena!
RFB
Wow. RFB, you've really got me going
there.
I can't remember the robot from "Lost
In Space" saying anything like that,
or any robot/android/computer from
Star Trek.
I can remember some other Sci Fi shows
with robots in them, but still:
I draw a complete blank.
Best Wishes,
Bruce, GNAT 90.9, SLUG 88.3
The robot could fly by a back mounted rocket pack.
It had an ancient Egyptian king's headdress.
It could shoot missiles from it's fingertips.
It could shoot beams from it's eyes that would neutralize anything electrical.
It took on the "Gargoil" leader and rocketed both the leader and himself to a final demise with a collision into an asteroid.
Imagine that robot as an antenna, or holding a 3 meter antenna up in the air for you! 😉
RFB
Using an LED (light emmiting diode) a tight beam of light would shoot three-meters from a one-eyed robot, be reflected back by an active mirror.
An active mirror is defined as a mirror that would send the return reflections at a rate of 1550kHz.
The 3-meter beam of pulsating light (1550kHz) would be amplitude modulated with very pleasant country western music from the 1950s.
A new antenna type is born.
The indoor baseboard ground idea, stringing wire along the baseboard of a room to compensate for lack of a true ground point, works in one way.
It allows bringing the indoor antenna to resonance according to the instructions supplied for using a loading coil with the AMT3000.
But, as RFB explained, the fact that baseboards make many right angles throughout the house, depletes the effectiveness that would result from a straight line 2-element ground radial.
The Spectrum Analyzer gives a reading of 70dBm when the antenna is resonant and the transmitter grounded to the center point of a 48-foot baseboard wire.
Trying to boost the dBm to a higher level, I added 20-feet of wire to one side of the baseboard wire, which I thought would resonate and build on the output, but it did the reverse: the output dropped to 66dBm. Retuning the transmitter output by trying other coil windings did not improve on that loss.
We will often remind the reader that indoor antennas will always be inefficient, we are simply trying to improve on the result available.