In the first tests comparing our AMT3000 with the new AMT5000 we discovered that the AMT5000 out performs the AMT3000, but we also recognized that our methods needed better organization. These are the New Formal Tests.
Test Date / Time / Temp: Monday October 17, 2011 Between 11 AM and 12 Noon, Farenheit Lower 50s;
AMT3000 received with grade A signal to a point 435 feet from transmitter;
AMT5000 received with grade A signal to a point 643 feet from transmitter;
The auto radio followed a straight line street in front of neighborhood housing;
The same antenna was used for both transmitters, located in the rear of the house, therefore the received signals came from back behind the buildings, not line of sight;
The transmitters were located indoors on an extended window sill 21″ above the floor, grounded to a single long heavy gauge copper wire that exits the house at ground level and is buried in a southerly direction going uphill;
The RF output of the transmitters are attached to a 4.5′ aluminum window frame with indoor attached vertical wire from window to baseboard and outdoor vertical wire from top of window to overhang. Total antenna length 10′;
The AMT3000 was attached directly to the antenna array;
The AMT5000 was attached to the antenna array with a 20 pF ceramic capacitor to compensate for capacitance;
The AMT5000 was set for output to final of 99 mW.
ANECDOTAL COMMENTS: In a previous test the AMT5000 had been set to 113 mW for one trial, and to 105 mW for another, and the differences in distance were noticeable in feet.
By reasonable estimates the achievable distance would increase substantially with a well installed outdoor antenna.
CONCLUSION: The AMT5000 lives up to its Specifications and is a Professional Class Transmitter.
Power Settings
For accuracy sake, both TX’s should be operating at the exact same power setting..or in this case the 5K set to operate with the same power limit of the 3K. If the efficiency is there in the 5K unit, you should notice not just an increase in range, but also a decrease in current between them..the 5K having the lower current reading.
RFB
Here’s the Deal
I think I’m right to say that the AMT3000 would require unsoldering of a part to be able to take a current reading, and I am not going to do that, although if some other tester does it would be interesting.
The manual spec reports that the input power to AMT3000 is 100 mW, and that’s why I got the AMT5000 to 99 mW. I tried for awhile to get exactly 100 mW but I kept overshooting by a little bit. The granularity of the setting is very fine. The manual includes a caveat that one should not become too concerned about hairline accuracy, and allows that + or – 10% is acceptable.
Of course one important comparison here is over the efficiency of the final stage in transferring that 100 mW to the antenna, so I guess this does expose a weakness in my approach.
I’m standing aside for now and hope others conduct tests of these two interesting transmitters.
Analysis of the results
Taking Carl’s results at face value, the range ratio between the two transmitters is 643/435 = 1.478. Range is roughly proportional to field strength, and power is proportional to the square of field strength. The AMT 5000 has a little more than twice the RF radiated power output from the antenna as the AMT 3000. From these results, the AMT 5000 is roughly twice as efficient as the AMT 3000.
Conclusion
Carl posted: “CONCLUSION: The AMT5000 lives up to its Specifications and is a Professional Class Transmitter.”
I don’t see this as a conclusion given the data presented. The data only show the 5000 range was greater than the 3000 range under similar conditions. This is not to detract from the 5000’s performance nor from Carl’s report but rather to associate the conclusion to the data presented.
Tech tip: It is often possible to measure the current in part of a circuit without cutting into the circuit by measuring the voltage drop across a resistor through which the current flows and calculating the current as I = V/R.
Neil
Good Feedback
The feedback and interest in this new transmitter is very good. I’m keeping a list of the points that could contribute detail to further observations, including these:
RFBurns suggested that the 20 pF coupling capacitor which I only applied to match the AMT5000 to the antenna, perhaps should also to be included in the AMT3000 hookup for consistency. I will try that and see what happens;
RF also pointed out that knowing the input power of the AMT 3000 would go farther to validate the results, since the point of the test is to compare efficiency of the new unit.
Radio8Z has brought to mind the method of measuring output current of the AMT3000 without undoing circuit parts, and if I recall he has done an extensive description of this process in a different place on the site. I’ll learn how to do that.
Reaching my grand CONCLUSION was over-dramatic, as I think it was just the end of the morning. Now it’s evening.
But I do love the AMT5000.
EDITOR BACK AND IS SMARTER: I just looked and indeed the current reading in the AMT5000 is simply a tap across R3, which connects in series between modulator and final, and the same type of tap can easily be done somewhere within the AMT3000. I think that’s what Radio8Z is telling us.
EDITOR BACK YET AGAIN: It looks like a current reading across R8 (22-ohms) at the emitter of the AMT3000 modulator, through which the final stage is cascaded, would provide the desired measurement.
Doubt
Not so sure about the current being taken from R8 in AMT3000. The reading would give voltage between emitter and ground. Then the voltage reading would also be the same voltage between emitter and ground, times itself, divided by 22. Could that work?
Found 8Z’s AMT3000 Input Measurement
In a post titled AMT3000 INPUT POWER MEASUREMENT July 7, 2009, Radio8Z measured the final input as 91 mW and gives the formula for repeating the measurement on your own transmitter.
I happen to have printed a copy of his instructions, but perhaps it could be searched by using the title.
I think the approach I started to discuss is insufficient.
Document This
Over on the other AMT to AMT Comparison thread, Radio8Z told an interesting story from his science instruction, the logging of extra detail so future observers can more easily verify the findings.
You may wish to know the serial number from my STANLEY measuring wheel, so it can be tested for accuracy if you can ever get your hands on it.
INSPECTED BY 323049
Either STANLEY has very many product inspectors, or they printed the serial number on INSPECTED BY slips, and may not actually have inspectors over there where this thing was no doubt made. Probably by two-year old slaves. The device doesn’t have the usual “Made in Taiwan” imprint, but it definitely has an over seas look.
The sticker is already peeling loose, but see? Now we have a documentation of that number!
Inspected By 19.5 @ 33.3 x 66.6 x 99.9 As Above..So Below
That looks more like an identifier of a QC worker rather than a serial number.
Those measuring wheels can be found at any hardware store or lumber yard. Heck I think even wally world has them over in the lawn and garden section.
As long as the thing can track the feet/meters and inches/centimeters, any make should be adequate.
Or the old fashioned way….100 ft measuring tape and two people, or one person and an alligator clip at the end of the measuring tape, clamp on and pull away….repeat.
RFB
To KC8GPD
This Question Is For KC8GPD, Since I Played The Low Power Hour About The AMT5000, how well is it working for you and what do you think of the transmitter?
FORMAL COMPARISON TEST AMT5000 / 3000
Carl,
I probably missed it somewhere, but what frequency were you on when doing the comparisons?
The Frequency
Good Morning.
Frequency for all of these comparisons was 1550 kHz
FORMAL COMPARISON TEST AMT5000 / 3000
Carl,
Something is very wrong with your comparison results, but I don’t know what. I don’t particularly doubt your measurements. Maybe the discrepancy is wrapped up in your unique antenna and ground situation. Your results show only a 47% range increase over the AMT3000 (using the internal inductor tuning). The AMT3000 internal tuning inductors are extremely inefficient and were originally intended for a compact and easy solution for in-home broadcasting. By comparison, the AMT5000, with its class E efficiency and internal toroid coil, will result in about 15 times the field strength over the basic AMT3000. Note that I am talking about the basic AMT3000 with internal tuning, not the AMT3000 with external base-loaded antenna. Many customers have reported good, predicted range with the AMT3000 with base-loaded antenna, and many have reported the small range of the AMT3000 with internal tuning. The AMT5000 with internal tuning outperforms the AMT3000 with the base-loaded antenna.
Since your results show only a 47% range increase instead of predicted 1500%, there is something else going on. Whatever it is, I cannot say, but it simply doesn’t add up for an absolute apples-to-apples comparison.
What we really need is a comparison of the AMT5000 against either the AMT3000 with external base-loaded antenna or a Rangemaster with the same antenna elevation and ground system.
“Reality is what it is, not
“Reality is what it is, not what we would make of it.”
E.T. Whittaker
To Be Or Not To Be….That Is The Fork In The Road
“Reality is what it is, not what we would make of it.”
To a point perhaps.
Example: A person wishes to have a new porch. They think to themselves “I can built it myself, or have someone else build it”. The person can do one of three things. Build the porch, hire someone else to do it, or simply sit there and think some more about something else.
In the above example…how many realities could possibly come to pass?
Just one of course, but one potential reality out of 3 possibles. That suggests in this example that reality is not set in stone until the person acts, which in turn creates one of those 3 possible outcomes…or reality.
RFB
Expected and actual results
Carl has made impressive experiments in the past and I consider him to be a good experimenter, producing valid results. Phil would prefer different results more in keeping with his own expectations, but that is not what happened in Carl’s experiments.
Undoubtedly there will be other results from other experiments. The comparisons between the AMT5000 and other transmitters are only beginning.
Similar Situations
“Since your results show only a 47% range increase instead of predicted 1500%, there is something else going on.”
Well I believe that Carl’s tests results are quite valuable for those operating under similar situations…ie using an unusual antenna such as the window pane.
His test was specific for the type of antenna. No doubt there will be far different results when testing through a proper outdoor 3 meter setup.
With Carl’s antenna, he did show that there was a significant increase in the performance and efficiency between the 3K and 5K units.
From my prospective, that test proved that the 5K unit can demonstrate its greater efficiency over its predecessor.
Even if it was a 5 percent increase, that is a + increase nonetheless. If anything, Carl’s test provides the “worst case” scenario that put the 5K to the “real” test of “real world” situations. And the test gives kudos to the 5K.
RFB
FORMAL COMPARISON TEST AMT5000 / 3000
There is an error in my last reply in this thread. I stated the field strength should be about 15 times higher with the AMT5000. I should have said “power” instead of filed strength. The field strength will be about 4 times higher or 400% higher.
Not Surprised
During my comparative tests of the two sstran transmitters I several times called attention to the limitations of the antenna employed. The most I offered with this trial was a glimpse of how the transmitters perform in a compromised situation. While we were able to see a performance improvement with the AMT5000, the fact that it did not exhibit it’s full improved capacity is probably proportional to the ineffeciency of the antenna.
My test was intended from the outset to leave room for the next round of tests, with a full outdoor antenna with radials, loading coil, or Rangemaster setup, which remains to be undertaken by a member of the group.
I am at least 6-months away from having an outdoor antenna.
I’m curious, how do you
I’m curious, how do you define a Grade A signal? For that more than anything else appears to be determining the ranges as reported here. And I’m wondering just how accurate that measurement is. Perhaps it might be more accurate to measure to the limits of listenability, i.e., you can barely hear the signal.
A comment re the predicted field strength increase in the AMT5000. How does field strength map to that listenable signal? Is it linear, as you’re suggesting?
Very Astute Question
By questioning my use of the term “Grade A Signal” you have zeroed in on the most subjective part of my comparison tests between AMT3000 and AMT5000.
In the tests “Grade A Signal” means a “listenable signal with full quieting.” This judgement was made by me while in motion passing an estimated point along my measured route.
To make the subjectivity or variability go deeper, the test was only made with one radio receiver, whatever it is installed in my car.
I can add, based on your asking about “just barely audible,” that at this frequency, 1550kHz, with this antenna, the “barely listenable point” is reached very soon after the full quieting starts to fade: perhaps another two lots, or about an added 120′
I have another antenna in service which is much more effective, but I deliberately did not bring it into these tests, because it would have added confusion. I limited everything to my poorest antenna so that a “low efficiency” antenna could be analyzed using transmitters of two quality levels.
My other antenna is of no consequence at this time, because it is not a fully outdoor, coil loaded, radial equipped antenna.
The door is now open for a test using the classic ultimate antenna with open space, loading coil, and radials. I hope someone is equipped and inclined to perform that test.
Now, that makes more sense (4
Now, that makes more sense (4 times the field strength rather than 15 times). Which should equal 4 times the range of the AMT3000, all things being equal.
When I tested out the AMT3000, I put it into the same environment as the Rangemaster. It went into a weatherproof box, a 102 inch whip on top, and grounded to the metal mast it was mounted on.
I got 1/8 to 1/4 mile range of good signal from the AMT3000 – obstructions and other interference weren’t a real factor due to the limited range. I get, in certain directions with limited interference, at least a mile and often more (generally due to the weather) of good signal from the Rangemaster. My subjective measurement of good signal is that it’s easily listenable, with some noise (it’s hard to eliminate the noise from the AM equation, very different from FM where you either have the signal, or you don’t).
If you’re going to compare oranges and oranges, you should also mount the AMT5000 similarly to the way I mounted my 3000. In my opinion (and my opinion only), using a base loaded external antenna is cheating – I believe there are reasons why I’m not aware of any manufacturer that is FCC and/or Industry Canada certified and using such an antenna system (the coil can be considered part of the length of the antenna, putting it way over the 3 meter limit).
It would seem to me to be rather simple overall to compare the 5000 and the Rangemaster. Beg, borrow or steal a field strength meter, mount the 5000 identically to the Rangemaster, and measure the field strength of both. A tangible, measureable number that cannot be disputed. Saying that the 5000 will perform better than the Rangemaster with an external base loaded antenna is rather meaningless, since the Rangemaster cannot be operated in that fashion, and the legality is at best questionable.
Seeking reasons for Carls performance discrepency
I believe Carl’s comparison is valid for comparing the AMT5000 to the AMT3000 with internal tuning. I am seeking the reason why the range increase was only 47% vs 400%
Carl,
I believe at least part of the discrepancy may be related to the 20 pf cap you inserted. I assume you connected the cap in SERIES somewhere in you antenna hookup. You stated you are getting it to tune at tap position S5. With the C1 slug in mid position, this puts the antenna capacitance as seen at the transmitter at about 26 pf. It appears that you inserted the 20 pf cap somewhere other that right at transmitter antenna terminal, possibly between the wire from the antenna and the window metal frame. Knowing where and how you positioned the 20 pf cap will help to zero in on the possible discrepancy from a technical point of view.
Why not a bench test?
Anybody who has both the AMT3000 and the AMT5000 can compare the two transmitters (using the internal loading coils corresponding to each transmitter) accurately on the bench provided that he has a calibrated scope and a good 10x scope probe. Make a dummy load consisting of a mica or ceramic capacitor in series with a carbon composition or film resistor. The capacitor represents the antenna capacitance, which Phil has repeatedly posted is near 30 pf. The resistor represents the ground resistance of the antenna system. If you think you have low ground resistance, use about 10 ohms. I’d use something more like a 22, 27, or 33 ohms. The exact value really doesn’t matter much because this will be a comparison test. Connect the capacitor lead of the dummy load to the hot antenna output, and the resistor lead to the antenna ground. Operate near the upper end of the AM BCB–around 1600 kHz.
Connect the oscilloscope probe across the resistor of the dummy load and tune the transmitter for peak output power for 100 mW input power. Look for a few volts p-p (peak-to-peak) on the scope. Measure the p-p voltage across the resistor of the dunny load. The power output is P = (E^2)/8R. R is the resistor value in ohms, and E is the p-p voltage read on the oscilloscope. Suppose R is 27 ohms and E = 3 V p-p. Then P = (3^2)/(8*27] = 9/216 = .0417 W = 41.7 mW.
This same test is repeated for both transmitters to get the comparison.
[By the way, do not, under any circumstances, use a DMM (even if you have a very good one, like a Fluke) for measuring the voltage across the dummy load resistor. A DMM absolutely and positively won’t work. A good DMM can be used, however, to accurately determine the dummy load resistance.]
The two parts of the AMT3000 that may have lower efficiency than the AMT5000 are the output stage and the loading coil. These two parts in combination will determine the efficiency of the transmitter under test.
2 pF Cap Location
The AMT5000 is placed conveniently on an extended window sill 20″ from the floor. About a 5″ antenna wire exits the back of the transmitter and connects to a small connector block, the 20 pF cap is connected within the block to a 24″ lead in wire that aims downward at a steep angle to the baseboard below a south facing window, travels up the wall straight vertically, passes under the closed window, connects to the aluminum 4.5′ window-frame, etc.
20 pF Cap Location
Thanks for the details Carl. The 5″ wire from the TX to the 20 pf cap is essentially a direct connection at the transmitter, which is a good thing. I think it is close enough to validate this part of the circuit. There may be a pf or so of stray capacitance and there is cap tolerance deviation and calculation errors that can easily account for the 26 pf that I expected. One thing seems to stand out. The TX side of the capacitor is very nearly 20 pf indicating the capacitance on the antenna side of the 20 pf cap is indeed very high as you have previously stated. Since the formula for series caps is C=C1*C2/(C1+C2), As C2 gets very large, C approaches C1 but never exceeds C1 (20 pf). Also as C2 drops, the total C will drop below 20 pf. For example, if C2 were 100 pf instead of 4000 pf as you previously stated, C would be only 16.7 pf. This seems to validate your 4000 pf reading for the antenna.
Let’s check the AMT5000 operation and tuning. At 1550 kHz and close to 100 mW and a capacitance of 26 pf, your “RF INPUT CURRENT” voltage reading tuning curve should be very close to the values in the tuning graph I previously posted: http://www.sstran.com/public/TuningPlotAt1550kHzWith28pfAntenna_1.gif
With the RF INPUT PWR ADJUST control at mid-point, he peak reading should be close to .65 V and the best efficiency reading should be around .35 to .40 volts. Does this agree with your readings during tuning?
Now, back to the AMT3000. You previously stated that you can tune the AMT3000 to you window antenna without the series 20 pf cap. With it tuned, what are the settings on the 4-position DIP switch, S5? The thing that puzzles me is how you can tune it when the minimum inductance setting is 56 uH. Resonating with a 4000 pf antenna would require the inductance to be way down around 2.6 uH. Looking at it another way, the maximum antenna capacitance to resonate with the 56 uH inductor is only about 180 pf. If the antenna capacitance is above 180 pf, it won’t tune to peak, even at the minimum setting of trimmer C5. The measured voltage may rise and fall as your rotate C5 through the minimum setting, but it won’t be a true peak unless C5 is not at minimum when the peak voltage occurs.
There is major disagreement between the tuning of the two transmitters in relation to your apparent antenna capacitance of 4000 pf.
Still searching for the root problem here. Let me know the answers to the above questions.
On the Job
Just a word to tell you I am on the job gathering the information you requested.
Results within the hour.
Results Part 1
Here is a check list to be sure I made the right moves:
R1 = mid
audio = off
coil tap = S5
Freq. = 1550 kHz
current at peak = .6321
current at 1-full CW turn = .2942
Results Part 2
How I tuned the AMT3000 for the comparison:
No meter was used. Instead, I used the RF level control on a Zenith Transoceanic Radio located 40-feet away and set based on audio level coming from the transmitter.
The first setting tried for S5 = off off on on = 138 uH, the range given for 1550 kHz;
On the radio,
I turned the RF level down so no signal was received at 1550 kHz;
I turned the audio level up all the way;
I turned the RF level up until the audio transmission was just barely audible.
Then I peaked C5 for a sharp rise in audio level on the radio.
Next I tried 82 uH, S5 = off off on on, and was able to get a louder RF peak.
But the top range, R5 = off on on on, 56 uH, provided the strongest audible peak, so I kept it.
Results Part 2
Thanks Carl. Digesting…
Two Additional Items
Item 1
On Oct. 13, the day I added the 20 pF cap and found peak for the first time, the readings were different than the ones I took yesterday. In the intervening time the only change was from a long dry spell to a long period of rain. Since my window frame-antenna is mounted in a wood frame, the moisture content of the wood is likely to cause a capacitive change.
The AMT5000 readings on 10/13 were:
peak = .5798
1-full-turn CW = .3183
Item 2
I just reviewed the method used to measure the capacitance of the window frame-antenna, and I will describe it now.
B&K Digital Capacitance Meter
Measured several capacitors to see readings generally close to the posted values;
Placed the red probe on the lead-in wire from the bottom of the window frame – antenna, black probe to the ground wire that travels approximately 100′ on the ground outdoors. There was no ground connection to the electric service ground.
Window Frame – Antenna capacitance = 4.028 nF
Window Frame Electrical Characteristics
Carl,
The capacitance you report that you measured for your window frame seem too high to be the “capacitance to the universe” for something this size. I speculate that something is affecting the measurement. Electrical noise was mentioned by someone earlier but it could be another effect such as proximity to metal (pipes, wiring, or siding). Aluminum siding, intermediate sheathing, and stucco present large surface areas of metal. If you do a DC resistance check between the window frame and ground you might discover that there is a connection.
If the capacitance is actually this high and results from proximity to a grounded object then a good part of the signal is probably being shunted to ground and not radiated.
Given this and the fact that no one else has your particular window frame situation it is not going to be possible to extrapolate your test results to predict with reasonable accuracy what others will experience by switching from the AMT3000 to the AMT5000. The addition of the 20 pF cap further complicates this and leads me to believe that your radiating element is the lead wires and ground leads and not the window frame.
May I suggest that you base your comparison tests on a more conventional antenna even if it is just a 3 meter length of wire strung straight and not near any conductive material?
Neil
Convinced of Change
Thank you Neil, I have become convinced that the window frame needs to be abandoned. You are absolutely right about the stucco and its metal mesh, in fact I just had a section of the wall rebuilt and have a left over roll of mesh. Yet, my two window-frame antennas fulfill their original purpose, which is to radiate fully quieted signals indoors and outdoors at the same time.
I have not been interested in range increase because the population in the area are not radio DXers nor people in search of audio culture. Sports, cable tv and Rush Limbic are their daily habit.
But returning to the objective of meaningful comparison tests of the transmitters….. deliberating.
My Conclusions
Carl,
I digested your input and read the thread beyond my last post. All of the info in Neils post is valid. The aluminum window frame capacitance is way too high and I think this is most likely due to close proximity to the surrounding stucco wire mesh. This situation would result in almost all of the signal being diverted by capacitive coupling to the wire mesh which may or may not be grounded. Even if the mesh isn’t grounded, close proximity of the mesh to AC wiring throughout the house will cause capacitive diversion of the signal to ground.
I think the signal you are receiving on the car radio along the street out front is mostly or all due to power line radiation. Power line radiation is typically characterized by a fairly constant signal until you pass a disruption (transformer) or end of branch, after which the signal falls off abruptly. Direct antenna radiation is characterized by a more gradual decrease of signal with rise and fall until you reach the end of the fringe range.
Assuming you are actually receiving power line radiation, here is a scenario that would explain your measured range differences between the AMT3000 and AMT5000:
You reported AMT3000 range = 435 ft. and AMT5000 range = 643 ft. Suppose the “abrupt end” due to power line RF discontinuity is at 383 ft. Then the range beyond that for the AMT3000 is 435-383 = 52 ft. So, the range for the AMT5000 would be about 4 times farther or 52*4 = 208 ft. The expected range for the AMT5000 would be 435+208 = 643 ft., which equals your measurement.
All the values are of course dependent on you subjective measurements, but the fundamental relationship still holds true.
Depending on the goals one sets for the range of a transmitter, one may opt for a simple indoor antenna to cover a house, or go for maximum external range with a 3 meter antenna over a reasonably good ground radial setup out in the clear of obstructions. Indoor installations tend to produce power line radiation due to less than good earth grounding and the presence of surrounding complex house wiring. Outdoor installations minimize power line radiation in favor of direct antenna radiation.
This is one possible explanation for your results. Whether or not it is on the money depends on too many unknown variables. Unfortunately, I don’t think this particular comparison really proves a whole lot, other than the range of the AMT5000 is better than the AMT3000 with internal tuning. At least that is one good result!
Looking beyond, I welcome comparisons of the AMT5000 to the AMT3000 (with external base-loaded antenna), and comparisons to the Rangemaster and Procaster. Any comparison should ideally be made with the same transmitter/antenna location, height and ground radial system. This likely won’t happen until I introduce the outdoor version of the AMT5000, which should happen in the next couple of months.
Great Experience
This has been a great experience learning about the complexities of house antennas.
I wish I could speed up my building of an outdoor antenna, but there must be someone in the Part 15 community who is already setup and ready to try the AMT5000….. I have seen pictures here or somewhere of impressive outdoor installations.
For idle curiosity I plan to spot the electric pole transformers between here and the signal drop-off point…. my electric feeds from a transformer 100′ east of here, so there’s likely another few transformers to the west where the test was centered.
Phil, you have one convert to the AMT5000, ME!
More on the AMT3000 and AMT5000 comparison
Drink the Kool-Aid only sparingly, Carl. Why not do the bench test comparison? Maybe you don’t have a scope. Then why doesn’t SSTRAN do it?
Anxious to see results
Hi everyone,
After reading these posts for over a year, I finally decided to register.
My name is Andre and I live in Gatineau Quebec (Canada), just minutes north of Ottawa Ontario.
I collect and restore antique radios. But when all local AM stations converted to talk/news, I decided to broadcast my own music.
After receiving my first AMT3000, I went crazy (according to my wife) and spent a lot of time trying to get the ‘perfect’ transmitter set up. I built the base loaded antenna on top of a 6 foot mast, with 4 8′ ground rods and thirty 20 foot radials.
After a lot of tuning trial and error, I now get the claimed strong signal out to a mile and decent signal out to 2 miles. And for some strange reason, there’s an intersection about 4 miles east where my signal seems to shoot out from the ground. AM is funny that way. My transmitter has been transmitting 24/7 since June 2010. Even during extreme cold and covered with show.
So now, since I heard about the improved AMT5000, I can’t wait to get it and set it up. Unfortunately, I won’t have time for another month or so but I will try to get it set up before snow season starts. Hopefully, I’ll have some test results before Xmas 🙂
Andre
Difference?
“the outdoor version of the AMT5000”
Outdoor version? I am assuming one without the internal matching network, leaving it all up to the builder to use their existing antenna..which will have its own matching system (loading coil).
Maybe I am a little confused..but isn’t the current version capable of bypassing this internal matching circuit, passing on the duty to the external antenna loading system?
Perhaps Phil could fill us in (no pun intended) on what exactly the differences will be between “version A” and “version B” regarding the internal/external loading/matching.
If I am not mistaken, doesn’t the 3K unit also have an internal matching network which is also equipped with a bypass jumper? Are there two versions of the 3K?
I do not quite understand the approach but why would you want to be marketing a transmitter that is equipped with the ability for internal matching and external matching by simply moving a jumper, and then shortly after its release, market a 2nd unit that is built only for external matching systems?
In other words, you already have a unit capable of both options now, and IMO, is the choice I would make even if there was a “version 2” unit on the shelf simply because the current unit has the option between internal and external matching already.
Unless you intend to build everyone’s loading system for their external antennas, and expect everyone’s environmental conditions everywhere to be the same..I do not see where the advantage will come from a second unit built only for outdoor use.
The current unit can be used outdoors…simply place into a wx proof box…like all the rest does, and use the internal matching, or bypass that and use the existing matching system (loading coil).
Enlighten us.
RFB
Hardly
“I think the signal you are receiving on the car radio along the street out front is mostly or all due to power line radiation.”
I seriously doubt it. That transmitter barely has the power push to resonate a “perfect” Part 15 antenna much less a power line.
Besides that…the return path going through an AC wal wart or ground wire from audio sources creates an INCREDIBLY short return path. 99 percent of the signal just makes a short trip to its return leg back into the TX right at the power socket and audio connections on the back of the TX. It is NOT going to travel 400 feet away from the power line at a mere 100mW RF drive without proper coupling.
It is MORE likely Carl’s wire mesh in the walls of the house are acting like a passive resonator and merely re-coupling the signal emitted by the window pane antenna and thus turning the entire house into an antenna…all with the return path also located in the walls with the house wiring.
A CC system which loads to the neutral MUST have an isolated return path in order to work. When a CC system loads up to the “HOT” lines, the return path is the NEUTRAL line, thus no isolated ground is needed. And the signal will be roadblocked by the utility transformers.
In neutral loading, the transformers have NO effect on the signal because the signal is not passing through those transformers. It is riding on the neutral line, bypassing those transformers completely.
If there is any signal being put onto the power lines by Carl’s setup, that would be such a miniscule amount that only within his dwelling would that signal be adequate enough to even bother listening to.
Tell you what Carl….here is a very simple test you can do to verify if your signal is going the distance due to the power line, or from your window antenna.
Take a portable radio and start walking down the street. When you reach the point where the signal fades out, walk up to the nearest power pole and place the radio near the ground wire that runs down the pole.
If you pick up your signal at that point, then your tiny signal is traveling down the power grid. If not…well that pretty much puts a monkey wrench in the notion of your signal going down the power line.
Even at MW frequencies, the power grid wires absorb a heck of a lot of that injected signal, even for a real CC system. This is why it takes WATTS of power to make a CC system work effectively.
I would say that if your getting a CC effect, it is just barely there to indicate a CC effect is taking place..and that will be incredibly localized.
RFB
Hardly
RFB,
“Besides that…the return path going through an AC wal wart or ground wire from audio sources creates an INCREDIBLY short return path. 99 percent of the signal just makes a short trip to its return leg back into the TX right at the power socket and audio connections on the back of the TX. It is NOT going to travel 400 feet away from the power line at a mere 100mW RF drive without proper coupling”.
But, don’t forget that the RF current is flowing in the power wiring which is part of the path you described. This current is sufficient to produce a good signal on a car radio along the power line within a short radius from the power line when it isn’t disrupted by a transformer or end of branch. It really doesn’t matter much what the indoor antenna situation is as long as you properly tune the transmitter which in turn produces the highest current flow in the AC path.
I have observed this consistently many times over the years. I use a 3 meter wire hanging horizontally under the joists in the basement shop as for testing purposes. This is likely worse than Carl’s window frame antenna. The signal is strong throughout the house. When backing out the 150 ft driveway, the signal drops quickly and then picks up dramatically under the power lines. In one direction on the road it goes about 500 ft and abruptly drops out where the power line branch terminates. In the other direction, it is strong for about 1500′ and then drops out abruptly in either direction after a “T” intersection. There is a transformer on the pole feeding my house, so it feeds in both the directions.
This pattern still holds true when I experiment with higher transmitter power levels when using the indoor antenna. The range beyond the AC power line disruptions increases by a relatively small amount. This matches what Carl is seeing with his setup.
When I use the AMT3000 with the outdoor base-loaded antenna, the pattern is very different. The signal is still strongest within the limits mentioned, but it goes on beyond the power line disruptions. In one direction it goes up to 2.2 mi. before it is totally undetectable. In other directions it goes a lot less, but is still beyond the “power line only” range of the indoor antenna.
This situation was the subject of one of my posts a long time ago where I said the range of an AM transmitter should be measured carefully. Just judging range by driving along a road outside a house may not be a good judgment of real radius range.
A good outdoor antenna installation with a good ground radial system results in a lower ground resistance at the antenna. This diverts RF current away from flowing in the power wiring feeding the transmitter and increases the radiated power from the antenna.
Re-Radiate
Granted the power lines can act as re-radiators, but most likely they are acting like re-directors, changing the pattern, more in one direction than another.
It is acting like a CC effect, but in actuality is not a CC system nor operating in a CC configuration. In this case much of that low level signal is being scattered by the power lines and yes..will distort measurements and distort the emitted pattern.
If you were coupled to the AC lines properly, the signal would travel down the line a lot further even when meeting the 15uV/m @30m limit from the line. At 1670Khz, that is roughly about 93 feet. At 640Khz its about 230 feet, both being distance OFF the line, not down the line.
So if your getting more signal emitting off the line further than what the rules call for, that is a violation and will most certainly award you with a NOUO.
In my experience..over 30 yrs with this stuff, those power lines are acting more like directional re-radiators rather than an actual carrier of the signal like that in a CC system. If conditions are right, the power lines can extend the range considerably, but is the result of a side effect that is dampening the purpose of the outdoor antenna system not to mention creating an attention grabber. An inspecting field agent will expect to find a CC system in just such cases. But if they find something else…well then its up to the field agent to determine what’s next.
RFB
Months Later
It was way back in October 2011 when the AMT5000 went into service at 1680 kHz driving our Wintenna, consisting of an aluminum window frame extended by vertical wire attached below (indoors) and above (outdoors. The advantages of the antenna are, it keeps the transmitter indoors, it provides a very decent signal indoors and outdoors.
The eastern throw of the signal seems to be much greater than any other direction, and today with a very moist ground and rain, it goes for blocks and blocks.
In the spring an empty yard space will be implanted with radials and a stick, with an outdoor AMT5000. It is predicted that the coverage will be even greater. But that poses a quandary.
For peace of mind I won’t feel safe with the signal going farther than it does, but of course the good coverage is a daytime phenomenon and is much less at night, so the solution will be to use the existing Wintenna transmitter in the daytime and the outdoor radial antenna at night. Perhaps that will bring the two coverage patterns closer to being equal.
Glad To Meet You
Dear Andre pro20g:
VERY happy to see you on the site, someone with the outdoor antenna with radials…. we will happily wait a year for those results!
To the Best
Best of my knowledge the outdoor version is equipped with a custom outdoor box crafted to exactly and perfectly fit the AMT5000, which I think would not be such a glove-like fit with a hardware store box.
It will still have the onboard toroid coil.
Correct me if I’m wrong.
Custom Box
“Best of my knowledge the outdoor version is equipped with a custom outdoor box”
Ahh. Well then the actual transmitter itself will not change, just it’s enclosure.
Maybe offer a choice between a kit with the indoor box, or a kit with the outdoor box.
Let the market decide. LOL!!
RFB