"the amt5k wants to absolutely see phils suggested capacitance range. you will not get that peak without it."
Which is what I have been pointing out. It has a narrow window of tolerance to obtain that sweet spot. Since it is designed around that, the loading becomes crucial in order to reach and maintain that peak point.
Your also going to find that an Isotron, or variant of it, is just as sensitive to external inductive influence as a 3 meter monopole, perhaps a bit more. This may pose a problem with the 5K and maintaining that sweet spot, again what I pointed out before.
This isn't bad news or an attempt to point out flaws. It is to inform those who seek to set one up on an outdoor antenna system and the potential issues that will be encountered.
Your testing confirms my previous points.
So the next step is to find a way to reach that peak point with antenna systems other than the wire. What comes to mind is some form of padding or isolation, but not so much as to dampen the efficiency factors matching up, but to stabilize as much as possible to hit that sweet spot, or at the very least, near it as close as possible, while keeping external influences from throwing it all off kilt.
What comes to mind, though not exactly the solution, is the approach to what the CC couplers provide, a constant loading impedance to the input, while providing maximum transfer efficiency to the load. In CC systems, the load is the power grid or power wiring in a building subject to constant load inductive changes. The coupler must be able to properly match up to those constant variable loading changes, but maintain the proper loading of the transmitter. Something similar to the CC coupler may be needed for the 5K.
Just tossing thoughts.
RFB
A CC system under part 15 has an advantage not available to antenna type part 15 transmitters.
A true CC transmitter has a power range, typically between 2-Watts and 20-Watts, intended to compensate for inefficiencies in coupler matching between transmitter and power line.
This difference is so profound that it invalidates any comparison between the two types of part 15 transmission.
A CC system under part 15 has an advantage not available to antenna type part 15 transmitters. ... This difference is so profound that it invalidates any comparison between the two types of part 15 transmission.
The difference for a permissible radiated field may not much favor §15.221 CC systems over systems operating under §15.209 or §15.219.
For examples of these three, legal systems at 1650 kHz:
§15.209 permits a radiated field of 14.55 µV/m at a distance 30 meters away from the transmit antenna system.
§15.219 has no limit on radiated fields, as long as the input power to the final r-f stage in the transmitter does not exceed 100 milliwatts, and the total length of the radiating conductors in the antenna system does not exceed 3 meters.
§15.221 permits a radiated field of 15 µV/m at a distance 29.92 meters away from the ac- wiring or leaky coax cable used for the transmit antenna system. Note that this limit is virtually the same as permitted by §15.209.
The clear winner here as far as legal radiated fields is a system operating under §15.219 -- although probably that was not the intention of the FCC when they added §219 to Part 15.
The subject was using a CC coupler to match a 100mW part 15 transmitter to match with an Isotron antenna.
"The clear winner here as far as legal radiated fields is a system operating under §15.219 -- although probably that was not the intention of the FCC when they added §219 to Part 15."
It's amazing what the FCC intended given the confusion also added to something which is pretty darn simplistic, but not very well defined in any manner.
Now if we want to talk about advantages of one over the other, how about I throw in one that blows 209, 219, 239 completely away with a 221?
A 221 can send that signal DOWN RANGE on that line for miles, sometimes several miles depending on the grid configuration.
Though the signal cannot emit FROM that line per the formula in 221, it can go for as long as it can travel down range on that line and into homes/businesses, which very well can be several miles or more.
Try that with 219 or 209 or 239...ain't gonna happen.
A second advantage...221 is not subject to being drowned out by nighttime skywave and reduced to a whimpering 1 block range at night like 219 does.
A third advantage...221 LPB equipment is the same equipment used by Part 73 stations, which means that equipment is built like a tank and with design and construction meant to last and take a beating.
Back to the show.
RFB
"The subject was using a CC coupler to match a 100mW part 15 transmitter to match with an Isotron antenna."
Indeed. Why the subject of one method having an advantage over another, or the topic of field strengths and power levels was thrown in is still puzzling, since from the onset the discussion was going in the direction of kc8's most recent report, and the hypothesis I made months ago, that the 5K unit is going to have a wee bit of a problem reaching it's sweet spot when connected up to anything else other than the simple wire..thus mention earlier about taking the TCU concept and adapting that in an attempt to solve a theorized issue, which has been confirmed by real world testing..aka kc8's latest report.
Ok..so everyone..can we now focus on the issue at hand..ie matching up the 5K unit to sensitive loading situations of that encountered by kc8?
Please?!!!
Now...getting back to the show.
Here are some more thoughts wandering back and forth in my head over this newly confirmed issue.
When LPB marketed their first coupler, the TCU-8, it was designed to work with their existing transmitters, which were the RC-# series..tube units which put out 5 watts or more.
Later along came the TCU-30 coupler, designed to work with much less input power, even far less than 2 watts.
Knowing this, since I have the most experience with these LPB's and CC systems in this discussion, and by taking that TCU-30 coupler and connecting a Talking House V5 transmitter to it, and observed a 4 block coverage radius, perhaps by sizing down the TCU-30's input power rating with smaller toroid transformers might be the solution to taking the 5K's low power and match it to it's designed parameter loading for the sweet spot, while at the same time on the coupling output, match up to the typical 3 meter monopole or Isotron or even the power grid?
More total recall if you please:
Anyone here remember my TH coupler project? IE..the small simple coupler for CC applications, which uses much smaller toroid inductors than that in the TCU-30 coupler unit.
Well...put 2 and 2 together here...connect the dots and put the puzzle pieces together to form the picture I have in my mind for this wee lil problem.
Do you see what I see?
More thoughts later.
RFB
"A true CC transmitter has a power range, typically between 2-Watts and 20-Watts, intended to compensate for inefficiencies in coupler matching between transmitter and power line."
Are you aware that the TCU-30 coupler is the SAME unit used in LPB's TIS systems?
And are you aware that some months ago I reported that the Talking House transmitter is able to push it's flea power through that coupler and shoot the signal down the power lines 4 blocks?
And...most important of all, I was NOT talking about the power differences or field strength differences between 219 and 221.
I was talking about taking the TCU concept of coupling and providing constant transmitter match and adapt that in some form to matching the AMT5K unit to the sensitive Isotron or other antenna in order to achieve and maintain the "sweet spot"?
Is it just me or is the approaching planetary alignment affecting what is written and being translated incorrectly somehow?
I don't mean to sound disrespectful here, but the recent two postings to kc8's analysis and my response with the TCU coupler concept to try to overcome the problem by 2 posts with irrelevant things isn't helping at all. Sorry if it sounded otherwise.
RFB
..the hypothesis I made months ago, that the 5K unit is going to have a wee bit of a problem reaching it's sweet spot when connected up to anything else other than the simple wire..
As I said in a previous post, the AMT5000 was designed and verified to cover the frequency range of 1350 kHz to 1700 kHz for all antennas with capacitance in the range of 19pF to 37pF.
Per FCC rules, the absolute maximum height is 3 meters (118 in.).
#22 wire (118 in. length supplied with kit)
minimum length=108 in., C=19pF
maximum length=226 in., C=37pF
102" CB whip, OD=.2 in.
length=102 in., C=24.46pF
1/2" Copper Pipe OD=.625 in.
minimum length=56 in., C=19pF
maximum length=132 in., C=37pF
3/4" Copper Pipe OD=.875 in.
minimum length=50 in., C=19pF
maximum length=120 in., C=37pF
Antennas with less than 19pF capacitance will shift the tuning range upward. Antennas with more than 37pF capacitance will shift the tuning range downward.
The tuning range of 1350 kHz to 1700 kHz was chosen because of better antenna efficiency at the high end of the band.
The capacitance range was chosen to include the most common Part 15 antenna element types.
Widening the tuning range and capacitance range significantly would necessitate a toroid with many more taps and/or a larger trimmer capacitor, both of which would reduce tuning network efficiency.
..the hypothesis I made months ago, that the 5K unit is going to have a wee bit of a problem reaching it's sweet spot when connected up to anything else other than the simple wire..
As I said in a previous post, the AMT5000 was designed and verified to cover the frequency range of 1350 kHz to 1700 kHz for all antennas with capacitance in the range of 19pF to 37pF.
Per FCC rules, the absolute maximum height is 3 meters (118 in.).
#22 wire (118 in. length supplied with kit)
minimum length=108 in., C=19pF
maximum length=226 in., C=37pF
102" CB whip, OD=.2 in.
length=102 in., C=24.46pF
1/2" Copper Pipe OD=.625 in.
minimum length=56 in., C=19pF
maximum length=132 in., C=37pF
3/4" Copper Pipe OD=.875 in.
minimum length=50 in., C=19pF
maximum length=120 in., C=37pF
Antennas with less than 19pF capacitance will shift the tuning range upward. Antennas with more than 37pF capacitance will shift the tuning range downward.
The tuning range of 1350 kHz to 1700 kHz was chosen because of better antenna efficiency at the high end of the band.
The capacitance range was chosen to include the most common Part 15 antenna element types.
Widening the tuning range and capacitance range significantly would necessitate a toroid with many more taps and/or a larger trimmer capacitor, both of which would reduce tuning network efficiency.
"The capacitance range was chosen to include the most common Part 15 antenna element types."
How was that determined? Based on your list, it appears to be missing one important part of outdoor antenna systems already in place..those that incorporate a ground radial system, elevated or ground mounted.
KC8's testing confirms the unit prefers to operate without a ground radial system, and tunes good into antenna elements like that listed without the ground radial system.
Sure it would be a simple matter of disconnecting the radial system if someone wishes to install the 5K unit outside on their existing antenna systems. The testing done to date also finds that using a simpler ground system comprising of a ground rod and nothing more, aids in the unit's performance.
In other words, there will have to be a change in existing antenna systems for the 5K to match up and hit that window of efficiency, which is no biggie, a simple disconnection of the radials while leaving the ground rod at the base.
Now we get to the loading sensitivity of the circuit driving an antenna system which is inherently subject to external inductive influences. So it comes down to this...can you have your cake and eat it too?
IE..reach that high efficiency while not adversely affecting that tuning window range that will be encountered in outdoor systems..as noted by kc8's recent testing report.
Or will there have to be a little bit of sacrifice in efficiency to obtain stable matching and functionality?
Seems to be looking like that will be the case. I doubt you have plans to start a new version with the wider toroid tap ranges, maybe so..that's your call. However in the meantime, and possible for permanent solutions if a different version of transmitter with the added toroid taps is not created, something is needed to achieve both functionality and stability right?
Taking the TCU example of coupling isolation and load impedance stability/matching, building a smaller version of that TCU to reap the benefits of it for the transmitter to be stable into these antenna systems.
Let me give an example.
I took a TCU-30 and mounted that underneath a plain old 102 inch long whip and drove that coupler with a home built transmitter of Class E final design with an output network close to what your 5K unit hits..ie 27pf capacitance and a load resistance of around 32. Although that TCU is designed for 50 ohms, I found the operation of that Class E final was unaffected by the load side of the coupler tied to a 3 meter system, even when directly touching that radiator, the current and voltage measured across that Class E final was constant, as was the power input to the coupler and SWR between the TX and coupler (input).
Then further tested the whole mess by coupling into the power grid, which has even more swings of load inductance changes. Same result..transmitter to coupler stability maintained no matter what the load changes were taking place on the coupler output.
It was a couple of months later I started thinking of a small coupler for the TH units to run CC..all based on those field tests. Regardless of the TH's mode of operation in it's final, the goal was to see if operation from a low power TX could work effectively as a CC system, and to see if the varying load changes would affect the performance of the TX. Putting that home build Class E unit into the mix confirmed that the coupler provides the necessary isolation so that wild load swings don't throw the tuning out of whack and at the same time, maintain coupling efficiency factors for maximum signal injection resulting in maintained signal coverage.
RFB
"The capacitance range was chosen to include the most common Part 15 antenna element types."
How was that determined? Based on your list, it appears to be missing one important part of outdoor antenna systems already in place..those that incorporate a ground radial system, elevated or ground mounted.
KC8's testing confirms the unit prefers to operate without a ground radial system, and tunes good into antenna elements like that listed without the ground radial system.
Sure it would be a simple matter of disconnecting the radial system if someone wishes to install the 5K unit outside on their existing antenna systems. The testing done to date also finds that using a simpler ground system comprising of a ground rod and nothing more, aids in the unit's performance.
In other words, there will have to be a change in existing antenna systems for the 5K to match up and hit that window of efficiency, which is no biggie, a simple disconnection of the radials while leaving the ground rod at the base.
Now we get to the loading sensitivity of the circuit driving an antenna system which is inherently subject to external inductive influences. So it comes down to this...can you have your cake and eat it too?
IE..reach that high efficiency while not adversely affecting that tuning window range that will be encountered in outdoor systems..as noted by kc8's recent testing report.
Or will there have to be a little bit of sacrifice in efficiency to obtain stable matching and functionality?
Seems to be looking like that will be the case. I doubt you have plans to start a new version with the wider toroid tap ranges, maybe so..that's your call. However in the meantime, and possible for permanent solutions if a different version of transmitter with the added toroid taps is not created, something is needed to achieve both functionality and stability right?
Taking the TCU example of coupling isolation and load impedance stability/matching, building a smaller version of that TCU to reap the benefits of it for the transmitter to be stable into these antenna systems.
Let me give an example.
I took a TCU-30 and mounted that underneath a plain old 102 inch long whip and drove that coupler with a home built transmitter of Class E final design with an output network close to what your 5K unit hits..ie 27pf capacitance and a load resistance of around 32. Although that TCU is designed for 50 ohms, I found the operation of that Class E final was unaffected by the load side of the coupler tied to a 3 meter system, even when directly touching that radiator, the current and voltage measured across that Class E final was constant, as was the power input to the coupler and SWR between the TX and coupler (input).
Then further tested the whole mess by coupling into the power grid, which has even more swings of load inductance changes. Same result..transmitter to coupler stability maintained no matter what the load changes were taking place on the coupler output.
It was a couple of months later I started thinking of a small coupler for the TH units to run CC..all based on those field tests. Regardless of the TH's mode of operation in it's final, the goal was to see if operation from a low power TX could work effectively as a CC system, and to see if the varying load changes would affect the performance of the TX. Putting that home build Class E unit into the mix confirmed that the coupler provides the necessary isolation so that wild load swings don't throw the tuning out of whack and at the same time, maintain coupling efficiency factors for maximum signal injection resulting in maintained signal coverage.
RFB
There seems to be a prevailing notion that the AMT5000 has some kind of limitation. This seems to me ridiculous and without merit.
With my transmitter experience, with both models of ssTran transmitters, I have found that it is possible to get a resonant load into an antenna system with a minimum of ground radials, which verifies kc8gpd's report.
But here is what was overlooked in that report...
While the antenna system with no radials may be resonant, there is no range. All the power is dissipated in the near field.
With proper radials the far field range opens up.
Debunking the AMT5000 is a goofy waste of time. It is probably the most well designed part 15 transmitter on the market.
There seems to be a prevailing notion that the AMT5000 has some kind of limitation. This seems to me ridiculous and without merit.
With my transmitter experience, with both models of ssTran transmitters, I have found that it is possible to get a resonant load into an antenna system with a minimum of ground radials, which verifies kc8gpd's report.
But here is what was overlooked in that report...
While the antenna system with no radials may be resonant, there is no range. All the power is dissipated in the near field.
With proper radials the far field range opens up.
Debunking the AMT5000 is a goofy waste of time. It is probably the most well designed part 15 transmitter on the market.
This is not an attempt to debunk the transmitter. It is simply reporting field tests beyond indoors and the bench, with reminders and points remade about certain concerns regarding outdoor installations..something that everyone should be made aware of so that there are no surprises or expectations that will become disappointments.
Unless reporting real world field tests are not wanted around here...I believe making such reports and comments on said reports should be more than welcome at this forum.
After all...isn't this place about exchanging information...as accurately as possible?
Regardless of personal perspectives, isn't it better to report the facts than try to try to cover them up?
Now who is to say that kc8's findings will be the same somewhere else? So far..after how long that thing has been on the market, has anyone done real world testing beyond the confines of controlled environments?
Only one that I know of. So keeping that in mind..the jury is still out on making a final conclusion. In other words..insufficient data at the present time.
RFB
This is not an attempt to debunk the transmitter. It is simply reporting field tests beyond indoors and the bench, with reminders and points remade about certain concerns regarding outdoor installations..something that everyone should be made aware of so that there are no surprises or expectations that will become disappointments.
Unless reporting real world field tests are not wanted around here...I believe making such reports and comments on said reports should be more than welcome at this forum.
After all...isn't this place about exchanging information...as accurately as possible?
Regardless of personal perspectives, isn't it better to report the facts than try to try to cover them up?
Now who is to say that kc8's findings will be the same somewhere else? So far..after how long that thing has been on the market, has anyone done real world testing beyond the confines of controlled environments?
Only one that I know of. So keeping that in mind..the jury is still out on making a final conclusion. In other words..insufficient data at the present time.
RFB