- Posts
Here at kdxradio.com we are planning to install and test a carrier current station and will report the experience here and on the Low Power Hour.
Here at kdxradio.com we are planning to install and test a carrier current station and will report the experience here and on the Low Power Hour.
The first trial will connect us to the electric mains, by which I mean the two “hot” connections and ground/neutral wire, which I think is a “classical” carrier current setup.
As RFB has said, this method may reach a roadblock at the transformer out on the pole, unless there are bypass capacitors, in which case the signal would keep going onward and outward.
There is no visible evidence of bypass gear up on the transformer, and at this time it appears the transformer feeds four or more houses, but we do have automatic metering, whereby the electricity use is measured without need of a human meter-reader, so perhaps there is a bypass.
Also, our AMT5000 transmitter, being radiated by antenna, has a very distinct signal that can be heard in the background for several miles, all along the power lines, and the inventor, PhilB, estimates that this can be explained by unintended carrier current emission, which, if true, is another hint that our transformer is bypassed.
Total posts : 45366There may be slight effects off nearby power lines at short ranges from a 3 meter stick with 100mW on it. However it’s not going to go several miles as “loose” coupling via some wire near an electrical conduit, the signal will get absorbed rather quickly.
Most likely this is happening because you have your transmit antennas (wire) hung inside the house along a wall near a window with a romex line nearby and that is picking up the signal and the use of ground off the outlet or your equipment ground, which probably the ground path is radiating more than the wire is, thus will cause some CC effect.
With your latest acquisition, you can do CC for real and not have a side effect CC from a piece of wire.
Just remember that there IS a big difference between the neutral and ground of the AC grid, as well as in your breaker box and outlets.
ISOLATED EARTH GROUND:
If your breaker box is the primary “break” point after the mains leave the meter outside, the neutral (white) and Earth ground (green) will be connected together within the breaker box.
There may even be a grounding wire ran from the meter box down into the dirt attached to a buried ground rod, or connected to the cold water main service into your house.
Start probing around between the cold water main and the utility ground/neutral. Hopefully it is isolated. If not, then installing ground rods will be your only choice for the isolated ground.
Coupling to the “hots” is extremely dangerous and should be done very carefully. There will always be that 220vac potential inside the coupler, and never never NEVER run an isolated ground path to the coupler when coupling to the “hots”!!! Not unless you want to create a new ground path for lightning strikes and voltage spikes. POOF!
Become familiar with your breaker box, its wiring configuration and use a 220 breaker at the least amperage rating possible for quickest flip response time of the breaker in case of a problem. 220vac really is not that much voltage considering 7,000 and up rides on those upper wires on the grid. But the amperage capacity on those two “hots” is well into 150+ and that is what is the killer.
Place a rubber mat on the floor in the work area where the TX and coupler will be installed. This will help to keep you from becoming a human ground rod in case of accidental contact with one of those hots. And I would keep that rubber mat there even after installation so that way if you had to re-peak the coupler, or check connections, your standing on isolated surface instead of cement or other hard surface that could become conductive from moisture. Had a friend who learned that lesson the hard way and now his entire right arm is disabled and looks like a twisted tree twig. And that was working around the 220 single phase hots. Imagine what 440 3 phase will distort!
Good luck and keep us updated. If we see a mushroom cloud, we will disavow any knowledge of your mission and existence and declare it a freak accident. 😉
RFB
Total posts : 45366Thanks RFB:
ELECTRIC SERVICE
A couple years ago I had an ancient 60 Amp power box replaced by a modern high Amperage box, I forget, either 150 or 250 A.
The electrician who did the install was like a stage magician. With no help whatsoever, he followed my instruction to move the box from a corner to a more central spot on the basement wall, and he quickly whipped all the old and new wiring over to the location and had it finished.
The neutrals are grounded in the box, like you said. According to code, there is a giant twisted copper wire that traverses the basement over to the water pipe where it is grounded.
The twirled 3-conductor “drop”cable out about 100′ to the pole does not see ground again until it reaches the pole.
There are no ground rods around the house/property.
The first installation site is already to plug in without the need for dangerous wiring, it is a large 3-flat-blade socket which belonged to the drier. My only part will be to wire a 3-blade plug to the coupler for connection.
Your suggestion of going low-Amperage on the circuit breaker will be taken care of before it is turned on. Thank you for that.
Guess what? The doorbell just rang, and it’s the LPB Coupler from the eBay auction! It got here right away.
Total posts : 45366Glad to see the coupler made it so quickly and intact.
TIME TO PARTY!!!
Well wait…not so fast!
I can only imagine that your sitting there glaring at the TCU-30 coupler and dreaming of millions and millions tuning in!
Isn’t radio fun!
The dryer outlet will make a good coupling point for your first attempts, and be a lot safer than tinkering around inside the breaker box. I am assuming this unused dryer outlet is already fixed with it’s own breaker in the breaker box?
If not, it should be.
Also will this area where the coupler and TX will be..is it fairly well ventilated? In other words, it doesn’t get too hot in that room with washer and dryer running. A small fan will help vent out the warm air inside the TX through its vent holes and keep things cool.
When the TX 2-20 arrives, be very careful of that power adjustment pot. DO NOT ATTEMPT TO ADJUST THE POWER WHILE THE TRANSMITTER IS TURNED ON! That power adjustment pot is incredibly sensitive to external inductive objects such as your hand, and will make the power spike upward like a shooting rocket, and potentially blow out the finals.
Begin with the power pot adjusted 1/4 turn from its lowest setting, and adjust in steps after that between power on and power off cycles.
To solve the issue of the sensitive power pot, simply replace it with a flat surface mount type so you can use a tuning tool directly above the pot instead of the original sideways mounted pot. Replacing the pot with a flat surface mount pot solves the sensitivity problem in all of them, and you can then adjust the power while the TX is running.
More tips later.
RFB
Total posts : 45366The drier outlet does have it’s own circuit breaker, but I will need to change it from 30-Amps, or whatever it is now, down to the low Amperage you recommended.
The basement is cool and there is no drier, since I use the good economy of drying clothes using free air and coat hangers.
Thanks for the power control tip on the transmitter.
The unit inspects to be in good condition. The “scratch” on the meter is more of a superficial streak, it is not etched into the plastic.
The power screw-terminals look weathered, but a little Dioxit will clean them up.
A neatly printed schematic is included, but no instructions for calibration.
Total posts : 45366Looking at the ATU-30 Schematic it is easy to spot the connections for neutral, line, line, and …….. there is a connection for a 3rd “line” but that will go unused.
Therefore the first installation, using the dryer 220-VAC plug, will be simple. The hardest part will be changing the circuit breaker down to a low Amperage, but I’ve made circuit breaker changes before, so it will be familiar work, with extreme care.
What I do not know is how to use the various controls on the coupler, starting with “calibration.”
The meter offers somewhat of a clue, as it has several scale-markings, the topmost being a setting for transmitter input Wattage, up to 30-Watts.
The lower scale consists of a short green strip, which I guess indicates a minimum SWR (standing wave ratio) and a larger red space which probably signals that the SWR is too high and needs to be reduced.
There are 3 switch settings that will need explaining, “Test”,”Calibrate”, and “Power.”
There is a silver sticker on the coupler saying “AVOID UNIT DAMAGE. DO NOT LEAVE IN “POWER” “CAL” OR “TEST” FOR MORE THAN 3-MINUTES.”
I also remembered only this morning that I never asked what frequency the transmitter is set for, but I’ll need to get a crystal for 970kHz, so there is another detail.
Lunch?
Total posts : 45366LPB divided the MW band up into 3 sections and made low pass filters for each of these 3 sections of the MW band.
Low-Mid-High
Low is 530-830
Mid is 830-1270
High is 1270-1710
I think that 2-20 unit was set up originally for the high section of the band and then changed to operate for the low section of the band, but you will have to check with Tommy on that to make sure.
It’s is not difficult to change the LPF components to work another section of the band. Just about every TX manual of these series has the LPF part chart for the 3 filters used.
On to the TCU…not ATU. You will not be using this or that RS CP-15 as “ATU’s”. Although both can certainly be used as an “ATU”..they are not intended for that purpose nor can either of them couple up to a 10 foot wire. The wire would have to be at least 120 feet long and the coupler would require an isolated Earth ground system kin to that of a MW broadcast tower’s ground system.
There is a way to get them to couple to a short wire..but I’m not going to disclose that to end up being the suggestion source when someone get’s tagged for exceeding 219.
On with the coupler:
The TCU 30 coupler has 3 main adjustment controls. Going from left to right, two of them are for the capacitance decade. The third is for the inductance range.
The lone wolf control below the 3 above is a function control with 4 positions. “POWER”, which is the first step and position this control must be in to begin the tuning process.
“CAL”, which is “CALIBRATE”, is the second step in the tuning process. Once you set the power level on the transmitter with the TCU’s function switch in “POWER” and reading the indication on the on-board meter which will indicate your RF power out of the transmitter, the function switch is then turned to “CAL” and you adjust the “CAL” variable control to set the meter to FULL scale.
The next section of the function switch is “TEST”. This position of the function switch lets you see your tuning on the meter. You tune for lowest SWR by rotating the inductor selector first, then the 1000pf decade control, then finally the 100pf decade control. Then you repeat the process from the inductor selector, to the 1000pf selector, then the 100pf selector for minimum SWR on the meter.
Once you adjust for lowest SWR on the meter (needle in the green), your ready to move the function selector to “OPERATE”.
The RS CP-15 has two inductor selectors instead of one. This gives you a little bit more inductance range and a little more capacitance decade range. I found no real useful benefit of the extra inductance and capacitance range in the CP-15 versus the TCU-30. The CP-15 unit was really intended for TIS applications and night time power operations of licensed stations. It just so happens that both the CP-15 and TCU-30 can serve both CC systems and short tower antennas.
The setups for the CP-15 are the same process as the TCU-30 with the exception of the extra inductance and capacitance ranges.
RFB
Total posts : 45366If I am right about this that would make me smart.
I am thinking that maybe the DataKit 80-035 PLL-EXP1 Experimenters Package can be used in place of a crystal to put the 2-20 Transmitter on 970kHz in the mid-band. Huh?
GOOD, now I will print out the Instructions for the TCU-30, and I downloaded the manual for the CP-15, so we are very close to carrier currency.
Total posts : 45366Yes. The DataKit PLL can be used to replace the crystal and its oscillator IC. You will need to make an oscillator that will either operate at the 6x frequency, or one that operates on the intended frequency and not use the divide counter IC.
On the exciter board there is a test point below the meter labeled “FRQ TP”. This is where you would inject the oscillator signal if the oscillator is operating at the intended frequency. If the oscillator will operate at the 6x frequency, you need to leave the divide counter chip in the circuit and inject the PLL oscillator into the divider chip, exact pins forthcoming.
ADDED:
To inject in-band oscillator frequency, remove IC “A2” and “A3”. Inject the oscillator signal at PIN 8 of IC “A3″‘s socket, or at the FRQ TP stud.
To inject a 6x frequency, create the crystal equivalent with a tuned circuit and keep both “A2” and “A3” IC’s in circuit. Use the crystal socket as a mounting point for the small PC board containing the oscillator circuit being PLL’ed by the DataKit.
Remember, ALL of the solid state LPB’s use a frequency that is 6 times than the intended operational frequency.
For your frequency of 970Khz, you would need a 5.820Mhz crystal, or a tuned circuit capable of oscillation at 5Mhz and let the PLL do the rest.
NOTE: When using the PLL to operate on the intended frequency, punch in the intended frequency on the keypad…ie for 970khz punch in 000097. For the 6x frequency, punch in 005820.
RFB
Total posts : 45366You solved another puzzle with the information about using the PLL Circuit in place of a crystal. Now the next question.
In the Instruction Manual, page 4.0, it says:
“It is important to note that the TX-2-20 Transmitter MUST be used with the T-8 Power Line Interface.”
This covers ground covered before on this thread, but I only now see this STERN INSTRUCTION and therefore ask once more if we are still safe with the TCU-30 Coupling Unit.
Total posts : 45366RFB wrote “LPB divided the MW band into 3-sections and made low pass filters for each of these 3 sections of the MW band. Just about every TX manual of these series has the LPF part chart for the 3-filters used.”
But not the Manual for 2-20, which has no description of the 3-different bands.
The only clue that something special is going on are several parts in the parts list shown as “Factory Select.” Of the 6 such parts there are 2, namely C25 and C37 which say “Frequency Dependent”.
The only thought I have is that LPB tailor made the 2-20 for particular frequencies.
I will consult with the seller (Tommy J.).
Total posts : 45366The manual I sent is specifically for the exciter board type used in your particular version of the TX 2-20.
The power amp section is the same as the AM-25/30 and what is used in the combined transmitters forming the 60/100 P models.
I will send you the manual to the AM 30 which does have the filter component chart and parts list which are applicable to the power amp module in your TX 2-20.
At the time of the publication of the TX 2-20 manual I sent you, and the model released at that time, covers the exciter type that you will find in your TX 2-20 unit. And at that time, the coupler then was the T8.
Don’t worry, your TX 2-20 will work perfectly with the TCU-30 or CP-15.
RFB
Total posts : 45366I printed the low pass filter data from the AM-30 Manual and compared it to the 2-20 Unit, and just like you said, an exact likeness.
The caps, C31 to C35 have the same numbers, the chokes or coils have different part numbers but refer to the same parts… L4 = L2 and L5 = L3
Wow, it’s lucky that LPB printed this info, because elsewhere in the AM-30 Manual they write,”To change the band of operation return the transmitter to the factory.” Whoever wrote that was optimistic about the future.
Total posts : 45366Well at one time they were the best choice to re-frequency these transmitters, although changing the frequency and LPF components require no greater than a skill level 1.
It was more of an advertisement offer than an actual technical requirement. It was also a reminder to those who had these transmitters still under warranty and needed the frequency and band change.
Yes, there are a few of the LPF components that are the same for both the low portion and mid portion of the band. The only one that is the lone wolf which uses different parts all the way through is for the 1270-1710 segment.
It made sense for LPB to start using the same power amp board and components for all of their solid state units. The only unit that uses different finals, but still uses the same PC board, bias, bypassing and filtering is the TX-5 from 92 up. The finals are smaller cousins to the SD1407’s, specifically they are SD1285’s.
This approach by LPB also made it practical on both their part and for the end user to have interchangeable modules, cutting down their manufacturing costs as well as cutting down the costs to the end user.
As to the energetic employee who wrote the note of returning the unit to the factory for a frequency/band change…well that was during an era of prosperity, jobs a plenty, industrial growth and manufacturing, the 80’s version of “Happy Days”.
No such thing these days…except manufacturing toothpicks and paperclips…..with imported raw materials.
RFB
Total posts : 45366Carl I bought a TCU-30 a few years ago and it came with the manual. It’s complete with setup instructions, schematic, parts layout, etc.
If you’re interested I can scan and make the info available.
I also have a Radio Systems Phase II 20 watt transmitter which came with some info regarding the transmitter and their CP-15 carrier current coupler if anyone is interested.
When I bought the Phase II it was on 640 kHz. I ordered the parts kit to modify the amplifier section moving it to 1500 kHz. I have the instruction sheet for that mod also.
- You must be logged in to reply to this topic.
