"The signal was there for the 1st block. The signal was there for the second block. In the 3rd block the signal was suddenly gone. That's about the same result we got when the coupler was wired into the hots, but of course neutral is safer to work with."
Remember, your not transmitting off a central located antenna radiator, your transmitting off the power grid lines and that is going to have very different propagation results than from an antenna. For clarity..the TRADITIONAL antenna.
There I said it so don't need emails describing the difference or similarity!!
Just because the car radio lost the signal at the 3 block point doesn't mean the houses within that 3rd block can't pick it up on their radios plugged into the AC outlet. The road test is only a part of the field reception testing. Your car radio won't pick up the "far field" radiation at all because CC is NOT a far field transmission system. It is an INDUCTANCE FIELD transmission system.
I suggest going to someone in that 3rd block area and knocking on their door, introduce yourself, what your doing and why, and ask them if they could check it for you on one of their plugged into the AC outlet radios for the signal. If your PR skills are still intact, this should not be a problem. Just look presentable, don't carry around a briefcase as that is the sure sign of a door to door salesman and ye be met with a flying iron skillet to the head, and be neighborly.
Long way to go yet. But your making progress.
RFB
"I'm going to go real slow at this LC thing! 330 volts is nothing to sneeze at!"
Will grab you by the booboo if your not careful! It will put a new meaning to the term "bedhead".
One of the variable caps, not sure which, but one of them at least will have that 330V potential on it. What I suggest is tracing it out. Find the output point from the tube socket to that variable cap, that will be the one with the plate voltage potential on it unless there is a coupling capacitor between the output point of the tube socket and the input of the variable cap. Even if that is the case, there is still danger in that area when the unit is energized. Even a 6 watt RF signal will cause a little burn.
RFB
Based on the game "musical chairs," the CC Project is requiring a round of "musical tuners", as I need to move one FM tuner and replace it with a second FM tuner.
The Techniques rack-mountable has been the STL (Studio Transmitter Link) delivering audio to the AMT5000 at AM 1680, the STL channel being 101.9 FM. But the tuner overshoots its shelf by about 3-inches, requiring care in walking past, and is now needed in the rack housing the CC equipment, as the STL for the newly arriving AM 970 CC.
The tuner, re-conditioned this very day, a Panasonic, will be the replacement STL for AM 1680.
We need a traffic-directing wand for all this tuner juggling.
I had a problem doing that a few times.
When the FM tuner was placed next to
the AM transmitter it was feeding - I had
unexpected trouble.
The RF field from the AM transmitter was too
strong in this case. The FM tuner lost all of
it's sensitivity because it was sitting in that
near field. The frequency difference didn't
matter. As you go fourth and increase your
wattage, you might have this problem. Or you
might have it now.
The only solution that worked for me was separating
the FM tuner and the AM transmitter - and then running
a long audio cable between them. I suppose RF beads
or chokes, or something like that might help.
Also, you might want to turn off 1550, 1680, and 13.560
when you try this. Because with all of these transmitters
running, you might have RF mixing occurring somewhere.
Just a thought.
And RFB, I really appreciate all of your comments. i am going
very slowly with this CC thing. I don't want to mess up
this nice old transmitter by shorting something out. (And
zapping myself in the process.)
Oh - I have received RF burns from ham radio equipment
several times. Everybody read that carefully. RF Burns has
not come over to my house. (Although I wouldn't mind.)
But seriously folks, RF burns feel really really weird, and they
hurt, too. And man - it doesn't take much power, either.
Best Wishes,
Bruce, DOGGRADIO STUDIO 2
Our new 970kHz Carrier Current Service to several square blocks of world terrain will be Opening Soon.
Today the 970 crystal arrived, the tuck-pointing on the west wall complete, and the LPB System tuned for 970, bringing the lowest SWR (Standing Wave Ratio) of any of our test frequencies, 1:2
For now a tone is going out, but tonight the audio gets finalized and program tests are set to begin!
Now the same people who already can hear us at 1680 AM will be able to change their mind and switch to 970 AM. Those with extra sensitive radios can try 1550 AM, and around .4% of the population might chose 13.560mHz SW.
Only one of our radio stations doesn't exist, I'm talking about 167kHz LW.
We're all pretty excited about this, Carl!
Keep us posted!
Bruce, DOGGRADIO STUDIO 2
As I have mentioned, my attempts
to put the LPB RC-6A on 1020 have
to wait a little while. This is the ideal
channel, but the rig will have to be
modified a bit for it to tune up correctly
there.
My plans are to put the transmitter back
on 860 and continue the experiments.
The RF out from the transmitter will go
to a 10 dB attenuator which will isolate
the transmitter from my homemade coupler.
There will never be a direct RF connection to the
AC line. This is sort of a "poor man's" circuit
that I want to try just for fun.
The problem is: the transmitter puts out six watts
and my attenuator circuit can only handle five watts.
The attenuator circuit isn't built yet, but I have all
of the parts. I'm gong to try it anyway. I don't have
enough parts right now to build an attenuator that
can dissipate more energy.
I guess the worst that will happen is I might burn up
some resistors. Maybe I can test it for short periods
of time or detune the transmitter slightly so it puts
out five watts instead of six.
That's where we are right now.
So GO! CARL! Let us know what happens with your
set-up!
Best Wishes,
Bruce, DOGGRADIO STUDIO 2
Bruce your progress is slow because you want to get every detail just right, and that's exactly why my projects take so long to complete.
All day yesterday was spent re-building that old FM tuner I talked about which is needed to complete the carrier current project.
The slowest thing today was spending about 4-hours hunting down my rack screws which I haven't needed since the mid 90s, and strangely enough, I spotted the box at the exact moment I was about to give up for today.
Now the Techniques tuner needs to have a cable with rca on one end and screw-terminal connectors at the other. Maybe I'll do that tomorrow.
To heighten the excitement I am listening to the background noise at 970kHz, and there's a ball game that pumps in and out with ionospheric wobbliness.
Got the Techniques Tuner mounted in the rack, put the "T" shaped antenna up in the rafters, just below the Wholehouse 2.0 up stairs at 107.1 mHz, getting a marginal signal which probably can be improved by fiddling with the receive antenna.
The first RCA to wire-terminals cable I used did not work, and I found the ground side had come unsoldered at the RCA plug, so I tried a second one which got us on the air, carrier current, 2Watts, 970kHz, with under-modulation.
But it really sounds good. There's no hum at all, very very low standing wave, and even though the VU in the LPB isn't moving much, the on-air audio is only slightly lower than average stations, and sounds very good.
There will be two ways I can up the audio level...
1.) remove the 630-ohm terminating resistor in the LPB designed for professional balanced lines that need 600-ohm termination;
2.) install the Volumax 4300 so that I can drive full level into 600-ohms, have fast limiting, and convert un-balanced to balanced.
I guess I'll do the latter, since the Volumax has no other purpose.
The carrier current system is now on the air and testing.
Last night I streamed "Mischke" from WCCO and noticed that when I walked across the room (main floor) the FM receiver (basement) would "swoosh" as I interfered with the STL (Studio Transmitter Link) signal being sent to the LPB AM transmitter.
The FM transmitting antenna is a vertical cage-monopole suspended on an indoor 3-leg tower made from bamboo poles and setting atop a stool.
The FM receiving antenna is a T-dipole and was strung horizontally.
Simple solution. I tipped the T on its side, making it vertical, and the STL is now rock solid.
About the STL frequency... which had been set to 101.9mHz. Well, the cage-monopole transmitting antenna had actually been cut for 107.1, so to get the extra edge of efficiency I re-set the Wholehouse 2.0 for 107.1
Re-tuning the tuners left out one tuner, which I over-looked, namely that feeding 13.560, the Big Talker shortwave station, which has been sending a silent carrier for over a day with me pre-occupied with looking for rack screws. Now it's fixed.
The grass needs cutting.
For the first full day KDX CC has been carrying the day's programs on 970kHz at 2Watts.
The audio system is still a simple connection from the Techniques Tuner with somewhat low modulation, but the carrier is so quiet that it is perfectly listenable.
As a 4 PM storm was mounting I drove west and noted that the signal coverage, from the vantage point of the auto radio, is a very consistent 2.5 blocks. This has been true with every test to date, even on different frequencies and when we had more SWR (Standing Wave Ratio).
The 3 frequencies tested include 570, 670 and 970 kHz, and it appears that the combination of this transmitter and this power line connection defies normal carrier current performance in that the HIGHER the frequency the better the result. It's usually the other way around.
Another thing that has come to light is that on radios connected directly to the A.C. the signal is stronger than on portable or auto radios, and on one radio in particular, a Zenith Transoceanic, the mid-band is somewhat clobbered by 970, and the audio is very present over a wide area, possibly swamping a few nearby signals. This requires further scrutiny, but the stations in question happen ALL (3 of them) to be religious stations. Although it is a condition that does not affect all radios, the key question is whether someone on the immediate power transformer wants to listen to these stations. If so, I need to back up. The rule is blunt: "...Cannot cause interference."
Because this CC installation is proving SO efficient on 970kHz at 2Watts, I may need to lower power, which of course is doable.
And once more let us remember, the success of this project is due entirely to the guidance of RFB, without whom I would be trying to figure out where to store a very clunky bad purchase.
Is it true that the lower the frequency, the more opportunity for interference? Electric motors, power transformers, florescent lights, etc., especially down low.
I forgot what coupler you're using. OTOH, I think it's great that it's working!!
The coupler is an LPB TCU-30.
The whole day today was carried on KDX CC at 970 AM. All went very well.
At 11 PM when I shut the carrier, I heard a station coming in with fund raising for wpr.org. Never having heard that before, 970 is usually a mish-mush of indistinct stations, I traced it to Wisconsin Public Radio, coming from WHA in Madison, Wisconsin, with only 51 nighttime Watts!
In the daytime WHA has 5kW, but is not heard here.
"Is it true that the lower the frequency, the more opportunity for interference? Electric motors, power transformers, florescent lights, etc., especially down low."
Yes. Even more so these days with far more florescent lights (energy savers) and switching power supplies replacing linear based power supplies.
Also things like BPL can wreak havoc across the entire MW band, some days its really bad, others the bizz buzzing is hardly there.
Another factor is this clutter noise one day may make the lower 3rd useless but at the same time across town the noise is non-existent. It is as if the noise likes to bounce around along the grid, parking itself for a time in one area, then moving on to another.
These and other problems that vary from one site to another is why CC is not by any means a one method or approach applies to all. For example...the "myth" about the lower third of the MW band being the best for CC. It really depends on how the grid is configured for a given area because even in the same town or city, one section of it's power grid is configured one way, while another is a little different or a whole lot different.
These differences in the grid system is why every CC location will have it's own unique problems requiring unique solutions.
RFB