A commercial coupler is on it's way.
I really enjoyed the "home made" coupler
experiment tremendously, but I would
like to really get "on the air."
My messages might be shorter and farther
in between - I have been working 7 day weeks
recently.
And RFB, this last description you just made about
how CC works is greatly appreciated. I'm not an
engineer like you are, but reading the stuff over
and over helps me understand.
The LPB RC-6A is a joy to behold.
Best Wishes,
Bruce, DRS2
We don't have a lot of data on these RF
interaction problems: That is - a Part 15 station
with an outside installed ground level
3 meter stick/transmitter AND a CC installation
running at the same time in the same location.
I may be way off here, but I only know of Carl's
set-up. When he gets the AMT-5000 outside
we may see some new and interesting RF interaction
problems.
Bruce, DRS2
"We don't have a lot of data on these RF interaction problems: That is - a Part 15 station with an outside installed ground level 3 meter stick/transmitter AND a CC installation running at the same time in the same location."
Most of the "data" with this particular case of CC and a 219 setup operating in close proximity is pretty much just like the "data" available on practical working installs of a CC system alone from one location to the other. The "data" is site specific as is the "data" on solutions for each site's specific problems. Most of that information is either locked up in some retired engineer's head, some buried notebook under a pile of boxes filled with old files and books at some storage room at college USA, or has passed on into the universal CC either.
However as we all know, putting transmitters and their antennas too close can and will cause problems. So we take basic steps to avoid that. These same steps can be taken to the installation of a CC system and an outdoor 3 meter antenna/ground plane system.
Chances are, any interaction that will take place will be when either the 3 meter system is pushing too much power or the CC system is, which in either case alone could flood audio and/or power cabling or other nearby devices with RF. The key to remember is even at 1700Khz, the distance of the inductive field's influence for causing reaction, or interaction issues is within the 221 spec of 92.3 feet, so if there is too much power from the CC system, interaction could and probably will happen within that 92.3 feet.
Regardless of that, a CC system does not rely on brute force. A CC system inductively couples the RF onto the power lines or neutral line and the lines carries this signal wherever it goes until it hits a roadblock like a transformer, or end of the run of line. And besides all that, why would you want to run a CC system beyond the amount of power necessary to provide clean coverage while observing 221(157k/f 15uV/m).
If a CC system is operated beyond what is needed, the obvious results are seriously over-driving AM radio receivers and making land line corded telephones pick up the signal and perhaps even cause the neighbor's stereo speakers to never shut up. (har har!) 😉
Now the same thing can happen if a 3 meter outdoor antenna/ground plane system is driven with too much power. It will produce a very strong inductive field in close proximity to that antenna. The range of interactive induction effect would depend on how much power is applied to that antenna system. Even if it was out of tune, if enough RF power is applied, it WILL produce a VERY strong inductive field and quite possibly with just the right amount of sugar and spice, everything inside that puppy hut will not be nice..like burnt arc pitted loading coil etc.
Oh..and the same effect of over-loading AM radios within range of that strong inductive field.
So in closing as we get back to the basics of setting this stuff up, be it a piece of wire or antenna system outside or CC system on the breaker box, planning and good judgement (the FCC calls it good engineering practices), one can reduce the potential for those new interesting RF interaction problems!
RFB
AM 970 CC has been on the air part time, pending a professional field test measurement coming soon.
There does not appear to be any interaction with the other two AMs, at 1550 and 1680.
Even when the outdoor radial system goes in (AMT5000) it will be way in the back yard, where there are no power wires. The power line is in the front.
As the next few months disappear into outer space, I will have tons of additions to this Journal. But let's be simple.
Carrier current under part 15 is complicated by the measurement requirements.
The rules about this were written by drunk fcc attorneys and are nearly incoherent. But the way to get on in the world is to pretend.
As the first attempt to make believe that these rules can be followed, we have ordered a professional spectrum analyzer.
This is a large expense for a station that has no intention to reach an audience; which only operates for the pleasure of science experiment.
In the interim our CC station is turned off most of the time, and is set at a harmless 1/2 Watts during short tests.
The hallway monitors who track this sort of thing may be uncertain whether to pass this on.
You know what Carl, you have done more to check your CC system than what most colleges did back in the hey day of CC. I see no reason why your not operating regularly.
Fear and intimidation will be the destruction of both this nation and this hobby.
Remember, its "Home of the Brave"..not home of the chickens.
RFB
Many brave souls are homeless in the new "Homeland."
Intimidation is like an olympic torch that needs a good runner (as in "run away," to quote the Telletubbies.) Torch is short for torture.
"When they came for the part 15ers there was no one left to stand up for us."
Messages of Pessimism have been brought to you by CC 970, "The Downer."
Over on another string wildbill says he got a Sencore FS134. That sounds like something.
Good meter. Such test gear shows up sometimes over on ebay and other listings.
Here is a free tip. Keep tabs on small two way radio shops that are either upgrading their test gear or going out of business and selling off that test gear. Most of these radio shops are geared for the new digital communications and they may have some unused analog test gear sitting around doing nothing and might sell them just to get rid of them.
Of course there are the ham fests and things.
It's all a matter of just how far you want to go in detail about monitoring and proofing your stations. And I can state for the world wide public record that a field agent of the FCC who inspects a Part 15 station equipped with ANY sort of testing gear to measure it's signal, be it a field strength meter or spectrum analyzer, it impresses that field agent and clearly shows the operator taking "good engineering practices" to ensure compliance. And what else would the agent want and expect anyway?!! Everyone is happy as a fat clam.
They are also happy if one has something to show that steps are and have been taken to be in compliance, like using the radio with the S meter and walking a parameter checking the bands for spurious etc and strength of the signal with the S meter. Document those results and keep it on file, even for 219, 209 and 239 operations.
Proof is always in the proof...so provide some, in some form.
RFB
At 4 this afternoon I switched on the CC at 2-Watts for periodic checkout, during this time while we await our final field test measurements.
For months and months, with the coupler feeding the neutral injection method, the settings have been ultra constant for maintaining a match and keeping the SWR low. But today a surprise.
Some different settings all of a sudden allowed lowering the SWR by quite a lot, lower than it's ever been. This might be because two days ago I let the hose dribble outside by the RF ground rod to moisten the earth alongside the building during this drought.
RFB has often advised keeping the ground moist for RF reasons, and it shows up big time on the tuning meter.
Keeping the ground moist helps conductivity with the ground rods and radials. Some setups have runs of swamp cooler hose to each ground rod and at the base, some even have the hoses ran from the base outward right above the radials buried 1 or 2 inches below the surface, adding even more help to conductivity for that return path, meaning greater peak efficiency.
RFB
Since wetting the dry earth three weeks ago and finding the excellent coupler response, with settings never before seen for achieving the lowest ever Standing-Wave-Ratio, things have sure changed.
The drought has not relaxed and the earth has dried way the heck out. The standing wave is still not bad, it's shy of 1.2:1, but all those capacitive settings that tweaked it even more are no longer there.
What we'll do is re-water the area to get back to that optimum state.
But here's an update on the carrier current experience:
Because our carrier current radio station is still in the construction phase, it is not on the air everyday.
Now that the carrier current station is built, and able to efficiently broadcast, the next stage of development is obtaining the field test measurements required by the part 15 rules.
As a preface to this step, we are analyzing the signal from every means available to discover how far we are able to go with our own methods to satisfy the documentation.
The new Signal Analyzer goes a long way toward giving us control over the signal measurement, but not quite enough.
Meanwhile, as a test, we are broadcasting at the lowest possible setting of the LPB2-20 Transmitter, 1/4 Watt, with the high likelihood that this power level is well underneath the legal limit.
It is also fascinating to imagine that our station might be received somewhere down the power line as if it was an out of town station.
A DX catch, close to home.
There is still a lot to do.
But it appears my signal is IN
the power lines now, at least
1000 feet up the street. I can
tell because I hear nothing on
my radio beyond the near field,
but when I put the radio up next
to telephone poles, the station
audio is audible. In tests last
spring, the situation was not
that defined.
The near field appears to be acceptable
in strength as per Part 15.209.
I don't have a lot of time for this,
but little by little, we are getting
somewhere.
Bruce, Carrier Current On 1020 kHz,
Using An LPB RC-6A Vintage Vacuum Tube
Transmitter From 1971
That is exciting, Bruce. Now you should go door to door and ask people if you can conduct carrier current reception tests in their kitchens and living rooms.
What kind of coupling are you using?
Hi Carl!
There is a family down the street
that I can go see. We are very
good friends.
When I can (which may not be too soon)
I will go down there into their house
and check the signal.
As for the coupler:
Well - it's a coupler alright, but I didn't
say it was a GOOD coupler.
I don't intend to stay with this coupler -
because it isn't good enough.
Here's the deal. The transmitter goes
into that 10 dB attenuator. So the transmitter
is protected and it's seeing the SWR it wants.
After that, there really is nothing to the
coupler. It's just a cap and a fuse going
into the neutral line. And that's all. Oh -
the transmitter is grounded in the house.
This is an experiment. Some of my Part 15
experiments become actual Part 15 stations
that really get listeners. I don't know
what will happen with this.
The good part about this experiment is that
the RF is actually going down the AC line.
Before, when I was using all of those big
huge tuning coils, the coils were radiating
like antennas. I did not have any clear
indication that the RF 1020 kHz signal was
confined to the AC line. I believe that
set-up might have been in violation of
Part 15.209. That's why I did not keep it
on the air. It was only brought on for
brief tests and I decided I did not like
the way things were going.
This present coupler does not address the
impedance mismatch between the
transmitter/attenuator and the AC line.
OOOOOps. I have to go. I'll be back.
Bruce, 1020 CC
So anyhow - to conclude my
above note - the transmitter
is happy SWR wise, but the
RF power transfer to the
AC line is probably not
very good.
The set-up is now legal.
I don't have to worry about
running it and it is safe.
And the signal is now going
down the AC line. (If putting
the radio up next to telephone
poles and hearing the signal is
a good indicator.)
But the reactance between the
coupler and the AC line still has
to be tuned out for efficient power
transfer. This set-up does not
accomplish that. This set-up is
a lot like those longwave intercoms
that we talked about on this thread
a while back.
If I don't get the commercial coupler
soon, I will keep working on an RF coil/cap
inpedance match design that does not radiate.
Gosh, I guess that's all I have to say.
Whew.
Bruce, 1020 CC