For Carl's control issue, that can be solved by adding a remote power switch using low voltage DC controlling a small SPDT relay across the power switch inside the TX. Add a power on indicator (tap the red LED) and wala.
The capacitor voltage rating of 1Kv will suffice for experimenting purposes, but make sure you add a fast blow fuse no higher than 1 amp. You might also want to add a 100uH choke, perhaps two or more, in series with your capacitor/fuse direct coupling circuit so as to add some inductance to the path which will help "tune" down to the lower impedance for better results.
RFB
Some fuses are rated at 250 volts.
Say the fuse is rated at one amp/250 V and
the voltage in actual use is 120.
If more than one amp goes through the
fuse at the lower voltage (120 vs 250)
will the fuse blow?
I never stopped to think about this -
is the fuse's actual point where it
blows based on JUST CURRENT?
Or is it the VOLTS x AMPS that determines
when the fuse will blow? Or perhaps there
is a characteristic curve that applies?
Then my mind asked - maybe different
kinds of fuses blow under different
conditions. (I'm not talking about thermal
fuses, though - they are a different animal,
I guess.)
Thanks for the additional info on the RF chokes,
Yup, that sure does make sense to me.
Bruce,DRS2
You have two things working in your favor. The low level RF being applied and the isolation capacitor/fuse connection. No current is being drawn from the source. The RF voltage applied from the attenuator is well below the 250v rating of the fuse.
600mW is .6VA. The 1 amp rating is a very good choice with adequate head room but not so much the protection is out of reach if there was a problem..such as the 1Kv cap shorting.
RFB
I've learned more from Part 15 radio in a few years -
than 40 years of ham radio!
Thanks again!
Bruce, DRS2
The voltage rating on the fuse is for the flash over rating of the fuse enclosure. If it's rated 1 amp, it doesn't matter what the voltage is up to the rated voltage. The fuse will open when you exceed that current.
So, if you buy a fuse rated 1 amp 12 volt you would not want to use that if the open circuit voltage exceeded 12 volts. In your case you should be OK up to 250 volts.
We bought bulk amounts of inline fuses for vehicle use. They look identical to the higher rated voltage fuses but only carry a 24 volt rating. Not a good choice for AC line applications.
Hmmm ... I wonder if that might work ... to get the injected signal to go further.
The TH I'm using right now seems a lot more stable than I would have expected for what it is. Even at very close proximity, it doesn't seem to splatter into adjacent frequencies very much. Maybe I just got a 'good -un'. So adding power with a good clean RF amp should work ....
What say?
Well the TH external ATU output has no low pass filtering so any linear used would need to have a very good low pass filter like that found in LPB's transmitters.
The TH will drive an LPB linear just fine. 🙂
If intending to drive an LPB linear, and depending on intended operating frequency, the filter may need to be changed for the particular section of the MW band where your frequency will be.
Low 530-830
Mid 830-1270
Hi 1270-1710
RFB
MRAM, thank you for the
additional explanation on
fuses. This is real good
info to have. I don't want
to blast the transmitter
into orbital space!
And Ken, good luck with
what you are trying to do.
You're a better man than
I am!
Best Wishes,
Bruce, DRS2
Glad to hear you got CC up & running Carl, I have been busy as hell, but am following your progress! RFB, give me a call.
Tommy j
The Cat 87.9fm
Hi! It looks like I have
almost all the parts you guys
mentioned to couple directly
into the AC line with the CC set-up.
My only problem is the cap.
I was only able to get a 2 pack of
.01 uf caps - the problem is they
are rated at only 500WVDC max.
I also happen to have a metal-film
.01 uf cap - but it's voltage rating
is lower - it's 400 WVDC.
No problem with the 100 uH chokes and
I have a 1 amp 250 volt fast acting fuse.
My question is about the caps. Can I use one
.01 uf 500 volt disk briefly
for a few minutes to see if
the CC system works, or is that a really
bad idea?
How do caps fail - do they short? (I bet
the answer is yes.)
That wouldn't be so good.
If I put a couple of caps that were
1/2 the value in parallel?? Would that
solve the voltage problem? (2 .005 ufs
in parallel?)
My lack of knowledge is showing here.
Thanks and best wishes,
Bruce, DRS2
P.S. I placed a jumper across the output
of the 10 dB attenuator, and the SWR hardly
went up at all, so I guess that part of the
system is working OK.
I used "Start Page" to search for the term "Carrier Current" and have enough links from now until Christmas.
I decided to come up for air and share a few things I've found.
Bruce, a college CC station recommends 1uF 1kV caps for coupling to the power line.
I didn't know that CC can be used for covert surveillance, but it can; little devices can be hidden in sockets, power strips and appliances which send audio AND VIDEO by CC!
There are instructions for detecting CC signals on the power line.
My idea is to put a wide-band jamming transmitter on CC and take a nap.
As I sort through this stuff I will link some of it, if it hasn't already been linked in the past.
ECHO ECHo ECho Echo echo
Yup, after asking that last
question - I have decided to
wait on this "direct to AC Line"
circuit, regarding the isolation
cap.
Radio Shack does not have one that
is a high enough voltage and I
don't want to mess around with
this thing.
There is a really cool electronics
store that will have a nice big
jumbo conservatively rated cap.
I'll just have to arrange to get
a ride over there as soon as I can.
It's pretty far away, but it will
be worth the wait.
Thanks again Carl and everybody for
all of the advice.
Best Wishes,
Bruce, DOGGRADIO STUDIO 2
The daily carrier current operation from here has been operating at the temporary frequency of 670kHz for several weeks at a power of 2-Watts.
Now having explored the radiation from the power lines using both the car and a portable, it seems like the signal is reaching less than 100-feet away from the power lines.
As is often mentioned, the rule of thumb for safe compliance is 200-feet, so today I inched the power up to 2.5-Watts, and we'll do more surveying to see what has changed out in the field.
Hi Carl!
It will be interesting to see what
the results will be from the
increased power.
I think what you are doing is great.
Bruce, DOGGRADIO STUDIO 2
Thanks for following the progress, Bruce, as we are with your experiments in CC.
Since my last posting, only an hour ago, a violent storm started to happen, so I went through the shutdown drill, all transmitters and computer off, antennas disconnected, and radio silence being maintained.
That spoiled the fun for the storm and it turned off.
So all the re-connections were made and we returned to the air and stream, only to hear the storm coming back.