"My 550 kHz CC signal goes nowhere. It could be something
in my homemade coupler."
Most likely it is the coupler. Increase windings..both sides.
RFB
I will try it!
I'll also try to find that
RC-5A schematic. I know that
I have it. It's just a matter
of going through a bunch of
stuff.
Bruce, W 60 HZ
WE WON'T GET FOOLED AGAIN
Even though the tuning circuits
of my LPB RC-6A are very touchy,
my inability to get on 550 or
970 kHz was not caused by that,
as far as I can tell.
On 970 and 550, as I tried to
tune the rocks up on the RC-6A, I
occasionally heard some squealing
noises. I began to wonder about
crystal stability, activity and
the effect it would have on the
6AL11 oscillator's ability to
drive the final RF amp.
My brain said, "Brain, get that
1020 rock back in again and try
it." So now, the 1020 rock is
back in the transmitter. The
1020 crystal is in a big holder. It's at least an
FT-243, but I think it's larger.
I'll have to look that up. The
970 and 550 rocks are smaller.
So I put 1020 back in, (not with
my brain, but mostly with my
arms, hands, and fingers.) The LC
was tuned up
and BINGO!, the resonance light
came back on and I got 5 watts
instead of... one. As of late,
one watt was the best I could
do on 970 and 550.
Well, I'm happy. The old LC
net isn't badly damaged, as I had
feared. It's not great, but
the problem is those two
"low activity crystals."
So my CC is back on 1020 for
now, and all is well. And the
neon light is on!
The ultimate 620 kHz channel
will have to be done by external
RF generating circuitry going
into the 6AL11 RF osc. side.
And eventually, it will be.
But for now... 1020 kHz,
which is fine.
We won't get fooled again.
Bruce, W 60 HZ and X-13
Wow, this CC Journal ran for about 1-year and has been silent for awhile, but look at all the entries!
Something new happened and the CC Journal needs to be told.
My one and only CC transmitter is an LPB 2-20 TX, which was carefully checked out and put into service where it has run as a neutral injection experimental carrier current station until today, when it stopped working.
Last Friday it was turned on at 9 AM and run 24-hours a day all weekend with a scheduled shut-down last night, but I fell asleep and left all my carriers on all night.
This morning I tuned to the CC frequency, and there was no carrier! So I thought, "At your age maybe you went downstairs and turned it off after all."
But no. I went down and found a cool transmitter that would not turn on. I removed the two fuses, F1 and F2 and brought them up for checking. They are both good! Now I know two parts that are not at fault.
These LPB transmitters still show up on ebay, but they are getting very old and no longer worth the high prices they have been getting. I bid on them, but others are willing to invest larger amounts and ebay sends me a "sorry you did not win" email.
The only new CC transmitter is made by Radio Systems and costs big time money, not the kind of budget Part 15 stations tend to have.
Sure, we'll sit here and tinker with this relic, it might even work again. But CC could very well become a past experience.
Really sorry to hear about that.
Bruce, DOGRADIO
I have really enjoyed the CC experimentation.
Like nothing I have ever done before.
One goofy thing: After a lot of figuring, I realized
that 620 kHz was the very best AM BCB channel.
I could never find a suitable crystal. Then about
a month or two ago, a 620 crystal appeared on E-Bay.
I missed it. I never saw it - didn't know it was there.
Bummer.
Bruce, DOGRADIO
Dear Mister Bruce Dog Radio...
What you must do is visualize a world of tomorrow in which another 620 kHz crystal appears. Be watching for it.
You are the best person here at Part15.us. All the rest of us are just lucky to be here.
Before the 620 kHz "almost got it,"
experience, I had been on 1020 kHz.
Not the greatest channel, but empty
during the day. The other thing was,
my transmitter was only made for the
low end of the AM band. I just barely
got it to work on 1020: by "stretching"
the tuned circuits to go there.
.
Some of you have heard this before,
but some might not have.
I was only running 600 mW into
the AC line. I used a 10 dB attenuator
to help the AC line "matching circuit"
operate in a working fashion. This
isolated the 6 watt 50 ohm output
of the transmitter, and made a match
possible, which successfully transferred
the RF into the AC neutral. I did work.
16 houses down the street, I could hear
my transmission inside a friend's house.
But only on one side of the livingroom
where the AC line entered the house.
(It was a battery powered radio, a Grundig
S-350 (not the 350 DL.) A good signal,
but yeah - with a sensitive receiver.
I don't think my circuit was the
greatest thing in the world - but it worked
to some degree - and the signal did stay
inside the AC line.
So I guess what I'm saying is: a Part 15
100 mW transmitter could be used for
CC - IF one knew how to match it correctly.
My 600 mW into the neutral worked sort of -
with a questionable matching scheme. 100 mW
might go a pretty good distance into a good
matching network for CC. But I think most
CC matching networks want to see 50 ohms.
And most 100 mW Part 15 AM transmitters
want to see a different impedance.
Bruce, DOGRADIO
Nice to hear from you!
I missed your note. We must
have put our last entires in at about
the same time.
I love the way you word things.
Bruce, DOGRADIO
This is not a boat anchor, it's a "dead in the water" LPB2-20 TX carrier current transmitter. So far we only know 3 things:
1.) it doesn't generate a signal;
2.) the LED power light doesn't light;
3.) the two fuses, F1 & F2 are both good.
Let's add a 4th thing:
4.) it worked for a whole year without any problems.
Without having so far done any meter measurements I'm looking at the schematic and wondering, "What could shut down the whole transmitter without blowing a fuse?"
The mystery is actually fun. Yes, the Part 15 way is the best way to live.
What should I check next?
No power to the unit?
The two devices in the carrier current rack are the transmitter itself and a Technics FM tuner, which delivers the audio signal.
The devices plug into a three-way industrial size AC source consisting of a 2-foot extension cord with its own switch and indicator light. The light shows AC presence, and the Technics tuner powers on and off, suggesting the power source is good.
But the final check of the socket serving the LPB needs to be verified.
Thank you. I'll go do it now.
Wondering why DL, the light-emitting-diode power light wasn't lighting, we noted that the light's voltage is delivered by D3, 1N4007, which has scorch marks on the circuit board at both of its leads.
D3 also supplies 15VDC to the exciter board, and if it blew out, there could be a problem on the exciter board.
The scorch marks might have a historic explanation not related to this problem, but it's something to check.
After thinking about it for several days, so as to avoid physical labor, we have a PLAN A to get this CC transmitter back on the air. Or back on the wire, as it were.
YES we suspect D3 as having poofed and believe that maybe two electrolytics on the power supply board should be replaced.
Experience tells us that after 23-years, electrolytics often go bad, sometimes shorting out.
Of course once these parts are removed from the depths of the transmitter enclosure they can be checked with capacitor checker and whatnot, but we can't develop a PLAN B until trying PLAN A.
If we had some holy water we could just dunk it, but we used it all up curing ailments.
The only carrier current transmitter on hand is down for repair, and I'm thinking about finding a backup transmitter so we can stay on the CARRIED CURRENT during these down times.
The only CC transmitter we know about is the pricey one from Radio Systems, but hey... here's the question I have been leading up to for the past 10-minutes...
There are many licensed AM stations that lower power at night to 2-Watts, or 6-Watts, really low.
What kind of low power transmitters are they using?