There was an interest expressed for tube based carrier current transmitters. This is a simple CC transmitter from Popular Electronics circa 1973. Also available as a PDF FILE.
Not the one I was searching for but similar.
There was an interest expressed for tube based carrier current transmitters. This is a simple CC transmitter from Popular Electronics circa 1973. Also available as a PDF FILE.
Not the one I was searching for but similar.
All You Need
Five-Watts is a lot of power for CC from the home, in my newly acquired opinion.
I am running 2-Watts carrier current and it seems to be “topped off” to the point where any more power would overload most radios.
Doggradio2 is running 6-Watts but throwing most of it away in an attenuator but still getting strong coverage.
This 5-Watter could put some more people in business.
Reduced Power
Per the article, sounds like the power can be adjusted somewhat in the tuneup. And some modification may be required regarding the coupling method.
Those low power, low frequency FM wireless (read CC)intercoms cover a fairly good sized building proving you don’t need much.
Blast from the Past
Nice post, thanks.
While in college, I was involved with the campus carrier current operation (it was a student fee sponsored activity) but we had little money for equipment. My room mate and I copied and modified a 25 watt tube AM design from an ARRL handbook for use as a CC transmitter in one of the dorms. It would tune to 25 watts input and at this power it covered the dorm nicely.
I was the “Chief Engineer” for the station and kept the many distributed dorm transmitters tuned and operating properly, however, since I was on a co-op program I was absent for alternating three month periods. When there were problems, the station administrator (a non technical type) would try to fix things himself rather than call me for help. I once received a call from the licensed campus FM station where they told me that they were receiving interference complaints from listeners who confused the CC AM identification with theirs which resulted from the Admin tweaking the transmitters with his “golden screwdriver”. After this it took a while to regain our good relationship with the FM station.
I resigned my post over a problem with the faculty adviser. The phone lines to the remotes were driven by a push-pull tube audio amplifier which was housed in the distribution patch rack. While troubleshooting bad audio I found one of the output tubes was dead and I removed the amp to replace this and for a general check out. The advisor entered the studio and saw this and chewed me for taking the station off air. He wouldn’t accept that the signal was not listenable and this had to be done since we were effectively off the air anyway. From a conversation with him regarding my role at the station I concluded that I could not continue to function in that environment so I left.
A few years later I learned that after I left some “genius” decided that it would be a good idea to string a wire between the lamp posts at the stadium and use it as an antenna with it directly attached to the 25 Watt transmitter. The signal was heard at a FCC monitoring station and the FCC shut the station down for a year while they got their act technical act together.
Fortunately, the station returned under new management and became a viable operation which continued for many years.
Whats the old say that goes something like “I am the engineer on the train, I can only ring the bell. But when something else goes wrong, guess who catches hell.” or something like that.
Neil
How Did That Happen?
I put a reply to Neil Radio8z’s management blog, but my post seems to be way up the column (Titled: It’s Management)
That’s different from the way it worked in the past.
Studied
Printed and studied the PDF regarding the 5-Watt CC Transmitter and am fascinated by the straight approach to coupling with the AC.
This design only feeds one of the 110-VAC branches, whereas the professional couplers feed both legs of a 220-VAC line.
There is no way to monitor or tune the SWR (Standing Wave Ratio) either, but that’s also true of the CC intercoms, which work anyway.
Under the guidance of RFB this 5-Watter could feed the neutral line, requiring the planting of one new ground rod outdoors.
Guidance By Combining
“Under the guidance of RFB this 5-Watter could feed the neutral line, requiring the planting of one new ground rod outdoors.”
Construct a low pass filter to match the output tank of the final to a 50 ohm output and then connect up to a coupler such as the TCU-30 or CP-15, or even Bruce’s “Air Toroid Coupler”.
Perhaps placing a rheostat at grid 2 (screen pin 6) to vary the B+ of 250VDC by half should give some power adjustment ability.
RFB
It’s Management
Wow does that story of mismanagement ring a few bells.
Having also had a back ground working for many “masters” I can boil it down to two kinds:
One, managers who fully realize they need someone who knows the score and thus ends up with a well oiled machine, or, two, the managers who think they know something or discount what the expert knows, and ends up with a leaking ship.
We might suppose that the whole of our technical world is failing and succeeding precisely because of the worldwide effect of the two types of management.
I bet that in this age of down-sized radio stations, there will be more and more licensed stations sinking in the sunset because of poor management.
1973?
This makes me feel old – I remember this article. I also remember one using a 6C4 and 5763 final that I modified for non-CC use, but that’s another story.