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Post by Admin on Jan 5, 2018 18:49:39 GMT
FROM: Tim Reed January 5 at 12:19pm Radio Systems TR-20 Carrier-Current AM transmitter. 20 watts $485 - Van Wert, OH Radio Systems TR-20 carrier-current transmitter. Adjustable to 20 watts max. output. SO-239 output connector. CAVEATS: Unit was operational when removed from service, but has been in storage for several years. Chassis has some blemishes and could use a cleaning inside and out (canned air would do wonders). I would count on at least re-capping it and spraying the pots, so I am NOT going to guarantee it will be usable out of the box. It may very well be, but I have no way to test it. Selling AS-IS - no returns. However, these transmitters are easy to work on, all the ICs are in sockets, and Radio Systems is still in business. Complete manual of instructions, adjustments, full schematics, and parts list is at: www.radiosystems.com/Manuals/TR-20TransmitterManual.pdf Unit is on 530 KHz. If you want to put it on another frequency, quartslab.com makes crystals (and RS may have them in stock). The TR-20 crystal frequency is 4X the operating frequency. Mike Patton & Associates also makes a synthesizer board that replaces the crystal entirely. Link to Facebook Post: CC TX for sale
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Post by thelegacy on Jan 5, 2018 19:57:42 GMT
If only I were sighted and able to afford this thing Today it would be in my possession. Especially the connector it has. The variable wattage a definite plus. I'll have to watch for these deals when I do get money and hopefully someone who is an electrician.
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Post by Admin on Jan 5, 2018 23:08:35 GMT
It's a little pricey. When I bought mine the guy was selling several and the price was about half.
The coupler I later found cost almost as much as the transmitter.
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Post by part15engineer on Jan 6, 2018 1:01:48 GMT
yes a little over priced. maybe worth $200 shipped conus.
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Post by thelegacy on Jan 6, 2018 5:15:53 GMT
Hook it to an antenna and start off at 0 and slowly turn it up to what is needed however overpriced for that. You know since the Rangemaster is 50 ohm you could connect that into an amp, coupler and be on your way too. AM Amps do come from Greece so that is something that will work for the Rangemaster and the ASPISYS.
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Post by jimhenry2000 on Jan 6, 2018 6:20:13 GMT
Are carrier current transmitters covered under Part 15? If so what is the maximum power permitted?
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Post by Boomer on Jan 6, 2018 14:00:19 GMT
They are under Part-15, and go by field strength that's found away from the lines that the signal is being carried on. Fortunately as an inductive method of broadcasting, the signals decrease rapidly away from the lines, and come up very fast as you get near.
If carrier current is being done right, that's the way it should be.
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Deleted
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Post by Deleted on Jan 6, 2018 15:40:51 GMT
Carrier Current on the AM Band
15.221 Operation in the band 525-1705 kHz.
(a) Carrier current systems and transmitters employing a leaky coaxial
cable as the radiating antenna may operate in the band 525-1705 kHz
provided the field strength levels of the radiated emissions do not
exceed 15 uV/m, as measured at a distance of 47,715/(frequency in kHz)
meters (equivalent to Lambda/2Pi) from the electric power line or the
coaxial cable, respectively. The field strength levels of emissions
outside this band shall not exceed the general radiated emission limits
in § 15.209.
(b) As an alternative to the provisions in paragraph (a) of this
section, intentional radiators used for the operation of an AM
broadcast station on a college or university campus or on the campus of
any other education institution may comply with the following:
(1) On the campus, the field strength of emissions appearing outside of
this frequency band shall not exceed the general radiated emission
limits shown in § 15.209 as measured from the radiating source. There is
no limit on the field strength of emissions appearing within this
frequency band, except that the provisions of § 15.5 continue to comply.
(2) At the perimeter of the campus, the field strength of any
emissions, including those within the frequency band 525-1705 kHz,
shall not exceed the general radiated emission in § 15.209.
(3) The conducted limits specified in § 15.207 apply to the radio
frequency voltage on the public utility power lines outside of the
campus. Due to the large number of radio frequency devices which may be
used on the campus, contributing to the conducted emissions, as an
alternative to measuring conducted emissions outside of the campus, it
is acceptable to demonstrate compliance with this provision by
measuring each individual intentional radiator employed in the system
at the point where it connects to the AC power lines.
(c) A grant of equipment authorization is not required for intentional
radiators operated under the provisions of this section. In lieu
thereof, the intentional radiator shall be verified for compliance with
the regulations in accordance with subpart J of part 2 of this chapter.
This data shall be kept on file at the location of the studio, office
or control room associated with the transmitting equipment. In some
cases, this may correspond to the location of the transmitting
equipment.
(d) For the band 535-1705 kHz, the frequency of operation shall be
chosen such that operation is not within the protected field strength
contours of licensed AM stations.
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Deleted
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Post by Deleted on Jan 6, 2018 15:51:58 GMT
Carrier Current Lore
The question: "...what is the maximum power permitted?"
The answer: It depends.
The strongest CC transmitter produced by the one time leader in the field, LPB Inc., was 50-Watts.
50-Watts is anecdotally the maximum transmitter power, although I've yet to see this in the rules, but the measurement requirements described in the rules require adjusting the power so as not to exceed field strength at certain distances from the power lines. That's why CC transmitter power is adjustable within the unit.
Large dormitory or industrial buildings might require larger powers to permeate the wiring in a large structure, but more ordinary applications usually require from 5 to 20-Watts.
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