Long wave part 15 transmitter

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Long wave part 15 transmitter

Does anyone know where I can find a part 15 long wave transmitte? North country Radio had one but it was discontinue.

The Historic Palomar LW Transmitter

Long Wave From the Past

Palomar Engineering, a company that still exists, long ago discontinued their part 15 long wave transmitter, and they no longer respond to inquiries about it.

The unit has shown up rarely on Ebay.

This schematic might make it possible for you to build.

Palomar Legnedary LW Transmitter

Carl Blare

Morse Key Only

Looks like an easy build, but it also looks like a CW transmitter. No voice modulation, unless you are in an experimental mood. 

Darsen the III


Am Modulating...

Instructions for AM modulating are included in the text of the pdf.  It's quite simple to do. 



Part 15 Long Wave

Capt. Kidd asked:  "Does anyone know where I can find a part 15 long wave transmitte? North country Radio had one but it was discontinue."

Check this out:

Looks easy

looks easy enoug. I may have to give i a try. Thanks 

That Mosquito transmitter

That Mosquito transmitter looks nice but it is 1w transmitter if the power is not adjustable the you can not use in the US.  Would be cool to test for a few hrs to see how much range you could get with 1w on am, maybe 6 to 8 miles with a good antenna with a decent amount of height. 

Ongoing History

Several years back a group of us here at part15_us started designing a long wave transmitter on paper, but the poroject got set aside until the day when we pick it up again and continue.

The name of the project is "Deep Voice" and there's even a link to the incomplete work, which I will post here sometime.

2018 looks like a good year to complete that project.

Carl Blare

Mosquito Xmitter

Reply to comment # 7...."That Mosquito transmitter looks nice but it is 1w transmitter if the power is not adjustable the you can not use in the US."

When you look at the ad, it explains that it also will broadcast on the 160M band.  So, it actually IS legal in the U.S.  on some frequencies in that band--you can have 1 watt and approximately a 50' antenna.  However, it would NOT be legal to use it in the 'broadcast' band.  I posted the ad in response to Capt. Kidd's question about a long wave transmitter.  With a proper antenna and grounding sytem on the 160M band, it could have a pretty good range.

Not LW

The spec for the Mosquito show frequencies from 450 kHz to about 2 mHz.

Long wave Part 15 operation is 160 to 190 kHz at 1 watt into a 15 meter antenna

So as stated if you turn down the power it could be used on the AM BCB.

160 meters is an Amateur Radio band from 1.8 to 2 mHz.  Hams can use any antenna and much more than 1 watt.


Charter Member - Association of Low Power Broadcasters

Member Station - ALPB

LF station range

LF band rules

LF band (160-190 kHz) AM is allowed under FCC Part 15.217. It's similar to Part 15.219 we are familiar with in that a DC input power and a maximum antenna length is defined. For 15.217 it's 1 watt to a 15-meter antenna. 

Antenna and intentionally making it lossy

A major parameter driving the antenna design is bandwidth. We need enough bandwidth to pass a 10 kHz or wider signal and this sets our maximum antenna Q as 180kHz/10kHz = 18. The ratio of antenna reactance to system loss can be no higher than 18. Using EZNEC we see that a 15-meter mast having a diameter of 10 cm has a reactance of about 5000 ohms and a radiation resistance of about 0.04 ohms. To achieve a Q of 18, system loss must be 5000/18 = 280 ohms. One might have to add series resistance to get the Q this low. 

Radiated Power

The radiation efficiency of this antenna is 0.04ohms/280ohms x 100% = 0.014%. Contrast this with the 0.25% radiation efficiency of a simple MF Part 15.219 AM BC antenna; the difference is a factor of 18, meaning 1 watt into the LF antenna radiates a signal like 0.056 watts into the MF antenna. 


So far it looks like our LF range would be similar to our MF range. But given the higher ambient RF noise level on the LF band our range could be much less. The graph at the link below (curve C) shows approximately 25 dB higher ambient noise. If we need 500uV/m at MF to have a useful signal we need 25 dB above 500uV/m at LF. This is about 10 mV/m and in the far-field the corresponding magnetic field is about 30uA/m. For average ground, and 1 watt to this antenna, EZNEC shows 30uA/m at a range of 50 meters. This analysis assumes the same antenna factor at LF and MF, which might not be the case.!!PDF-E...

My interests are antennas, transmitters, studio equipment, and setting up a useful Part 15 AM radio station. 

Talking Low Band

Very excellent workup, daveC.

If my previous studies are correct, the U.S. has never used long wave for broadcasting but has used it for aviation related use, which may still be true on some frequencies.

There's also (I think) experimental HAM on some frequencies.

It has been used for carrier current baby monitors and 2-way intercoms, but with lower power than the AM band carrier current rule.

It is used for carrier current power utility communications for the power industry.

Long wave has been a very strong broadcasting service in Europe using 9 kHz channel spacing, but in the U.S. since no standard exists one may use either 10 kHz or 9 kHz channels (so I think I was told by someone).

I have a CFL light bulb that seriously dominates the LW band so I only use that bulb on rare occasions.

Carl Blare

Mosquito Xmitter

This is a reference to what can be used in the U.S. on the Mosquito 1 Watt Am transmitter.

"A LowFER is a low frequency radio propagation beacon (or occasionally other type of station), run by a hobbyist under FCC Part 15 rules. The word is an acronym of Low Frequency Experimental Radio.

Unlicensed LowFER operation is allowed in the frequency range 160 - 190 kHz, the so called 1750 meters band.  In this frequncy range transmitters may not use antennas longer than fifty feet (including any transmission line between the transmitter and the antenna). RF stage input power is restricted to a maximum of 1 W. Due to these restrictions, LowFER transmitters are usually located at the base (feeding and grounding point) of a vertical antenna.

LowFERs usualy transmit morse code telegraphy, slow speed telegraphy and various digital modes. Speech transmission (AM or SSB) is also allowed but seldomly used.

Most of the tranmitting equipment for the LowFER band is homemade, but commercial equipment becomes available occasionally.

Even with such limited stations, LowFER stations have been received at distances approaching 1000 miles by listeners using sophisticated receiving setups at electrically quiet locations."

Again, I only mentioned this in answer to the orginal question by Capt. Kidd about a long wave transmitter.

Another reference:
LOWFERs sometimes use Morse

LOWFERs sometimes use Morse code at around 1/2000 word per minute. It can take 30 minutes to send a callsign and the signal is observed on a waterfall display. The receiver setup consists of a very stable receiver, a PC, and some free software. The receiver bandwidth is 0.01 Hz, giving LOWFERs a 1,000,000-to-1 advantage over a 10 kHz AM signal. 

Adding a top hat to the 50 ft antenna can potentially quadruple the radiation resistance and reduce the antenna reactance. While maintaining the Q-of-18 needed to pass an AM signal we might aim for a 10X radiation efficiency improvement and 3X range improvement. 

I recall reading somewhere that the first SSB transmission was performed at 50 kHz with the limited antenna bandwidth being used to attenuate one of the two sidebands. 

My interests are antennas, transmitters, studio equipment, and setting up a useful Part 15 AM radio station. 

A correction on the LOWFER

A correction on the LOWFER Morse code speed: it's around 1/2000 word per second and that is about 1/30 word per minute. The bandwidth is closer to 0.03 Hz. 



My interests are antennas, transmitters, studio equipment, and setting up a useful Part 15 AM radio station. 

A Lot for a Little

Setting up a 50-foot tower with industrial sized loading coil requires a lot of effort for a station that wants the little result described above for an AM modulated Long Wave signal.

Yet it's in the plans so KDX can say we are one of America's only Long Wave radio stations.

Trouble is, if I really do it, it will be harder to convincew people I'm not crazy.

Carl Blare

Carl, your LF BC station

Carl, your LF BC station project sounds like fun and I'll help out if you'd like.

It shouldn't be very difficult to get a proper antenna installed. The 50' antenna can take many forms. A standard 43' amateur self-supporting aluminum mast with a CB whip, or HamTenna, on the top, will work. Or, a ground lead up the side of a building with the remainder of the antenna being a guyed TV mast would also work. A third option is an inverted-L. The antenna goes vertical for some distance and then horizontal; like 25' up and 25' out. A shorter antenna can be made to work with the tradeoff being reduced range. With the series broadbanding resistance, the antenna impedance will be high (around 300 ohms) and the transmitter needs to be designed for this, or a matching network can be inserted between the transmitter and the antenna. 

The loading coil does not have to be a big, loss-loss type used by the LOWFER guys. Because we need loss to broadband the antenna the loading coil can probably use #22 or thinner wire. I can work out the details (loss, size, etc.) if you'd like. An example of an air-wound 5mH coil is  600 turns of #22 bell wire close-wound on a 4" PVC pipe. The coil dimensions are 3" x 13". The ground system need not be low loss and a ground rod will do the job. 


My interests are antennas, transmitters, studio equipment, and setting up a useful Part 15 AM radio station. 

Upcoming Plans

Great, davec! Thank you for the offer to help with the build of a part 15 LW transmitting system.

The inverted-L sounds interesting. Is it directional and if so what determines its direction?

I'll check around town for a HAM antenna installer, a professional 25' vertical tower might go better with picky neighbors.

I've built some coils for MW and enjoy doing that.

Also this year I want to arrive at a way of running 100' cables back to a 3-meter antenna for 1680 kHz AM.

I want the MW antenna to be as far from the building as possible for the fun of receiving the station from a distance.

The 25' tower could be attached to a building wall, which probably would dictate which direction the horizontal wire would be hung.

Carl Blare

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