HF – Page 7 – Engineering Radio

Radio Before Broadcasting

Before anyone ever though to click a mouse and play the latest Ke$ha “song,” or spin Stairway to Heaven for the millionth time, radio was used for a different purpose. Early radio was developed to transmit messages between ship and shore or between continents. Radio apparatus consisted of spark gap transmitters, which were very simple devices only suitable for sending Morse code. Some did experiment with voice modulation methods, but the quality was poor. It was not until Lee Deforest developed the vacuum tube that the state of the electronics art was capable of transmitting voice and music.

ATT developed AM (amplitude modulation) for point to point long distance service over high frequency radio circuit. This is how early inter continental long distance phone service was first established. In fact, up until the early 1970’s much of the long distance telephone traffic was routed via high frequency stations like WOO, WOM and KMI to Europe and Asia. It was this development that allowed Ham Radio operators to begin transmitting music and other programming to their neighbors and the idea of broadcasting was born.

The Coastal Radio stations that for years transmitted and received messages from ships and sea, transmitted navigation warnings, weather broadcasts, news and responded to distress calls have all but faded away. The operators of those stations often become nostalgic with the memory of sitting in a small room late at night straining to hear what might be faint SOS call under all the other chirping CW notes. Successfully “working” a distress call is considered the pinnacle of a shore operator’s career. High Frequency Continuous Wave (HF CW)(Continuous Wave is the technical description of Morse code modulation) has several distinct advantages for distress work. A small signal can travel long distances and still be well received. The average life boat CW transmitter had 5 watt output and often they could be heard across an ocean, 1,000 miles away.

I put together a few lists of these Coastal (ship to shore) radio stations. The first are commercial public stations, these were responsible for sending message traffic to and from ships at sea. They often had other purposes like transmitting signals point to point or High Seas Telephone service. High Seas Telephone is just the way it sounds, persons on board a vessel at sea could place a telephone call. It was hugely expensive and was replaced by INMARSAT, which is only moderately expensive.

Call Sign	Location	Owner	Services	Notes
KFS	Palo Alto, CA	Federal Telegraph/ITT	Coastal	Sold to globe wireless, ceased operation 7/12/1999
KPH, KET (point to point)	Pt. Reyes, CA	RCA/MCI	Coastal, point to point	Sold to globe wireless ceased operation 7/1/1997
KLB	Seattle, WA	ShipComm, LLC	Coastal	In service
KMI	Dixon, CA	ATT	Coastal, High seas phone service	Ceased operation 10/8/1999
KSM	Pt. Reyes, CA	MRHS	Coastal	In service
WBL	Buffalo, NY	RCA	Coastal (Great Lakes)	Ceased operation 1984
WNU	Slidell, LA		Coastal	Sold to globe wireless ceased operation 7/12/1999
WLC	Rogers City, MI	United States Steel	Coastal (Great Lakes)	Ceased operation 1997
WCC	Chathem, MA	RCA/MCI	Coastal	Sold to globe wireless ceased operation 1997
WLO	Mobile, AL	ShipComm, LLC	Coastal, (oil rigs)	In service
WOO, WDT (point to point)	Toms River/Ocean Gate, NJ	ATT	Coastal, High Seas and point to point	Ceased operation 10/8/1999
WOM	Pennsuco, FL	ATT	Coastal, high seas phone service	Ceased operation 10/8/1999
WSC	Tuckerton, NJ	RCA/MCI	Coastal	Ceased operation 1978
WSL	Brentwood, Sayville, Southhampton, Amagansett, NY	Federal Telegraph/ITT	Coastal, point to point	Ceased operation 1984

This is by no means an inclusive list as at one time there were hundreds of these stations licensed to the US. There were many inland stations on the Great Lakes and rivers. These are the most common ones that I’ve heard, heard of and or seen personally.

KPH

Most people mark the end of commercial Morse Code as July 13, 1999. There is, however, one station, KSM, which still is open as a public coastal station. That station is a part of the Maritime Radio Historical Society, which operates from the former KPH facilities in Pt. Reyes, California. KPH suspended operations in July, 1997 while other station continued on for the next two years.

Mercury Vapor Rectifiers from PW-15 transmitter, courtesy of MRHS

Press Wireless was a company used by newspapers to transmit articles and pictures. They developed their own transmitters and operated point to point sites in Hicksville, NY and San Francisco, CA. A few of their transmitters survive today at KPH.

RCA H series HF transmitter, courtesy of MRHS

The 1950s H and K RCA HF transmitters were built to last. The carrier power is 10 KW and can be used for CW, SSB, and RTTY.

KPH is the best preserved Coastal Station, when the facility closed down in 1997, the US Park Service took ownership and left it mostly untouched. In 2004 volunteers and former station employees began to restore the equipment to operation. Eventually, these efforts led to the licensure of KSM, the only operating commercial CW station in the US. KSM uses restored donated equipment from KPH and KFS. Restoration work continues and if I lived closer, I’d volunteer my services. MRHS also operates amateur radio station K6KPH.

WOO

Other facilities survive in parts, the former WOO is home to the Tesla Radio Foundation and Museum. Anyone that knows anything about radio will recognize Tesla as one of the founding fathers, perhaps much more so than Marconi, who often gets more credit than is due. During it’s day, this was a huge facility, connecting North America with Europe, Africa, South America and Asia. Point to Point service included programming relays for the VOA, Long Distance phone service and so on.

WOO transmitter floor, courtesy of Tesla Foundation

ATT seemed to use the same design for their HF sites, the buildings at KMI, WOO and WOM all look alike, right down to the brown/yellow tile floors.

WOO transmitter, courtesy of Tesla Foundation — WOO (PW-15 ?) transmitter, courtesy of Tesla Foundation

Again, this facility was restored through the hard work of Radio Amateurs. Unfortunately, unlike KPH, the old CW transmitters where scavenged for parts and none where restorable.

All of the transmitters were routed to this antenna switching matrix. As you can plainly see, there were many, many antennas at this facility. There were also several types, rhombics, verticals, inverted cones, etc. They were (some still are) located in a tidal swamp. From this matrix, with a few exceptions, the transmission lines were routed through BALUNs which then fed open wire transmission lines.

These lines went to various antenna fields pointed at Europe, South America, Asia and Africa.

WCC

The former WCC receiver site is now home to the Chatham Marconi Maritime Center and has the amateur radio call sign WA1WCC. This is a museum that is open to public. The town of Chatham, with donations from Qualcomm and Verizon, has endeavoured rehabilitate the old receiver site and operations building. They have spent a fair sum of money on replacing plumbing, fixing the driveway and other necessary work to turn the site into a historical attraction and provide a center for Science, Technology, Engineering, and Mathematics (STEM) on Cape Cod.

WCC transmitting antenna, South Chatham, MA courtesy MHRS

We used to go to the public beach right next to this radio tower. It looks like a Milliken tower similar to WICC ‘s towers in Bridgeport. I believe the transmitter site in South Chatham was bulldozed and turned into a wild life refuge.

WLO and KLB are in service with HF voice and SITOR, PACTOR and AMTOR modes but not CW. These stations are operated by ShipCom, LLC.

Coast Guard Maritime Radio

The US Coast Guard operated a network of Coastal Radio stations as well. These where to communicate with Coast Guard vessels and aircraft but also interfaced with civilian shipping. They stretched up and down the east and west coasts, covered Alaska, Hawaii and territories like Puerto Rico and Guam. They ceased CW operations in 1995 and are remotely operated by the two surviving stations, NMC at Pt. Reyes and NMN in Portsmouth, VA.

Call Sign	Location	Services	CW close date	Disposition
NMA	Miami, FL	Limited Coastal, Military	1/4/1995	Remoted to NMN Portsmouth, VA
NMC	Pt. Reyes, CA	Limited Coastal, Military	1/4/1995	In service GMDSS
NMF	Boston, MA	Limited Coastal, Military	1/4/1995	Remoted to NMN, Portsmouth, VA
NMG	New Orleans, LA	Limited Coastal, Military	1/4/1995	Remoted to NMN, Portsmouth, VA
NMO	Honolulu, HI	Limited Coastal, Military, Point to Point	1/4/1995	Remoted to NMC, Pt. Reyes, CA
NMQ	Long Beach, CA	Limited Coastal, Military	1980	Closed
NMN	Portsmouth, VA	Limited Coastal, Military	1/4/1995	In service GMDSS
NMP	Chicago, IL	Limited Coastal, Military	1975	Closed
NMR	San Juan, PR	Limited Coastal, Military	1986	Closed
NOJ	Kodiak, AK	Coastal, Military, Point to point	1/4/1995	In service, GMDSS
NRT	Yokota, JP	Point to point	N/A	Closed 1992
NRV	Barrigada, GU	Coastal, Military, Point to point	1993	Remoted to NMO in 1992, then to NMC in 1995

This is by no means a complete list, there are several more stations that existed but were closed by the mid 1970’s.

GMDSS is the Global Maritime Distress and Safety System, an automated system consisting of satellites and HF radio that replaced the use of manned listening watches on ship and shore. A few years ago, the Coast Guard explored eliminating HF services all together, however the public outcry was loud and vigorous, thus they didn’t carry through with the plan. Even so, the voice weather and navigation broadcasts are computer generated simulated human voices, which are not a good as the real thing, in this former operator’s humble opinion.

Unlike their civilian counterparts, most of these stations where disposed of without ceremony when they were turned off. Some former Coast Guard Radio Stations were sold off for land, others which were part of existing bases, were dismantled. The only exception to this is the remnant of NMY (New York) on fire island, now administered by the National Parks Service.

There are a fair number of former Coast Guard radio operators with fond memories of working at these places and the satisfaction of a job well done.

If you are interested in history, check out those sites and or pay them a visit if in the neighborhood. You may learn something you didn’t know before.

Continental Shortwave Transmitters

I started my radio career working in HF radio, albeit somewhat different than broadcasting. I enjoy the long distance aspect of HF communications and there is something about the high power shortwave (HF) rigs that interest me. This is a video of a Continental 418E HF transmitter. The carrier power is 100 KW capable of 100% modulation, when means peak output power is 400 KW. This particular model has a solid state modulator, which is in the cage where the guy is walking around. From the video, it would appear they had several blown fuses in the modulator section. The fuses protect the individual IGBTs in the modulator.

This is an older transmitter that is getting upgraded to a 418F. The heavy cable is the connection between the solid state modulator and the RF final section. Depending on modulations levels, it carries around 33 KV.

From the Continental Electronics website that details the SSM unit:

The modulator consists of 48 series connected modules which are switched on or off to provide the high voltage DC and the superimposed high level audio voltage. The switching is accomplished with Insulated Gate Bipolar Transistors (IGBT). A low pass filter follows the series connected modules which removes the switching signals and allows the DC and audio signals to pass to the RF amplifier. Because each of the modules is either in full conduction with very low loss, or turned off, again with very low loss, the overall modulator efficiency is in excess of 97%.

A full description of the SSM is on the Continental Electronics SSM website. It is an interesting read, including the description of the 12 phase transformer setup.

Finally, a video of the VOA transmitter site in Greenville, NC.

This is part 4 of 5, if one wanted to, one could click through to Youtube and watch the rest of them. The VOA stuff is, as the transmitter engineer notes, 1950’s technology. No solid state modulators in these rigs. Those are some old transmitters, still in service and likely to remain that way until the VOA closes that site down, some point in the future.

Like their FM counterparts, Continental HF transmitters are the gold standard when it comes to high power tube transmitters. Sadly, they no longer make transmitters for Standard Broadcast (AM MW).

The K9AY receiving loop antenna

Not to take anything away from Gary Breed, K9AY, who makes and sells these things under the corporate name AYTechnologies, I decided to make my own K9AY antenna system and controller. Basically, after looking at the currently available commercial version, I figured I could make a better unit for less money and be happy.

The basis for the K9AY antenna is that it has a steerable null. The gain around the antenna is close to unity, except for the terminated side of the loop, which has a deep null. This can be switched around using a combination of relays that change the loops and termination. This comes in very handy for MW and SW listening, when co-channel stations can create annoying interference and hetrodynes. I have had good success pulling many stations out of the muck, especially in the AM band using this antenna.

This antenna requires a good ground to work against. For optimum installations, I would recommend placing two radials under each side of the loops. This will keep the ground conductivity below the antenna fairly constant, thus the value of Rterm will remain consistent for each band.

My other idea is to add a preamp right at the antenna to overcome transmission line loss and the loss from a 4 port passive receiver coupler. Something around 10 dB, low noise (obviously), low parts count and rugged. I decided that a Norton preamp was a good design, with only one active device, a common 2N5109 BJT. Most of the time, this preamp is switched off and out of the circuit. There have been several occasions, however, where an extra 10 dB made the difference between no copy and good copy.

This is the schematic of the relay board and preamp combined:

The parts list is as follows:

Symbol	Part	Symbol	Part
C1 – C5	Ceramic 0.1 uf capacitor	R1	2 Kohm ¼ watt
FB-1	Ferrite bead, Amidon FB-43-101	R2	8.2 Kohm ¼ watt
K1 – K3	Omron G6K-2F-Y small signal relay	R3	100 ohm ¼ watt
L1	22 uH ¼ watt	R4	51 ohm ¼ watt
L2	100 uH ¼ watt	T-1	9:1 balun
Q1	2N5109 w/heat sink	T-2	Norton feedback trans

The 2N5109 transistor is a CATV unit and it has a 50 input and output, that reduces the number of impedance transformers required. The value of Rterm is determined by which band one wants to operate on. I used Omron G6K series low signal relays. Again, because this is a receive only antenna, those relays will work well.

Terminal board connections, TB1:

Terminal	Use
1	SW loop
2	SE loop
3	NW loop
4	NE loop

Wire loops go between Terminals 1-4 and 2-3.

Control terminal board connections, TB2:

Terminal	Use
1	Preamp power
2	Rterm
3	Rterm ground
4	Ground
5	Relay 2
6	Relay 3

To create a low noise preamp, I decided to use surface mount devices and to try and make all the traces as close to 50 ohm impedance as possible. I created this SMT printed circuit board:

From this, I ordered 6 boards from PCB express:

This is the board with all passive components installed:

This is the board completed:

My current K9AY is an amalgamation of parts removed from various equipment. The relays are large, 12 VDC units which do not have the best contacts. It works well enough, but I’d love to get one of these units into the control box at the base of the antenna. Unfortunately, my antenna field is still in about 18 inches of snow, so it will have to wait until some of the snow melts off.

I would position this antenna as far away from transmit antennas as possible to avoid overloading the preamp and or causing problems with the switching relays. For the average amateur set up, 75 to 100 feet separation should be more than enough.

ABC turns to HF during tropical Cyclone

Super Tropical Cyclone Yasi, a category 5 storm, came ashore this morning between Cairns (pronounced Cans) and Townsville, Queensland around midnight Thursday (9 am Wednesday, NY time).

Radio Australia carried Australian Broadcasting Company (ABC) Queensland coverage of the storm, which was extraordinary. Spot coverage, emergency information, sheltering information, updates and calls from listeners in the midst of the storm. Some of it is pretty intense. One fellow, John, out in the country all by himself in the height of the storm sounded somewhat forlorn, I hope he makes it.

Due to the size of the storm, wide spread power outages are expected and may last for weeks or months. As a part of this, there are numerous outages and potential outages in their AM and FM broadcasting chain. To that end, ABC has two shortwave frequencies available for their Queensland service; daytime (8 am to 8:30 pm local time, 2100 – 0830 GMT) on 9710 KHz and night time (8:30pm to 8 am local, 0830 – 2100 GMT) is 6080 KHz.

Once again, HF (shortwave) radio gets the job done when local stations, cell towers, and internet connections to dead. Sometimes it is the low tech answer.