Diplexed Directional AM stations

Pictures and story sent along by occasional reader John.  I worked on diplexing an AM station in 2003, it was a 5 KW and a 10 KW on a single tower.  Those power levels require using some pretty large components, however, the set up was pretty straight forward.  Each station had it’s own ATU (antenna tuning unit) which was then fed into band pass filters to isolate the other station and coupled to the tower.  The ATUs were set up as low pass and high pass filters respective to their frequency.  The whole thing had something like 45 dB isolation, which worked(s) very well.

Doing this with a directional antenna system is another problem altogether.  Add to that the tight filter networks required as the station are only 100 KHz apart.  One saving grace, the power levels are relatively low.  The higher the power gets, the more the magnetic fields build up around the coils and mutual coupling becomes an issue.

As John notes:

1560 (WGLB) owns the site and has been there for about 8 years. Originally WGLB was in Port Washington, WI with a BTA-250M running into a 2-tower array. The city of license was changed to Elm Grove, and this necessitated a move about 30 miles south to the site shown. A 6 tower combination array was needed to protect 1550 in Lake Geneva, WI, 1550 in Madison, WI, 1550 in Morris, IL, 1540 in Hartford, WI, 1570 in Appleton, WI, 1530 in Cambpellsport, WI and 1530 in Elmhurst, IL. A 4-tower in-line array is used on 1560 during daytime, and a 4-tower parallelogram with the two south towers switched in and the North two in-line towers switched out (floated) for 1560 nighttime operation.

WGLB WJTI combined directional antenna system
WGLB WJTI combined directional antenna system

Looks interesting.  Fortunately the towers are not required to be painted or lighted, that is a big maintenance headache.

WGLB WJTI antenna field
WGLB WJTI antenna field

Another thing to note; the site looks well maintained, the grass is mowed, no trees growing up by the transmitter building, the building is painted, etc.  Likely these stations are locally owned and making a modest profit, not some abandoned after thought.

Antenna Tuning Units
Antenna Tuning Units

Each tower has separate ATU’s for each station.  The ATU’s then feed what is likely a very tight band pass filter for each station, which then combines the two signal and feeds the tower.  John continues:

An arrangement was designed when 1460 approached 1560 about leasing tower space for moving 1460 (ND-D) from Racine, WI north to West Allis, WI. This design is ingenious in that the array tower usage between the two stations is reversed for day-night operation! In other words, the 4-tower in-line array is used for 1460 nighttime, and the 4-tower parallelogram array consisting of the four south towers is used for 1460 daytime operation.

WJTI Phasetek antenna phasor
WJTI Phasetek antenna phasor

The 1460 pattern is pretty tight to protect 1470 at West Bend, WI approximately 30 miles north, and nighttime also to protect 1460 in DesMoines, IA. The friendly folks at Phasetek (Quakertown, PA) did the 1460 phasor and notch traps at each tower to prevent cross-modulation (inter-modulation) of the two signals feeding the towers, and after assembly on-site tuned up like a dream!

And that is saying something.  I have dealt with phasor manufactures before, sometimes they nail it, sometimes they don’t.  Tune up can be a real challenge, which tends to put everyone on edge.

I might add that the high-tension electrical transmission towers nearby were de-tuned at 1560 years ago, and upon checking were broad enough to not require any further de-tuning at 1460! Another attribute of this design is that if something ever changes in the future, the deal can be easily be dissolved, because there is no mutual ownership of any equipment on site! It is truly one of the best “Win-Win” instances of AM station directional antenna combining I have ever seen!

It is good to see stations taking advantage of co-location these days.  It is a great way to save money on real estate and hassles with the zoning boards, who all see dollar signs when someone talks of putting up a tower.  With the amount of computing power and the lessons learned in the past 90 years or so, we are beginning to get this medium wave broadcasting thing down.

The first radio station licensed to Albany, NY

Although not the first station in the area, that honor goes to WGY. In fact, RPI licensed WHAZ in 1923, which makes it the second regional station.  Starting on 1430 Khz as WOKO in New York City in 1923, the station made a few stops along the way.  One of those was on Mt. Beacon from 1928 until 1930.  The original transmitter building is still there, although the tower was taken down in 2005 to make way for the DTV stations that moved in.    I always wondered why an FM tower on the top of a mountain had a base insulator.

WDDY towers
WDDY towers, Bethlehem, NY

In 1930, WOKO was sold and moved to Albany, NY, becoming the first station licensed to that city.  The transmitter site is located off of Kenwood Avenue in the town of Bethlehem, about 4 miles south of down town Albany.  It first signed on with 1 KW, increasing to 5 KW in 1947.   This is the original transmitter site, but the towers were redone in the mid 1970’s.  The towers themselves are 130 electrical degrees (235 feet) tall.  Like all AM stations, for years it serviced the community until it was gradually reduced to a satellite repeater, now owned by Disney.

WDDY transmitter site
WDDY transmitter site

The original transmitter building is in the back, the front was added in the 1970’s when the studios and offices colocated with the transmitter.  Prior to that, they were in downtown Albany.

Nautel XR6 Medium wave broadcast transmitter
Nautel XR6 medium wave broadcast transmitter

The Harris BC5H transmitter was replaced with a Nautel in 2006.  The Harris AM H series transmitter has a pair of transistors on the audio driver board which were unique to that transmitter and no longer manufactured.  There are no equivalent replacement part.  Once those transistors fail, the transmitter is done.

I really think that AM could make a comeback, but the following conditions need to be met:

  1. Kill AM HD radio.  Kill it dead.
  2. Cut away the dead wood.  Those stations that are not making money, have not made money and have no hope of ever turning a profit again.  Most of these are owned by large consolidator that cannot yet afford to write off the bad investment.  More and more will be spun off and given to MMTC and others.  If they can make a go of it, good.  If not, then the stations will go dark and eventually surrender their licenses.  We have one like that around here that basically turns it’s transmitter on one day a year to avoid license forfeiture.  That should stop, either they use it or loose it.
  3. FM radio will continue to be the investment bank darling, in spite of lower and lower listeners and revenue.  This will lead to more and more translators, HD radio, LPFM and other things being shoe horned into an already crowed band, creating AM like conditions on the FM band.
  4. Those that can take on the challenge of an AM station should immediately begin looking at reducing maintenance costs.  Directional antennas are money holes, if at all possible, get rid of the DA in favor of single tower closer to town.  Diplexing with another AM is a great way to save money and the costs of building a new tower.  Using a taller tower, up to 190 electrical degrees, will daytime signal and reduce the radiation angle (vertical) of the tower, thus permitting better PSSA, PSRA and or night time operation.
  5. Local programming.  Local sports, local politicians, local bands, local church services, local events, etc.  Local.

But anyway…

Where will they put a radio station this time

In the time that I have been working as a broadcast engineer, I have seen some pretty unique transmitter sites. The aforementioned power plant, with the antenna mounted on a smoke stack. The more traditional AM station, located in a swamp. Other stations both AM and FM combined into one antenna, etc.

WGDJ AM transmitter site
WGDJ AM transmitter site

This is WGDJ, 1300 KHz, Albany, NY.  It is located in what might be a swamp, if we were not experiencing marginal drought conditions this summer.  The transmitter is located along route 9J.  It is a four tower directional daytime, 10 KW and a six tower directional night time, 5 KW.  Nothing spectacular, 90 degree towers, spaced 90 degrees apart.  Since they are below 200 feet, they don’t need to be lit or painted, which is nice.

WGDJ directional antenna towers
WGDJ directional antenna towers

The building and all the towers are on 20 foot high steel stilts.  The area is right next to the Hudson River and often floods in the spring time.

Back of WGDJ transmitter building
Back of WGDJ transmitter building

The transmitter site sort of reminds me of something I once saw at coastal radio stations WCC and KPH.  They were located along salt water bays.

Phasor with Nautel XR12 transmitter
Phaors with Nautel XR12 transmitter

The station signed on the air in 1963. Initially, it was a 5 KW daytimer only.  They added night operation sometime in the seventies. Around 2006 or so, they went to 10 KW day, 5 KW night.  The phasor is gigantic for a 5 KW station, or even a 10 KW station.  I’ve seen smaller phasors on 50 KW directionals.  It has a “Quakertown, PA” name plate on it, which may be the forerunner of Phasetek.  There is a rare art form to creating a functional, yet space economical phasor.  Harris could sometimes pull it off, RCA did well, Kintronics seems to be the one of the top phasor makers today.

The main transmitter is a Nautel XR12, which as a very similar look as the V series FM transmitters.  The backup transmitter is a MW5A, which, quite frankly scares me.  The site was just recently air conditioned, which means the MW5A transmitter was sucking swamp air through it for 25 years.  I do not want to turn that thing on under any circumstances.

Nautel XR12 medium wave transmitter
Nautel XR12 medium wave transmitter

All in all, the station has a pretty good signal into the capital city of New York.  It nulls to the west, somewhat.  Being on 1300, it doesn’t carry as far as some of the other class B AM station like WROW 590 Khz, but it does alright.

After years of neglect, the station is making a bit of a come back in the Albany market.  They do a lot of local talk radio, which, when the other station is carrying almost all satellite syndicated talk, is making an impression.  Being the state capital, there is a lot of fodder.

Copper theft and how to avoid it

One of the unfortunate signs of the times is increased theft of valuable materials. Copper, while not as expensive as it once was, still fetches a fair amount at the scrap dealer. One local telephone company has been having a difficult time keeping their aerial cables intact in certain areas. For radio stations, the situation is compounded by remote transmitter sites with lots of copper transmission lines and buried ground radials around AM towers.  Reduced staffing levels also means that the weekly trip to the transmitter site is now every two weeks or perhaps once a month or even less.

Site that are not visited or monitored very often are prime targets for copper theft.  Forget asking the local constabulary to patrol more often, the few times I tried that I was met with a blank stare.

A few common sense type things that I have learned over the years may keep your site intact:

  1. Keep  up appearances.  A neglected transmitter site is more likely to attract the wrong type of attention from the wrong type of people.  Clean up any rubbish, dead equipment, keep the weeds and trees cut down, etc.  If a site looks well tended and often visited, a thief may think twice about lifting valuable metals.
  2. Along with #1, keep things buttoned up.  Secure all transmission lines to ice bridges, remove any dead lines, etc.  If there are ground radials poking out bury them, same with ground screens, copper strap, etc.  Out of sight, out of mind, leaving this stuff exposed is asking for somebody to come along and give a tug.
  3. Fences and locks.  Towers are required to be fenced and locked to prevent electric shock hazard.  It is also a good idea to fence the building, generator and fuel tank if possible.
  4. Post all sorts of warning signs, RF warning, high voltage, no trespassing, under video surveillance, pretty much anything to deter trespassing and vandalism.
  5. Add video cameras with a video recording device since most theft occurs during non-working hours.  Last year, the company I used to work for traded a video surveillance system for the studio location.
  6. Compensate a neighbor to keep an eye on the place and call you if they see any suspicious activity.  It doesn’t even have to be money, I once worked out a deal with a neighbor for some T-shirts and CD’s.   That was the best alarm system we ever had.

In the long run, keeping all the copper parts where they belong is a great way to avoid those annoying “the station is off the air” phone calls not to mention the expense of replacing damaged transmission and ground systems.