Happy New Year!

After a bit of reflection and a few good conversations over the New Year’s Holiday, I decided that I should continue my work on this blog.  I would like to thank all those that have stuck by and waited.  I have received numerous emails and messages off line, all of which have been read and appreciated.

Since the abrupt stoppage last July, which was absolutely necessary for me, many things have happened within the business.  Fortunately, during the hiatus, I was still taking pictures.  After sorting through them, here are a few interesting things that happened:

At one of our client’s AM transmitter sites in Albany, NY a 2.6 Million Watt solar system has been installed.

WROW-AM Steel mounting poles on antenna array field
WROW-AM Steel mounting poles on antenna array field

This project required many steel mounting posts be driven into the ground around the AM towers.  I don’t even know how many, but I would hazard a guess of over three hundred.  Each one of those mounting posts was hand dug down a depth of 6-10 inches to look for ground wires.  Where ever a ground wire was found, it was moved out of the way before the post was set.

WROW-AM ground wire moved out of way
WROW-AM ground wire moved out of way

Basically the solar array covers about 1/2 of the antenna array field.  All of the steel mounting hardware is tied into the ground system, making, what I am sure is a pretty large above ground counterpoise.

WROW-AM solar panel mounting hardware
WROW-AM solar panel mounting hardware

View from the south looking north:

Solar Array installed on WROW antenna array, Glenmont, NY
Solar Array installed on WROW antenna array, Glenmont, NY

View from the north, outside of the transmitter building, looking south:

Solar Array installed on WROW antenna array, Glenmont, NY

Power company interface and disconnect:

Solar Array utility company disconnect, Glenmont, NY
Solar Array utility company disconnect, Glenmont, NY

The utility company had to upgrade the transmission lines to the nearest substation to handle the additional power produced by the solar system. All in all, it was a fun project to watch happen.

At a certain studio building, which is over 150 years old, the roof needed to be replaced.  This required that the 3.2 meter satellite dish and non-penetrating roof mount be moved out of the way while that section of the roof was worked on.

3.2 meter satellite dish

Dish ready to move, all of the concrete ballast removed and taken down from roof.  The roofing contractors constructed a  caddy and the entire dish and mount was slid forward onto the area in front of it.  Since the front part of the roof was not reinforced to hold up the satellite dish, we did not reballast the mount and the XDS receivers ran off of the streaming audio for a couple of days until the dish was put back in its original position.

3.2 meter satellite dish ready to move
3.2 meter satellite dish ready to move

A couple of other studio projects have been underway in various places.  Pictures to follow…

One of our clients sold their radio stations to another one of our clients.

There has also been a bankruptcy of a major radio company here in the good ol’ US of A.  Something that was not unexpected, however, the ramifications of which are still being decided on in various board rooms.  One of the issues as contractors is whether or not we will get paid for our work.  All things considered, it could be much worse.

Learned a valuable lesson about mice chewed wires on generator battery chargers.  I noticed that the battery charger seemed to be dead, therefore, I reached down to make sure the AC plug was in all the way.  A loud pop and flash followed and this was the result:

Arc burns, right hand
Arc burns, right hand

My hand felt a bit warm for a while.  The fourth digit suffered some minor burns.  There is at least one guy I know that would be threatening a lawsuit right now.  Me, not so much…  All of the high voltage stuff we work on; power supplies that can go to 25 KV, and a simple 120 VAC plug is the thing that gets me.

The return of the rotary phase maker.

Rotary phase maker, Kay Industies T-10000-A

Mechanically derived 3rd phase used when the old tube type transmitter cannot be converted to single phase service.

Those are just a few of the things I have been working on.  I will generate some posts on current projects underway.  Those projects include a 2 KW FM transmitter installation, another studio project, repair work on a Harris Z16HD transmitter, etc

It is good to be back!

Прощаться!

This information is from an occasional reader who wished to remain anonymous.

Another AM station surrenders its license, this time from north of the border. CKSL, London, Ontario, Canada is gone for good.  Current owner, Bell Media, has determined that it would cost more to repair the deficiencies with the antenna system than economically feasible, especially considering it’s low ratings.  Here is their filing with the CRTC:

Bell Media is the licensee of CKSL-AM 1410, assuming stewardship of the station in 2013 as part of the Astral Media acquisition.

A technical review of the transmitter site was recently completed both by Bell Media and contractors, which has resulted in the determination that the AM array poses an unacceptable risk from a health and safety perspective.  The five towers are experiencing serious structural degradation and also require repairs to the aviation safety lighting system. In addition, the building which houses the transmitter has shifted off its foundation (as have several of the individual tower sheds).

Given these problems, Bell Media would need to make a significant financial investment to bring CKSL-AM’s transmitter up to compliance with Human Resources Development Canada, Industry Canada and NavCanada operational codes and standards, all of which is estimated to exceed $3 million dollars.

From a market perspective, CKSL-AM has consistently ranked last out of all ten commercial stations in the London market, both in audience share and revenue generation, over the last several years.  In fact, since 2013 the London market has seen radio revenues drop 4% and CKSL-AM generates the least amount of revenue of the stations in the market. Even with a significant investment in programming, this trend is unlikely to be reversed. 

In light of the significant capital costs coupled with the absence of revenue and audience share, Bell Media is respectfully requesting the revocation of the CKSL licence.

Well, 24/7 comedy will do that to you.  Somebody in the business said to me recently “The listeners are abandoning radio!”  No, it is the broadcast station owners who are abandoning their listeners and their cities of license.  I have a news flash for all current broadcast station owners; as surprising and radical as this might sound, bland, boring, canned, completely irrelevant, dismal, uninformative, unimaginative, unentertaining, dreary, stale, unenjoyable programming will drive away even the most loyal listeners.  People really want to listen to radio, it is an easy habit and readily accessible.  Radios are ubiquitous; they are in our kitchens, bedrooms, cars, hotel rooms, offices, restaurants, barber shops, etc.  That, however, may not always be the case, as more and more people move Spotify, Pandora, or Apple radio when they are tired of the disappointment.  I was listening to a certain sports radio format the other day and I kept waiting for something interesting to happen.  I waited and waited. I would say to myself; okay, this will be the segment when I will learn something or be entertained.  This upcoming guest will say something interesting.  Sadly, those expectations were never met and I will never tune into that station again. Elevator music would have been better.  Worse than sports radio, 24/7 comedy is the absolute death knell.  This is like saying; we are out of ideas and we do not care.

Here are a few pictures of the former CKSL-AM transmitter site:

CKSL antenna array
CKSL antenna array
CKSL_transmitter
CKSL transmitter building
CKSL_transmission
CKSL transmission line bridge
CKSL_tower
CKSL tower base

Actually does not look too bad, at least the field is mowed. I have seen much, much worse.  Those bolt together towers, though. I would bet that they are the real problem, bolts are deteriorating faster than the tower steel. Very likely all the towers need to be replaced and that is why the license is being surrendered.

If you are a radio geek, get out there and take some pictures of your favorite radio station.  If the current trends continue, eventually they will all be gone.

A Linux based remote control system

We are extending LANs out to transmitter sites for many reasons; backup audio, control and monitoring, security systems, VOIP phones, etc.

I am casually (very casually) toying around with creating my own Linux based remote control system.  The ongoing Windows 10 upgrade debacle continues to not end, I can’t help but think that there are many potential clients who could use a reliable transmitter/studio remote control and monitoring system based on a stable operating system.  Hmm, sounds like a sales pitch 😉

Anyway, I have run across several Ethernet board manufactures that offer a variety of boards with 8-12 contact closures and a variety of analog and digital inputs.  Most new transmitters have some sort of web GUI which are great for transmitter control and monitoring.  As we all know, there is more than just a transmitter at any given transmitter site.  In addition to the transmitter, I would like to control and monitor things like tower lights, interface and control of coax switches, temperature monitoring, generator status, the old non-web interface backup transmitters, STL signal strength for those old 950 MHz links, etc.

Since Google is my friend (when they are not storing my search data), I came up with this: Internet-ethernet-12-channel-relay-board

That particular PC board is made in Bulgaria, which is home to this: Mount Buzludzha

What I like about these particular boards is the DRM software (DRM has, apparently, many different meanings) which will run on Linux or Windows.  There are also iOS and Andriod applications that can be used as well.  It appears that the GUI can be customized for various uses.   This seems like it is written in Java, so perhaps I could have some Java expert customize it for radio use.  It looks like up to 32 boards can be controlled by a single instance of the DRM software.  Alarm reporting would be via SNMP trap and email.

I don’t know, there is one particular cluster of stations that needs new remote control gear at almost every transmitter site.  Perhaps a little alpha testing is in order?  It could be fun…

Anyway, just a thought…

 

Medium Frequency ATU design

This is a topic I have covered before, but it is worth doing it again for future reference.  The previous post covered downgrading an AM transmission facilities for WGHQ, Kingston, NY.

This is part II of that process.

WGHQ transmitter site, towers 1 and 2 removed
WGHQ transmitter site, towers 1 and 2 removed

The old towers have been cut up and put in a scrap metal dumpster. They are off to China to be melted down and made into a submarine or a missile or a tank or something useful like that.

Towers scrapped
Towers scrapped

The directional array had a three towers in a straight line with a common point impedance of 60 Ohms.  Dropping two towers greatly changed the electrical characteristics of the remaining tower, therefore the existing ATU needed a bit of reworking to match the 50 Ohm transmitter output.

First step, correct a few deficiencies left over from the old array.

Vise grip tower feed
Vise grip tower feed

This vise grip RF connection has to go. The problem is where the tower erectors attempted to solder the copper tubing.  That tower base plate is pretty big and I would wager they didn’t use enough heat to make the solder connection.  They were probably working in the winter time, thus the “temporary” fix.  This tower was put up in 1993, so that temporary fix lasted 23 years.

I removed the offending tool and soldered the connection to another part of the tower with silver solder.  The smaller cross bar made a good connection point.

RF feed correctly connected to the tower
RF feed correctly connected to the tower

After soldering, I cleaned up and sprayed some grey primer on it to prevent rust forming where I scraped the paint off.

Next, I made an impedance measurement:

WGHQ tower base impedance measurement
WGHQ 920 KHz tower base impedance measurement

That junk on the upper part of the graph is coming from WHVW on 950 KHz. The tower itself looks pretty good, 77.6 Ohms resistance with 130 Ohms inductive reactance.  Since this is not a part of a directional antenna system, the ATU design is pretty straight forward.  Given that WHVW on 950 KHz is located 10.41 miles away, a low pass filter design is optimum.  A basic low pass filter T network has inductive input and output legs with a capacitive shunt leg to ground.

T network diagram
T network diagram

Each leg is used to match the 50 Ohm transmission line impedance (R1) to the 77.6 Ohm tower impedance (R2) and cancel out the 130 Ohms of inductive reactance.  This is a vector impedance problem, much like a vector force problem in physics.   Some basic arithmetic is required (always include the units):

X1, X2, X3 = √(Zin x Zout)

X1, X2, X3 = √(50Ω x 77.6Ω) or X = 62.28Ω

The value of inductance or capacitance for each leg is calculated using the basic inductance or capacitance formulas:

L (μH) = XL / 2πf(MHz)

And

C (μF) = 1 / 2πf(MHz) XC

Thus the input leg, or X1 = 62.28Ω / (6.28 x 0.92 MHz) or 10.78 μH

The Shunt leg, or X2 = 1 / (6.28 x 0.92 MHz x 62.28Ω) or .0028 μF

The output leg is a little different.  The tower has 130 Ohms of inductive reactance that needs to be cancelled out with a capacitor.  Rather than cancel out all of the inductive reactance, then add an inductive output leg, the tower reactance can be used as part of the tuning circuit.  The design calls for 62.28 Ohms inductive reactance, so 130Ω – 62.28Ω = 67.27Ω, which is the value needed to be cancelled by a capacitor:

Output leg, or X3 = 1 / (6.28 x 0.92 MHz x 67.27Ω) or .0025 μF

A little Ohm’s law is used to calculate the base current for both the day and night time operations.

Ohm's law pie chart calculator
Ohm’s law pie chart calculator

Thus the daytime base current is I = √(P/R) or I = √(1000 W/77.6Ω) or 3.58 Amps.

Night time base current is I = √(38 W/77.6Ω) or 0.70 Amps

Current handling requirements:

Base current is calculated to be 3.6 Amps at 1,000 Watts carrier power.  Allowing for 125% peak positive modulation makes it 5.7 Amps.  Having safety factor of two or 11.4 Amps output leg and 14 Amps input leg.

Voltages: 353 maximum input voltage, 439 output.

Thus, 20 amp, 10 KV parts should work well.

The designed schematic for the ATU:

WGHQ ATU Schematic diagram
WGHQ ATU Schematic diagram

Putting it all together.

Since the tower looks fairly broad at 920 KHz, we are going to attempt a nice broadband ATU to match it.  This station is currently programmed with a classic country format, and I have to tell you; those old Conway Twitty, Merle Haggard, Patsy Cline, et al., songs sound pretty good on the old AM radio.  The Subaru stock radio has HD, which also has a nice broad IF section, thus allowing all those lovely mid-high range frequencies through.

This is the existing ATU, which I believe was built by Collins in 1960:

WGHQ Tower 3 ATU
Existing WGHQ T network ATU

The ATU building is a little rough, but the ATU itself is in remarkable shape for being 56 years old.  The input leg inductor is in the center and will be reused as is. The large Jennings vacuum capacitor at the bottom is a part of the shut leg.  Its value is 2000 pF at 15 KV.  The top vacuum capacitor is series output cap, its value is 1000 pF at 15 KV.  The basic plan is to move the upper cap down in parallel with the bottom cap.  The shut leg inductor will be kept in place to tune out any access capacity.  For the output leg, I have a 2500 pF mica cap and a 10-100 pF variable cap connected in parallel.  The inductor on the output leg will be removed.

After some re-work on the ATU components, I tuned everything up.  The easiest way to do this is to disconnect the legs, measure them individually and adjust them for the desired reactance, which in this case is 62.28 ohms or thereabouts.  The output leg was measured with the tower connected since the tower reactance is a part of the tuning circuit.  The input leg was right about 10 μH.  The shunt leg turned out to be about 0.002 μF.  This is often the case, theoretical values are slightly different than field values due to stray capacitance and inductance in the connecting straps, etc.

This is the load, as measured at the output terminals on the transmitter:

WGHQ tower load as measured at the transmitter output terminals
WGHQ tower load as measured at the transmitter output terminals

Slightly asymmetric on 910 KHz, but overall pretty good. There is a fair amount of phase rotation in the transmission line due to the length from transmitter to tower (855 feet, 260.6 meter), which works out to be 0.93 wave length allowing for the 86% velocity factor of the transmission line.

Time to pack up and go home.