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Tube Amp

Audioromy M828A amp based on 829B tube (GU-29/FU-29)
Audioromy M-828A push pull tube amp based on 829B tube

I have dipped my toe into the world of tube (or valve) audio.  The first thing that I learned was that in general, tube amps are expensive.  It seems that the least expensive amps run about $1,000 US, and from there it seems the sky is the limit.

There are a number of less expensive Chinese versions floating around, most of the tube audio experts call them garbage.  Myself; I am not so sure.  There are also a lot of somewhat dubious claims made by the same experts about speaker cable, AC power conditioning and so on.

I was going to build a single ended tube amp based on the KT88 design found here:

That is a whole series of videos, eighteen in all I think, on the design and construction of a single ended KT88 audio amp.  If you have the time, well worth it to watch.

Then I decided that I really do not have a lot of time for that and I just wanted to try a tube amp and see if there is really that big of a difference.  Thus, I purchased one of the Chinese designs based on the RCA 829B tube, which is kind of exotic looking:

FU-29 Chinese equivalent to RCA 829B dual pentode tube

FU-29 equivalent to RCA 829B dual pentode tube

That is the Chinese version FU-29, there is also a Russian радиолампа GU-29.  The good news is that there are lots of these tubes available for not too much money.  New Old Stock (NOS) RCA 829Bs run about $25-30 each.  A Ulyanovsk GU-29 (NOS) runs about $10.00 (made in the USSR).  Somewhat more rare are the 3E29 tubes, which were designed for VHF pulsed radar.  These are dual pentode tubes which can be run ether parallel (single ended) or push pull.  They were originally designed for VHF transmitters, but have been put into use in HF transmitters and audio amplifiers.  The USSR versions are long life militarized versions and designed for aircraft radar; flying upside down at Mach 2 in -50 C temperatures 18,000 meters AMSL…  My Russian friend tells me I am joking.  I am joking.

Reflector factory, 6N3P-E dual triode tube

Reflector factory, 6N3P-E dual triode tube

The driver tubes and phase inverters are 6N3P-E (6N3, 6N3P, 6N3P-EV, 5670, 2C51 or 396A can also be used) which is a double triode tube, made by Reflector in Sartov, Russia.  These tubes are also militarized long life versions.

Audioromy M828A push pull tube amp

Audioromy M828A, power transformer and output transformers

The Audioromy M-828A amplifier seemed like a good compromise between price, power and workmanship.  I ordered the amp from Amazon and it took about a week to arrive.  The first thing I did was take it apart and look at it.  I was expecting poor workmanship and cheap components, etc.   Overall, it seems to be pretty well made. There are two printed circuit boards; one for the power supply, the other for the front end before the two power amp tubes.  The power supply uses solid state diodes, which some view as a compromise to a tube amp design.  There are also several power supplies on one board; 440 VDC B+ for power tubes, 220 VDC screen supply, a -25 VDC grid bias supply, 12 VDC for the audio switching relay, +6 VDC for the driver/phase inverter filaments.  I like the idea of DC filament voltage on the driver tubes.

Audioromy M828A underside

Audioromy M828A underside

This amp is configured for push pull and rated at 30 watts per channel.  I will test all of that plus measure THD, frequency response and so on.

There is no manual, which I find a little bit annoying.  Also, there is a lack of a schematic diagram nor any instructions on biasing and balancing the tubes when they are replaced.

Being thus annoyed, I did some deep diving on the intertubes and found that some people had posted on how to re-bias and re-balance the thing after tube replacement.  There where also several modifications suggested.

  1. Replace the input potentiometer with something a little more substantial.  It does seem to be a little bit cheap and I do not like the notches in the volume adjustment.  I will do this mod.
  2. Replace the coupling caps with oil filled units.  Not so sure about this one, but I might try it just to see if it makes a difference.
  3. Install a bias regulating circuit using an LM317 voltage regulator between the cathode and ground.  This seems like a good idea.
  4. Roll (replace) the input and power tubes with better versions of US made or Russian made tubes.  The input tubes are 6N3P-E tubes from Reflector (Sartov, Russia) which are already pretty good tubes.  I might replace the FU-29’s with a set of GU-29’s at some point.

There appear to be several schematic diagrams with slight variations based on the changes in design over the years.  Several designs have different input and phase inverter tubes.  Some have different power supplies, still others show no anode resistors or a cathode resistor.  This is the diagram for the amp that I own, which was produced circa 2018 or so:

Schematic Diagram, 829B push pull audio amp

Schematic Diagram, Audioromy M-828A 829B push pull audio amp

After all my investigations where finished, I put the amp back together and plugged it in.  I then ran my known CD’s though it and it sounded a bit rough.  I was a little bit disappointed until someone said that it takes about 10 hours or so for a tube to break in.  I connected it to my speaker test load (8 ohm, 50 watt resistors) and let it run for a day.

What a difference a day makes.  The second listen to the same CD proved to be much, much better.  There is definitely some coloration from the tubes.  A side to side comparison between my solid state Kenwood VR-309 amp and the Audioromy M-828A has the tube amp sounding much richer.  There is no real way to say it; it sounds full while detailed and clean all at the same time.  Playing though my homemade speakers, which are mid range deluxe, stringed instruments sound very detailed.  You can hear the pick hit the strings on an acoustic guitar.  You can hear the bow scrape across the strings on a cello.  It is unlike any amp that I have ever owned.

I am enjoying very much listening to Dave Mathews and Tim Reynolds Live at Luther College CD as I am typing this.

Now, I don’t know what the difference between this amp and the $10,000.00 version of the same tube amp made in Canada, other than the $9,500.00 difference in price.

A few comments about this amp and the 829B push pull amp design.  First of all, since the screen grids are connected internally, there is no way to run this tube in ultra linear mode.  Usually, ultra linear mode involves taking feedback from the output (anode) or the output transformer and feeding it into the screen of the power tube.  

Secondly, it is widely commented on that these amps are notoriously difficult to bias and balance.  One or both sides of the output tube will red plate due to over current.  I am hopeful the the LM-317 bias regulator circuit will take some of the difficulty out of this.  With an ordinary push pull amplifier, the balancing issue is taken care of with matched tubes.  Since both tubes in this push pull circuit are in the same envelope, getting a matched pair is not likely.  So, the tricky act of balancing the two outputs from the same tube will have to be carried out each time the tubes are replaced.  That being said, hopefully a set of those Soviet tubes will last for a long time.

One thing that I did do is make a bunch of voltage measurements and noted them on the schematic diagram.  If there are every any problems with this unit, having a set of base voltage measurements should go a long way toward troubleshooting and repairing it.

Finally, while the 829B is a rather exotic tube, it likely does not perform to the level of an EL86 or KT88 single ended design.  That being said, I have no problems with purchasing this amp and I am enjoying the toob audio sound very much.

The Temporary AM antenna

One of those things that I have written about before, but seems to be common these days as older AM towers need to be replaced. One of our clients had just such a tower. Erected in 1960, the hollow leg stainless tower was rusting from the inside out. When the tower crew came to put up the translator antenna, they discovered that there was a hole in one of the legs and climbed back down.

The tower condition was somewhat known about, there were braces installed several years ago at certain levels to keep the tower standing. The new owner had planned to replace the tower eventually, so those plans where moved ahead.

Temporary Wire antenna, WKNY, Kingston, NY
Temporary Wire antenna, WKNY, Kingston, NY

A temporary utility pole was installed near the transmitter building and a wire was strung to another customer owned pole about 170 feet away. At 1,490 KHz, that proved to be a pretty good length. The issue with these medium wave temporary antennas is always the height above ground. In order for the radiation resistance to be somewhat reasonable, the antenna needs to be at least 1/8 to 1/4 wave length above ground. That means a minimum of 78 to 157 feet at 1,490 KHz. The utility pole installed is 35 feet AGL.

WKNY temporary ATU

Thus, the wire antenna has a fairly low resistance, with loads of inductive reactance. Something on the order of 20 ohms, +j480. Since this is temporary, we reused the existing ATU that was designed for the series excited tower. With a capacitor installed on the incoming wire to cancel out some of the inductive reactance, a simple T network was configured to match the 50 ohm transmitter output to the 20 ohm antenna.

In the end, we were able to run about 400 watts into the wire, which covered the city of license fairly well. While the new tower was being erected nearby, we had to reduce that to about 100 watts to protect the tower workers from the hazards of non-ionizing radiation.

WKNY new tower build

The new replacement tower has been constructed. It is the exact same height as the old tower, but has a twenty foot pole on top instead of a normal tower section. The pole was installed to mount the translator antenna. In addition to that, there will be other wireless services installed on this tower.

WKNY will have a six wire skirt installed in the next few days. As this tower is close to 160 degrees at 1,490 KHz, the skirt can go anywhere from 60 to 120 degrees up the tower.

A few updates

Sorry for the lack of posts.  I have been very busy with mostly mundane tasks that do not seem worth writing about.  Other than that, hockey season has been in full swing.

The following will be kind of personal in nature.  Feel free to skip to the end.

I cannot say enough good things about youth sports and hockey in particular for the development of kids these days.  When I was growing up, we had the great out doors and that was pretty much it.  Nowadays, there are constant distractions with video games, youtube videos, social media and whatnot.  Getting my son interesting in athletics early on has made a big difference.  There are the obvious physical development advantages; speed, endurance, balance, hand/eye coordination, strength, etc. 

Taking the shot

Taking the shot

But there is something more important than that. My son is a fairly gentle soul. He tends to look out for others and put himself last. People have commended him on this, but it worries me. There are some people in this world who will see his good nature and compassion as weakness. Being exposed to aggressive personalities has taught him that not everyone thinks the same way he does. Learning to deal with aggression; both other people’s and his own has been a very valuable life lesson.

Learning to take the shot and risk failure is another big one. Nobody wants to make a mistake, that is true. However, being risk adverse often closes the door on opportunities which only come around once in a while. Learning when to take a calculated risk (calculated for the best chance of success) is another life lesson. As The Great One said:

“You miss 100% of the shots that you do not take”

Facing adversity and dealing with setbacks builds character. Too often, parents do not let their children face any difficulties. These are the helicopters you see hovering around in the background to make sure that everything goes exactly as it is supposed to. Life is not like that. Learning to deal with adversity is key to becoming a resilient human being instead of an emotionally fragile person that folds like a cheap suit at the first sign of trouble.

Finally, having a passion about something adds depth to a person. There are many young people today who seem to care about nothing. They are devoid of any unique personality characteristics. They spout the latest fad issue as seen on social media without understanding. Having character and confidence is rare and refreshing.

So, that is what has been going on.

Box One

I have been remiss in updating this thing, even for Christmas and the New Year.  It has been a busy time, but also, it seems that there is nothing exciting to write about.  Continuing on writing about another transmitter installation or studio project seems redundant.

That being said, I have moved into the realm of high quality audio.  I miss that days when a good audio was the general rule, in both home audio and broadcast.  People have become used to crappy .mp3s played through crappy computer speakers or cheap ear buds.

Knowing just enough to be dangerous, I figured I should do a little bit of research before spending a lot of money foolishly.  I discovered that there are gobs and gobs of information on various forums and other places around the intertubes.  Most of it seems to be good, although one has to be careful and backup whatever is out there with science.  There are several books about DIY speaker building, amplifier construction, turntable maintenance, etc.  Picking the thing that I thought would be easiest and lead to the  biggest improvement in my own audio system, I set out to build a pair of speakers.

Most people probably don’t realize this, but there is quite a bit of work that goes into a well designed pair of speakers.  I began by thinking about what the end use will be, which eventually is a single ended tube amp based on a KT88 design.  As such, I figured the efficiency of the drivers was an important detail.  Power handling capability of the driver could be quite low, 30-50 watts or so.  Searching through several speaker manufacture’s web sites, I found a small sized, full range driver that is fairly efficient and has excellent reviews.

The Tang Band W4-1337SDF has a published sensitivity of 89dB/1 watt/1 meter.  Its frequency response is 70-20,000 Hz.  It also has a titanium speaker cone.  There have been many an article written and much ink spilled on metal cone speakers, so I did not quite know what to think of the titanium cone.  I did spend a goodly amount of time reading all of the reviews on this particular driver and decided to take the risk and buy two of them.

Next step was to calculate the proper interior volume of the speaker enclosure for a vented box.  Vented or ported speaker enclosures are generally more efficient than sealed units.  Vented boxes are a little bit more exacting to build correctly.  Again, lots of information available on line, some of it is good.  In the end, I downloaded a free software package called WinISD.

WinISD takes into account all of the Thiele/Small characteristics of the driver and generates  a basic box design.  I looked at the proposed box and decided that the internal volume was the important part, the actual shape of the box is secondary so long as it is not an exact cube.  Instead of the 2:3 ratio rectangle, I choose something different; a 1:4 rectangle.

Making cuts for speaker boxes

Making cuts for speaker boxes

Next, I began looking around at available materials.  I have plenty of wood laying around from previous projects, so I decided to make the boxes from 1×6 clear pine.  This is also contrary to conventional wisdom, as MDF is the preferred choice in speaker cabinets.  This is because natural wood has a resonate frequency, which can create problems.  As these are low power units, I figured, if it was a huge problem I could always make another cabinet out of MDF.  In the mean time, the wood, glue, paint, screws, foam insulation, tung oil finish where already in the shop.  Why buy more stuff?

I also wanted to add a tweeter (Peerless D19TD-05) to cover the high end and a simple 1 pole (or first order) cross over.

Speaker box work

Speaker box work

Thus, parts ordered, I started working on the boxes.  I decided that rabbit joints where a better choice than mitered 45 degree joints.  I used the router table to make the joints, cutouts and round the cabinet edges.  During the sanding process, I discovered that the wood boxes do indeed resonate somewhere around the 300 to 400 Hz region.  More on that later.

Speaker box glue up

Speaker box glue up

The fronts and backs are made out of 1/2 inch plywood, painted flat black.  There is a one inch rear firing port.  The box itself is larger than what is called for.  I made it thus because there where a couple of different recommendations on box volume and I wanted to add some cross bracing, which takes up space.

Speaker box, foam dampening and bracing

Speaker box, foam dampening and bracing

I thought about ways to dampen the wood box resonance and came up with a bit of rigid foam insulation, again left over from some long ago renovation project.  My idea was to take up some of that excess internal volume, but they might also work to dampen the resonance.  I cut several pieces of this material so that they fit snugly into the box.  I then used the sander to resonate the box and see what effect the foam insulation was having.  In the end, I came up one piece at the top and bottom and one approximately in the middle.  Once I was happy, these were glued in place.  This significantly dampened the resonance.  I also added quite a bit of acoustical foam inside the box.

First order crossover

First order crossover

The cross over is designed for 4000 Hz.  It consists of a 5 uF capacitor and a .31 uH inductor.  I am a minimalist at heart.  I thought about nixing the inductor altogether, but I think running both the driver and tweeter at the same time would lower the impedance too much over the high frequencies.

Completed speakers

Completed speakers

The completed project was bench tested using a software program called DATS:

Speaker impedance sweep

Speaker impedance sweep

The Tang Band driver is resonant at 60 Hz or so.  After the F3 frequency, calculated to be 101 Hz, the impedance looks good all the way out to 20 KHz.  It appears the F3 frequency is slightly higher, likely because the port is too short.

I messed around with the internal box volume by adding and taking away pieces of foam insulation.  In the end, I found that the original volume calculated by WinISD worked (and sounded) the best.

I set these up and took a listen.  Using a reference recording of Tschaikovsky (piano concert #1, B flat minor) I found these speakers sound excellent.  The stringed instruments and horns in particular sound very detailed.  The piano is open and natural.  If I close my eyes, it sounds like it is right in front of me.  Perhaps that is the wood box.  I tried them on several different types of music; jazz, rock and even Tom’s Dinner.  It may be a bit biased, however, I find these speakers to be far and above anything else I have owned in the past.  They sound great.

My only very minor gripe is the bass is not as responsive as I would like.  The low end starts around 90 Hz.  This showed up in the F3 frequency reported by WinISD.  I have a Polk Audio subwoofer that I am using (temporarily) to add the bass back into the mix.  I could also try tuning the ports a little bit to move the F3 down.  That may also require removing some if the foam from the box to increase the internal volume.

I also made a small mistake when cutting the wood for the box, as they are slightly too narrow and the driver does not fully fit onto the plywood front.  That is because I started working on this before I had the drivers in hand.  If I make another pair, I’ll make the cabinet a little bit wider.

Speaker frequency room response

Speaker frequency room response

I also ran a couple of sweeps with Room EQ Wizard.  That 300-400 Hz box resonance shows up in the sweep, but it is not noticeable when listening.  Without the subwoofer turned on, the bass does not start to pick up until about 70 Hz or so, which exactly the spec on the driver.  Funny how that works.

Speaker and subwoofer

Speaker and subwoofer frequency response

This is with the subwoofer turned on. Notice the little hum around 40 Hz, that is the hallway to the bathroom acting as a bass resonator.  Unfortunately, my listening room has some uncurable defects; I cannot get rid of the hallway to the bathroom because eventually that room comes in handy.  I need to get some acoustical material up on the wall and perhaps the ceiling.  I was thinking of a Helmholtz resonator in the wall.

Speakers mounted

Speakers mounted

They sound slightly better if they are moved off axis from the back wall.

My total cost was about $180.00, not counting the materials I already had on hand.  After listening to these for several days, I can say they stack up well against speakers that cost ten times what I paid.

Next project; the matching subwoofer.  I have some ideas…

Brief Update

All is well in Engineering Radio Land, just very busy with typical projects. Nothing really note worthy, but there are some interesting things in the pipe line, which will be posted once those projects begin. Regarding myself, Hockey Season is in full swing.

Ruined shot on goal

My son (in blue) messing up somebody’s shot on goal. Good stuff.

I received an interesting question from occasional reader Gary over the weekend:

Have you ever heard of, or looked into, the “Max Headroom incident”?

Yes, I have heard of it, but never really thought about it that much. At that time, I was in California getting ready to ship out to Guam. I remember some brief news reports on it when it happened. After some reflection, I sent along this reply:

Good question. I have done a little bit of work at TV stations from time to time. In the mid to late 80’s, most television stations used 6 GHz analog microwave links between their studios and transmitters. These where unencrypted. Most often, these links used Microwave Associates gear, which had transmitter power output of about 3 watts into a rectangular wave guide. That was coupled, via elliptical wave guide into a 24 or 36 inch parabolic antenna. As you know, parabolic antennas have a main lobe and side lobes in their radiation pattern. The smaller the dish size, the broader the main lobe is and the further out the side lobes are. Since the Chicago studio to transmitter path was fairly short, I’d hazard a guess that they where using 24 inch antennas. In major markets, there was often a backup STL system on a different frequency (as the Wikipedia article indicates). Later on, most stations had a third backup via the cable company using either directly fed coax or fiber optic cable.

Since cutting into the transmission line of the microwave link at either side of the system would almost certainly fail, what I think happened is the perpetrators discovered (easy to do) the frequency of the 6 GHz link and over powered the normal signal at the receive antenna. This is possible if they used a much larger antenna and where located in either the main lobe or a side lobe of the receive antenna. If you recall, in the late 80’s C band satellite dishes where very popular. It would not be too difficult to repurpose one of these dishes for a 6 GHz antenna. Most C band dishes where 5-6 feet in diameter, which would give them much more gain than a 2 foot dish. They simply would have had to figure out a way to feed the dish with elliptical wave guide and adjust the focal length for 6 GHz. I’d bet there where dozens of C band dishes on Chicago roof tops.

Anyway, that is my theory.

I watched a few youtube clips of the event. The fact the video was noisy indicates some type of co-channel interference. I think there was no audio because they guessed the microwave audio subcarrier frequency wrong the first time. The second incident, there was audio. Whoever did to this had to have pretty good knowledge of television STL system. Wikipedia article here: https://en.wikipedia.org/wiki/Max_Headroom_broadcast_signal_intrusion

What do you guys think?

In other news, I have begun messing around with a few ideas on single ended tube audio amps and contemplating a DIY tapered transmission line speaker build. Actually, there is some pretty interesting software out there for speaker design which would be fun to play with.

I have also been messing about with room EQ Wizard, which I think I will do a separate post on.

That is all from here, hope that all of you are well.

Differential Audio

Most professional audio facilities use differential audio or balanced audio within their plants.  The main reason for this is noise rejection, which was discovered by the early pioneers of wired telephony back in the late 1800’s.  Balanced audio is created by generating two audio signals that are 180 degrees out of phase using either a transformer or an active device.  These are usually labelled High and Low, + and – or something similar.  Those two audio signals are then transmitted across some distance and recombined at the far end, again by a transformer or some active device.

Noise rejection, differential signaling. "DiffSignaling" by Linear77 - Own work. Licensed under CC BY 3.0 via Wikimedia

Noise rejection, differential signaling. “DiffSignaling” by Linear77 – Own work. Licensed under CC BY 3.0 via Wikimedia

When an interfering signal is picked up, it is transmitted along both sides of the balanced audio circuit until the signals are recombined.  During the re-combining process, and common mode interference is cancelled out, as it becomes 180 degrees out of phase with itself during the re-combining process.

Differential signaling is used in analog audio, digital audio (AES/EBU), HDMI, Display Port, USB, Ethernet, POTS lines, ISDN, T-1/DS-1, E-1, etc.   It is a fairly simple concept, but one of the basic building blocks in broadcast studios.

When a studio project was completed at a disused studio/transmitter site location, a certain amount of RFI was being induced on the studio microphones by the unassociated FM transmitter in the next room.  The problem with microphone level audio is the relatively low level of  microphone output, which requires a good deal of amplification.  The amplifiers in this console have active balanced inputs, which might not be exactly 180 degrees out of phase.  In this installation, microphone level audio was run about 20-25 feet on standard microphone cable then it was converted to Cat 6 cable before going into the console.  It may have been better to use the shielded Cat 6 cable for the longer runs as it likely has better common mode rejection than standard mic cable. Another option might have been Star Quad cable.  However, none of those things were done.

Western Electric was the manufacturing arm of Bell Telephone.  In their day, they made some really good equipment.  One such piece is the WE-111C repeat coil.  These can be configured for either 600/600 ohms, 600/150 ohms, 150/150 ohms,  or 300/300/300/300 ohms impedance ratios.  Since this is microphone level audio 150/150 ohms is the appropriate setting.

WE 111 repeat coil, one of the best such transformers ever made

Over the years, I have found many of these transformers discarded at various transmitter sites and studios. There are five microphones feeding this console. I mounted five of these coils in a sturdy metal enclosure and wired them with RJ-45 jacks to be compatible with the Studio Hub wiring equipment used in this studio installation.  I also grounded each unit to a piece of copper strap, which is connected to a grounding lug on the side of the unit.

Western Electric 111C repeat coils mounted in box

Western Electric 111C repeat coils mounted in box

I swept the coils from 20Hz to 20kHz:

WE 111C coils, 20Hz sweep

WE 111C coils, 20Hz sweep

WE 111C coil 20kHz sweep

WE 111C coil 20kHz sweep

This shows a 0.4 dB difference from 20 to 20,000 Hertz, thus they are all nearly flat which is a pretty cool feat of engineering.  I would estimate the age of these transformers is between 50 to 60 years old.

These coils isolate each microphone from the microphone preamp in the console.  This completely eliminated the FM RFI and solved the problem.

Another small market build out

Finishing up another studio build out in an unrated market. There are some engineers who think that small market work is beneath them. That is fine with me, I enjoy it.  Once again, creating a nice, functional, modern facility while not breaking the bank poses some challenges.   I like to take sort of a minimalist simple approach while not compromising good engineering practice.  Another challenge is rebuilding an existing facility.  Each studio needed to be demoed one at a time with the stations playing hop scotch from studio to studio around the work.  There were four studios total plus the rack room.  There were also several other renovations going on at the same time as this project.

Looking at the overall facility, the client decided that one studio would be the main room where multiple guests could be seated, etc.  The other rooms would have guest microphones, but they are smaller rooms and limited to one guest each.  The smaller rooms have AudioArts Air4 consoles while the main studio has an R-55e.

WZOZ console, main studio, Oneonta, N

WZOZ console, main studio (Studio A), Oneonta, NY

The main studio had existing studio furniture that was in reasonable shape so we decided to reuse it.  While we had the studio ripped apart, the paint and carpet where updated.  The main microphone is an Electrovoice RE-20, the guest mics are Heil PR-20UT which are inexpensive and have excellent characteristics for a dynamic microphone.  Since this faces a fairly busy street, I put in some very basic DBX 286S mic processors with a little bit of downward expansion.  Adobe Audition is used for production.  I have also used Audacity which is available in both Windows and Linux flavors.  Acoustical wall treatments are coming soon.

Main studio, Oneonta, NY

Main studio, Oneonta, NY

The counter tops in the smaller studios were traded out with a local kitchen supply company.  We used Middle Atlantic BRK-12-22 racks with castors on them to install a limited amount of rack equipment.  Each one of these studios is nearly identical; a AudioArts Air4 console with JBL powered monitors.  The microphones in these studios are Heil PR-20UT with console supplied mic preamps.  These studios are used for WSRK, WDOS, WBKT and WKXZ.  All studios are off line when in automation, which means each can be used for production and other purposes.

Studios B-E, Oneonta NY

Studios B, Oneonta NY

Studio C, (WDOS) Oneonta, NY

Studio C, (WDOS) Oneonta, NY

Studio D, (WSRK) Oneonta, NY

Studio D, (WSRK) Oneonta, NY.

We started the TOC from scratch. This area was occupied by a bunch of empty file cabinets previously. The original equipment racks where in Studio A.

A riser was installed from the racks straight up to the roof for the STL, monitor antenna and satellite dish transmission lines.  Everything is grounded with a star grounding system connected to the main building ground which consists of driven ground rods and the water main.  The STLs have Polyphaser IS-PT50HN lightning protection devices installed.

900 MHz lightning protectors on STL transmission lines

900 MHz lightning protectors on STL transmission lines

The racks are Middle Atlantic MRK 4031.  Since this building was built sometime in the mid 1800’s, the floors are a bit uneven (along with almost everything else), so a fair amount of shimming and leveling was needed to get these units bolted together.

Racks and equipment

Racks and equipment

Each rack has its own UPS in the bottom and they are all on separate breakers.

A manual transfer switch controls a dedicated electrical sub panel.  All of the racks and studios are powered from this sub panel.  Below the transfer switch is a NEMA L14-30 twist lock male receptacle for generator connections.

Studio/TOC sub panel and transfer switch

Studio/TOC sub panel and transfer switch

The total load about 18 amps.  The station is looking to trade out some generators for various transmitter sites.  I suggested that they get a couple of the portable Honda inverter generators, which are very good have excellent power regulation, frequency stabilization and fuel economy.

The existing Scott’s Studio 32 system was updated with new computers.  This is an interim step until a new automation system can be installed next year.  Each station has it’s own BT 8.2ss switcher which can select any studio to go on the air with.  That flexibility makes moving from studio to studio easy.  It also allows for all the stations to be simulcast, which is handy in the event of an emergency.

Punch blocks are mounted on plywood attached to the back wall.  We left extra space for a new phone system.

The EAS monitor assignments are met with roof top yagi antennas.  I like drawings and diagrams, as the saying goes, a picture is worth a thousand words.  This is an image I created on Google Maps using the transmitter site coordinates for each of the EAS monitoring assignments.  That gives me good local aiming points for the various antennas needed.

EAS monitor assignment headings

EAS monitor assignment headings

Other drawings include a floor plan and block diagrams for each station.  I have a Viso template that I use for these.  I find that having these diagrams on hand in a book is very helpful in the event that somebody else needs to go to this station to work on things.

Block diagram for WDOS, Oneonta, NY

Block diagram for WDOS, Oneonta, NY

Finally, the wiring documentation which shows where each wire originates and terminates. Again, if I am not available and somebody else needs to do work here, this is very helpful. All the studios are laid out the same, so figure out one and then the rest falls into place.

Screen shot of wire run spreadsheet

Screen shot of wire run spreadsheet

There is still a little bit of clean up left and some old equipment to get rid of.  Otherwise, it’s a wrap.

Gone and apparently forgotten

Can a 50,000 watt AM station disappear from the airwaves and no one notice?

The answer is yes, if you live in the Albany, NY area.  WDCD, 1540 KHz, (formerly WPTR) has surrendered its license to the FCC last Friday, September 28, 2018.  Seventy years on the air and quite the legacy as a Top-40 station in the 60’s and 70’s.

Unfortunately, the station had fallen on hard times the last few years, being silent twice for long stretches of time.  In the end, I suppose it was simply time to pull the plug.

This was my first CE gig in the early 1990’s.  What I remember was, I had a lot of fun working there.

So long and thanks for the memories.

 

I almost hate to say anything, but

We have this certain transmitter which has been on the same tube since June 6, 2001.  Come to think of it, the transmitter itself has been on the air for the same amount of time without failure.  A testament to its designer…

Broadcast Electronics FM20T, WYJB, Albany, New York

Broadcast Electronics FM20T, WYJB, Albany, New York

According to my calculations, that is 151,691 hours or 17 years 3 months and 22 days.  The tube is the original EMIAC 4CX15000A that came with the transmitter.

I am a little nervous about turning it off to clean the cabinet.

EIMAC 4CX15000A tetrode

EIMAC 4CX15000A tetrode

We have a spare on the shelf for the eventual replacement of this tube, but I really want to see how long this thing will last.  This is also one of the last tube transmitters we have in main service.  There are several backup tube transmitters still around.

Interesting piece on WEQX

I found this video on YouTube about WEQX, Manchester, Vermont.  WEQX is a class B FM station with its tower located on Mount Equinox.  This gives the station a huge signal with a HAAT of 759 meters and 1,250 watts of power.  It comes in well south of Albany and while I am in the Albany area, I enjoy listening to it.

This piece is by CGTN, which one wonders how they ended up in Manchester, VT of all places.

The information below the video is also an interesting read. In part it goes into corporate ownership of radio in the US, stating:

In 1983, 90 percent of U.S. media was controlled by 50 corporations. Today, just six corporations control that 90 percent… Among the 10% (of radio stations) currently not controlled by those six corporations is an alternative rock station in the Green Mountains of Vermont.

That is misleading.  The “six corporations” they are referring to dates back an article published several years ago.  They are; Time Warner, Walt Disney, Viacom, News Corp, CBS and NBC/Universal.  As of this writing, none of those companies listed owns any radio stations.  Further, the media scene in general has become much more fragmented with the advent and greater acceptance of things like Pod Casting, YouTube and other social media.

There are three big radio station owners, which together own 1,613 radio stations. That represents approximately 14% of the licensed commercial AM and FM stations in the US. There are several medium sized owners; Entercom (237), Salem (118), Saga (108), Midwest (75), Forever (69), Beasley (63) and so on.  While iHeart (851), Cumulus (442),  and Townsquare (320) influence the way other station owners operate, by and large, the majority of radio stations in this country are still owned by small business owners.  Stations that are keeping it local continue to be noticed and hopefully rewarded with a successful business.

WEQX is certainly a unique station and it always has been.  In the late 90’s and early 00’s, I did some work for them at various times.  It was always fun and I enjoyed it.