The Horns of a Dilemma

Alternate title: Building and ATU in a truck body tool box.

Alternate title II: I should get paid extra for this shit.

There is an AM radio station that is near death but the owners do not want it to go away.  Nor to they want to spend very much money to keep it around, thus the dilemma.  At the transmitter site, there are a multitude of problems; leaking roof, very old rusty ATU, rotting support posts and transmission line bridge, equipment racks rusting out, nothing is grounded properly, the building is full of junk, snakes and mice have moved in.  To further complicate things, the tower and transmitter building serve as an STL relay point for two of the market’s FM stations.  There is also two translators with antennas on the tower.  The ATU and tower light choke box are rusting through, which is causing arcing and broadband RF noise that is interfering with the FM station’s STL receiver.  There was a home made isocoupler for one of the translators that was allowing AM RF back into the building which was creating havoc with everything.  Because of this, the AM station is currently silent.  In short, it is a mess.


The red box on the bottom is the ATU, the plywood box on the top with the peeling yellow paint is the home made isocoupler, the tower light choke box is behind the isocoupler.

Crumbling old ATU output capacitor in series with tower
Crumbling old ATU output capacitor in series with tower

This was the capacitor that was feeding the antenna, .0041uf, 10KV 8 amps.

We started remediation on this last February, which is not optimum time for replacing rotting wooden posts.  However, we were able to clean out the building.  The leaking roof has been repaired.  I was able to find a few old racks from a Schafer Automation system to replace the rusted out original racks.  I began the process of grounding the equipment racks, the incoming transmission lines for the STL, etc.

Cool morning, Garter Snakes warming themselves on top of a Moseley DSP-6000
Cool morning, Garter Snakes warming themselves on top of a Moseley DSP-6000
Garter Snake
Garter Snake

We will have to find out how they are getting in, the plug up those holes.

Then there was the ATU and tower light choke enclosures.  Original to the 1952 sign on, they were past their serviceable days.  Since this is all being done on a budget and nobody wants to spend money on an AM station that has little or no listeners and even less revenue, we had a problem.

Then somebody suggested building an ATU in a truck body tool box.  Well…  This isn’t the Meadowlands, so if there are no other alternatives then okay, I guess.  Off to Amazon to order a tool box.  This particular unit seems fine, my only comment is on the gauge aluminum (or aluminium if you prefer), which is slightly thin for holding up all those parts.

ATU built in a truck body tool box
Fabrication shop, ATU built in a truck body tool box

Still, the box itself is nice enough and certainly better than the old one.  I was able to reuse the inductor and the Delta current meter but the old Sangamo capacitors crumbled in my hands when I removed them.  I also saved the feed through bowls, J-plugs and other parts.  I used some copper strap to run a good RF ground from the input to the ground connection.  Overall, I am pretty pleased with the finished product.  It is a little bit tight in there, but this station only runs 1 KW, so it should be fine.

Replacement ATU mounted
Replacement ATU mounted

So, new pressure treated posts installed, the box was mounted and the transmission line connected.

Replacement ATU under power.
Replacement ATU under power.
Reused Schaffer Automation racks, much better than the 1950's Gates racks
Reused Schafer Automation racks, much better than the 1950’s Gates racks

The reused racks are old, but serviceable and a big improvement over the old, rusting out racks.  I was able to bond each rack to the ground strap that used to connect to the RCA BTA-1 transmitter.  There is one more rack to install to the right of these two.  That should give us more than enough rack space for this site.

The station is back on at full power and not interfering with the FM STLs or the translators.  You can actually touch the rack and not get an RF burn!

We are also working on an air conditioner.

Other work at this site; cleaning out the building, replacing the tower light photocell, installing a ground buss bar, some STL lightning protectors, dress the transmission lines, etc.  It is a work in progress.


11 thoughts on “The Horns of a Dilemma”

  1. Who doesn’t love a good challenge??? Nicely done on the truck box conversion, that’s a very clever solution (certainly ought to outlast the station 🙂 ). Good one to keep in the mental file. Everything else tidied up nicely too, looks like someone finally cares, and I’m sure the snakes are happy to have received such a fine home makeover!


  2. I would love to have seen the inside of that homemade isocoupler. Based on everything else at the site before the upgrade and repairs, it must have been interesting. Great job, Paul, and very creative. Not sure I would have thought of a truck tool box as an ATU cabinet. Kudos.

  3. What a night and day difference! I’ll third the motion on that truck toolbox being a creative solution. I’ve walked past those at TSC and never thought “ATU enclosure”, but it’s darn near perfect for a 1kW station.

  4. I think it was Josh Bohn who came up with the idea. Truth be told, I would recommend the heavy duty tool box over the one that I used, but that is my only complaint.

    Rene, the home made isocoupler looks a lot like an isolation coil from an AM sample loop, probably because that is what it is. Next time I am out there, I’ll take a picture of it.

    Also, I must have done something right; they had some crazy thunderstorms this after noon and everything stayed on the air. Than never happened before.

  5. Yes, that was me Paul. I actually got the idea from Carl Sampieri at Clear Channel. Bohn Broadcast did this exact same thing about 2 years ago for WSLV in Ardmore, TN. I used the oversized white powder coated steel box. It worked very well. Couldn’t find one on Amazon though. Had to get it from some online truck accessory place. We also built our own base current meter system.

    Glad to see you were able to get it done!

  6. Looks great Paul!!! Much better! It’s hard to see a grand old lady of the airwaves suffer like that.

  7. Awesome job. I know of many smaller AM sites that suffer the same issues. Someone either needs to do what you have done here…in the big scheme of things it is not that expensive…just takes time and commitment. I recently put in order one of my large market DA sites that had been neglected and carelessly engineered for 30 years. Makes a real difference in operation, efficiency reliability and looks….Nice Job. Josh is a very helpful go-to guy. Glad I know him.

  8. Looks great. Is that a Kintronic isocoil lying on the ground over by the fence?

  9. Josh: It is working out well. Thanks for the idea you definitely saved me a few headaches.
    Don: I’ll shoot you an email next time we are out there, you are welcome to come over and see it. The place is starting to clean up nicely
    Allen: You know your Kintronic equipment well. We are going to re-use that at another site.
    Gary/Bob: Thanks!

  10. Paul,

    Nice job saving a site which is a disaster. And one I’d nominate for “Ugly Transmitter Site Of The Week” and “Innovative Transmitter Site Repair Of The Week” at the same time. A nice save from the brink of D. Decent looking now, instead of Le Dump!!!

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