Rocky Mountain Update
Amanda Hopp, CBRE

My First NAB

This year was the first year I was able to attend the NAB spring convention. I am grateful for the opportunity. It was a bit overwhelming, and even though it has been two weeks at this writing since I returned, I am still digesting everything. I was only able to have two full days on the floor, and those two days were packed with educational sessions and meetings with various vendors. It was great meeting some of the engineers that are responsible for the operation of our equipment.  We were able to discuss issues we have had and offer suggestions on what we would like to see. We have already discussed it more with them once they all returned to their home office. It was wonderful putting faces to the people I have spoken to many times on the phone or over e-mail. I hope I can continue going each year, but only time will tell.

Tractor Maintenance

I was able to take a Saturday morning last month with my husband and get the Kubota tractor ready for the season. This meant changing the oil, oil filter, fuel filter, air filter and greasing all the various points. It took a couple of hours, but we are good to go for the season. Dylan was also able to do the oil maintenance on our John Deere riding mower. We still need to get the weed eater and push mower ready to go for the season, but those should not be too hard to do. Things are greening up fast and growing. We’ve had a lot of moisture as of late, which prevents us from mowing, so hopefully we can find some time here and there between storms and get some of it done.

New Transmitter!!                           

We received our new transmitter for 95.3 FM, a beautiful Nautel VX-150. Installing it was a chore, which had nothing to do with the design of the transmitter. First off, this is a site that is in the mountains of Colorado. It is about 30 minutes outside of Denver. The road to our site is a steep incline that is very shaded. We typically avoid it in the winter because there is too much snow. When we installed the new antenna for this station back in March, we nearly got stuck going up the road as did the tower crew.

When we took the new transmitter up in April, the snow was deeper and impossible to drive through, so we had to hike up the road. This meant grabbing bags and filling them with the tools we would need and hand carrying the transmitter up to the site so we could do the work. Even then, the screw stick I brought could not finish the job, so I ended up having to do everything with a regular screwdriver, which was a blast. We had to rearrange equipment in the rack only to find that certain cables were not long enough. We called it and the next week (after the NAB trip) we went back, and although we still had to hike up, we had a plan. We made the cables we would need and got everything in the rack where we wanted it. We did notice some anomalies having to do with the filter we have on the frequency. The transmitter does not like the skirts on the filter passband with modulation, so we do get periodic high-VSWR alarms. This is one of the things we were able to discuss with the Nautel engineer.

The other anomaly we found had to do with the modulation loss RF mute. We had it set to 60 minutes on our BW transmitter and duplicated that value on the new Nautel.  However, as soon as we would turn the transmitter on it would immediately mute itself. After going back and forth with engineering, they were able to replicate the problem and found it worked at 24 minutes and eight seconds but not a second more.. So, for now we have it set to 20 minutes while they continue working to correct it in a future software update.

Another thing Nautel is working on is RDS. This transmitter has its own RDS encoder, which is great. However it does not allow DPSTEXT=, which on the Inovonics RDS generators populates both the Radio Text and Program Service fields. Doing that allows all radios to decode DPS or TEXT depending on what the radio uses to display title/artist metadata. Short of using some sort of middleware, there is no way to do both without that DPSTEXT command and Nautel only allows DPS or TEXT for this. They will have an update soon for us to allow the full command, and I think once it has done, we’ll be off to the races. For now, we’re using the Inovonics 730 external RDS generator.

A/C Woes

It is that time of year when the air conditioners will be running more. At the KLTT transmitter site, it runs year-round. Earlier in the year, the main unit would go down and the system would switch to our backup unit. This is immensely helpful to us as it means a trip to the site can wait a little bit if needed. I recently took some time and went to the site and found the filters needed changing and a couple fell inside the unit and the economizer filters fell out of the unit. Those secure oddly, so it was no surprise. I went ahead and changed the filters inside both units and made sure the economizer filters were secured. After that, the main unit seemed to run fine until right before the NAB trip, when I noticed it had again switched to the backup. I was able to get service contractor Wern Air out to look at it, and they found the thermostat was not working properly. It was calling for cool but the unit on the roof did not get the message. He replaced the thermostat, and it was working. We thought we were good. The next day, I went out to set up the Wi-Fi access on the thermostat so I could keep an eye on things, but noticed it was off. The backup A/C unit was running again. We could not get the main unit to come up at all. Wern Air came back out and found the breaker on unit’s low voltage power supply was tripped. He reset it and it worked for about a day. I am currently waiting for them to make another trip out to troubleshoot. Something is causing it to trip and they need to find it.

Upcoming

I have said it the last two months, but mowing will begin any day now. The first week in May we will take the water tank and pull-behind sprayer out to KLVZ and lay down some herbicide to get rid of the Canada thistle before it gets big. We have a project coming up that includes us moving the 250-watt 94.3 FM into the transmitter building. It is currently located in a weatherproof cabinet at the tower base and just does not operate as well as we would like – temperature swings are too great with the transmitter running at 600 watts into a half-wave-spaced antenna. We believe moving it into the main transmitter building will allow it to operate properly. Plus, it would make it easier for us to work on. It is gearing up to be a busy season here in Denver. Hopefully for you, it is not as chaotic. That about covers it for May. I pray you all stay safe and well.

 

 

Random Radio Thoughts
Cris Alexander, CPBE, AMD, DRB

 

NAB 2024

Another NAB spring convention is in the books. I’ve lost count as to how many NAB conventions I  have attended over the years, but this was my first in quite a few years (2016 was the last time if I recall correctly). I had several years of health issues, and then COVID, and then I was trying to avoid getting COVID (again!). This year, the time seemed right, and it was. It was an exhausting trip, but worthwhile, and nobody in my entourage got COVID, thank God! In fact, I haven’t as of this writing heard about anyone getting it at the convention, a sharp contrast from the last few years.

We attended several sessions and spent a few hours on the exhibit floor meeting with manufacturers, engineers and vendors. All that was time well spent, and we checked off everything on our list of  things to do. In addition to that, we had a number of other meetings, and it was great to renew old friendships. It’s always amazing to me how small a universe our business really is, and that is  apparent at the NAB spring show.

So what did we see at the show that was of interest? We got a good look at RCS Zetta and were able to ask a bunch of questions. We will, over the next few years, be transitioning from Nexgen to Zetta,  so it was important for us to really see it work. I plan to do some more in-depth exploration of that platform in the coming months using some materials that RCS provided.

We spent some time with the Nautel folks, asking a lot of questions about the VX-series of low-power FM transmitters. Right before leaving for the show, we took delivery of our first VX transmitter, and our early experience with it raised a number of questions that we were able to explore with  some of Nautel’s engineers. We also requested certain features and modifications.

Over at the Inovonics booth, we spent a productive hour with Ben Barber and one of his engineers,  discussing the new FM and AM monitors as well as other products. Those folks are the best. They’ve come a long way from their humble beginnings making solid-state electronics for Ampex reel-to- reel tape decks! Their name is entirely appropriate for the innovative products that they manufacture.

 

After a session on dashboard displays and metadata, we met with the folks at Broadcast Electronics and discussed TRE+. We even met the Australian engineer that wrote the code. More on this later.

Burk showed us some of their new products, including their Arcadia NOC system and Climate Guard TOC monitor. Exciting stuff.

Over in the Central Hall, we spent some time with Frank Foti and our other friends at Telos. It’s  always great to see them, and they always have some new, innovative and interesting products to show us.

Also in the Central Hall, we met with Jacob and the other folks at Tieline. The new Bridge-IT was the hot new item that we were interested in. Just when you thought a product couldn’t get any better…

We met with vendors, including RF Specialties and BSW, discussing pricing models and new procedures.

And we spent some time at the SBE booth talking with Megan, Chriss, Jim and Cathy about various SBE activities. We regularly interact with those folks throughout the year in our functions as Certification Committee member and local certification chairman, and Amanda as chapter chairman, but it’s always good to see them in the flesh.

At the end of our two-day stay, we were exhausted but excited at all we had seen and learned. We  should be just about recovered by the time next spring’s convention comes around!

Dashboard Displays

A couple of months ago, I wrote in these pages about metadata. Our friends at Radio World picked that column up and ran it. Since then, I’ve done some thinking about metadata, and the conference session further stimulated some thought.

One of the things I got from an interaction with the NAB’s David Layer last fall was that car radio manufacturers (and automakers) handle metadata differently, particularly with RDS. There are two fields of interest: RT (Radio Text), and PS (Program Service). According to various RDS equipment manufacturers, RT should contain title/artist metadata and PS should be a string describing the  radio station. Oh, that it were so!

I recently helped Amanda install a new Nautel VX150 FM transmitter at our Denver Lookout Mountain site. We had hoped to utilize the internal RDS generator so that we could keep the  outboard Inovonics RDS generator on the aux transmitter, but we found that the internal Nautel generator does not have a function that will populate both the RT and PS fields with the same string.  We ran it for a couple of days with just RT populated, and lo and behold, just like David Layer said, a  lot of radios, including the Pioneers in my work car and Amanda’s car, stopped displaying title and artist! As I noted in that earlier column, missing or inaccurate metadata is at best a listener irritation and at worst, a tune-out factor. That could not stand.

The short-term fix was to use the outboard Inovonics generator with the new transmitter. The Inovonics generator has a DPSTEXT= function that populates both fields with the same string.  Nautel needs that same function, and I have submitted a request both with support and  engineering. Hopefully it won’t take long to get the change made.

That little exercise was an eye opener for me. It brought home what I already knew. And I will restate  it here: all our stations should be populating both RT and PS with title/artist metadata. If you’re not  doing that, you’re going to irritate or run off listeners.

While we’re on the subject of dashboard data displays, we have purchased TRE+ licenses for our Chicago/Rockford market stations as well as WDCX-FM in Buffalo, and we hope to get it up and running in the coming days. Right now we are awaiting development of an ingest for Nexgen. We were initially told at the product demos that we could use the RCS Zetta ingest, but when we tried it  in Chicago, it didn’t work. The formatting is different in Nexgen. BE has developed an Nexgen ingest,  but it’s still not quite working.

Mod Monitors

In two of our markets over the past months, we were part of a beta test program for a new AM modulation monitor from Inovonics. The monitor is the 526, and it’s a Jim dandy.

The folks at Inovonics asked a lot of questions during the development phase, and I was very pleased to see the  features and functions that we had asked for in the beta unit. One (or two, really) of those functions were dual high-level RF inputs for main and aux transmitters. Monitor input switching has always been a chore. The 526 not only has two inputs but they are remotely  selectable by GPI, so it’s fairly easy to make the monitor follow the transmitter that’s on the air.

We warned the engineers at Inovonics that there may be situations out there where tube-type transmitters are still in use and the RF pickup mechanism may be… unsophisticated. A hefty voltage could possibly be applied to the inputs of the monitor, so some protection should be in   place. They listened and it is.

There is a great GUI as well as a very readable local screen on the unit. Metering includes RSSI,  positive and negative carrier modulation, demodulated audio level, loudness and MDCL. There is also a spectrum plot that will show any significant issues with emissions. Bandwidth is selectable, as is average or peak detection. And there’s even an oscilloscope display of the IF or demod audio.

The monitor will email you with alarms. It will stream demodulated audio to you over the internet so you can remotely give a listen, and if you live in the AOIP world, you can feed the output to your system via AES67. What more could you ask for?

We’ve got 526 monitors ordered for the AM sites in Birmingham, Buffalo/Rochester, Detroit, Costa Mesa and Oakdale and KLTT in Denver.

Last month, we purchased 551 HD Radio mod monitors for our FM markets. This, too, is an amazing device. We’ll get one of our FM chiefs to tell you all about it sometime.

Rocky Mountain Update

Amanda Hopp, CBRE

 

Be a Team Player

As I have been working on getting things to a good place at each of my transmitter sites I can’t help but think that if you are in this business as an engineer, you have to be willing to do the little stuff, the mundane, the things you think you are too good for. I was raised to be that way and my dad leads by example.  He is at the corporate level at our company and he still goes out with me at times to help me with mowing, with plumbing issues, even with cleaning at times.  He knows, as do I, that if we don’t get the work done, no one will.  You should never just leave it to the next person.

Catching Up

With that mindset and the fact that I am a one woman show now, I was able to take a couple days and mow at one of my tower sites.  This site is a trouble site with mowing in that if the Canadian thistle gets too long and goes to seed, the county will write us a love letter.  They don’t like it when the seed gets into the river because it then gets into the farm crops.  I had mowed in June and typically we only mow once a year.  But this year, with all the rain, things grew up again.  Thankfully it didn’t go to seed but I still needed to get it taken care of.  The whole site wasn’t grown up so it only took about a day and a half to finish.  My next step is to spray some hard core herbicide that should take care of the thistle the rest of this year and next.  We are looking at rain this next week so I will have to time it so the herbicide doesn’t get wasted.  This will be my first time doing something like this.  We typically use RoundUp or something of the sort and spray small areas, mainly in the tower bases.  The trick will be speed and making sure I don’t run out of water since I can’t see the actual sprayer while pulling it.

Breath of Fresh Air

September brings fall, yes, it’s near the end of the month, but it is something to look forward to.  We get a break from all the heat and some of you have had record heat this year.  Fall brings the wind that will take the leaves off the trees.  Fall also brings a sigh of relief.  The year is winding down.  Any projects at work have more than likely been completed.  I am now having to plan ahead for 2024 and get any requests turned in in the next month.

Closing Thoughts

I will close this with the reminder to not be too good to do the little work.  If you are able to do it, just get it done.  Don’t ever think you’re too good to do the work asked of you.  Be a team player.

I hope to see you later this month at our next meeting.  And remember, go to our Facebook page and like it:  www.facebook.com/SBE48. And check out our website: www.sbe48.org

 

 

Random Radio Thoughts

Cris Alexander, CPBE, AMD, DRB

 

All-Digital AM

Regular readers have no doubt seen in these pages that we are converting WYDE(AM) to the MA3 all-digital AM mode effective September 1. In preparation for that, we had to file a notification with the FCC that subsequently went on public notice. The trade press picked up on that, so you may have seen bits in different trade pubs about the change as well.

Apparently, this conversion will make our station only the third in the nation to be (currently) operating as all-digital. That really puts us on the bleeding edge.

What are our expectations from this? As I told our friends at Radio World and Inside Radio, our expectations are totally based on what we’ve heard and read about Hubbard’s five-year “experiment” with all-digital AM on WWFD in Frederick, MD. The results there have been encouraging, but so much is dependent on factors beyond the technical.

For one, is the number of HD receivers in the Birmingham market significant, or are there just a handful? That’s hard to determine with any certainty, but with so many auto manufacturers including HD Radio in their entertainment systems these days, our bet is that a lot of people have the capability but don’t know it.

Some of the results are dependent on us and our ability to get the word out by way of on-air promos that we have the all-digital offering. I have a couple of thoughts on that, and I need to really flesh out those ideas in the coming days.

My initial inclination is to run an aggressive schedule of on-air promos (that will air on both the all-digital AM and on both simulcast FM signals) telling listeners that we have an all-new totally digital signal up on 1260 kHz and encouraging listeners with HD Radio capability to tune in. The all-digital AM coverage will undoubtedly eclipse that of either of the FMs.

I don’t, however, want to do that until we have had an opportunity to thoroughly evaluate the performance ourselves. We certainly would not want to send listeners to listen to this cool new digital signal if it sucks. I’m not too concerned about that, because we did run some brief overnight tests and know that it does work, but in the presence of skywave interference and with limited time available in the experimental period to drive the signal, we got only a cursory look.

So… by this time next month, we should have a much better idea of how well the all-digital signal performs, and hopefully we’ll get some good listener feedback as well.

 

Licensing and Management System

Well, they finally did it. Sort of. In late July, the FCC moved AM to its Licensing and Management System (LMS). They moved TV to that system before repack, then followed with FM some time later.

We were all dreading the transition of AM to the new system, and I was hoping they would give up and just leave it on the Consolidated Data Base System (CDBS), where it had been running so well for many years, but it was not to be. The move has been made, and while it has not quite been an unmitigated train wreck, neither has it been a smooth, seamless transition.

LMS has been a long, long time coming. I remember attending an NAB Radio Show in Washington, DC many years ago and watching an LMS demo provided by the FCC’s Jim Bradshaw. It was exciting, and it seemed that the transition was somewhat imminent even back in the late-2000s, but here we are almost 15 years later and are just now completing the transition.

There are a lot of good features in the system. It provides “one-stop shopping” for Media Bureau filings, which is very handy. Even AM direct measure applications can be filed online in LMS, a huge improvement over the paper filings that we were stuck with in CDBS.

The problem from my perspective is that the transition was made just a bit prematurely. One critical table in the database, the one that has information on international coordination, is not populated. This is important information, as the international coordination status of applications, permits and licenses affects how we deal with them in various studies, particularly night limit studies.

For example, if Mexico or Canada sends an application to the US for coordination and we object because it would produce impermissible interference to a US station, the US would object to that application and it would, in the database, carry an objected status. When running a night limit study, we would ignore that application in night limit calculations. But without that information in the database, we don’t know how to treat foreign records in night limit studies.

So what do we do? The FCC pretty much told us (offline) to continue to use CDBS for night limit studies. That works pretty well. There are very few new filings in the LMS AM database since late July, so the CDBS database is still mostly current. We just have to also run the studies in LMS to make sure that there are no new records that must be considered. And that extra step requires making some judgment calls that make any such study anything but automated.

I really don’t know what the holdup is here.

It would seem to me a fairly simple matter to propagate the LMS table with data from CDBS, but there must be something else going on. The FCC folks assure me that the fix is coming. We just don’t know when.

 

 

 

 

 

Rocky Mountain Update Amanda Hopp, CBRE

 

Exciting Things

I am excited for SBE Chapter 48.  We have several sustaining members of our chapter:  RF Specialties Group, SCMS Inc, Belden, Pro Audio, Rohde & Schwarz, Yellowtec and Broadcasters General Store.  The money we get from these sustaining members goes towards our chapter needs.  We have been having lunchtime meetings which include food.  We also have to pay for the hosting of our website and a few other things.  What doesn’t get used toward the meetings remains in our bank account to be used as needed.  Having these sustaining members helps tremendously and we couldn’t be more grateful for their partnership.

Annual Picnic

July 21 was our annual picnic up at Lookout Mountain.  Anyone who has been around Chapter 48 for a while knows this is the biggest-attended event we have each year.  We had Famous Dave’s cater the food, which was delicious.  RF Specialties Group sponsored the event, allowing everyone to have a free meal.  This was a big deal for us. In years past, we have had to charge $15-$20 per person to cover costs.  This year, we had 50 people show up for the event, including members and guests.  We had giveaways, cool swag provided by Pro Audio, Galvanized Endeavors, Broadcasters General Store and Telos Alliance.  Thank you to these great companies for providing items for us to give away.  Included in the giveaways were some Starbucks gift cards provided by Broadcasters General Store and Amazon gift cards provided by Telos Alliance.  After the picnic Paul Deeth from CBS took a group over to the Cedar Lake building for a tour of the site.  For any of you who attended, thank you!  It was great seeing everyone and getting to spend some time catching up.

Great Loss

We have lost two engineering members in our community.  Mark Smith passed away on June 26.  He had been working in the Denver area at one radio station or another for the better part of 30 years I think.  I first met Mark in 2008 when he helps Crawford Broadcasting move our 810-AM station to a new building at the tower site.  We had remained friends since then.  Then on July 26, Keith Peterson passed away.  While not an RF engineer, he had been employed by Crawford Broadcasting on and off since the mid-90’s.  He was able to help out with various engineering tasks as needed.  More recently, for me at least, he did much of the maintenance at my transmitter sites.  This allowed me to focus on the studio.  He also did most of Crawford Broadcasting’s corporate and station websites.  Keith helped me to rebuild our chapter website as well, making it look as good as it now does.  Both these losses will be felt for a long time.  We will surely miss Mark and Keith.

 

 

 

 

 

Upcoming Meetings

We have some good meetings coming up over the next few months.  Kirk Harnack from Telos Alliance will be joining us August 16. Then in September, Linkup Communications will be presenting.  In October, we will have David Layer from NAB presenting.  In November, we have a holiday gathering at Hacienda Colorado in Lone Tree scheduled.  It has been a few years since we last had any type of holiday event, so this will be a great time to gather before the crazy holiday season hits.  We will be providing lunch at all the meetings, which will be held at the same location: Crawford Broadcasting Company, in the basement conference room.  We are working at getting sponsors for our holiday event in November to help alleviate any costs to our members.  If you are interested in contributing towards this, please contact me and we can discuss further.

Some of My Own Thoughts

Now on to something not quite chapter related.  It’s been suggested to me lately that we should hire a landscaper to go out and mow our tower sites.  And it is a good idea, but that’s not how Crawford Broadcasting does things.  We have a nice Kubota tractor, a John Deere riding mower, two different string/blade trimmers, a chainsaw and a lawnmower.  All are in good working condition.

For as long as I can remember, the engineers around the company maintain their own sites. Is it fun? ot always.  In fact, it’s often miserable and hot.  But it gives us all a sense of satisfaction, knowing that the mowing being done is being done right.  We aren’t having to worry about some guy not paying attention and bringing down a tower or cutting a copper strap or sample line somewhere.  When we do it ourselves, we do it right.  Plus, if you do need to do work at the tower, you have a clear path.  I find it important to, even if you don’t mow anything else, to mow a good wide path to each tower base, to each guy anchor and all around the building.  Not to mention inside the tower bases.

Has anyone ever dropped a screw in some taller growth? Did you ever find it?  Me neither.  While I can’t guarantee keeping the grass and weeds cut short will help you find the screw you dropped, it will definitely help you when you are working.  I once had to set up a ladder at a tower base in some foot tall stuff.  Some of the growth is morning glory, and it just gets hung in everything.  I can’t tell you how many times I nearly fell trying to set the ladder up because of this.  Once I mowed, it made all the difference.

All this got me thinking about maintenance.  I have done some contract work in the past, and the sites are always in different conditions.  Some I can tell have someone that does go out often to check on things and clean up.  Others, though, are in rough shape.  I typically see all sorts of alarms on equipment at the sites that are more run down.

I have been an engineer since 2004 and chief engineer since 2008, and one thing I can say with authority is that if you maintain your site ‒ keep it cleaned up, check on things anddo the repairs that are necessary ‒ that the site just works.  Yes, we still have issues from time to time, but overall, they are few and far between.

If you work for a station group and are able to, check on things and take the time to make it right the first time.  Don’t cut corners.  If you set up some regular maintenance items, even things as simple as just regular clean up, I bet you’ll find things start playing nice again.

To me, this should and must be a part of every engineer’s job.  Even contract guys.  I know companies may not want to pay for you to go out and do this, but the importance of it should be pressed upon them.  Maybe they will realize in the long run that they can actually save money by allowing you to do some regular maintenance.

I’ll stop there.  I could go on and rant about this.  I hope to see you later this month at our next meeting.  And remember, go to our Facebook page and like it:  www.facebook.com/SBE48. And check out our website: www.sbe48.org

 

 

 

Random Radio Thoughts

Cris Alexander, CPBE, AMD, DRB

It was great seeing so many of you at the annual Lookout Mountain Picnic, always a highlight of the year. It’s a great occasion to catch up and to visit with folks that live in the same area but, because of busy schedules, we just don’t get to see that often. I could say the same thing about our monthly meetings, which have been well attended (but never with the turnout that we get at Lookout!). If you haven’t made a meeting lately, you really should come.

As I was visiting with some folks up on the hill during the picnic, the subject turned to broadcast STLs and how they have changed over the years. In my television years (back in the 1970s and early ‘80s), we used analog terrestrial microwave links, often in the 2 GHz band, to get audio and video between studio and transmitter site.

When I made the transition to radio, over-the-air STL links were in the 950 MHz band. Mono links were often on discrete 125 kHz channels, and early stereo links were paired mono links occupying 250 kHz of total bandwidth. Later, composite links became all the rage, with 500 kHz channels being the norm. Of course, we didn’t have all that many frequencies to choose from in the 944-952 MHz band, and in the big cities this was a problem, especially where transmitter sites were clustered on antenna farms. 950 MHz signals tend to scatter quite a bit, and even the largest grid antennas had significant off-axis lobes, which often made channel sharing a challenge.

Then along came hybrid digital aural STLs with codec add-ons like the Moseley DSP6000 feeding analog STLs. These had the digital advantages of very low noise, but they were sample-rate limited and could at best provide four channels of audio throughput. Still, they were a big improvement over straight analog discrete or composite STLs. I had issues using them over long, over-water paths (like our path from Long Beach to Catalina back in the day), probably because of continuously changing reflections off the water, but they worked well over land paths.

Full-digital STLs followed, with the Moseley Starlink and others providing true digital point-to-point links in the Part 74 aural STL band. Those sounded great (and still do – many remain in use today, and they are still in production). Their limitation was low power output, one watt standard and five watts in the high-power version. We had to use linear power amplifiers in many installations to get the required D/U ratio at the receive antenna in urban settings or to get the necessary receive signal on longer paths.

All these links were unidirectional, and for decades this was fine. Broadcasters used a number of different means for remote control, telemetry and status. 110 kHz subcarriers on composite STLs were common for outbound remote control, and 450/455 MHz Part 74 telemetry return links (TRLs) were used for telemetry/status backhaul, but there were only eight such TRL frequencies available, so only a few could use all RF paths for remote control. Others used subcarriers on their FM signals for backhaul, which was fine if the transmitter was working and on the air but absolutely useless if there was a problem. The rest had to use leased phone circuits.

At some point in the 1990s, Moseley came out with their LANLink, which was unlicensed in the 902-928 ISM band and provided a minimal amount of IP bandwidth, but that was often sufficient for remote control, RDS and PSD. The LANLink was multiplexed into the station’s 950 MHz STL antenna system, which worked okay and eliminated the need for additional antennas, transmission lines and tower loading, but there was insertion loss on both ends. Still, it was a viable solution for many stations.

As HD radio became more widespread and transmitter equipment began to feature GUI and SNMP interfaces, the need for more bandwidth grew exponentially. Transmitter sites with available internet service were in good shape, as connections could be routed over the public internet to supply the site with the needed device-specific throughput. But many sites were remotely located and there were no public internet options, so broadcasters had to fend for themselves. It was in the early 2000s that bidirectional Part 101 links started coming into use by broadcasters.

Part 101 (Fixed Microwave Services) offered many bands from 932 MHz to 95 GHz, but the most practical were the 6, 11, 18 and 23 GHz bands. While channel bandwidths up to 80 MHz were available in some of those bands, 10, 20 and 30 MHz channels were the most frequently used (and easiest to coordinate, for obvious reasons). Employing 2048 QAM, throughput in a 30 MHz channel could exceed 100 mbps, which was more than adequate in most cases.

There was, however, one problem with broadcasters using Part 101 fixed microwave links as STLs. There was an FCC rule that prohibited the use of a Part 101 fixed microwave link as the final RF link to a broadcast transmitter site. On the surface, that would seem to prohibit the use of Part 101 links altogether for STL purposes, and clearly that was the intent of that particular rule. The FCC wanted broadcast licensees to stay in their own lane, so to speak, and utilize the Part 74 frequencies that were dedicated to broadcasters for that purpose.

In my company, we began using Part 101 links in 2010, and we got around the “final RF link” rule by employing an 802.11 5.8 GHz unlicensed link between the Part 101 radio at the tower and the network at the transmitter building. In doing so (and we specifically told the FCC what we were doing), we used the 802.11 devices as the “final RF link” and were in full compliance with the rule. That 802.11 link also gave us a way to cross the base insulator of the “hot” AM tower supporting the Part 101 antenna, so it served a dual purpose.

Thankfully, the “final RF link” prohibition was deleted in the early 2010s, and broadcasters are now free to use Part 101 links as STLs without limitation. And while we continue to use 802.11 links in many of our AM and FM facilities, we have made the move to fiber in many others, providing a direct but RF and DC isolated path between the on-tower microwave radio and the network at the transmitter site.

There are some caveats with Part 101 links. First, there is a specific procedure, outlined in §101.103, for frequency coordination. This process is called PCN, for Prior Coordination Notification, and it requires “…prior coordinat[ion] with existing licensees, permittees and applicants in the area, and other applicants with previously filed applications, whose facilities could affect or be affected by the new proposal in terms of frequency interference on active channels, applied-for channels, or channels coordinated for future growth.” This is a labor-intensive process for individual applicants, who would need database search and interference analysis tools to determine what frequencies/bandwidths are available for a particular path (in both directions) and who those “licensees, permittees and applicants” are. Thankfully, there are commercial frequency coordinators out there, such as Micronet Communications and Comsearch, that will do all this for you for a very reasonable fee.

Another “gotcha” is that in areas where there are DOD facilities, the 18 GHz band may well be off limits, and you may not find this out until your link is already up and running. I know this because in Denver, where we have Buckley Space Force Base, I prior coordinated, filed for and was granted an 18 GHz path and placed the equipment order. As I was awaiting delivery, I got a notice from the FCC that the DOD had late responded to the PCN notice and objected to any 18 GHz use in the area. The grant was rescinded. Thankfully I was able to change to an 11 GHz frequency and convert the equipment order before any antennas or radios shipped. So while 18 is an attractive option for typical broadcast STL path lengths, beware!

We now use Part 101 links all over our company as primary STL links; we have all but abandoned all our Part 74 950 MHz links. We need the throughput and bidirectional connectivity at most all our transmitter sites, FM and AM.

Here in Denver, we use mostly Cambium PTP820S 11 GHz links, but we do have one Trango 11 GHz link to Lookout Mountain. We also have one Cambium PTP450i link to our Englewood transmitter site. This arrangement puts all our transmitter sites on the studio technical network and eliminates the need to route anything, except at Lookout where we employ a dual-WAN router to permit seamless connectivity either over the Trango link or the internet. We use public internet backups on all our microwave links.

In the Los Angeles area, we have a mountaintop tower site that has no utilities other than power, which we brought in ourselves at great expense. We use an 11 GHz Cambium link there to provide everything – STL, remote control, SNMP, equipment monitoring/control, security, video surveillance and telephone. We use multimode fiber to connect the on-tower Cambium radio to our network.

There are many equipment options for Part 101 links, including Moseley, Trango, Cambium, Dragonwave and others. There are IDU/ODU packages with both indoor and outdoor (antenna-mounted) units, all IDU systems that employ waveguide runs to the antenna, and all ODU systems where the radio mounts directly to the antenna and is either powered directly with usually -48VDC or PoE. Most offer hot-standby options where two radios are mounted to a single antenna, although this has a 3 dB loss.

I personally prefer the shelf-standby option where a fully configured, ready-to-hang radio is on the shelf and available for each band in use. While lightning seldom causes damage to tower-mounted radios, it can happen, and if you have a hot-standby radio on the tower, chances are that it, too, will be blasted along with the primary. Shelf standbys are immune to this, but you will need a tower climber to swap out the radio. Still, that’s better than waiting months for delivery of a replacement radio or repair.

STLs have come a long way in my 47-year broadcast engineering career. We’re in a good place now with lots of options. Keep those options in mind, and don’t think you’re limited to the few Part 74 frequencies.