Lost in Translators

When I started at Iowa Public Television a little over 10 years ago, I inherited a conversion plan for the station's eight full powered and eight translator stations. The challenges and changes that we faced in implementing the plan for the full power stations has been well documented in this column. Because of the federal mandate, the changes in the mandate, the bumps in the economy and a myriad of other factors, the focus—out of necessity—was on full power television.

Prior to coming to IPTV, I worked for New Mexico Broadcasting, which like IPTV, was another statewide television network, only it was CBS rather than PBS. Another difference was that the New Mexico Broadcasting network was made up of only three full-power television stations and utilized almost 100 translators to reach a pretty significant number of people in geographically isolated communities throughout the market. All though the FCC deemed that translators were not a significant factor when setting up the digital conversion plan, there were a lot of broadcast engineers in the southwestern United States wondering how they reached that determination. So when I moved from New Mexico to Iowa where the reliance on translators was significantly less, I still focused attention on translators and what their future was within our system.


The translator plan that was in place for Iowa on my arrival was unacceptable. All eight of our translators had been displaced by digital television assignments. Channel searches had been performed and out-of-core CP had been granted for seven of the eight translators with the largest market, Ottumwa left with no service. I was greatly troubled that at seven of the sites, the plan called for moving to an out-of-core channel and then moving again to an in-core channel. The costs associated with this double move were certainly not inconsequential. Equally troubling was that the one translator that had an audience potential as large as the other seven combined had nowhere to go.

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FCC protected contour is the red circle, yellow to red wash is the Longley-Rice predocted contour.
Priority one in translators was getting Ottumwa a channel as it was on UHF channel 33—this was the DTV assignment for KTVO, the ABC affiliate in the Ottumwa-Kirksville market. The idea was to find an in-core channel that could be used for analog service and then flash cut to digital if possible. IPTV worked with consulting engineer Greg Best on this project. Greg was not only able to find an in-core channel that met the requirements but also noted he could get us a significant power increase if we wanted. This was an unexpected benefit and we moved quickly to file the CP and get the station on the air.

Even though I had construction permits for the other seven translators, I asked Greg to look at the other sites to see if he could come up with in-core channels that met the same criteria as the Ottumwa project. Much to our surprise, he was able to find channels for the remaining seven sites; curiously, three of the sites didn't actually need to change channels at all. This led to a modification of the translator plan which included the purchase of eight new translators for the sites from Axcera. The translators were to be supplied analog broadcast-ready with all of the materials and components necessary to flash cut them to digital when the FCC mandated the conversion of low-power services.

The analog translators were installed at all of the sites and now the process of conversion begins but of course, no plan is fool proof.


One of the challenges involves our two facilities in Decorah and Lansing in the northeast corner of the state. The original filings for these sites were done almost eight years ago and were negatively impacted by maximization filings of full-power DTV stations. This led to another channel search at these locations which resulted in two different in-core channels. Unfortunately since the translators had been purchased with the filters for on-channel flash cuts, we had to purchase new filters for the new channels and modify the antenna orders to change channels. This has resulted in a delay on these sites which may mean that their conversion doesn't happen until next spring. But that is a minor problem and certainly pales in comparison to the prospect of converting seven sites to out-of-core channels for analog followed by conversion of seven sites to in-core channels for digital service.

The first site that will be completed is Keosauqua, Iowa. When I started at IPTV, Keosauqua was operating on channel 54 using a 100-watt translator with an effective radiated power of approximately 640 watts. Fig. 1 shows the projected coverage of the site. The FCC protected contour is the red circle while the yellow to red wash is the Longley-Rice predicted contour. I recognize that many question the accuracy of Longley-Rice but one of the beauties of Iowa is that because we are so flat, even the FCC contours are pretty accurate and our experience is that they tend to under predict as opposed to over predict coverage. Since the conversion to digital mandated changes to our facilities, we decided to look at them as opportunities to improve service, especially in rural areas where the choices are more limited and the disposable income tends to be lower.

Fig. 2 shows the coverage predicted by moving to channel 24. We installed a 5 kW solid state translator at the facility and a directional antenna which gives us an ERP of approximately 114 kW. Clearly there was significant service improvement for the site, even to the south where the directional null was placed. Based on 2000 census figures, we estimate an increase of about 400 percent in population coverage. Now obviously not all of those people tune in but at least they have options that don't require a monthly subscription. Additionally the population that was tuned in are seeing a more robust and reliable service.

Fig. 3 is the projection for the station once the conversion has been completed. The translator stays on channel 24 and the digital ERP drops to 15 kW. Based on projections it appears that the digital coverage will be even better than the coverage of the analog service on channel 24. Since this will be our first translator conversion we will be doing field measurements once the site is operational to compare the projections with measured data. Based on our experiences with our full-powered stations I expect that we will be pleased with the performance but this will be the first UHF station we have had the opportunity to measure and compare the on-channel analog and digital service performance.

Why are we so focused on converting our translators when there is no mandate to make the conversion? There are a couple of compelling reasons. One is that in hybrid markets like Ottumwa where there are both digital full-power and analog low-power, it is difficult for the viewers to deal with the differences. This is especially true for the majority of viewers that have converter boxes because even if they purchased boxes with the pass-through capabilities, the viewer is still required to use two tuners to watch services and no matter how you slice it, that is detriment.

The more important reason is that we offer services on our digital channels that aren't available on our analog translators and we are all about service to the audience. We don't believe that anyone should be disenfranchised or made to feel less important because they choose to live in a rural area as opposed to a city. Providing access to Iowa Public Television to all Iowans is part of our charter and since their tax dollars support the network, we don't think they should be required to pay a subscription to get all of the services we supply.

Bill Hayes is the director of engineering for Iowa Public Television.

Bill Hayes

Bill Hayes, director of engineering and technology for Iowa PBS, has been at the forefront of broadcast TV technology for 40 years, 23 of them at Iowa PBS. He’s served as president of IEEE’s Broadcast Technology Society, is a Partnership Board Member of the International Broadcasting Convention (IBC) and has contributed extensively to SMPTE and ATSC.  He is a recipient of Future's 2021 Tech Leadership Award.