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Orban describes its XPN-AM/HD is its state-of-the-art AM/MW/SW processor.

The company says that it uses the latest generation MX limiter and provides unparalleled processing capability.

The processor is software-driven and controlled. One instance of XPN-AM software realizes a stereo AM and stereo HD Radio/netcast audio processor.

[Check Out More Products at Radio World’s Products Section]

Each processor consists of the following cascaded processing elements: input DC removal, stereo synthesizer, mono bass, left/right phase skew corrector, stereo enhancer, two-band defeatable AGC with window gating, ratings loop-through, equalizer/high-frequency enhancer, subharmonic synthesizer, multiband compressor, peak limiter, automatic loudness controller (HD only), transmitter equalizer (AM only) output.

The AM and HD processors split after the ratings loop through. An input/output delay allows for correlating processing delays. Processing handles 44.1, 48, 96, or 192 kHz sample rates.

Orban had planned to demo XPN-AM/HD with a Nautel NX-5 transmitter running MDCL (Modulation Dependent Carrier Level) with AMC of 6 dB at the NAB Show. In recent field tests with Nautel and TownSquare Media, Orban demonstrated that through aggressive processing with the XPN-AM, they were able to significantly reduce the transmitter’s power without impacting fringe coverage and without adding significant distortion to the signal. In one test, the NX5’s power consumption was reduced by more than 50%.

Info: www.orban.com

 

The post Orban Offers AM Processor appeared first on Radio World.

GatesAir says it is extending the proven operational benefits of its liquid-cooled UHF transmitters to VHF and DAB digital radio with the global debut of its Maxiva VLX-OP Series.

The high-efficiency, frequency-agile transmitter line covers DAB/DAB+ radio, low-band VHF (Channels 2–6) and high-band VHF (Channels 7–13). The VLX-OP Series offers the same software-defined modulations as Maxiva VAXTE air-cooled transmitters to support global analog and digital standards.

According to the company, like the Maxiva ULXTE liquid-cooled UHF transmitters, the VLX-OP Series integrates redundant, liquid-cooling pumps that efficiently move transmitter-generated heat to building exteriors. The system minimizes cooling requirements inside RF shelters, and especially reduces utility bills at medium-to-high power levels. It also offers the power density of Maxiva transmitters to reduce size and weight, and hot-swappable modular designs to streamline maintenance, according to the company.

Info: www.gatesair.com

 

The post GatesAir Rolls Out New VHF and DAB Transmitter appeared first on Radio World.

Techsurvey 2020 from Jacobs Media is out, and as usual some trends are as expected, but there are always surprises. Overall, the future looks bright for AM/FM radio.

The media pyramid shows AM/FM with 90%, surpassed only by smartphones with 92% and TV/video with 95%. The bad news is radio has dropped by 1% for the past two years. The pyramid also shows radio’s popularity almost evenly divided between men and women.

What’s the main reason for listening to AM/FM radio? At the top of the list with 69% is easiest to listen to in the car. The next most popular reasons — it’s free, DJs/hosts/shows, hear favorite songs/artists and feeling a connection with radio.

“One of radio’s primary advantages is its local feel.” Forty-five percent of Techsurvey’s respondents strongly agree with this statement, while 42% agree. Even more interesting, the percent that strongly agree and agree has risen from 77% of respondents in TS 2016 to 88% in TS 2020.

“I really feel a sense of connection to the station that sent me this survey.” Seven in 10 of those surveyed strongly agree or agree with this statement, again suggesting how important localism is. There is a slight gender difference, with 69% of men and 74% of women agreeing.

There is some very revealing information for commercial radio in the Net Promoter Scores (NPS). This number is derived by asking respondents on a scale of 1 to 10, how likely they would be to recommend the station that sent them the survey. Christian and public radio lead the NPS scores with 77% and 71% respectively, even though they are not commercial radio, and not part of this Jacobs survey. Rock is the top commercial NPS radio format, trailing with 55%. Whatever Christian and public radio are doing, commercial radio might be well advised to do more of it as well.

Finally, the survey asked about station bumper stickers. They generally fell out of favor during the 1980s, but maybe it’s time to bring them back. More than one in four say they would put their home station’s bumper sticker on their car if it were available. Of that group, most listened to rhythmic urban, 49% and rock, 47%. Clearly, some stations haven’t given up on bumper stickers, because 3% of respondents said yes, they already have one.

 

The post AM/FM Holds Fast in a Volatile Media Landscape appeared first on Radio World.

Zach Wiedenfeld of Sound Devices shows off one of the new shields.

Sound Devices manufactures portable and installed production sound and video products for professional applications. Now the Wisconsin-based company also has begun to make face shields for healthcare workers to help protect them from the COVID-19 pandemic. The company is selling them at cost to hospitals. Radio World asked co-founder Matt Anderson about it.

Radio World: What kind of gear is involved, and how did this come about?

Matt Anderson: We’re making disposable face shields to help protect the health care workers who are on the front lines taking care of patients. The design for this shield is an open source project, which can be read about here. Luckily, we’re right near the University of Wisconsin, and these are local businesses are friends; we are indebted to them for the design.

We got on board after I read about the shortage of these in the news. I came in last Monday and asked our sales folks to call some hospitals and they verified the need, so we started buying materials that day and were producing them en masse 32 hours later.

RW: Radio station engineers know Sound Devices for audio equipment. How hard is it to adjust your capital plant and workforce to produce these types of products?

Anderson: Converting our lines was not too difficult, in that our workers and the folks who run the plant are phenomenally flexible and hard working. At present the assembly of these items is all manual, and we’re able to produce about 5,000 per day. We’re working on tooling up the assembly process to dramatically increase these numbers.

One of the most difficult aspects of making high volumes of this product is procuring enough material, especially in this unique business climate. Fortunately our purchasing folks are very determined. Last week two of them were driving from store to store throughout Wisconsin buying up all of the elastic they could find. And added to this, we have longstanding relationships with the suppliers of the foam and the plastic material as these are suppliers we use every day for gaskets etc. for our audio products.

RW: How will these products be sold or distributed?

Anderson: We are selling these products direct to hospitals at our cost to make them. Hospitals can reach out to sales@sounddevices.com. We’re also now selling them on our web store at www.sounddevices.com.

RW: What else should we know?

Anderson: It’s been a humbling experience to see everyone step up and pitch in for this cause. My engineers and I worked this entire weekend each day via Zoom, from 8 a.m. until 10 p.m. on designing tooling to ramp up production. I’m happy to say that I emerged from my garage with all digits still intact and with a fully functioning “shield press.”

Though the workers at our company are normally very hard-working, they are really going to the next level — from sales, to purchasing, to production, to engineering — and absolutely no complaining, just dedication. Though this situation we’re in is terrible, it is gratifying to see how much positive human spirit can come out of such a situation.

The post Q&A: Sound Devices Now Making Face Shields for Health Care appeared first on Radio World.

The author is vice president of engineering for Riverbend Communications.

IDAHO FALLS, Idaho — One of our stations was operating with an older Harris transmitter, which was no longer supported, and it was due for replacement. We have two transmitters operating in the room, and it was so noisy you couldn’t have a conversation in there. I was interested in replacing the transmitter with something that would run quietly. I have experience with one brand of solid-state transmitter, and it is definitely not quiet. And, naturally, I expected a new transmitter to bring cost savings in terms of using less electricity, reduced air conditioning costs and not having to purchase replacement tubes. The Harris needed a tube which would cost nearly $3,000 rebuilt.

I surveyed the market for a solid-state transmitter that would check all my boxes. This meant considering liquid-cooled transmitters — a leap of faith for a guy used to working with forced-air cooled transmitters for 40 years. I knew the high-power UHF TV guys have been using liquid cooling with their high-voltage tubes for years but most of them seemed nervous. It was an attitude adjustment.

I reviewed the details for two brands of liquid-cooled transmitters, one of them the Rohde & Schwarz THR9, as well as the air-cooled transmitter I was already familiar with. I obtained price quotes for both the liquid-cooled units.

I did not pursue the air-cooled transmitter because it did not meet one of my requirements, since it exhausts all its heat into the room, it does not reduce the need for cooling. It required the same amount of air conditioning that the previous Continental tube rig needed.

The liquid-cooled transmitters have an external heat exchanger that installs outside the building, and the heat goes there. There is no need to draw in outside air or provide tons of air conditioning. I ended up selecting the R&S THR9 20 kW transmitter, based on three factors: the splendid worldwide reputation of Dr. Ulrich Rohde and his company which includes high-end test equipment and VHF TV transmitters; the favorable price quotation; and warranty coverage that provided peace of mind.

The THR9 comes with enough coolant hose to install the heat exchanger up to 60 feet from the transmitter cabinet- it can be located further if necessary. I decided to locate it just outside the front of the transmitter building, and the THR9 sits in the middle of the room. It is compact and I wanted to retain access to all four sides of the cabinet, a decision I do not regret. The old Harris remained in place as a backup transmitter. It wouldn’t have been possible to remove it anyway — it must have been installed before the walls went up.

R&S assigned a factory tech to support our installation, and he contacted me by email. He gave me a useful tip or two, but I did not find it necessary to contact them further during the install, which took me about one day after the electricians finished the AC hookup. I did read the factory manuals thoroughly before proceeding — they are translated from the German, and Google Translate was my friend.

Now that the THR9 is in operation, the transmitter room is much quieter than it was. The only sound in the room is the soft whoosh of the forced-air cooling in the grounded-grid transmitter of our other station at the site. The R&S transmitter is virtually silent. The only way to tell if it’s running or not is to read its meters. And it has no physical meters. The front panel has an LED touchscreen with metering and control, which retracts inside the cabinet when not in use. This screen is available remotely and we can view it anywhere. The transmitter has two network connections available to use.

There are two coolant pumps inside the single cabinet. If one is removed from service the remaining pump will carry the load. Similarly, the heat exchanger has two cooling fans and if one fails, the remaining fan is sufficient to carry the load. There are four power amplifier modules in the 20 kW transmitter, and if one fails, the remaining amps pick up the load and operation continues uninterrupted. Amps can be easily and quickly removed without losing a drop of coolant.

We have two years of experience with the R&S THR9 transmitter now, and I am thrilled with its performance and reliability (and silence). And when the grounded grid transmitter is replaced, it will be with another THR9.

 

For information, contact Rohde & Schwarz in Maryland at 1-410-910-7800 or visit www.rohde-schwarz.com.

The post User Report: Rohde & Schwarz THR9 Is Cool and Quiet appeared first on Radio World.

Lawo Power Core MAX is a new version of the Power Core AoIP mixing engine that can support multiple physical or virtual mixing surfaces — two, three, or even four mixing interfaces per engine, depending on mixing requirements.

Power Core has 96 available DSP channels, 80 summing busses, an internal 1,920 x 1,920 routing matrix, plus 128 dual-redundant MADI channels and 128 AES67/Ravenna channels, standard.

[Check Out More Products at Radio World’s Products Section]

Operators can use the eight rear-channel I/O expansion slots to accommodate more analog, digital, AES67 and Dante audio signals. There’s also ST2022-7 Seamless Protection Switching for dual-redundant AoIP network connections, and ST2110-30 compliance for seamless interoperability of audio and video equipment in combined radio / TV broadcast plants.

Lawo says that these capabilities, plus the ability to connect to as many as four independent Ruby mixing surfaces, makes Power Core MAX perfect for large multi-studio projects. In addition, broadcasters with medium-size or smaller facilities can use it as an I/O gateway and mixing engine for an entire radio station.

Info: www.lawo.com

 

The post Lawo Powers Up appeared first on Radio World.

The Congress has approved and President Trump has signed a $2 trillion coronavirus relief bill aimed at offsetting the economic impact of the spread of COVID-19. In that package was an additional $75 million for the Corporation for Public Broadcasting “to maintain programming and services and preserve small and rural stations threatened by declines in nonfederal revenues.”

This support is very welcome among the many rural stations the National Federation of Community Broadcasters interacts with. Yet the reality is stations across America need much more.

How serious is it? COVID-19 is the sort of financial calamity that threatens to wipe out community media.

[Read: Community Broadcaster: To Pledge or Not to Pledge]

Many of our country’s most vital stations rely on local underwriters, community events and listeners for the means to provide news, culture and education. What happens to these stations when businesses shutter, donors lose their jobs and our towns’ traditional gathering spots are no more? And, as critically, what happens to the life of a city when a community radio station dies?

Right now, there is not simply anxiety about the coronavirus cases stations are hearing about in their respective states. The stress about local economies is quite evident. There is hope the stimulus package will boost many communities. Hope, however, is not a promise. And in a pivotal year, where illness and elections bewitch the public consciousness, noncommercial media needs that promise now more than ever.

The cynic might say people can find their news on the internet. Still others would question whether these outlets playing music and local talk shows are relevant today. Yet the truth is that radio remains crucial to the overwhelming majority of Americans. Why? If the argument about ubiquity holds, wouldn’t hundreds of millions of people just be satisfied with getting their online channels of news and music?

A few are, but more are not, because they agree with people like Free Press’ Craig Aaron. Choice, localism and democracy are dear to all of us. “People need trustworthy news and information that isn’t hidden behind a paywall and more educational resources for kids who will be home from school for the foreseeable future,” Aaron writes. “This money isn’t for ‘Downton Abbey’ reruns. It should be earmarked specifically for emergency support, education, and especially local journalism.”

What’s more, increased federal and state attention on community radio stations should come with an appreciation for its effect on a city. Stations contribute to local creative economies and spark employment. The art galleries, restaurants, bars, live music venues and public spaces that find fellow travelers in community media make towns into destinations. Like businesses, noncommercial media must stay around.

CPB is incredibly valuable in this dialog, and its standards are an important starting point. However, as necessary are concerted investments by states and federal agencies into stations around matters like emergency preparedness and core infrastructure. In addition, the attitude of institutional and regional funders must change from the strictly transactional – you do this news story, you get this money, and somesuch — and more toward longer lasting community partnerships and investments that go 10 years and longer. Finally, I echo my colleagues who believe local journalism deserves greater support. The problem with an unnuanced approach is that media organizations with significant monies such as universities, or the networks disproportionately get major journalism funding while community radio is left to fend for itself. This is why long-term investment is necessary.

The coronavirus pandemic affects everyone and this situation is not changing soon. Emergency funding is excellent. It is also the prompt for new conversations on how states and regional leaders can fund on-the-ground media where it is much needed.

 

The post Community Broadcaster: COVID-19’s Threat to Community Radio appeared first on Radio World.

Delay in Filing Deadlines to Give Broadcasters Flexibility

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Henry Engineering’s SuperLight is a logic/control interface for controlling low-voltage studio tally lights. It can directly power 12 V DC LED tally lights that draw up to 500 mA. SuperLight includes a flasher circuit, as well as a DPDT relay output that can be used for any low voltage switching, speaker muting, or other utility use.

[Check Out More Products at Radio World’s Products Section]

It is compatible with WheatNet Blade, Axia xNode and similar network protocols. Cat-5/Cat-6 interface can control multiple units using one cable.

The LED output can supply 12 VDC at up to 500 ma; it can also “sink” up to 2 amps if used with an external power source. The LED output can be set to “flash” when on for use with on-the-air warning lights. All control, relay output, and LED output connections are via plug-in Euroblock connectors. Two RJ45 connectors are also provided for control wiring compatibility with WheatNet-IP Blade and similar installations that use Cat-5/Cat-6 wiring.

Info: www.henryeng.com

The post Henry Engineering Turns on SuperLight appeared first on Radio World.

The National Association of Broadcasters welcomed the historic federal stimulus package, and has posted a list of key provisions of interest to broadcast businesses.

“NAB is grateful to Congress and the White House for passage of the coronavirus relief package today,” said President/CEO Gordon Smith in a statement. “Allowing businesses with fewer than 500 employees to gain access to forgivable Small Business Administration loans will go a long way towards keeping many broadcasters and local businesses afloat during these difficult times.”

Smith said the devastation to local businesses “and to local broadcasters who support those businesses to drive commerce in hometowns across America” is unprecedented. He said NAB plans to advocate for further relief for broadcasters.

Examples of details called out by NAB in its summary of relevant provisions:

• The Small Business Administration Loan Program will support loans of up to 250 percent of average monthly payroll, up to $10 million. This effort is targeted at small businesses, nonprofits and veteran organizations with up to 500 employees; self-employed and “gig economy” individuals; and other specific industry sectors. The loans are to available immediately through SBA-certified lenders (banks, credit unions, etc.).
• Corporate tax changes will allow employers to defer payroll taxes incurred through the end of 2020, with half to be repaid by the end of 2021. There will be Treasury loans for “distressed industries” from a $454 billion pool. This is designed to target entities that might not otherwise be able to secure lending.
• The Treasury Department is being asked to implement a program that provides low-interest financing to lenders that make direct loans to eligible businesses and non-profit organizations where uncertainty of economic conditions makes loan necessary to support ongoing operations. Funds will be used to retain at least 90 percent of workforce until Sep. 30, 2020, with other requirements.
• Other points include enhanced unemployment insurance payments; an additional $600 per week for every person applying for unemployment benefits, over and above normal state benefits; and an employee retention tax credit program.

Find the full list here.

The post NAB Highlights Key Provisions in Stimulus Package appeared first on Radio World.

Here’s a Friday review of how broadcasters are innovating and adapting with new sources of content and new challenges in a news cycle and daily lives dominated by the realities of the COVID-19 pandemic. Don’t forget to let Radio World know about your station’s strategies, and be sure to share stories about how radio is helping out our communities.

— SiriusXM says daily White House Coronavirus Task Force are now available on demand via SiriusXM’s streaming services and satellite channel 121 and Pandora. The satcaster-streamer also says it plans to add state government COVID-19 briefings soon.

— Voiceover talent Harry Legg collaborated with Benztown to create this COVID-19 promo for Local Media San Diego’s XHRM. Listen below.

— This is the time of year when baseball would normally return to the stadiums and the airwaves, so many sports radio stations are getting creative to avoid dead air and keep fans tuning in.

Dickey Broadcasting‘s Ed Kennedy shared one idea on Facebook, saying that Atlanta’s WCNN(AM) aired a live-but-simulated Atlanta Braves vs. Arizona Diamondbacks game Thursday in lieu of the scheduled Opening Day broadcast. That’s an innovation combination of esports and radio that other broadcasters may turn to as the pandemic continues.

— Nielsen is out with new numbers showing how radio is faring under the coronavirus “stay home stay safe” directives. Check out the chart below to get a sense of how audio is being consumed in the current environment.

Also, 42% of consumers indicated that radio has helped them deal with the outbreak, and another 46% agreed that radio helps them know what stores are open and where to shop locally.

— In New York, iHeart Media’s Z100 is teaming up with the Empire State Building to provide new entertainment for those sheltering in place. At 9 p.m. Friday March 27 through Thursday April 2, the station will broadcast and stream Alicia Key’s “Empire State of Mind,” which will be synced to a light show as part of the new iHeart Living Room Concert for America. A new show will then begin April 3.

The post New Ways to Hear On-Demand COVID-19 Briefs, Broadcasters Play Ball and More appeared first on Radio World.

A U.S. federal agency is giving broadcasters special consideration to help assure continuity of operations during the coronavirus national emergency.

The National Communications Coordination Branch of the Cyber and Infrastructure Security Agency issued two letters in mid-March, letters intended to help broadcasters maintain access to their facilities. One specifically mentions the ability to obtain fuel, the other addresses access to facilities and travel freedoms.

The National Association of Broadcasters is recommending broadcasters keep the letters to show to law enforcement if curfews are put in place or fuel supplies interrupted for generators or other critical equipment.

CISA is part of the U.S. Department of Homeland Security. It listed eligible workers, including communications sector workers “who support radio, television and media service, including, but not limited to front-line news reporters, studio and technicians for newsgathering and reporting.”

In part the CISA letters state: “Critical communications facilities are necessary to ensure first responder, emergency responders, public messaging and 911 communications providing lifesaving capabilities are functional during this period of National Emergency.”

The bearer of the CISA letters “may travel and access the infrastructure facilities during curfews and restricted travel periods” in order to prevent loss of service or restore of critical communications services, according to the letter.

NAB says it has shared the CISA letters with its members. Copies can be found online in NAB’s Coronavirus Response Toolkit at www.nab.org. The letters are under the Operational and Editorial Resources tab. State broadcast associations have also been circulating them.

NAB noted, “CISA’s guidance is advisory in nature and not a federal directive or standard. In the end, final discretion whether to grant access to broadcast facilities and other locations rests with state and local emergency management authorities. Broadcasters are encouraged to coordinate with their state or local authorities regarding their need to access facilities and other locations in order to continue providing critical emergency information to their viewers and listeners.”

In addition to the declaration of a national emergency, some states have ordered non-essential workers to stay home during the coronavirus pandemic, and CISA makes it clear that “state, local, tribal and territorial governments are ultimately in charge of implementing and executing response activities under their jurisdiction.”

Federal law already defines broadcasters as “essential service providers” and allows such providers access to their places of operation in order to “respond to an emergency or major disaster.” Most industry observers believe that the provision allows essential broadcast station personnel access to their studios, transmitters, towers and other places of business for purposes of staying on the air. An NAB official Radio World that the association “believes that is a fair interpretation of the law.”

Also, some states have programs that designate “first informers” and “essential broadcaster” credentials to help assure broadcasters access to facilities and guarantee fuel deliveries to auxiliary site.

A senior NAB official says the current situation is “like nothing we’ve seen” and requires “preparation, planning and a great deal of flexibility” on behalf of broadcasters.

“Each station or community is likely to face different challenges depending on resources and how individual states, municipalities and authorities are responding to the pandemic. Broadcasters will need to take the necessary precautions and utilize all the tools in their tool chest to maintain operations,” the official said.

The post CISA Letters Support Radio Stations During National Emergency appeared first on Radio World.

The FCC-required proof-of-performance was an annual ritual for broadcast engineers from the earliest days of radio up to deregulation in the 1980s. 

In the early 1970s, many engineers might have fantasized about making those measurements with high-end gear such as an HP 204 audio oscillator, 403 AC voltmeter, 330 distortion analyzer, a Hallicrafters communications receiver and a Tektronix oscilloscope. 

The oscillator, voltmeter, distortion analyzer and communications receiver were required items for the annual FCC Proof of Performance measurements. An oscilloscope was useful, but not essential. The reality in the workshops of most small- and medium-market stations was usually a bit different than what the engineer might have wished for. 

The workbench of a 1970s small- or medium-market station might include a Waveforms 510-B audio oscillator, Daven VT-795-6 attenuation network and Heath IM-12 distortion meter.

Pictured is an ensemble that might be more likely in a small- to medium-market operation in 1970. For the audio proof, a Waveforms 510-B audio oscillator, Daven Type VT-795-6 attenuation network and Heath IM-12 distortion meter. The RF portion of an AM proof might be accomplished with a Heath GR-54 communications receiver.

The audio oscillator and precision 600-ohm attenuator were often two separate units. As with many high-end oscillators, the Waveforms 510-B had a 0-10 volt variable output control and a 600-ohm balanced transformer output. The Daven VT-795 600-ohm decade attenuator provided precision attenuation in 10, 1 and 0.1 dB increments. The AC voltmeter and distortion meter functions for this 1970 package were provided by a Heath IM-12. Although of simple design and modest cost, the IM-12 could measure distortion down to 0.1%. The GR-54 was a six-tube, single conversion communications receiver covering 180 kHz to 30 mHz. It was Heathkit’s mid-line shortwave receiver at the time.

TUNING UP THE CHAIN

In the days of analog vacuum tube broadcast gear, this test equipment was used heavily. Most stations took advantage of the FCC’s designated experimental period from midnight to 6 a.m. Monday to tune up the entire broadcast chain. A lot of things could have gone wrong in the preceding seven days. 

The emission of tubes could fall past the critical point, or they could become microphonic. Wax coupling and bypass caps could overheat and short out, often taking plate load resistors and other components along with them. Carbon composition resistors, particularly in grid circuits, could become noisy, generating lots of white noise. Electrolytic caps in power supplies or decoupling circuits would eventually dry out and lead to increased ripple or motorboating. And of course, any of the hundreds of contacts in tube sockets, audio and RF connectors could become noisy or intermittent.

Between this ongoing maintenance and troubleshooting, a lot of test equipment was checked only once a year, usually right before the proof was conducted. 

The good thing was that all measurements required by the FCC were relative, and not absolute. For example, frequency response in measured in decibels, and is really the relationship between two voltages, so the absolute value is irrelevant. It’s the same idea with distortion. Harmonic distortion is a percentage of the original signal voltage. That being said, good engineering practice suggests that test equipment be kept as accurately calibrated as possible. 

The first step in getting test equipment ready for the proof was checking the response of the oscillator into the AC voltmeter. For an AM proof, that meant checking the response from 50 to 7500 Hz, referenced to 1 kHz. FM proofs required a flat 50 to 15,000 Hz response referenced to 400 Hz. Any deviations greater than 0.2 dB needed to be noted on a calibration chart, and these deviations were subtracted from the transmitter response deviations before logging them on the proof forms.

The next step was measuring the distortion level of the test equipment. The audio oscillator is connected directly to the distortion meter. The total noise, hum and distortion of the combo is measured, and for FM proofs, it needs to be 0.25% or less, for AM, 0.5% or less. For test equipment of the day, a figure of around 0.1% was average, as long as you were careful to avoid ground loops. With response and distortion checks complete, the model and serial numbers of  the equipment could be recorded on the proof sheet, and the actual work could begin.

The commission’s requirements for checking harmonics and spurious radiation of an AM transmitter were about as open-ended as the audio portion was prescribed. All that was stated was that the engineer needed to measure the transmitter’s spurious and harmonic radiation, and that such emissions be suppressed sufficiently to avoid objectionable interference to other radio services. 

Taking these measurements at the transmitter site was ill-advised due to the possibility of receiver overload. They were usually done at the studio with the communications receiver connected to an outdoor antenna. The receiver was tuned slowly across each band, checking at each harmonic of the station’s carrier frequency. Checks were made of the first 10 harmonics, although the second and third were usually the most problematic. Issues with excessive harmonics were usually the result of capacitors in the harmonic traps that had gone open due to lightning strikes, or loose or corroded hardware and/or connectors.

WORKHORSE GEAR The Waveforms 510-B had performance specs comparable to HP audio oscillators of the day but it was much more compact.

The Waveforms 510B audio oscillator was a real workhorse. It was a textbook resistance-capacitance tuned oscillator built very compactly, and with precision components. Tube lineup consisted of a 6X5 rectifier, 6SJ7 oscillator, 6AK6 cathode follower and 6AK6 output.

No space was wasted inside the Waveforms 510-B. Note the sockets for easy replacement of twist-lock electrolytic caps. Why more manufacturers didn’t use these is a mystery.

Although sighted more frequently in manufacturing facilities, physics department labs and R&D environments, the 510 occasionally surfaced on radio station test benches. Specifications called for a range of 18 Hz to 1.1 mHz , a response of  +/- 1 dB from 18 Hz to 200 kHz and distortion less than 0.2%. Noise was 60 dB below signal. These were the guaranteed specs, but the performance of some units was much better. Pictured with this 510-B is the T10 matching transformer, mounted on the bottom of the oscillator. It provided a balanced 150/600-ohm output and a response of 20 Hz to 50 kHz. The 510B’s specs were comparable to the HP audio oscillators of the day, but the 510 was much smaller, measuring just 4 inches wide by 6 high and 6 deep.

The Daven VT-795 was simplicity itself, consisting of 10-, 1-, and 0.1- dB/step attenuators, wired up in series. Double banana jacks were provided for input and output. There were no other components, and no maintenance was required.

The IM-12 harmonic distortion meter was to be found on many workbenches. The theory behind these meters is rather simple. To determine how much distortion has been added by an amplifier, simply subtract the input signal from the output signal. What is left over was generated by the amplifier, mostly harmonic distortion, usually with a bit of hum and noise thrown in. A Wein bridge, with a negative feedback network across the bridge circuit is used to null out the fundamental frequency.

The simplicity of Heath test equipment is evident when looking inside the IM-12 distortion meter.

Regular maintenance for the IM-12 consisted of checking its six tubes, going over switch contacts and adjusting the tweaks for voltmeter calibration, coarse balance and hum balance.

The Heath GR-54 was in production in kit form from 1966-71, with the price increasing from $85.00 to $135. If assembled carefully, it would perform well, although sometimes it was not without “issues.”

The Heath GR-54 communications receiver could be used for the harmonic check portion of the AM proof, and to calibrate the FM modulation monitor prior to the FM proof by using the Bessel null method.

The GR-54 had all major components on three circuit boards: IF-audio, RF-oscillator-mixer and band switch. All of these boards relied on a solid mechanical connection to the chassis for grounding. This was never a good idea. If the kit builder didn’t adequately tighten the mounting hardware, or left the lock washers off, erratic and unusual problems could result. The same thing occurs to most GR-54s after being stored for a few decades in a damp basement, as corrosion takes its toll. 

Circuit updates for the GR-54 are readily available online. Full restoration can be a tedious but not complicated process. The result is a solid, well-performing receiver.

The Heath GR-54 communications receiver could be used for the harmonic check portion of the AM proof, and to calibrate the FM modulation monitor prior to the FM proof by using the Bessel null method.

The 510-B and the Daven attenuator shown with this article came from a college surplus grab in the early 1970s. They saw regular use in contract engineering duties through the mid-’80s. The IM-12 was a gift from a fellow contract engineer, who was relocating, and didn’t have room to pack it. The GR-54 was acquired about 20 years ago from a non-technical friend who purchased it at a yard sale. It didn’t work well, and got handed off to me. After downloading a manual and rounding up the usual suspects, it was returned to good operating condition.

Tom Vernon is a longtime contributor to Radio World. He wrote last September about the history of remote control systems; read it at https://tinyurl.com/rw-remcon.

Comment on this or any story. Email radioworld@futurenet.com with “Letter to the Editor” in the subject field.

The post Proof of Performance, 1970s Style appeared first on Radio World.