Davicom's Blog

Burnt DV-Micro is NOT toast!

Published by Davicom on August 4 2017

       RF Gaskets do double duty

As is well known in the industry, Davicom’s remote site management products are robust and designed to handle the harsh RF environments often found at remote transmitter sites. One design feature used to attain this “RF robustness” is our integration of flexible RF gaskets into the chassis design of certain products.

Davicom RF gasket

Photo 1. Sample of RF gasket used in Davicom’s DV-Micro.

Davicom intelligent site management systems RF gasket

Photo 2. Close-up view of RF gasket.


The use of these gaskets and other design features allows the DV-Micro to operate reliably in electrical fields of up to 10V/m at frequencies between 30MHz and 1GHz. The flexible metal gasket prevents any RF leakage from being emitted outside the chassis, but more importantly, it also prevents any high RF fields from entering the box and affecting operation of the electronics inside.


Who would have thought that these little gaskets would also serve a purpose during a site fire?

On June 4th 2017, a fire destroyed KHCB’s Madisonville, Texas FM transmitter site.  Lightning is the suspected catalyst for the fire.

Transmitters at site after fire

Photo 3. View of transmitters

rack after fire

Photo 4. View of equipment rack

Paul Easter, KHCB’s Technical Director and his engineering team quickly put the site back on the air with a temporary shelter and backup equipment. While cleaning-up the site, Paul noticed his remote-control unit (a Davicom DV-Micro) blackened, but still mounted in its rack. He took it out and brought it back to his Houston headquarters. Even if, on the outside, it didn’t look pretty, Paul decided to try powering-up the unit to see if it was operational. When it did power-up, he decided to try connecting to it and downloading the site’s event log, which he did obtain.

As it happened, I was visiting Houston to do a presentation at the July SBE lunch meeting, so Paul gave me the unit and I brought it back to the Davicom factory for complete tests and a repair estimation.


front view DV-Micro after fire

Photo 5. Front panel view of DV-Micro that was in fire

DV-Micro back after fire

Photo 6. Rear panel view of DV-Micro that was in fire


Once back at the office, I gave the unit to the production department and asked them to take the unit as it was, and to run the full post-production tests on it, as if it was being shipped out to a customer. Apart from the blackened chassis and semi-melted front faceplate, it passed on every count!

See a video of this unit being powered-up here:

DV-Micro after fire internal view

Photo 7. Internal view. All circuits and parts inside the chassis were clean and operational.

Our theory is that the RF gasket prevented any fire or hot gasses from entering the chassis and destroying the electronics inside. The following pictures show the detail of these gaskets.


DV-Micro RF gasket cover

Photo 8. View of one of the 4 RF gaskets used on the chassis of the DV-Micro


DV-Micro cover

Photo 9. Close-up view of RF gasket showing burned outside and clean inside


All this goes to show that good design costs more, but always adds value, sometimes in unexpected ways!


DV-Micro front view with fire

John Ahern

July 2017

Special thanks go to Paul Easter and to the good folks at KHCB for allowing us to use their pictures and to tell the story of this unfortunate event at their Madisonville site.

Dear Daddy

Published by Davicom on January 13 2016

From: Becky Dornster [mailto:becky.dornster@gmail.com] Sent: January-13-16 10:22
To: Bucky@wkrp.fm
Subject: I never see you any more

Dear Daddy,

I’m sending you this e-mail because I never get to see you anymore. When I get up for school in the morning, either you’re already gone, or you’re sound asleep because you worked all night at that transmitter site of yours. Come to think of it, that transmitter site woke me up twice last night when the phone rang. I could hear you muttering about all those false alarms you could do nothing about.

When I was little, you explained to me why your work was so important, about how your transmitter site had to always be ready in case of emergencies like tornadoes or hurricanes, about how people counted on you to keep them connected, informed and involved in our community.  I understand that and am proud that you are such an important link in this chain.

I just wish you’d give yourself a chance. This is 2015, why do you have to travel 2 hours to go to a transmitter site when I can control a telescope on the Canary Islands by using my iPod?

So why can’t this transmitter site be controlled and tested from home? Why does it have to keep calling on the phone in the middle of the night and waking us all up? Why doesn’t the site call your boss, Mr Carlson every night to wake him up instead?

Like you keep telling me for my homework: work smarter, not harder. So I Googled “intelligent transmitter remote control” and found this web site from a company called Davicom. They have a box that can control and monitor everything in your transmitter site, and do it intelligently, without sending you all those false alarms. They even have an App to control these sites. I tested it out on the school’s iPad with Mr Nessman in science class and he was impressed.

Now why couldn’t Mr Carlson let you buy this Intelligent Remote Control? I’m sure he’d agree quickly enough if HE was the one being called every night. That Davicom company says that if you save one trip a month to your site, their smart box would pay for itself in one year. And that’s just the money side of things. If you weren’t gone all the time and up every night, you’d be more relaxed and would have time to see how good I am at soccer now.

If you need help, I can send an e-mail to Mr Carlson telling him I miss you and that I think this Davicom box will help you a lot in your job (and let you sleep at night!)

Promise me that if you do save that one trip a month, we’ll go out for ice cream with Mom and Jenny.

Your 14 year-old, loving daughter,

Becky Dornster

Hats off to CCBE for the “IP Networking Technology for Broadcast Engineers” workshop

Published by Davicom on October 6 2015

WOW !!

Hats off to CCBE for the “IP Networking Technology for Broadcast Engineers” workshop at their 2015 annual conference.

The CCBE has established a relationship with the Society of Broadcast Engineers (SBE), and arranged an all-day workshop seminar. The seminar was presented by Mr. Wayne M. Pecena, of Texas A&M University and sanctioned by the SBE. As recognition of their presence and to complement their career development, all attendees received a certificate. The course also prepared attendees to apply to the SBE to take the CBNE – Certified Broadcast Networking Engineer exam, an important career credential for all those currently working in the rapidly changing field of broadcast technology.

Mr. Pecena gave a most enlightening, and easy-to-understand description of the technology behind TCP/IP Networking, and how it all comes together to allow world-wide communications over the public Internet and private WAN/VPN networks. If you wish to get a handle on this technology and understand what is going on when your computer connects to a remote device, system, or broadcast site, over private and public networks, the complete presentation is available at the link below.

Mr. Pecena has graciously accepted that we publish the download link on our site, and share it with all who are interested. We invite you to do the same.

CCBE 2015 “IP Networking Technology for Broadcast Engineers” >> http://www.sbe.org/sections/documents/CCBE_Sept15.pdf


A NOC in your Pocket

Published by Davicom on June 3 2015



How the Dav2You App is turning out to be a NOC in your pocket!


 When we initially planned and designed the Dav2You app for smartphones and tablets, our goal was to provide a simple means of communicating with our Davicom Intelligent Site Monitoring Systems. This means would take full advantage of the rich feature sets provided by the Apple (iOS) and Google (Android) Operating Systems of these smartphone and tablet devices.

Graphic User Interface (GUI) features, such as maps, would allow users to easily identify the location of their sites. Scrollable lists would give users full access to large site reports and logs while notifications would warn them of problems at the site.




Once we had this all programmed-up and running, we realised that there was no limitation on the number of sites we could receive notifications from. With the maps providing an overall view of the network and the lists and logs providing a database of alarms, Dav2You was turning out to be a Network Operations Center (NOC) on your smartphone, or even better, a NOC in your Pocket!




See the video of our new Lightning Detector, the DVLD-1 on YouTube

Published by Davicom on May 15 2015

See the video showing our new Lightning Detector, the DVLD-1 here:


We have a number of these detectors in operation around North America collecting valuable data and e-mailing it to us on a daily basis.

Stay tuned for more news in the coming weeks and months!


Published by Davicom on April 30 2015

In North America, most consumer and professional electronic equipment must conform to FCC or Industry Canada standards. These standards govern the unintentional RF emission levels allowed from equipment and are useful as far as reducing the overall “RF background” noise present in our society. Without these standards, bad design and the race to the cheapest product would quickly make the electromagnetic spectrum unusable due to the generation of parasitic signals.


On the other hand, our modern lives are increasingly dependent on intentional RF emitters such as cell phones, Wi-Fi networks, microwave links, television and radio broadcast transmitters, public safety radios and mobile/fixed radios and repeaters. These intentional emitters legally produce RF signals (some at very high levels) in many frequency bands of the electromagnetic spectrum.


In our line of business, I’d say that electromagnetic immunity is more important than electromagnetic emissions since our monitoring equipment will often be used on remote sites with RF transmitters. Since there are no mandatory standards for immunity in North America, and since we do want to ensure our equipment will operate correctly in complex/hostile electromagnetic environments, our fall-back solution is to use the European CE Immunity standards that are part of the European EMC Directive.


These standards, which were developed in the mid to late 90’s have evolved over time with the addition/refinement of different product categories. The category under which we now test our Davicom Remote Monitoring and Control Units is Information Technology equipment and the levels of immunity for this category are defined in the EN 55024 standard.


The actual procedures for the tests are described in another set of standards. For example the Radiated RF immunity procedure is described in EN 61000-4-3. In these tests, a device under test (or DUT) is placed in a high-level RF field and monitored for any change in its behaviour. This field can be produced by an antenna in an anechoic chamber, or by a transmission line in a Transverse Electromagnetic Cell (or TEM Cell). Comlab uses a large TEM cell.


Electromagnetic immunity is concerned with much more than just radiated RF. Think of any time a spark jumps from your fingertip onto your computer’s keyboard (and your computer crashes!).  These sparks are known as electrostatic discharges (or ESD) and are also the subject of an EM immunity standard, in this case the test procedure is described in EN 61000-4-2. Tests are carried out with an ESD Gun that generates sparks of up to 15kV which are applied to the DUT while monitoring its behavior.


EM immunity extends into the wired aspect of electronic equipment also. By different inductive and capacitive principles, RF energy can be coupled into various conductors leading into and out of equipment. This RF energy can wreak havoc with circuit and software operation if it is not controlled, filtered and eliminated. The procedure for carrying out these tests for immunity to conducted RF energy is described in EN 61000-4-6. The tests are performed with a high-power RF signal generator and a clamp-on inductive loop to inject the RF energy into the cables of the DUT while monitoring its operation.


EM immunity even covers the field of utility power. Although you may have a tendency to take your utility power for granted, and assume that it is delivered to you as a nice clean 120V, 60 Hz (or 240 V, 50 Hz) sine wave, this is never the case. The utility power spectrum is a jungle of parasitic signals, harmonics, overloads, glitches, back EMF peaks and even lightning surges. This is another area where testing the immunity of equipment is important to ensure reliable operation.


If lightning hits the power utility pole feeding your site, you want your equipment to survive this back-door attack into your system. This is where the tests for surge voltages described in EN 61000-4-5 come in handy. These tests are performed with a special device that capacitively injects large surge voltages on the power cord while checking for proper behavior of the equipment.


If your power line is also feeding large motors, air conditioning compressors, and your high-power transmitter, you don’t want power glitches, such as your transmitter suddenly shutting down for protection, to crash your remote control system. The tests described in EN 61000-4-4 simulate these conditions.


When these standards first came out, they seemed very intimidating and difficult to satisfy. However, hard work, good design practices, practical RF experience and continuous testing in our EMC lab over the years have produced consistent results at satisfying and even surpassing these standards for all our products.