GETting The Most Out of SNMP

Published by Davicom on January 22 2018

GETting the most out of SNMP

As SNMP becomes more widespread across many industries, it is important to understand some of the subtleties of using it to interface with various pieces of equipment.

One of the important points to consider when using SNMP is the syntax of GET commands, and the ability of SNMP managers, appliances or hardware to make sense of the data returned by a GET command.

The results returned following a GET will always be made up of a binary code, but what this binary code represents is of key importance. The code could be defined as a number, a text, a string of bits representing switch positions, an IP address, a true or false or a whole set of other meanings, and the definition of what these bits represent is called the syntax.

The SNMP standard has defined a certain number of syntax types varying from integers to display strings all the way through IP addresses and counters. However, some rudimentary SNMP managers or devices can only accept basic syntax types like integers, counters or truth values, and this can leave users in a bind if the devices they need to monitor via SNMP provide their data in other formats. In these cases, the monitoring device will not be able to do anything useful with the data, it won’t have the capability of understanding the results. Something like Lost in Translation!

Davicom’s built-in SNMP manager understands many different syntax types. This ensures easier communications between monitored devices and monitoring units.

The table below shows the principal syntaxes supported by Davicom units:


Integers 32-bit signed integer (can be sent to a metering input, and may need to be multiplied or divided—see below)
Octet Strings Binary number that is similar to a display string, but not strictly ASCII
Display Strings ASCII or Unicode values
Object Identifiers Yes, an OID within an OID!
IP Addresses Plain IP address like
Physical Addresses MAC (physical-Ethernet) device address like ‎30-8D-99-6A-29-FD
Counters32-bit counter
GaugesValue that can be sent to a Metering input
Time TicksIndicates time since last power-up of device. Can be used to check if a device has powered-down since the last checkup. Similar to what is used in Linux systems
Bit StringsValue like 00001000, where a single bit indicates a condition.
Unsigned IntegersImportant distinction with the Integers shown in #1 above
64-bit countersSelf-evident
Truth Values1=true and 2=false (go figure—this is the SNMP standard!)


In addition to these standard syntax types, Davicom has added extra functionality to ensure its RTU’s can understand “special dialects”. One of these additional syntax types is the Float from String type. This syntax is not part of the SNMP standard, but it is extremely useful for taking readings from devices whose designers have used “poetic license” in their equipment.

Some equipment manufacturers code actual numerical readings in the “Display String” format. For example, one transmitter manufacturer codes the data returned to a GET request as the ASCII values for the readings. So for a 100W power, they return ASCII 1 followed by ASCII 0 and ASCII 0. This is fine if the final goal is just to display the returned value, but if we wish to have a machine monitor that value and check it continuously for out-of-bounds conditions, the process isn’t simple. If the value had been coded as a direct 32-bit integer, it would have been easily readable and useable by a machine.  This is exactly what the Davicom unit’s Float from String type does. It converts a string of ASCII characters into a floating-point number that is readily useable to check for out of bound conditions.

It is crucial to know what type of result will come out of your GET command, so that you can get the most out of SNMP.



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 [] Sent: January-13-16 10:22
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” >>


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!