Monthly Archives: February 2015

Amateur Radio Station Grounding – National Electrical Code

First and foremost, we are required to comply with National Electrcal Code (hereafter referred to as NEC). This is what all electrical systems and their associated “things” must follow in the United States. All of your home or business electrical systems must be constructed and maintained in accordance with NEC. This electrical code is written with the intent to ensure that life and property is protected.

In fact, it is written that the following is the purpose of NEC:

“(A) Practical Safeguarding: The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity.

B) Adequacy: This Code contains provisions considered necessary for safety. Compliance therewith and proper maintenance results in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use.

(C) Intention. This Code is not intended as a design specification or instruction manual for untrained persons.”

Life safety is priority #1. Everything done as part of electrical systems revolves around life safety, from the service main, to the breakers, to the wiring in the walls and the outlets. It (NEC) also covers things like how conductors or wiring should be routed, protected from damage, short circuit and overload protection, and obviously grounding and bonding.

Our little part of the world, amateur radio, is also covered. This is referenced in Article 810 NEC. You will find both receive only, and transceiver systems covered here. The requirements for amateur stations aren’t unique to anything in particular however they do build upon/reflect all of the other requirements in the other sections of the code. You’ll see things like wire size (gauge) requirements are the same here, as they are elsewhere. Additionally, the same requirements for protecting exposed conductors, and using UL-Listed components still stands when being applied to your amateur station. Over time, we will dive deeper into Article 810 and examine it closer. There is a lot in there, and it can be confusing and overwhelming to many folks. For now I will try and summarize some key points, or what I think is important to come away with until I can explain things a little further.

So what does this all mean? It means the station you have at your home or business must meet the requirements of the NEC. A ground system of some sort must be constructed and all antenna masts, lead in conductors, station equipment etc must be bonded to it in accordance to the rules as defined. There are no variations permitted. NEC will state the minimums for things such as wire gauge, ground rod (electrode) lengths, spacing requirements, etc for the system and components and those are expected to be met. Unfortunately for many folks, NEC wasn’t written for the layperson to read and comprehend. Remember earlier, point “C” of the NEC purpose? It was written for engineers and electricians and those working the in trade. It’s expected that one understands that just because the code requires you to say, connect two wires together it doesn’t mean use whatever you have laying around to do this with. Rather, you’re expected to reference the appropriate section for splices in wire or conductors in a given circumstance. Hamming it up is not permitted.

It is important to also understand that NEC is not concerned with how well your station operates. This is of no concern to the NEC. The sheer fact that you can’t talk to that rare dx entity or dxpedition doesn’t mean you can install your station haphazardly or dangerously. The only thing that is important is that the station complies with the rules and therefore be determined to be safe for those who use it or others who might be exposed to it (equipment) or the electrical hazards associated with it.

Your local Authority Having Jurisdiction or AHJ may require details that are more stringent than NEC does. In these cases, you must comply with the more stringent of the two. For example, if your local AHJ says you must not use any conductors smaller than 500MCM and all underground or buried splices must be exothermically welded, then you must comply or expect to deal with the ramifications of non-code compliance. This is a greatly exaggerated example but I give it to make a point.

While we are here I think it is prudent at this point to discuss industry standards. You’ll find a lot of places online or during the discussion of this topic with folks that some may mention references to industry standards such as Motorola R56, or EIA/TIA standards, FAA, NWS, or BICSI, etc. These standards are written with the intent of providing guidance and rules if you will, for communications sites in the industry or otherwise. You’ll find a lot of things that seem excessive such as statements saying “conductor size shall not be smaller than X AWG”. There are scientific reasons why these are called for.

You might say “why don’t they just follow what NEC requires? Why do more? Doesn’t NEC know best?”. Well, the NEC has determined their wire size requirements for example, meet the minimum requirements to provide adequate protection from the electrical hazards that may be encountered. It might seem silly to say “no conductors smaller than #2 AWG may be used” but that requirement for the industry standards is derived from the fact that the industry knows the larger, or coarser wire sizes can conduct more current more effectively during lightning strikes. The purpose of the bonding conductors is to help shunt and direct the excess energy away from the folks who use and maintain communications gear, in addition to the equipment at the site. Unlike NEC, the industry IS concerned with equipment.

You must understand that these standards are not replacing NEC. In fact it is quite the opposite. The standards all are based on NEC, just like your local electrical codes set forth by the AHJ in your area. You’ll never find them saying anything that is not in line with code (at least not intentionally) anywhere. They simply take the minimums and improve on them. And, in all cases these standards provide above-and-beyond protection of life and property when they are applied correctly.

As responsible amateur radio operators, we should strive to meet these industry standards if at all possible whenever possible. However, at a minimum we must comply with NEC and local codes. This means no stand-alone electrode systems, no failing to properly protect lead-in conductors, etc. We will go over these things later on in this series.

I apologize in advance if some of this is long winded, but I feel it is important to address at the start. I cannot stress enough how critical it is to follow the requirements as set forth by the NEC and the AHJ’s. It is not written to be considered excessive or unnecessary. There are sound engineering and scientific reasons for all of it. As I have said before, just because your Elmer or person who you seek advice from says “bah don’t need that it’s all hogwash!” doesn’t relieve you of the requirement to comply with electrical codes. Yes it is expensive, yes it is time consuming and yes it generally results in back breaking labor. However at the end of the day, you can sleep better knowing you have done things right and have tried to protect your station, your family, and yourself the best you can.

 

Until next time, 73 de N7AMD sk sk sk

 

How to build a tunable repeater on the cheap (Part 2)

In my last post, I went over the basic parts of a repeater, and said the parts I selected for our build.  I will go into the choices further and give some information about getting the baofeng working with a COR output.

The radio I selected was the Baofeng UV-5R.  Its schematics are available online, and I found that the radio only lights up its green RX LED circuit when the PL circuit breaks squelch when using tones (unlike other handsets that show receive, even though they don’t break squelch). This seemed like the perfect place to add a link from the hand held to the controller.

baofeng-rxled-schematic

The transistor shunts the circuit to ground (with the battery on the other side) when a signal comes from the radio’s PIC.  So we will have to keep a positive voltage on the COR line with a resistor so that when it shunts to ground, we can have the COR circuit go low when active (ACTIVE-LO polarity on the I/O menu of the ID-O-Matic).

So, I took the UV-5R apart (instructions are already on the web, so I will not duplicate them here), and found where the circuit physically is. It is by the PTT button, and wraps around the VFO-MR orange button.

UV-5R RX Led Circuit

You do NOT need to remove the LCD screen for this mod.  But you should remove the speaker from the board connections, and the case, so you have room to route the wire out.  I drilled a hole in the case on the opposite side (where in front of where the mic/headset plugs are).  I soldered it directly to the bottom of the two transistors (the correct circuit in this case).

Here is when I was testing the circuit before I added a ground between the two (this will be added permanently when I add my Byonics HTK2P cable that will power the controller, and give me the speaker output all at once).

Once I verified that COR was working correctly, I packed it all back into its casing with the cable done in such a way that it could be used in the future.  The Baofeng is now modded to be used as a Receiver radio with the ID-O-Matic.

Stay tuned for more information on how to build a tunable repeater on the cheap!

Amateur Radio Station Grounding

Recently there has been a lot of discussion (and arguing) on station grounding at the various “hang outs” online that I frequent, as well as questions directed to me from amateur operators. I think it is time I write a little bit about this, from my own perspective. It seems to me that there is a lot of “stuff” out there on the subject that is mostly good, but there is a lot of bad information which sort of ruins all of the good. There is also the issue of the old mentality “well my elmer did it this way, and his elmer did it that way so I am going to do it that way! Anything else is a waste and not needed. They’ve never had problems so neither will I!”.

misc-are-you-fucking-kidding-me-clean-l

That is about as reckless as you can get, when it comes to protection of life and property. Notice that life came before property. That is a key part to understanding and implementing station grounding.

I will attempt to “cut the crap”, and provide some basic guidance on station grounding in my following blogs. These are to be considered as supplemental guidance if you will, in the design and implementation of the average amateur radio station system ground system. There are the requirements to comply with National Electrical Code (NEC) in the USA and those will be addressed as well. After all, the station ground is required to be compliant with NEC if you reside within the United States. I cannot comment on stations outside the USA as I do not have experience with their regulations or codes.

My goal right now is not to provide the be-all-end-all bible of station grounding, but rather to help folks understand what is required and why.

Stay tuned for more.

FBOM, de N7AMD sk sk sk

How to build a tunable repeater on the cheap (Part 1)

I recently set off on a small quest of building an inexpensive same band repeater for portable and special uses where there are no current repeater coverage.  I wanted something low cost, portable, and tunable without special software.

I finally settled on using some parts I already had, and other parts which I could build.  Lets take a look at what the main components of a same band repeater are:

  • Receiver Radio
  • Controller
  • Transmitter Radio
  • Duplexer

Most people know what Receiver and Transmitters are.  This isn’t a repeater that is going to be used much, maybe one weekend a year.  Therefore, I decided to use the Baofeng UV-5R I have as the receiver radio since I will not be transmitting with this radio.  The Baofeng is what I consider a disposable radio, coming in at under $50 most of the time.

For the Controller, I selected the ID-O-Matic IV by Ham Gadgets with the additional Voice Module.  This kit cost me $49.  It does Time Out Timer (keeps the repeater from being keyed up too long), morse ID, and a voice ID.  It has a simple USB (serial) interface to change settings and update firmware.  The only problem with it and the baofeng, is that it requires a COR input to know when the receiver is receiving (and to PTT the transmitter), and the baofengs (and most hand helds) do not have this output.  Also, some controllers deal with the PL codes.  However, we will be using the PL decoder/encoder on our radios, so these can easily be changed in the field.

The Transmitting radio is where you would want to spend money.  I am using a mobile Kenwood TM-D710G as my transmitter radio.  Normally, this radio can do crossband repeating by itself (and even do ID when in this mode), but we are going to just be using 1 side of the radio for this project.

Finally, the all important Duplexer.  This is the hardest part to come by cheaply.  The Duplexer / Cavity filters are important so you can use one antenna between both antennas, but not have the transmitter desensitize the receiver.  These need to be tuned, so they only allow the two frequencies you want out of the duplexer for each radio.  Cheaper duplexers you can find on Ebay from china can work, but you must make sure they are tuned correctly!.  I selected a Chinese made UHF 6cavity duplexer, and requested them to tune it to specific frequencies for me.  This included a +5Mhz offset, like normal repeaters use.

Of course, there are other things that will need to be looked at, like power, and maybe a GPS unit to supply time to the controller, but those are generally things that you can build / pickup cheap locally and use for other projects too.

In Part II, I will be writing about adding the COR circuit to the Baofeng UV-5R, and getting the repeater wired up to the receiver correctly.

How to build a tunable repeater on the cheap (Part 2)