Friday, March 14, 2008

Power Supplies and Batteries for Hams


Why have Battery backup? How much Power Supply or Battery for the Station? What connectors?

One of the items found in most ham shacks is a battery or a DC power supply. The reason for this is simple enough: most of our equipment is meant to be used in a mobile environment and that means a DC. power supply in the 12.5 v to 13.5 v range. Even a lot of our base equipment has the provision to be run from a DC. Supply.
How big a power supply to get has been the subject of some heated discussions on the air, so how do you pick a supply for the home? Past experience is that we tend to outgrow an existing supply. If you stay in this hobby long you keep on adding equipment that runs off DC and soon you are popping fuses. Start by looking at the equipment in the shack and adding up the currents in amps. Lets say that the Radio, Linear Amp and TNC add up to about 7 amps. The general rule of thumb is to double that number, in this case 14 amps, and then look for a supply in that range. In this case a 15 amp supply should serve you well and leave you room to change equipment around at a later date. Don't buy the biggest supply you can afford. If you have too little load on a supply, they don't regulate well. Picking a supply for mid range seems to be the
best compromise. Supplies on the surplus market have their hazards. Computer Power Supplies often use switching type regulators. These can generate harmonic interference on your radio. Supplies meant for the audio industry can break regulation when they get in a RF Field.
Since a lot of us want Battery Backup we tend to sooner or later get a battery that will run the station. For those of us who work the "Thons" (Walkathon, Bikeathon, or Runathon) or other Public Service Events the ideas of a battery for these events become very attractive. Batteries tend to become a ten ton liability after a few of these events. We tend to buy something like a Boat or RV battery to run a handi-talkie for 4 to 5 hours. You are never stationed near the car and lugging this battery all over the place gets old after an event or two How do you pick a battery that is the best comprise between weight and length of service? Batteries are rated in "AMP HOURS" meaning that 25 Amp Hour Battery can deliver 25 amps to a load continuously for 1 hour. Most radios only draw maximum current when transmitting so the specifications on the radio are broken up into Transmit and Receive current draw. A mobile radio (for example: 35 W output) draws about 10 amps when transmitting and 0.7 amps when receiving.
A 25 Amp hour battery would last 2.5 hours continuous transmit (25/10=2.5) or 35.7 hours receive only (25/0.7=35.714285) for most of these events. Unless you are the Net Control Station (NCS), this battery is much too large. When trying to size a battery for these
events, figure on a 30% transmit and 70 % receive cycle. A small battery such as a 1.2 Amp hour will power a 5 Watt handi-talkie for about 4.7 hours in receive and 18 minutes in transmit (These numbers assume a transmit current of 1.3 amps and a receive current of .250 amps.): more than ample for a public service event. Connectors for power sources vary widely from automotive lighter plugs to Banana Plugs and Jones Connectors and everything in between. The ARRL Field Service recommends the 2 pin **Molex connector. Regardless of the Battery or Power Supply you choose please have in addition to your connector, an adapter with standard RACES Connectors on your DC source. This lesson was recently learned the hard way this spring during a midwest tornado. Operators who were not in Emergency Service Organization such as RACES or ARES brought their equipment in to help. Some of this equipment could not be used without extensive modifications and there just wasn't time to tinker with it at the time.

Batteries and power supplies have become as much a part of the shack as Radio and antennas. Having the ability to help in a pinch is a great asset. Even if it's not a major emergency, being able to bring up the net when the lights go out in your neighborhood is a great comfort to you and your family.


**NOTE: Since the writing of this article the norm now is to use the Anderson Powerpole connectors in wiring for EMCOMM situations. See the link on this Blog re. the Powerpoles.

Its Coming!!



Field Day is coming! This coming June, Saturday and Sunday the 28th and 29th. We (EAWA along with Hancock County EMCOMM) will be operating once again from the Lamoine Beach site where we have operated for the past few years. This is a great chance to do some operating, test our emergency capabilities and all in a fun competitive event! Last year EAWA placed first in the state of Maine in our category. We will be using the Hancock County EMCOMM Communications trailer along with Mark, N1TDO’s Comm Trailer. Make it a point to keep abreast of what will be coming up as far as planning in the next few months and pencil these two fun days in on your calendar! Keep checking this blog and the EAWA website www.eawa.org for further information. 73!

Tuesday, March 11, 2008

Good Net Procedure Article

Below is a good article on basic net procedures! Enjoy.

From: Pat Scolla WB0EGR, EC, Harford County MD
Subject: General Repeater Operation Pointers

Here is some information I take for granted and I want to thank those who reminded me of this for pointing it out to me. This info is being passed along for everyone's benefit, and with a little practice will become second nature to everyone. Repeaters, which one may or may not know, normally have timers on their receivers. While transmitting into them one must unkey their microphone every 2 or 3 minutes for a few seconds to reset the timer. On the .775 machine, the timer resets when the courtesy beep or tone is heard after releasing your PTT. Some repeaters do not have a courtesy beep or tone, but still reset the timer as soon as you let up on the mic. During typical repeater operations (especially net-related), please wait for the beep, or longer, before transmitting after the other fellow has turned it over to you. It may normal for the repeater to keep transmitting for several seconds after the tone in order to minimize wear and tear on relays and other components in the repeater system. Please note: not all repeaters have a "hang time". Whether or not there is a hang time typically is left up to the discretion of the repeater owner/maintainer. The timer is there for a number of reasons. One is so no one operator can hog the frequency, which can takes some getting used to if one is used to working mostly simplex with long transmit sessions (repeater transmissions tend to be short back and forth transmissions). Anyone transmitting too long 'times out' the repeater, which means the repeater's transmitter simply drops out until the station transmitting into it unkeys, at which time the repeater resets. No one will hear you after the repeater has timed out, and it's generally considered embarrassing. Another function of the time out feature is to prevent inadvertent transmissions from someone mobile who might be sitting on their mike or gets their mic jammed between the seats (trust me it happens) and ties up the channel all the way to work. This can be extremely embarrassing too, especially if one is unaware it's their mic which is keyed and they have been on a cell phone or making comments about things they see on their way to work. Another, and possibly the most important feature of the repeater time out function is it forces one to break frequently to allow others access to the repeater if they need to get in to join a QSO or to report an emergency or urgent situation. During a net operation, once you have checked into the net, it is extremely important the net control station (NCS) knows the status of all the stations on the net at that instant. The NCS presumes you are present and located where you last reported you were unless you tell him differently. During a directed net, like the Tuesday night ARES nets, technically no one is supposed to leave the net for any reason until released by net control. If something comes up and you need to scoot, wait for the next break, which with repeaters will be soon, then be quick and toss in only your call as soon as the other fellow unkeys. The NCS will acknowledge your break. A competent NCS will acknowledge you instantly. During Emcomm operations, breakers have a very high priority and are dealt with instantly. At the time the NCS acknowledges you, tell him you must leave and ask to be released from the net. The NCS will then release you. Until he does so, one technically still is

logged into the net. And weekly net logs are kept, for a variety of reasons. During a net operation, the break between transmissions is the time to jump in if one needs to, and then it is done only by stating your call. Again, a competent NCS will acknowledge you instantly. Do not say 'BREAK' or especially 'BREAK EMERGENCY' unless you truly have an emergency. If you do have an emergency, do not hesitate to break, and these are the words to use on any repeater, net in session or not, *if you have an emergency*. All that said, we live in the real world and sometimes things happen, you have to go to the bathroom, your radio croaks, your battery dies or whatever. Should this happen to you and you cannot strictly follow the net procedures don't lose any sleep over it. Just let the NCS know as soon as you can you are back in case they tried to reach you. The NCS will take frequent breaks for new check-ins, and this is the time to let him know you're back. It's not necessary to break in for a routine message such as you are back on frequency. Remember, in a directed net, it is rare you would make a transmission unless you either have an emergency or are responding to an appropriate request from net control. If during a net you have relevant questions, and the timing is appropriate, do not hesitate to ask the questions. Most training nets have a roundtable session for comments from each member logged in. In a formal net when the net is activated for a specific reason other than training, be more discreet but still don't hesitate to ask the question. If it's a bad time, the NCS will let you know and will normally get back to you as soon as the situation permits. This might be in a minute or two, a couple of hours, or immediately after the net. Plenty of others don't know either, and no one is born knowing all this stuff. The question you ask may answer a question someone else was embarrassed to ask. Feel free to ask questions on this forum or directly of the volunteers involved in EmComm operations. We're hams and one of the most basic tenets of hamming is working together and sharing knowledge.

A special thanks to WA3SWS and KB3KAI for their inputs! 73's Pat WB0EGR Harford County, MD EC

Monday, March 10, 2008

March 08, 2008 Meeting

A meeting was held on Saturday the 8th at Meadow View Apartments to discuss future plans for the Hancock County EMCOMM group. The major concern was as to what routes to take to obtain necessary training to fill any obligations with the Hancock County Emergency Management Agency to enable EMCOMM members get necessary ID Cards needed for events/incidents as they arise. Lynn O'Kane, KB1OTM, advised that everyone should complete IS-700, NIMS training, which is mandatory to enable groups to get further funding and training thru the US Government. The training gives those taking it an insight into what happens in an incident and what the structures are within a incident governing it. After that ICS-100 and 200 should be obtained. Incident Command System. There was also mention of basic Emergency Communications courses which are available, such as the Maine Emergency Courses offered thru Maine ARES on their website (see links) and the Kentucky ARES Communications Course (see links).
There will be a training/review session to be held on Thursday March 27th, the EMA Release is as follows:


The Emcomm group will be holding a training session on the National Incident Management System (otherwise known as NIMS or IS-700) on March 27 at 6PM at the Meadow View Phase 4 dining room in Ellsworth. Training manuals will be provided at the training. However if you would like an electronic version emailed to you please reply to this email. The files are Adobe pdf and approximately 1425 kb in total size.

If you aware of anybody that should be added to this email list or if you no longer wish to be included, please let me know.

Lynn O'Kane
Administrative Clerk
Hancock County Emergency Management Agency
(207) 667-8126