Tech Net Notes October 30, 2009

We didn't get very far into the tech net before the repeater went Ka-bloooey. During a transmission the repeater timed out...and that seemed to have done something to disable it's operation.

Thanks to those who tuned in...or at least, tried to.

Sorry, we'll give it another shot:
November 11, 2009 - 146.910 - 7:00 PM
November 27th, 2009 - 147.045, 443.850 & linked system - 9:00 PM

Enjoy the weather!

Don
ke5omv

Tech Net Notes October 14, 2009

On this one we started off again without a topic.

w5ydl, Dan, changed all that with a question: He said that he's planning on putting up a 6 meter dipole and working 50.125. He asked "Is there anyone who can tell me a little bit about working 6M?

(NOTE: See kd5njr, Scott's comments on this by scrolling to the bottom of this post and clicking on "comments".)

kb5vdb, Ron, checked in and reminded us of Paul's upcoming deployment to Afganistan. In addition Ron passed on the recent new of a husband, wife, and son who died while installing a ham radio antenna. It fell into a 13,000 volt transmission line. Apparently they were not hams, but putting it up for a friend.

ke5yoo, Mike, mentioned that kd5njr, Scott's loop antenna was at about 50 feet. Orientation was the bigger question, with vertical giving you a possibly lower take-off angle. In addition Mike mentioned that ke5otq, Dennis is going to make some 2M loops.

kk5edd, Ed, said that he has been doing PSK31 on 20 meters lately and has plans on mounting an HF antenna onto his 5th wheel, if he can get a good idea of a good way to do that.

ke5yoo, Mike, mentioned that height-wise, one wavelength off the ground is good, but with 6 meters and greater, the higher you get the antenna, the better.

kd5cny, Tom, suggested to kk5edd, Ed that screwdriver antennas usually work well on motor homes and such. He also said that a long wire, hung from trees works better with a tuner. He mentioned that another option might be a vertical.

kk5edd, Ed asked, "Is the vertical you're speaking of, a multi-band?"

kd5cny, Tom answered, "If you have a tuner, the vertical should be able to take care of working multi-band." He added, regarding antenna height, "It's good to get the load of the antenna over the 1st wavelength." He said that between the 1st and 2nd wavelength, there's not much noticeable difference... abpve the 2nd wavelength, there's a lot of difference. He also mentioned that kd5cuz, Craig, has had a problem working his Garmen GPS with his 10 meter radio. He said that when Craig turns on his 10 Meter radio, the GPS quits working. It wont receive satellite data. Turn the 10M radio off, and the GPS starts working again. The radio does not have to be transmitting, just turned on. No problems when he fires up on 2M or 440mhz.

kb5vdb,Ron says that it sounds like the IF is interfering with the GPS and causing the
signals to the GPS to cancel out.

ae5ln, Paul, said that he (also) has been messing around with PSK31. "Where's a good place to pick up a signal?"

kk5edd, Ed answered, "14.070 on 20 meters".

ae5ln, Paul said that on 20 meters he locks up his computer.

kd5cny, Tom, suggested that Paul check the shields on his coax jumpers.


End of Net

Tech Net Notes September 25, 2009

ae5ft, Gene, suggested that "The 2 Meter Band Plan" be a topic for the Tech Net. So tonight this is what we put forth. The following information was taken from an ARRL Repeater Director with a little info mixed in that I found on the net:

Frequency Spacing
States East of the Mississippi - 20 kHz
States West of the Mississippi (excluding Texas) - 15/30 kHZ

Popular Simplex Frequencies Nationwide
146.49
146.505
146.520 National Calling Frequency
146.535
145.55
146.56 (in Texas)
146.58

Simplex
146.4 - 146.58
147.42 - 147.57

SSB
144.200 Calling Frequency
144.20 - 144.275


ke5cub, Lee, was the first to check in with a question. The question was, "What's the difference between resonance of the antenna and low SWR, and how to they affect each other?

We had a few check-ins but no takers until ad5pe, Jay, offered an explanation to Lee's question. I wish that I could repeat Jay's answer, but I did not have my recorder set up and my note-taking failed me. With that in mind I will try to encapsulate that which I can remember. I will do this with the help of:
http://www.radio-electronics.com/info/antennas/basics/resonance.php
http://qsl.net/g3yrc/antenna basics.htm


To start off with, resonance is a vastly overrated concept. But what is antenna resonance?

An RF antenna is a form of tuned circuit consisting of inductance and capacitance, and as a result it has a resonant frequency. This is the frequency where the capacitive and inductive reactances cancel each other out. At this point the RF antenna appears purely resistive.

The capacitance and inductance of an RF antenna are determined by its physical properties and the environment in which it is located. The larger the antenna or more strictly the antenna elements, the lower the resonant frequency.

The magnetic field that your antenna puts out will produce an electric current on any metal surface that it strikes, however if the metal that the signal strikes has a length relation to itself, the current will be much stronger on the object. If the object that the magnetic wave strikes is 1/2 wave length, 1/4 wavelength, or 1 full wavelength, then the induced current will be much higher than if the signal struck an object that was not some appreciable fraction of the wavelength of the signal. An antenna is "tuned" at for an exact wavelength. For that exact frequency that antenna is resonant. Every antenna has at least one exact resonance point.

Antenna resonance is the frequency, in MHz, where the antenna is in a state of electrical balance, which is determined by the length of the antenna.

SWR (Standing wave reflected) is the phenomenon that exists when power which initially was sent into the antenna is reflected back toward the radio. The SWR is measured in a ratio, for example 1.5:1 (or 1.5 to 1). How much power gets reflected back into the radio is dependent on the impedance of the radio/coax/antenna. If it's matched perfectly, the power reflected will be near zero (or said another way, an exact match, 1:1).

The impedance of the antenna is a function of the frequency being transmitted and the point at which the antenna is resonant.

Though your antenna may be resonant at a particular frequency, It is more important that the SWR not surpass levels that would be harmful to your radio. You can talk fine on an antenna that is not very resonant, but a high SWR can burn up the
"finals" in your radio.

ke5cub, Lee, added that "Resonant means that the antenna vibrates at it's assigned frequency. Keep the SWR below 2.1:1."

ae5jz, Tom, checked in and said that on his "waterfall" on PSK 31, there is a signal line less than 7 cycles wide at various places along the band, without modulation. He asked if anyone had any ideas about what that was.

k5bbm, Brian, asked, "At what frequencies do you transmit PSK31 on 2 meters?

kk5edd, Ed, suggested that it may be (according to his reference material) that 144.144 for vhf and 432.2 for uhf.

I don't recall who it was, but I believe someone suggested that the 7 cycle line on Tom's waterfall may be associated to some of Tom's equipment.

With that there were no more check-ins, and the Net ended.

Tech Net Notes September 9, 2009

There was no topic for the Tech Net this time. Instead... we had rain. Lots of rain. Even though Tulsa proper did not get buckets full, Northeast Oklahoma received steady rain for the day and somewhat previous.

w9nbc, Steve, came on during the intro to report street flooding on Memorial from 101st to 111th. Though the rain was settling down a bit, the water, the rain, and the lightning was on our minds.

w2csl, Bob, was the first to check and posed two questions:

1. Why are we called "Hams"?
2. How many Hams checking in tonight have been commercial operators, licensed by the FCC?

kb5vdb, Ron, came on to take a stab at the first question. He mentioned that he had heard that it may have had to do with Hiram Percy Maxim, who is considered to be the "father of Ham radio". Ron said that his initials, HPM , may have been the source from which HAM was derived, although there is no known evidence to say that is definitely the case.

w9nbc, Steve, checked in and said that he had been FCC First Class licensed with radar.

ad5jl, Bob, said he remembered something in QST being written about the "ham" moniker, but doesn't recall exactly what was said. Bob was also licensed through the FCC as First Class. In addition he posed the question, "How do you check to insure that the safety ground lug in a receptacle in your house is wired correctly, going back to a ground rod?

wb5uuw, Earl, checked in and mentioned that he was FCC Licensed First Class. Regarding checking for a ground he said that first you verify that you have a physical ground (rod) tied to the breaker box. He mentioned that the ground should be connected to the ground bus in the breaker box. If that is the case, go to the receptacle and check the AC+ against the Safety ground socket for 110 (120) VAC. If it check's OK, check the return (wide part of the socket) against the Safety ground socket for 100 (120) VAC. If no voltage, that's good. You can then check for continuity between the return (wide part of the socket). There should be continuity.
It is important to mention here that you follow that sequence. Check for your voltages before you check for continuity...and...(of course) do not check for continuity between the AC+ (narrow part of the socket) and the Safety ground.

NOTE: Understand? If you've got voltage between two points and you try to check for continuity, it may melt your meter into your carpet...and it's so hard to get melted plastic out of your carpet. Plus it may blow up your meter and send the indicator needle through your forehead and into orbit. Those indicator needles are hard enough to replace as it is!

ke5lnn, Dave, said that he has one of the line testers (plugs into a receptacle and analyzes voltages and grounds) and that it's served him well. Dave also made the point that the the piece of equipment that your connecting to a ground needs to be opened up to make sure that the chassis is wired to the ground of the AC power cable into the unit.

ke5otq, Dennis, added that there are ground fault detectors that can be purchased which will do the trick. Regarding the origin of "Ham" he suggested that it may have related back to one of the first guys licensed.

Linking Repeaters

Linking repeaters is done all over the country. When one repeater is linked to another, whoever keys up on one, can now be heard on both. This can extend the range of a radio.

And if several, well placed repeaters are linked together, the ability to communicate over the total area of all the involved repeaters can be a valuable asset to communications (especially emergency, public service, and disaster related communications). Most of us are familiar with TARCs UHF network which serves much of Eastern Oklahoma with repeaters in:

Tulsa 443.850
Manford 442.000
Tahlequah 442.225
Cavanal Mt. 442.250
Muskogee 443.100
Stillwater 444.525
Mounds 444.600 (having some problems at this time)
Ponca City 444.700 (having some problems at this time)
Bartlesville 444.975 (having some problems at this time)
McCalister 444.975
Edmond 443.250
Fayetteville, AR 444.925
Decater, AR 442.850
Ketchum 444.875 (temporarily out of service)
Daisy 444.400

Also I just found that there seems to be a linked system that covers much of Western Oklahoma. This was pulled from the internet at: http://www.srh.noaa.gov/oun/skywarn/.

"The NWS Norman SKYWARN Radio Network should be thought of as a "liaison net" during severe weather. It is not intended to collect individual spotter reports, but rather to serve as a collection point where local spotter networks can relay information to the NWS. In other words, the individual storm spotter should use their local frequencies and procedures to report severe weather to their local organization. When the local spotter net receives a report of severe weather, a liaison from that group relays the report to the National Weather Service via the liaison net. Amateur radio operators at the NWS Office will also provide radar information and the latest warnings and statements to the liaisons, who in turn pass the information on to their local spotter network.

Spotters and anyone else interested in keeping track of severe storms are encouraged to monitor these frequencies, but traffic should be limited on the liaison net. You should attempt to report severe weather to your local spotter groups instead of on these frequencies."

Much of the following is taken from http://repeater-builder.com/rbtip/repeaterlinking.html


There are other areas around the country that have linked systems as well. For example:

Alabama - 29 repeaters

Arizona - 22 repeaters

West Texas (Davis Mountain)

Cactus Intertie - icludes parts of California, Arizona, New Mexico, Nevada, Utah, Colorado, & Texas.

Colorado - 15 repeaters

South Carolina - 4 repeaters

Illinois/Indiana

Tennessee

Target Link - Parts of Pennsylvania, Maryland, Virginia, and West Virginia.


The "Remote Base" type link system is the most common because of its simplicity and low cost. Basically a second radio (even an old hand held or mobile rig) is connected to a repeater that you want linked to another. It uses that new radio as if it was a regular "user radio" on the other system. The "link" radio need not be duplex because of the way the link and repeaters are configured. Naturally the link (remote base) radio will need to be on the same band, frequency, split, and PL as the repeater you are linking to.


ae5ft, Gene, had the following information on IRLP as a mode for linking radio systems.

http://www.irlp.net/

The aim of this project is to reliably and inexpensively link amateur radio systems without the use of RF links, leased lines, or satellites.

The IRLP uses Voice-Over-IP (VoIP) custom software and hardware. Coupled with the power of the Internet, IRLP will link your repeater site or simplex station to the world in a simple and cost effective way.

IRLP operates a worldwide network of dedicated servers and nodes offering very stable worldwide voice communications between hundreds of towns and cities. All this with unsurpassed uptimes and the full dynamic range of telephone quality audio.

kd5cub, Lee, asked if anyone had any information on the FT-2000 100 watt with pep upgrade. If anyone has information on this equipment please contact kd5cub.

wa5vxi, Manuel, asked if other repeater systems use modes other than rf to connect up between repeaters (in particular, maybe using the internet).

ke5okt, Jim, mentioned that the newly running 430 repeater in Sapulpa was recently connected to another repeater (I believe in the OKC area) via Echolink (which is via the internet) but that it is not normally linked up. It can be done (and is likely being done in other places).

kd5guu, John, said that he regularly checks into an Echolink repeater on a Railroad Net on Tuesday evenings that is run out of Wisconsin. He mentioned that is a very operational and effective system.

ae5ft, Gene, added that our (TARC's) system is rf to rf, but IRLP is a very valid and easy to operate system for internet linking. He provided the IRLP info a few paragraphs up.

ke5zcz, Mike, announced that he is a scout leader and that the scouts are selling popcorn, as a fund-raiser, and that those who may run across a popcorn-selling scout, please consider buying some to help support this very worthwhile organization.

End of Net -

Tech Net Notes July 31, 2009

Here lately the Broken Arrow Amateur Radio Club has been doing some work on their 145.450 repeater located in the Bixby/Leonard area. In addition TARCs 443.850 repeater was just repaired today after a few weeks of low audio.

Also, in the recent past, RCWA's repeater got hit by a surge or a lightning strike and was off the air completely. As an interim solution, ww5wow Larry, used a repeater set up he had that would receive your signal and then re-transmit it on the same frequency. Your transmission would be stored in memory and then re-transmitted. You would hear, along with everyone else, what you just said. And this would all occur in simplex mode. The repeater would be listening and repeating on the same frequency. It made for slower transmission rates, but it did accomplish the goal of boosting a signal beyond it's limits (in most cases).

As an extension of that repeater work going on in the Tulsa area, we will be talking about repeaters here on the Tech Net tonight.

kb5vdb, Ron, sent in this explanation of repeaters:

A ham radio repeater is basically a radio system that receives the weak signal from mobile and portable radios, and re-transmits the signal on a different frequency at a much higher power level. Repeaters are usually mounted on TV and Radio broadcast towers, tall buildings, high hills, or mountains to extend the range of the station as far as possible.

The basic components of a repeater are the receiver, the transmitter, the controller, the power supply, the feed-line, the antenna or antennas (whichever applies), possibly a power amplifier, and a duplexer (cans) if one antenna is used.

There are two ways to construct a repeater:

1. Mount a single antenna as high as possible, and use it to both transmit and receive. Feed it with a single feed-line after running the signal through the duplexer. The big problem with this design is:

a. The cans are expensive, ornery, and delicate.
b. They have to be properly tuned, which requires a lot of EXPENSIVE equipment and a very knowledgeable technician.
c. They have a tendency to drift and become un-tuned.
d. They cause a lot of signal loss. (You also have to figure in feed-line loss for long runs.)

2. Mount separate transmit, and receive antennas as high as possible, separating the antennas by at least 100 feet. The big problem is expense of two antennas, two feed-lines, and of course, having to place the antennas at different levels on the antenna support. The big plus is no cans (and subsequently no loss through the cans) and if the repeater operator can locate the repeater box as close as possible to the antennas, you get most of your signal out.

There is a little delay every time that you key up, with some delays being substantial. Always allow a second or two before you start to talk.

The controller, by the way, allows a radio to become a repeater by allowing the transmitter and receiver to both operate at the same time.

ac5jm, Jerry, checked in and mentioned that there are a lot of variations to repeater set-ups but that Ron's explanation was a good summary. The on-frequency repeater, ww5wow's, is especially good for an emergency or disaster situation. It also might have an application on 10-meters since there is only 100 khz bandwidth, but nearly impossible to do without a dual site antenna. It's a good back up to have stashed away in case you need it.

The low audio problem on the 443.850 machine was a level problem. The site owner changed the temperature in the equipment room which allowed the pots to go out of tune.

ae5ft, Gene, asked. "Regarding the cans that have to be tuned: How does that fit in with repeater operation?"

k6jxy, Paul, answered, "The cavities keep the transmitter from getting into the receiver. They operate as a set. They are usually a six-pack on a set."

ke5okt, Jim, said, "I still have a KendeComm repeater that I'd like to get running on VHF. If anyone has any information on this brand or type of repeater, please e-mail me at jim@mounds.org.

ae5mn, Hank, asked, "Is there circuitry that separates the signal by detection of signal direction?"

ac5jm, Jerry, answered, "The receive side of the duplexer filters out the transmit and vice versa. The cans are manufactured for a specific range of frequencies and have to be tuned to be resonant to the frequencies used.

ke5zcz, Mike, asked. "Which repeater is better to have, one antenna/duplexer or two antennas, for a base repeater and what is the price range?"

kb5vdb, Ron, answered, "If you have a tower tall enough to separate the antenna by about 100 ft. and can get the radio close enough, you don't have the duplexers and the problems associated with them. If you don't have a taller tower, it's best to go with a duplexer. As far as costs... in the neighborhood of $5000.

ke5vas, Tim, asked, "Are there other linked repeater systems that cover as wide of an area as this one? How is the care and maintenance of the other repeaters handled?

kb5vdb, Ron, answered, "Maintenance is taken care of by the areas clubs, volunteers, and whatever funds they can raise. There was a linked system called Buffalo. It's not around anymore.

ac5jm, Jerry, added, "There are a lot of different clubs that have joined because of the affiliation with the National Weather System. The linked system is laid out to support the NWS. Ther are a few exceptions to this: Stillwater, Edmond, and Ponca City.

Tech Net Notes July 8, 2009

On the day of the Net we had a bit of unexpected rain. For most of us, rain, and especially lightning, affects our radio activity. To reduce my exposure to lightning, I usually will move my radio operation to a battery powered radio hooked to an attic antenna. The base radio gets unplugged from AC. I physically unplug my power supply from the wall. In addition, I unscrew the PL-259 connector from the back of the radio and let it dangle, not allowing the antenna connector to touch anything. I do not ground the plug.

My question, to those who check in tonight is: What do you do with your radio equipment during a storm?

Ron, kb5vdb, said that he didn't know if there is anything you can do to protect yourself from a lightning strike. Air is the best insulator that we know of, and lightning passes through air easily. He mentioned that he unplugs from the AC source and may hook to a magnet mount antenna. He mentioned that he had a friend that was hit by lightning while driving a tractor. The lightning hit him in the head and came out of his foot; he lived.

The story below was found at: http//www.dailycognition.com/index.php/2007/04/27/story-of-a-man-who-was-struck-by-lightning-7-times.html.

"US Park Ranger Roy C. Sullivan from Virginia holds the record for the person most struck by lightning - and living to tell the tale. Between 1942 and 1983, Roy has the dubious distinction of being struck by lightning seven times. He was known as the Human Lightning Rod.

The first lightning strike in 1942 happened as he was working in a lookout tower and the lightning bolt shot through his leg and knocked his big toenail off.

In 1969 while he was driving along a mountain road a second strike burned off his eyebrows and knocked him unconscious. Another strike just a year later, while he was walking across his yard to get his mail, left his shoulder seared.

He was standing in the office at the ranger station in 1972 when lightning set his hair on fire and Roy had to throw a bucket of water over his head to cool off. A year later, after his hair had grown back, a lightning bolt ripped through his hat and hit him on the the head, setting his hair on fire again. It threw him our of his truck, knocked his left shoe off and seared his legs. A sixth strike hit him in 1976 while he was checking on a campsite, injuring his ankle.

The last lightning bolt to hit Roy in 1977 happened while he was fishing. It sent him to the hospital with chest and stomach burns.

Roy Sullivan was never killed by lightning - he committed suicide while in his 70's in 1983 reportedly distraught over the loss of a woman."

Mike, ke5yoo, added that on a direct hit, there's not a lot that you can do. As long as you have a good solid single point ground at your antenna, then you shouldn't have a problem. As the voltage increases from a surge, the potential may rise in all of your equipment, but your equipment needs to be unplugged. If you get hit by lightning in another part of the house, and the lightning finds another path through your equipment, you'll have damage.

It stands to reason that your exposure to lightning, or subsequent power surges resulting from lightning, is related to the exposed inputs into your equipment. For most of us there are two avenues that allow this. The AC input to your equipment is one and the antenna input to your equipment is the other. If you have computer or other devices connected to your equipment, they may also provide an avenue.

The ARRL has a two-part article that addresses Lightning Protection. The first part is found at: http://www.arrl.org/tis/info/pdf/0206056.pdf . The second part can be found at: http://www.arrl.org/tis/info/pdf/0207048.pdf .

Tim, ke5vas, mentioned that American Power Conversions has a number of Uninterruptable Power Supplies that provide a level of protection against surges, particularly power drops. He said that he is at the end of a line and suffers a lot of power drops.

APS UPSs are available from office supply stores such as: Office Depot, Office Max, and Staples. They can also be found at electronics stores, like Best Buy.

More can be found on APS at: http://www.apc.com

Paul, ae5pb, suggested the use of Polyphaser as a source for protection. "Various amateur catalogs (AES for sure) stock some Polyphaser products. Electronics supply houses generally stock a more comprehensive inventory. You can find bunches of them on the internet. These are the industry standard - USACE uses tons of them in radio and also remote sensing applications. I'll bet I've written purchase orders for over a hundred of them. Their lightning protection handbook is the best out there.

Hoffman boxes are NEMA (National Electrical Manufacturers Association) spec enclosures. Though this is a specific brand, it's kind of like kleenex or band aid, and has come to mean any such box.

AES sells one that will hold Polyphaser copper single point ground panel, with in/outs for two coax lines. I'm going to use one with three coax ports, with the Polyphasers on the ground panel inside."

Polyphaser's website is located at: http://www.polyphaser.com .

Dave, ke5lnn, said that he has extensively used Polyphasers on his rig on every coax. He had the electric company put in a surge suppressor on the other side of the meter. During a storn he unplugs everything that has a wire in it. The idea is that the coax comes into a connector outside with a copper plate. He said that he's also heard that you can use a glass insulator, like a bottle to put your connector into inside. But that could create a glass bomb!

Note: I couldn't find anything on the internet that mentioned the use of glass insulators for isolating your PL-259 connector. If anyone knows anything about this, I'd be interested in hearing about it. I imagine that unless the glass is pure with virtually no air pockets, then the heat from a lightning strike could possibly cause the air in the pockets to expand, quickly, causing a "glass grenade", much like what Dave mentioned above.

Hank, ae5mn, mentioned that his exterior antenna gets disconnected during a storm and that in the future he intends to disconnect the power as well.

Ron, kb5vdb, added that most antennas are DC grounds anyway, but that Hank's, being a j-pole, will not be.