Tech Net Notes December 10, 2009

We had a very short net on this evening. No questions (until the end) and very few comments.

ke5cub, Lee, made the announcement that he has a CD full of Ham Radio manuals that go back to 1928. If anyone needs a manual for an older radio, Lee will run you off a copy for no charge. If you can reimburse Lee for his ink/paper expenses, that's fine, but not required or expected.

If you have a need for a manual for a piece of ham gear, contact Lee, ke5cub, by phone at 245-0788, or by email at ke5cub@cox.net.

kk5edd, Ed, checked in and said he's trying to decide between an auto tuner and a manual tuner. He would like to know what the pros and cons are. Especially he's interested in folks who may have found advantages of one over the other. This will probably be a topic for our next TARC Net, January 29th.

See you on Wednesday, January 13th!

Tech Net Notes November 27, 2009

After enjoying Thanksgiving Day, and it being a holiday weekend for many, we convened the November, last-Friday-of-the-month, Tech Net on TARC's repeater system at 9:00 PM.

kd5und, Travis, checked in with a problem he's been having with a hum in his radio only when he uses an electret mic. When he changes to a dynamic mic, the hum goes away. When he changes radios, but keeps the electret mic plugged in, the hum is there. He's checked his grounding, changed power supplies, checked his mic shield and tried other radios and had narrowed it down to a problem with the electret type microphones only. Since it happens with other electret microphones, it probably not a problem with the microphones. When the hum is there and he places his finger on the radio chassis, the hum goes away. So the question is "What is the microphone picking up, and from where, and how can it be corrected?"

kd5und, Travis, also mentioned that he's got fork lift batteries for his back-up power and is using a UPS charging circuit out of an old APC unit (with bad batteries) to keep them charged up.

wb5mxo, Guy, checked in and mentioned a w3ff BuddiPole he saw mounted on a three wheeled bicycle. This was in response to an earlier e-mail communique.

n5kh, Will, suggested to kd5und, that he try lifting the ground pin to the AC house wiring to see if there was something coming in on the ground.

ke5wph, Andrew, said that he's getting prepared to put in a 45 ft. Rohn 25 tower and has a question, "What is the optimal guy tension for the guy wires. Regarding Travis' problem. Maybe an RF choke on both positive and negative.

kd5und, Travis, suggested to ke5wph that he tighten his guys to 3 - 6 inches of deflection on the guy cable.

n5kh, Will, mentioned an RF choke as well. Also, does putting a battering in parallel with the power supply filter the noise out? Are there cables running parallel to something that might induce a signal into the power cable. kd5und, Travis, mentioned that the problem does go away with a battery, but that he has not put the battery in the power circuit. It sound like it's either in the power supplies of the AC service to the shack.

kd0cdk, Don, suggested that the 2008/9 ARRL Handbook has a lot of information on noise problems and troubleshooting them. Also he suggested taking the house out of the power circuit with power going only to the shack to see if maybe there is something in the house wiring letting something in. If, during isolation, the problem goes away, you know it's something in the house. Also, have you tried installing a capacitor from the mic positive to ground? Also, are your computers on when you have this problem? kd5und, Travis, answered that he's turned the computers
off and the problem persists.

kd5njr, Scott, suggested that you can check the noise on the AC line with an oscilloscope by taking a few turns around the hot and connecting it to the 'scope probe. That ought to induce enough voltage to see what's going on without putting too much current into the 'scope.

n5kh, Will mentioned that Travis may want to keep an eye on the UPS charging system for his fork lift batteries as many of those UPSs are designed for a particular duty cycle, and the fork lift batteries might exceed that level.

kd5und, Travis, replied that he will start doing that and monitor the output voltage. He said he's been using that system for about 6 months with no problems yet and the system triggers it's alarms whenever he changes the load too greatly.

n5kh, Will, said that the idea to use the UPS charging system is a great idea.

End of Net

Continental Code vs. Morse Code

According to w2csl, Bob, what we now know and use as Morse Code was originally called "Continental Code". It was an upgrade from the first Morse Code that was developed in an effort to standardize code with other countries.

The picture shown above was found by David, my most recent AT&T U-verse installation tech. Dave responded to a call for help from me after I moved my computer back into our "office" from a recent remodeling fiasco.

We had AT&T out about two months ago to put in another Internet drop. The tech that responded then added a line to a temporary location in the house. He did not wire it into the system, but told Jim, our tile installer, how to wire it in when we're ready. So when we moved the computer from the office into our den, we just had to splice in the new wires. That tech told us that we could just leave it that way when we moved back to the newly tiled "office". When we did move (eventually) back into the office, we could not get the internet back up.

David showed up and found that the, now unused, temporary wiring still hooked to the system acted like an antenna and allow enough noise into the system that the signals would not sync in. Our 3-in-one package left us without TV, internet, and phones. All David had to do was disconnect the unused pairs and the system popped back up.

David noticed some of the HAM paraphernalia in the office and we talked a little about it. David mentioned that he had found a handwritten table of Morse Code vs. Continental Code inside a 1901 printing of Longfellow's Poems, brittle from age, which he bought at a garage sale.

David scanned the old document and e-mailed it to me. That is it pictured above.

A teeny bit of code history.



ke5omv
Don

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.