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.

Tech Net Notes April 8, 2009

Cross Band Repeat

What is cross-band repeat?

This is where a radio is set up to receive on a frequency on one band and then repeats what it hears on a frequency on another band. In most cases, when the cross-band feature is activated it works in duplex mode. That means that whatever it hears on one frequency, it repeats on the other. To be activated, it is necessary to program both frequencies into the radio and then activate the feature.

Application? For example, if you can't make it into a VHF repeater from your HT at home, if your home station has the capability, you can set it up to listen (and talk) to your HT on UHF, and to relay your transmissions onto the VHF repeater's frequency. With that activated you can walk around the house (or anywhere within range of your home station) and get into the VHF repeater through your HT.

In the above example, your home station has become your own personal repeating relay station. Of course, anyone transmitting on the same UHF frequency within range of your home station will be able to get in to the VHF repeater as well.

It should be noted here that you do not necessarily have to "repeat" into a repeater's frequencies. This can be done on simplex as well. For example, if you want to enjoy an evening of grilling on the patio at the same time your favorite Saturday Night Simplex Net is being run, you can now do that without moving your equipment outside. You can program in the Simplex frequency and the HT frequency into your home station, activate the feature, and from the comfort of your patio listen to and check in to the Simplex Net. Burgers never tasted sooo good!

If your mobile unit has the capability, it can act as a relay station as well. For example, you park your car on a hill where it can get into your favorite repeater and now you can talk through your HT to the repeater via your car's radio as you're hiking around the hills and valleys within HT range of your car.

If you operate the cross-band repeat station using a battery as a power source, realize that the radio will be transmitting anytime anything is heard on either frequency. If your power setting is at the highest level, and the frequencies are fairly active, you may run the risk of overheating your radio and/or running down the battery. For this reason it is recommended that you use the lowest power settings possible (especially on your HT).

ke5wsi, Ray, wanted to know if anyone knew how to set up his FT5100 for cross-band repeat. He doesn't have the manual for it anymore and needs help figuring it out. w5okl, Richie, mentioned that he has seen radios that will do cross-band repeat that don't have that feature documented in their manual.

ke5yoo, Mike, mentioned that he read that there are some ID requirements that may need to be met while in the cross-band repeat mode. ke5omv, Don, said that he had seen the same issue addressed in an article on the internet, and that it was suggested in the article that even if you are just "listening" while in cross-band repeat mode, it is necessary to identify every 10 minutes. The automatic code identifier can be annoying to other operators, so it's best to do it through voice transmissions.

ke5wga, Ray, asked if radios must be "dual receive" or said another way, have the ability to receive two separate frequencies at one time, in order to cross-band repeat. ke5lnn, Dave, replied that yes, radios must have the "dual receive" feature.

ke5lnn, Dave, added that he uses the cross band feature when he can't be in his shack for a net. He also cautioned that you need to make sure you turn the cross-band feature off when you're not using it. Sometimes it can get hung up, so you need to monitor it's use.

kc5uoq, Larry, said he's never used the cross-band feature, but a friend at work would use it inside the building where they worked to cross-band to the radio in his jeep. It worked great.

ke5ubr, Hank, said that he has been working with his cross-band repeat and that he had it disabled at this time because he did not want it hanging up the repeater. He has had that occur on occasion, and doesn't want to cause problems for the net. He sets his power to low on UHF and to high on VHF.

ke5mxh, Don, said that he had a visit from wb5mxo, Guy. Guy dropped by to show Don how to tune his amplifier. He added that on the Oklahoma City Tech Net, to reduce problems from doubling, they suggest to start your transmission with "This is..." then un-key, listen for others who may have keyed up, and then if clear, continue on with your transmission.

kc5qgq, Dan, suggested that when in cross-band repeat to set your squelch at minimum, then set your power at the minimum you need to get in, they adjust your squelch back up. Also, to reduce hanging up the transmitter, he suggested to the the transmission time ("tx time") to a shorter time, which would produce a shorter squelch tail.

ke5swu, James, asked if anyone had experience using Ham Radio Deluxe with a Yaesu FT-897. w5ydl, Dan, answered back that yes he has used it and that it works great. He added that you can completely control your radio with your computer.

kf5acd, John, asked what would be a good radio for cross band repeat. ke5omv, Don, suggested the Yaesu FT8800 and mentioned that Kenwood and Icom both have radios that cross-band repeat. kc5qgq, Dan, suggested the Yaesu FT-8900 quad-band radio and the Kenwood 733A as being radios he had good experience with. He added that the Kenwood's manual doesn't say anything about it, but he found out how to set it up from another ham and that it works.

ka5tro, Tony, said that the Alinco DR605T is an older radio, but that the cross-band feature in it worked very well.


Added Note: I ran across a website that explained the procedure that Ray would use to activate the Cross-Band Repeat on his Yaesu 5100. It is: http://www.radiomods.co.nz/yaesu/yaesuft5100.html

Tech Net Notes March 27, 2009

In the above diagram, the interface device, RigBlaster, is pictured in the middle toward the bottom (where the microphone is plugged in). This came from wb5mxo, Guy, via ke5lep, Stan. Thanks to both!

PSK31

The topic for the March 27th edition of the Tech Net was PSK31. We were lucky to have Guy, wb5mxo, sit in and be our "Elmer".

To start off, Guy gave us a brief summary of what PSK31 is: He compared it to teletype over the ham frequencies. Typically, in today's world, four items are needed to send and receive in the PSK31 mode:
1. A radio transceiver
2. A computer
3. In interface device between the two
4. A program for the computer

Since most of us have computers and radios, usually all we need is the interface device and the program. The interface device that Guy likes is the "RigBlaster", but Guy advised us that there are many available that will work and some you can build for yourself.

Once you have the interface device, you just need software. Guy mentioned here that there is a ton of software available, some free, some for sale. He said that much of the free software works just fine.

One issue that came up while in QSO with w5ydl, Dan, was that he had heard that even when the bands are dead, PSK31 gets through. So that even in poor conditions contacts can often be made. Guy, more or less, confirmed that by saying that there is a drop off at night on some of the bands, but daytime contacts are usually possible and often abundant.

In additon Guy mentioned that a lot of information can be found regarding PSK31 on wm2u's page at http://www.qsl.net/wm2u/psk31.html

Not only does wm2u describe how PSK31 works, but he has schematics for interface devices and mentions the software and other products available to make contacting easier. In addition, he has a lot information on contesting, if you're in to that sort of thing (as many PSK31'ers are!).

Also Guy furnished another link that has info on PSK31. It is http://www.mymorninglight.org/ham/psk.htm

Guy made a particular point in driving home two important issues.
1. Don't over-modulate your signal. That's a big no-no in the world of PSK31 in that is uses more bandwidth that is needed and practical, and it interferes with other PSK31 signals. You just don't need to do it, and it botches things up for others.
2. PSK31 is used on specific frequencies on each band on upper sideband only.

w5okl, Richie, related that he had downloaded some free PSK31 software and found a website (somewhere in Europe) that allows you to operate a receiver and listen in on PSK31 traffic. He was able to get a "taste" of this mode of communication without hooking up an interface or even using his radio. It will be necessary to look around internet for the site, but it turned out to be a great way to check things out.

kc5rbh, Jeff, asked if you can do this as licensed only as a Technician. Guy said that it is possible but, practically speaking, the bulk of the PSK31 traffic will be found in the General class frequencies.

w5okl, Richie, provided the following three address to sites that he has visited to "listen in" and control the radio in the PSK31 mode.

http://websdr.ewi.utwente.nl:8901/

http://www.globaltuners.com/

http://www.remotehams.com/

Tech Net Notes March 11, 2009

The net started with a query that wb5vst, Ben, relayed to me on the March 10th RACES Net. He was interested in knowing how to go about hooking up several radios to the same speaker.

With four or so radios in his car and speaker space sparse, having the radios share a speaker would help him manage the available space. What he wants is the ability for one speaker to carry the signals from four radios all at the same time (as if you have four radios on). So a switched speaker system would not necessarily work.

On the RACES Net, kd5und, Travis, suggested a mini-mixing board. A mixing board would tend to isolate the signals from each other and send them to one speaker output.

To start things off on the Tech Net, ke5yoo, Mike, relayed some information he discovered that related to the last Tech Net on February 27th, regarding coax. There was an issue of how to use various types of coax. Mike mentioned that RG58 is not a very good coax to use. It's only good for about 150 watts of power on VHF. In addition, Mike told us that as the frequency goes down, all coax types tend to work better.

ke5zol, Casey, checked in and had a question about the performance of his station. He said that yesterday evening, he copied the RCWA Net quite well, but could not make it in from about 31st and Harvard. He is talking on 10 watts with a magnet mount antenna on a piece of sheet metal in his garage.

kc5wsi, Ray, replied that Casey's equipment performance was understandable and that it is really performing well. Getting into the RCWA repeater with that set up, that far away, is not likely. In fact, Casey is doing well to get into the BA repeater as well as he is. ke5omv, Don, agreed.

ae5ft, Gene, related to Casey that he had a similar set-up when he placed an ultra-light MFJ magnet-mount antenna upside-down on his ceiling vent. Gene went on to mention that with that set-up, at his location, he was able to get into all of the Tulsa area repeaters.

ae5fa, Rob, (regarding 4 radios/1 speaker) suggested that installing a 4 to 8 ohm resistor on the signal side of the audio line coming out of each radio and hooking into the speaker with the return lines (or shield) wired in common and to the shield side of the speaker may work to keep signals from back-feeding into the other radios.

ke5wsu, James, suggested using diodes instead of resitors.

ae4fa, Rob, mentioned that diodes would just "clip" the audio and it would not work well.

kb5vdb, Ron, said that he found a device that you can use to hook up 6 radios to one speaker in the AES catalog, but that it may not allow you to listen to all of the radios at once. The part number is NCS 3220.

wx5lib, Matt, said that he has used a commercially available product to hook up four radios to one speaker in emergency vehicles. It is called a 4-channel combiner amplifier. The website for that is: http://www.fleetradioproducts.com/htm/model301b.htm

kb5vdb, Ron mentioned that you could re-wire a quadrophonic headphone to allow for a 4-input headset.

kc5wsi, Ray, said he found the four into one device from AES and it is called an interface kit with catalog numbers 3240 and 3230.

kc5uoq, Larry, announced the Storm-spotter training in Claremore for March 17th.

Tech Net Notes February 27, 2009

The theme for the February 27, 2009 edition of the Tulsa Tech Net was coax. As most of us have found out by now, there are a lot of varieties of coax out there. Big coax, little coax, medium coax, stiff coax, flexible coax, and stranded vs. solid center conductor. (not to mention the electrical characteristics variations) Some coax jackets are more durable than others. What we would like to know is, "What kind of coax do you use?" What problems have you encountered? What works best? What is your coaxial philosophy?

aa5ss, Glenn, said that he didn't have very good luck on one of his two meter antenna installations using coax. He said it was too lossy. He said that he was able to make some twin-lead work better for the installation of the antenna in his tree.

ke5lep, Stan, had a question, "What works well for jumpers? Big coax is cumbersome; small coax is lossy. Plus, it's understood that the more connections, the more the loss. What is the recommended size and type of coax between switches, meters, equipment, and antennas?"

ki6und, James, mentioned that using equivalent products would be best, in that the entire transmission line will take on the characteristics of the least common denominator, or "weakest link".

kd5njr, Scott, said that a good rule of thumb is that each connector will cost about .2db a piece. He said he agreed with the "weakest link" comment.

kd5vsf, Terry added, "Ground your system with heavy wire to a good ground. Check your specs for the frequency you'll be using most. One of the best instruments for checking things is the MFJ antenna analyzer. Also get good reference material, such as those publications from ARRL."

kd5njr, Scott, came back in and said that the Belden 9913 (or compatible) cable is a good type for jumpers.

ki6und, James, followed with another question, "Is there a way to negate the loss from a connector?"

kb5vdb, Ron, had to say, "Get the best connector you can get. A lot of the loss is relative to the frequency you are using. In some instances you can reduce loss by matching the connector with the frequency you'll be on."

kd5njr, Scott said "...just keep an eye on your connectors. Keep them clean. Use a light electronics cleaner. Keep them clean and free of debris. The worst thing you can do is splice your coax. LM400 is tough to beat."

ke5y00, Mike, says, "As far as coax goes, I just use what I have. As long as you keep it short, you can get away with a lot. I try to keep my length down."

kb5vdb, Ron, added, "RG8 is a military designation. There are several companies that manufacture it...just because it says "RG8" does not necessarily mean that it meets stringent operational specifications. There are a few quality companies out there that manufacture good products, such as Belden and LMR."

kd5vsf, Terry, said, "Keep an eye on that RG59, that can be a bad mismatch on an HT."

kd5njr, Scott said that compared to RG8, RG6 is better for antennas, loss-wise, even though it is 75-ohm and a mismatch. If you have a lot of RG59, look up "1/4 wave transformer" on the internet, for ways to use it.

w5taz, Dave said, "When they talk about balums, there is a big impedence, but when you're talking about the difference between 50 and 75 ohms, there's not that much difference."

Tech Net Notes January 30, 2009

The topic for January 30th's Tech Net was Echolink. Questions regarding Echolink were invited.

ke5okt - Jim - has had an echolink node set up for about one year. He offered his advise to anyone who might have a question.

wa5psa - Brad- checked in and mentioned his interest in QRP contacts.

ke5ysh - Justin - regarding LK500 amplifiers, asked if anyone had any experience and advise on new tube burn-ins.

ke5wga - Ray - Remarked that he found Echolink nodes very useful while driving a truck in communicating between the Preston and Durant nodes.

kd5njr - Scott - had two questions
1. Does ke5okt, Jim, know of any good conference servers? ke5okt, Jim's answer was that he did not have an occasion to use conference servers.
2. Addressed to wa5psa, Brad, regarding QRP contacts, is that with code and what kind of antenna do you use. wa5psa, Brad answered that he uses an 80 meter dipole running through his attic, with each end running through a peak at the side of the house and then down to fences on each side of the house. He added that he usually runs 5 watts using CW.

ke5ehm - Paul - checked in

kd5cny - Tom - checked in and said he may have more later.

ke5lnn - Dave - checked in

k16und - James - checked in, visiting Tahlequah from San Diego.

w5ggw - Greg - checked in and advised that he was going to try to link up the 147.045 machine, and advised that it had been successfully linked.

ke5iig - Mike - checked in

kd5cny - Tom - asked "Can a switch box be built for two different microphones to be connected on the same radio? Has anyone done that?"

Another ham - said he didn't see why not, that it would be the reverse of one mike for two radios, but that worked with only compatible radios.

ae5ft - Gene - mentioned that he believed he had seen a QST article regarding the building of such a box.

ke5ncp - Tom - checked in.

ke5urg - Steve - checked in.

k5bbm - Brian - checked in and said he had tuned into 147.045 and heard the net. (confirming the linking of the VHF repeater to the UHF system.)

kf5rd - Pete - referenced a September 1988 QST article, page 18 that addresses building a switch-box for two microphones going to the same radio.

ki6und - James - said that one can be found at "tinyurl.com/coxde5", made from an old style computer switch.

wa5psa - mentioned that all QST articles are now available on-lin. He also said he found one made by MFJ model# 1262 at Ne Communications Solutions for $300, nscradio.com.

w5ggw - Greg - added that you should be able to us a 25 pin parallel switch, and that it's just a matter of figuring out the wiring. One PTT wire, two audio wires, and whatever else there is.

ki6und - James - said that what Greg mentioned is like the one he found at "tinyurl.com". He added that the cost was $90, but that you could buy the parallel switch by itself for $7, and then it's just a matter of matching what goes to what.

No other traffic or check-ins past this point.



If you notice corrections or additions that need to be made to this, feel free to leave that info as a comment below.

Don
ke5omv

Tech Net Notes January 21, 2009

THE BELOW IS A SUMMARY OF WHAT WE TALKED ABOUT ON THE TECH NET. IT IS NOT COMPLETE, BUT IT COVERS MOST OF THE POINTS DISCUSSED.

1. ke5omv, Don asks, " When can you use ladder line as a feed line for your HF antenna? In other words, how careful should you be on where you run your ladder line? or, what are the parameters that exists in the running of ladder line?

kc5uoq, Larry, asks a trivia question, "How many counties in Oklahoma voted for McCain?" The answer is...all of them; Oklahoma was the only state that carried MCCain in all of the state's counties.

kc5uoq, Larry added, "My scanning antenna works good with ladder line. No experience with transmitting through ladder feed line."

ke5wga, Ray, had no experience with ladder line or HF gear at this point.

ke5otq, Dennis, also uses ladder line for listening only.

n5fem, Steve says that in his experience, ladder line is too difficult to use. If you use it, it is best to keep the ladder line in the open. Rather than using it he would rather use a balun with coax back to the radio.

kd5cny, Tom, "No experience with ladder line."

kd5jkh, Martin, "The advantage of ladder line is low loss."

wa5psa, Brad says about ladder line, " I run 80-6 meters on one dipole. It is low loss. The SWR on ladder line on the antenna side of the antenna tuner does not create the loss as it would on coax. I use it for that reason. Cross metal objects at a 90 degree angle. Mine runs loosely behind my desk into a closet, up to the attic, runs along some coax and rotor wire, and on to the attic antenna. Each end of the dipole goes through an eve of the house and then angles down to a fence. It works good.

2. ke5uiu, Chris questions - Why can you not use larger than 12 gauge wire on a dipole antenna?

ke5yoo, Mike, "I believe it doesn't really matter what size wire you use, most programs don't address larger than 12 gauge. The size may change the capacitive characteristics of the antenna.

n5fem, Steve, "Over 12 gauge you may be getting into solid wire. I normally use 14 gauge wire.

kd5cny, Tom, " My opinion is that stranded vs. solid signal travels on the outside of the wire, on a solid core the signal travels smoothly...if there is a kink or a bend it can affect the signal. Solid core should (normally) be better. The bigger diameter of your driven element, the broader the bandwidth. 8 gauge wire weighs more and will be harder to support.

wa5psa, Brad, says, "My gues is that the calculations shut off past 12 gauge due to structural considerations.




Note: If you have an opinion, feel free to leave it as a comment. And of course, if you have a question for a future net topic, leave it in the comment area as well.

Tech Net Notes December 17, 2008

1. ke5omv, Don asks, "How do I splice two pieces of coax together? Should I use 2 PL259s and a coupler, or something else?”

Kd5cny, Tom says, “Barrel connector, “N” connector is a little better but harder to put on. I would suggest a PL 259, a little more loss, but probably not enough that you would notice.

Ke5lnn, Dave, “Purist would advise you not to splice together like that because of the loss.” Tom says, “1/10th of a db loss on each connector”. Ray says, “Put waterproof tape around the connector. I had a little higher SWR when I used a splice with a barrel connectors.

Kd5cny, Tom asks, “At what frequencies will you be running through the coax?” Answer: “70 cm & 2-meter”. Tom says, “If running 440 I strongly suggest not using three pieces of cable”.


2. ke5lnn, Dave asks, "When I have my mobile radio on scan mode and engage my automobile cruise control, the radio scan is interrupted. How do I fix it?"

Ke5lnn adds, Dave says that ferrite RF chokes have not helped any. He thinks he may have to do something with the cruise control. The hot line goes to the battery. Ground goes to the chassis.

From another ham: The cruise control module is located either under the dash or under the hood. If you run your wiring anywhere close to the cruise control module, you may be picking up interference. You may want to try rewiring the power along a different route. You might try moving your ground and your power cord to a different location.

Jeff asks, “What does the cruise control module look like?” Ray, kc5wsi, “What is the year and Make of the vehicle?” If it’s a Chrysler product, they have been known to have cruise control units that affect other vehicle electronics. Dave says, “It’s a 2001 Toyota Tacoma.” Ray says, “The unit is probably going to be under the dash with four to 5 wires 1” x 3” x 5”. It should have a back plug on one end. I will try to find out specifically what it looks like and its location and get back with you next week.”

Kc5bgf, David says, “You might try a coax line for your power feed line. Older coax is often heavier and some is double shielded and makes a better conductor.”

Kd5cny, Tom, “Fuel pump noise in today’s cars is often a problem for interference.”

Tech Net Notes December 5, 2008

Editors Note: I know I'm not getting a lot of the answers right, so if you answerred and see that I did not get what you were saying, please leave a comment and I will correct the answer on the post.


1. kd5njr, Scott asks, "When exactly are you supposed to use a balun?"

ae5hq, "On ladder line feeding a dipole, you don't need a balun because it is balanced. On coax line feeding a dipole, you need a balun"

ww5wow, 300 to 1000 ohm use 4:1, you can use 6 turns of coax as a balance. On a wire fed antenna you need to bring a 300 or 450 ohm antenna down to 50 ohm, it is then that a 4:1 balun will be needed. Otherwise to make the transition from ladder line to coax a 1:1 balun will need to be used.

k5zdp, 4:1 is used to change the characteristics of the antenna to keep the signal off the shield.

kd5zve, Jimmy says, "Antenna modeling software is found by googling eznec and learning more about baluns.

2. ke5lep, Stan asks, "How do I get my Kenwood MC-57DM microphone to work in DTMF mode with my Kewood TS-2000 radio?"




3. ke5lnn, Dave asks, "When I have my mobile radio on scan mode and engage my automobile cruise control, the radio scan is interrupted. How do I fix it?"



4. w5amr, John asks, "APRS, on the receive side, I have never been able to get any of the software to show me a map of the location of the transmitters."

ww5wow, Larry - If you don't have a program to receive RF signals, you're not going to get anything from them.

ke5lep, Stan , "I can't contribute to your answer, but leave it as a comment and maybe we can get an answer." I am looking at www.openaprs.net, a website that has software that shows the radios by zipcode.

Software found by googling eznec

ae5jc, Bob says, "Try winaprs, www.winaprs.com, links to maps that can be downloaded for that."