Got a ham question/problem?

[Pat Palmer]

As an experiment, I'm starting this post. If you have questions about amateur radio just ask. If you have an answer to a question, post it!

 

[Pat Palmer]

Setting up a mobile station

Alright, you passed your tech exam, got your callsign, now what? You look in the magazines and catalogs and are confused by all the choices in radios and antennas. VHF, UHF, Dual band, dB, dBi, dBd, all the features, what do or don't I need?

First we'll start with the transciever. Resist the temptation to buy an HT (Handie-Talkie) right off the bat. While they're great for short distances on foot or for a nearby repeater, they lack the power to get a signal out when you're out in the field.
If cost is a consideration, consider a simple 2M FM mobile. Two meters is where you'll find a majority of repeater and simplex traffic. Most 2M radios will put out a respectable 50 watts or higher, which is more than enough to hit any repeater you can clearly hear. The prices are generally between $150 and $200. Used radios can be significantly cheaper, but let the buyer beware.
Dual band radios cover the 2 meter and 70 CM (also called 440) bands. They range in price from $250 to $800 depending on the features included. One feature that comes in handy is dual receive, where you can listen to both bands at the same time. This comes in handy when you are on a SKYWARN net on 2M, and a group of chasers in your area are on 440 simplex. Cross band repeat can also come in handy. If you get out of your vehicle to photograph or video, you can use the mobile to retransmit the low power signal from an HT, thereby freeing you from being right around the vehicle.
I wouldn't reccomend tri-banders, quad-banders, or all band dc to daylight rigs unless you are interested in doing more with ham radio besides storm chasing.
Mount the rig solidly in your vehicle to avoid it becoming a projectile in an accident. Consider getting an external speaker, you'll be much happier with the audio quality. Mount this solidly as well. Run the power leads through the firewall and directly to the vehicle's battery. Terminate the wire ends with ring terminals that fit your battery terminals, and the power leads.

Next we have antennas. Antenna advertisments can be the most confusing and downright misleading aspects of equipment shopping. Obviously, get an antenna to suit the radio you have (monoband, dualband, ETC...). You'll soon be asking what length and gain are all about. Gain is how much effective radiated power an antenna puts out when compared to another antenna, and is expressed in decibels (dB). A good rule of thumb to remember is that doubling your power is a gain of roughly 3dB.
Antenna companies will use gain figures to mislead you into thinking their antenna is better than a compareable one by playing with the gain figure. They will express gain in dBi, which means the antenna is being compared to an isotropic radiator, which is an imaginary point in free space that radiates in a perfect sphere. In reality, no antenna works like that. A more realistic reference is dBd, which compares the antenna to a halfwave dipole or a quater wave vertical. Subtract 2.15dB from dBi to get a realistic figure.
A commercially made 20 inch dual band antenna advertises 2.15dB on 2M, and 3.4 dB on 440. Adjusting the figure to dBd gives you 0dB on 2M, and 1.25dB on 440. There is no gain on a 20 inch antenna on 2M, because 18 inches is a quater wave at that frequency. As a half wave on 440, you will not even see a 50% increase in Effective Radiated Power (ERP).
By now you should be asking how does an antenna boost my power? Well, it doesn't. What a gain antenna really does is focus the signal towards the horizon so that the radiation field would look more like a disc than a fat donut. So your 50W radio is still putting out 50W, but it is all shooting towards the horizon instead of up to the sky and down to the ground. More of your signal goes where you need it.
Get the longest antenna you can comfortably put on your vehicle. Keep in mind tree limbs, drive-thrus, and garages. The longer the antenna, the higher gain you will get out of it.

Now that you have your antenna, how to mount it? When at all possible, drill a hole in the vehicle roof and use a through hole hard mount. That can be a horriffic thought to those owning newer nice vehicles. Using a mag mount does much more damage by scratching the paint, and rust sets in (I know this from firsthand experience). Mag mounts couple weakly electrially with the metal it's mounted on, and you will not see the full gain the antenna is capable of. A good ground plane is needed to get the most out of an antenna, and many will not function without a ground plane. The door, bumper or trunk mounts will work decently, but they are a compromise. You will not see the full potential in gain, and the antenna will become directional, that is, more powerful in the direction the most metal is. If you can't bear the thought of drilling a hole in your vehicle, use one of these.

Next is something most people don't give much thought to, coax. Don't use a longer run than you really need, but use at least six feet. Find a way to get the coax outside without pinching it in a door or window. Pinched coax will have an impedance of more than 50 ohms, and will throw the VSWR off. Try to use an existing through hole for the vehicles wiring harness, or running through the molding and headboard if using a thru-roof mount.

Use an SWR meter marked for use with VHF/UHF and check SWR in an open area at least fifty feet away from any buildings, telephone poles, wires, lightpoles, ETC... Check SWR at the bottom, center, and top of the band, and see where the lowest point is. If the lowest SWR is too low in frequency, adjust the antenna so it is shorter. Conversely, if the lowest SWR is too high in frequency, make the antenna longer. Adjustment is usaully done with an allen key from the bottom of the whip. All that is needed is a change of 1/8 inch to change SWR significantly. If the SWR is off the scale no matter what you do, check the coax, connections, and antenna ground. Check this before cutting the antenna shorter.

Get out and enjoy your new setup, hit some local repeaters and get some signal reports. If something's wrong, most hams will offer advice on remedying the situation. More often though, you'll get compliments on the job you did!

 

[Jon Miller]

Pat- are there any HAM antenna books or other sources that have plans for building a homemade mobile WiFi antenna ? Could you use an old mag mount 2M antenna cut down to the Wifi frequecy/ wavelength whatever that is ? TNX

Jon Miller
WTØRNA

 

[Pat Palmer]

Pat- are there any HAM antenna books or other sources that have plans for building a homemade mobile WiFi antenna ? Could you use an old mag mount 2M antenna cut down to the Wifi frequecy/ wavelength whatever that is ? TNX

Jon,
It is possible, but can be difficult. . Cutting a whip to get a quater wave at 2.4GHz would leave you with a whip barely 1.2 inches long. That doesn't give enough capture area to get a solid copy on a signal, and at 2.4 GHz, losses through the feedline, trees in full leaf, and even rain will attenuate your signal enough to eradicate it. For microwave frequencies, high gain antennas are a must. The easiest design I have found would be an omnidirectional colinear vertical (the same design as the high gain verticals for 2M and 440, but scaled down). I found a fairly easy to construct one at http://wireless.gumph.org

Construction will require sharp eyes, a steady hand, and some soldering experience. The parts you will be working with, and areas to solder (and not to solder) will be small.[/url]

 

[Patrick Ware]

-.-. --.-

How did you ever get above 20wpm using CW? I am struggling at 10 or less. There are many different opinions on the methodology, I was curious how you did it.

73,
KE5BAU

 

[Pat Palmer]

How did you ever get above 20wpm using CW? I am struggling at 10 or less. There are many different opinions on the methodology, I was curious how you did it.

Patrick, KE5BAU,
I started my CW journey with two programs, G4FON's Koch Method (freeware) and Numorse (shareware, but well worth the price).

First I learned the characters. After that I would cut and paste articles and stories I wanted to read to Numorse. The program will play back the text in CW at whatever speed you set it to. When I could almost copy all of it perfectly, I'd bump up the speed 1-2 WPM. Within six months, I went from 7-10 WPM to 20+WPM!

Koch Method starts you with only 2 characters at 20 WPM. When you know those two, it will bump it up one. You tell it to add characters, it won't do it automatically and overwhelm you. once you know all characters, including numbers punctuation and prosigns, you can set it to send random common words.

If you're still using pen and paper to copy, put them away! Get used to listening, and forming the words in your mind. This cuts out a step in the thought process. The sounds go directly into your mind as letters instead of translating on paper first. As you listen to CW, begin sounding the word in your mind syllable by syllable instead of spelling it letter by letter. This will make it feel more natural, and the words will begin to flow smoothly.

Most importantly, don't burn yourself out. Practice 10-15 minutes at a time, then take at least a half hour break. This will keep your mind fresh. If you begin to get fustrated or tired, take a break and come back refreshed. You'll find what you were stuck on coming smoothly.

Try as many different methods as you can, and find out what works best for you. I used to drive a truck for a living, and would use my laptop to play CW as I drove, kind of like "books on tape". Long hours on the road gave me plenty of practice time.

 

[RodgerHeckman]

I recently received my call sign and I have a dual band mobile rig. Now I need to purchase a dual band mobile antenna. I read in previous post about a glass through antenna which sounds interesting. My SUV is new, and still under warranty, so I am not too interested in a hard mount at this time. I had not thought about what damage a mag mount could do, thanks for that info. I do like the idea of being able to quickly move my mobile set up from one vehicle to another as I own two, and I may possibly take the set up on a my next out of state vacation. Let me know what you would suggest in my case and also, some suggestions on a good place or places to purchase an antenna and other ham equipment too.

Rodger
KI4HJF

 

[Pat Palmer]

I read in previous post about a glass through antenna which sounds interesting. My SUV is new, and still under warranty, so I am not too interested in a hard mount at this time.

Rodger, KI4HJF,
First of all, congratulations!

I have a glass mount dual band on my pickup as a back up. They work well enough, but they can't handle much power. They got very hot at 50W, which is the limit of what they can handle. They also transmit poorly due to lack of a ground plane. These antennas definately suffer when you are far from a repeater.

Diamond, Comet and MFJ make mounts which should suit your needs. If you have a luggage rack on the roof, that type would be the best. They clamp right on to the luggage rack, and can be removed in minutes. You would be able to place the antenna closer to the center of the roof to take advantage of the ground plane. If you don't have a luggage rack, there are mounts that will attatch to the top of a door or hatchback. They tighten with allen screws, and have a rubberized back that won't scratch the paint. They are also easy to move to another vehicle.

Along with these mounts, they make coax assemblies that have a short length of very thin coax that won't pinch in the door or damage weatherstripping. Mobile applications use coax runs short enough where loss through the cable isn't a factor to worry about.

Suppliers on the net abound. These are a few off the top of my head that have a wide selection.
www.aesham.com
www.gigaparts.com
www.hamradio.com

Again, welcome to the world of ham radio!

 

[Tim Stoecklein]

Congratulations Rodger! Welcome to the hobby!

This is great Pat, great answers, and great questions from everyone.

...Now, how do I hook up the Christmas lights on the outside of the house to my paddles so I can send CW blinking to the neighbors, hmmmm... :lol:

By the way, for those interested in a bit of history, I am reading a book titled Signor Marconi's Magic Box. It is written by Gavin Weightman. The book is about Marconi's invention of the first wireless transmitter. It's a great book for amateurs, or anyone else interested in radio for that matter.

73 de Tim

 

[Pat Palmer]

...Now, how do I hook up the Christmas lights on the outside of the house to my paddles so I can send CW blinking to the neighbors, hmmmm...

Tim,
You could wire a straight key right into the power cord, and make sure the knob is insulated.... :shock:
To use a paddle, wire 2 relays in parallel into one side of the power cord, run the control leads off the relays to a 1/4" stereo jack, and plug a keyer in. Your neighbors will look quizzically at your house for sure!

 

[David Diehl]

How do you Use the Cross BAnd Repeat for a ICOM 2720 mobil?

 

[Tim Stoecklein]

David,

From what I can tell in browsing the manual for the IC2720 online, it does not have the cross-band function on it.

EDIT: After looking at the product listing on Ham Radio Outlet, I think I see where the confusion comes from.

"V/V, U/U, V/U, U/V (Work dual or cross band)"

Their cross band reference is to the ability to use one channel on UHF while using the other channel on VHF. This is not Cross-band Repeater, but the ability to use the two separately. That is, unless I am missing something all together.

Tim

 

[Morgan Palmer]

That's exactly what that means.

My Yaesu FT7100M mentions that V/U, U/U junk, and is referencing receive, not repeat.

That's one function I wish I had on my rig, though aside from that it's a good mobile.

mp K5TVT

 

[Pat Palmer]

Morgan,

Did you have problems with the 7100M? I got one three years ago, and it had serious transmit audio problems. Six months and three times in the Yaesu tech center and it was finally fixed. It also has a very wide RX, lots of intermod on the sub band.

 

[David Diehl]

Thanks for the info, I could never find anything that would help me figure it out, but it makes sence, v/v, v/u so on, and so on.
:roll: