Category Archive: SWIARC University

Educational articles by SWIARC club members to help amateur radio operators everywhere.

Refurbishing a Horizontal Loop Antenna

Paul WB0GXD writes, “There were some near-catastrophe problems […] to overcome at the antenna party on Saturday November.” In this story you will learn from valuable experience as the volunteer crew refurbish an aging 75-meter horizontal loop antenna. Their work in a contribution not only to Paul’s antenna, but sharing their experience helps the rest of us build better antennas. Read the rest of this entry »

Generator Maint.

Notice plastic tube draining gasoline

Notice plastic tube
draining gasoline

SWIARC member Andy WB0WKC (SK) used to change the oil and gas in his generator 3 or 4 times a year. He was the one who brought a bright pink 100ft extension cord to a couple of our Field Days. It was made of very flexible (lots of strands) 3 wire #12. Andy was an electrician.
Do you want to hear about the several guys who said they were going to bring a generator to Field Day, but when the day came theirs didn’t work? Usually because it hadn’t been run in a couple of years. Gasoline turns to varnish if you leave it long enough. Gums up the carburetor. Conversely, oil lasts forever. Well, you have to clean and rerefine it maybe, but it’s good for a long time. Here’s my formula for keeping your generator ready:
Change the gasoline twice a year. Use the old stuff
in a lawnmower or your car. Do NOT use Gasohol.
My generator says “Don’t use E85. 10% is OK.”
(I think ‘OK’ means 100% gasoline is better.)
Change the oil once in awhile after a number of hours
or every year or so.
These guidelines apply to any small engine. Your car
can handle Gasohol. Your lawnmower engine cost 99 bucks.
They don’t spend a lot on fancy gasket material.

Tropospheric Ducting

Jake (ke0nkc) in South Dakota was one of several distant hams on the SWIARC 82 repeater Saturday night (7/22/17) talking with Albert (ke0lol) and some other locals. They were also making the trip from northern and eastern Iowa to north Nebraska.  Stations 200 miles away were talking on the club repeater, some full quieting.

Read the rest of this entry »

KE0GKF’s Digital Hotspot

STORYPIC0B-256x128Turn your home Internet connection into a minature repeater for your DMR, D-Star and C4FM radios so you’re always within range of a repeater and able to access a wide variety of digital networks. Two such products are now available. Read the rest of this entry »

Electronic Builder’s Toolkit by Russ AD0QH


Kit building has become very popular among local hams. Our club President, Russ, has provided us with a follow-up shopping list of supplies the kit builder will surely need as illustrated during his presentation at the January club meeting. Whether you made the meeting or not, you will undoubtedly find his Amazon shopping list useful.


Russ has put together a comprehensive shopping list using that you can view by following this link: Amazon Wish List AD0QH – Ham Radio


You would have seen many of these items during his January presentation. The presentation not only applies to kit building, but electronic circuit work, rework, and service. This is entirely an excellent starter kit for the electronics service enthusiast.


Here is a TEXT list of those items mentioned above:

*Carson LumiLoupe 10X Power Stand Magnifier With Dual Lens (LL-20)
*Chemtronics 10-25L Chem-Wik Rosin Desoldering Braid
*Excelvan M6013 Digital Auto Ranging Capacitance Meter Tester Capacitor Tester
*MagnifyLabs Headband Magnifier (Optical Visor / Binocular Magnifier) – with One Optical Glass Lens Plate (2.5x at 8″ Focal Length)
*Dual Wall Adhesive Lined Heat Shrink KIT – 85 Pieces – 3:1 Shrink Ratio – Size Range: 3/32″ to 1/2″ – Black, Clear, Red
*Hakko FX888D-23BY Digital Soldering Station FX-888D FX-888 (blue & yellow)
*PanaVise Model 201 “Junior” Miniature Vise
*Hakko CHP CSP-30-2 Wire Stripper, 20-10 Gauge Maximum Cutting Capacity
*Hakko CHP CSP-30-1 Wire Stripper, 30-20 Gauge Maximum Cutting Capacity
*Hakko CHP PN-2007 Long-Nose Pliers, Flat Nose, Flat Outside Edge, Serrated Jaws, 32mm Jaw Length, 3mm Nose Width, 3mm Thick Steel
*Hakko CHP-170 Micro Soft Wire Cutter, 1.5mm Stand-off, Flush Cut, 2.5mm Hardened Carbon Steel Construction, 21-Degree Angled Jaw, 8mm Jaw Length, 16 Gauge Maximum Cutting Capacity

Enjoy shopping!!!


note:  If Russ puts together some of his presentation notes with informative tips they will be added to this article as an update.  It pays to check back and keep track of whats on the SWIARC web site.

Transceiver Coaxial Cable Selector Switch


If you are going to connect two or more transceivers to a single antenna using an antenna selector switch, be warned, you need to consider how much RF you are dumping into the unused transceiver. There are antenna selector switches that cannot be safely used as a transceiver selector switch. Never assume you can use them interchangeably.

Not all antenna selector switches are up to the task of using multiple transceivers on the switch. They are typically designed for using a single transceiver on multiple antennas.

Two factors need to be considered when selecting a coaxial switch: 1. Output Isolation 2. Grounded Unused Connector

The first factor is the Output Isolation of the signal, which is to say how much signal from your transmission is bleeding onto the unused connection. The better the isolation the less signal will be getting into the unused transceiver. This mostly has to do with the spacing of the internal wiring.

The second factor is the grounding of the unused connector. Most low-end antenna switches do not ground the unused connection. Grounding the unused connection helps to bleed off stray signal to ground rather than into the unused transceiver.

The MFJ-2702 is an inexpensive antenna selector switch that should not be used to connect two transceivers to a single antenna. Although it has suitable output isolation at 70dB or more for the HF band, it does not ground the unused output connector. The MFJ-2703 does more than simply add an additional connector. It also has additional internal parts to ground the unused connectors, which helps mitigate RF from entering into the unused transceiver.

When you are using an antenna switch box as it is intended, to select from two or more antennas for a single transceiver, then these factors are less important in that they are relative to signal loss. When you are using an antenna switch box to connect two or more transceivers to a single antenna, then you take a chance at damaging an expensive transceiver. Don’t use a cheap antenna switch box unless you are certain that it can be used in this manner either by design or by carefully considering its output isolation as well as whether or not it grounds the unused connector. Some coaxial cable switch boxes are advertised as both a transceiver and antenna selector. You should still verify that the unused connectors are grounded rather than open.

Consider the Workman model CX-3 as an example of an antenna selector switch which is barely suitable for its intended purpose. With poor RF isolation of 42dB at HF frequencies and completely lacking a center conductor ground at the unused connectors it isn’t even an ideal antenna switch. If you planned to use it to connect multiple transceivers to a single antenna you risk damaging those transceivers because power from the selected transceiver is going to bleed into the unused transceivers. This would not be a problem at QRP power levels, however, at 100 watts it would be a bad idea. Although immediate damage may not necessarily occur, over time it would inevitably lead to failure of your radios.

Finally, when you are using a coaxial cable switch to connect two or more transceivers to an antenna, be care to observe the switch position before you transmit. Human error can still result in damage to your expensive transceiver. Make sure you never transmit when the switch is not set to the transceiver you are using.



Kit Built mini Power Supply

Variable Power Supply costs under $20 (on Amazon)

Variable Power Supply
costs under $20
(on Amazon)

Mike KC0FAN, Football At Nebraska, went to the Hearland Hams sponsored Kit Building program
in Glenwood IA recently, and has now built this cute little variable power supply. It’s only
eighteen bucks on Amazon, and comes complete with a transparent plastic case to keep your
fingers from contacting the 120VAC. He says:
It was a fun project to do. The board is laid out well and I do like the case so I’ll keep my
fingers out of the line voltage. If I was doing a class on kit building this project would make
a great starting point.
Toughest thing on this one was the IC base and mods to the display leads so it can be hardwired
and mounted to the board. I did use the ps last night to check the led (just for the fun of it.)
on the transistor checker.
The ‘transistor checker’ is Mike’s second kit project.

Car Antenna Hole Fix

Car Antenna hole fix using nylon parts

Car Antenna hole fix
using nylon parts

Sooner or later you’re going to sell your mobile and likely as not, the new owner
won’t be a Ham and won’t understand why there’s a hole in the roof. Here’s a fix.
First of all, go down to hte hardware store and buy a couple Nylon washers about
an inch diameter. Then, a small container of Nylon wall clamps or whatchacallit,
wall hole covers. Second, pull off your antenna and put down a Nylon washer over
the hole and the clamp with expanding stud (click on pic to see what I mean)
through it. The expanding stud expects a half inch of wallboard to work against
so put another couple, 3 or 4 more, Nylon washers on the inside of the hole.
Finally, tap the ‘nail’ through the stud to expand the bottom and you’re done.
Oh yeah, it helps if you bought a WHITE car to begin with, and no, this wasn’t
a roof mount antenna. The stick looks a lot racier on the trunk with a slight
backwards rake.
P. S. One more caveat: You shoulda been removing the antenna each year to
wax the paint under the mount. If not, in this case maybe twice in eight
years, you get a circle of rust around the mount.


-Rich WA0ZQG