I continue with the series "Building Low Budget Antennas" for Radio Amateurs. Nothing fancy .... no just simple low budget antennas!
In this article I will be looking at building a End Fed Halve Wave Antenna for 40 to 10 Meters. Now I know there are thousands of ways to construct this antenna, but how cheap can you build one? R10, R50 or R100. You decide how much such an antenna will cost.
In Part 1 I will describe how I constructed the 49:1 Balun for this antenna. In Part 2 we will be looking at the antenna wire, Nano VNA readings and the results when using this antenna.
General Specifications:
Resonant Frequency: 10.130 Mhz
Frequency Span: 7 - 28 Mhz
Antenna Impedance: 50 Ohm or very close to 50 Ohm
Use: General HF use but for now WSPR on 20 Meters
Enough said let's
start building the QRP EFHW 49:1 Balun.
Materials I used:
1 x PL239 Socket
Connector with two brass bolts and nuts
1 x Project Box
2 x Stainless Steel bolts, 4 x nuts and 2 x wing-nuts and 2 washers
1 x 1.5 Meter (1.5 mm) Copper Wire
1 x F82-43 Toroid
1 x 100pf 1kw Capacitor
2 x Electrical Lugs
1 x 2K7 Resistor to test the 49:1 Balun
Odds and Sods:
Cable Ties
Silicon Sealant
Insulation Tape
Solder
Solder Paste
5 -10 m Coax Cable (RG58CU Mil Spec) 50 ohm with 2 x Connectors
Self Amalgamating Electrical Tape
Tools:
Soldering Iron
Sharp Utility Knife
Screw Drivers (Small flat + Star)
Test Equipment:
HF Radio
SWR Meter
Antenna Analyzer (If you have one but not compulsory)
Coax Patch Leads
Mast (Non conductive)
Power Supply or Battery for Radio
Building the Balun and Antenna:
I am not going to go into detail how I constructed my version of this balun and antenna as there is more than enough info on the Internet. Google is your friend.
Here are two sites you can visit that might be of assistance to you if you want to construct this antenna.
Manual impedance transformer for 250 watts End Fed Antenna’s
Build an End-Fed Half-Wave Antenna From a Kit
I used what I had available on my shelves and in the junk box and came up with my version of the 49:1 balun.
The 49:1 Balun diagram:
Constructing the balun is straight forward and there are many videos available on how to wind the toroid. Just one word about the 100 pF capacitor. Is it really necessary? If you have a 100 pf 2 kV available then you can install it. If you run high power you will need at least a 15 kV capacitor. For 20, 30 and 40 meters you do not need a capacitor. However for 17 meters you will need a capacitor to flatten and lowering the SWR curve through to 10 meters.
Preliminary Test Results:
To test the balun before adding the wire and counter poise I used a 2K7 resistor on the ground of the coax connector and antenna connection. The attached NanoVNA images provide info on the results I obtained from the balun. I am sure the SWR readings will change once I add the antenna wire to the balun. The height and closeness of objects will also play a roll.
Finally: In Part 2 I will be looking at the performance the antenna and will also do more experiments and measurements using the NanoVNA and WSPR - Lookout for Part 2!
Images: Click on images for larger view.
Part 2 to follow soon.
