A Little More UnUn fun

This past week I wound a few more toroids using a 77 mix. The toroids are 0.5″ in diameter and wound with 22 awg insulated magnet wire. I wound one with a single core and one with a dual core. My goal was to try to get a little better low band performance. I get a kick out making a few contacts on 60-80-160 meters. The finished UnUns are 9:1.

We’ve been going through a heat wave this week with a heat advisory every day. I got up early and tried a couple different antennas. Using antenna wire from my Frankentenna, I built an end fed with a 65′ antenna and a 65′ counterpoise. I also tried the 65″ antenna with a 17′ counterpoise. The set up looked like this.

For this antenna, the best combination was a 65′ antenna wire, a 17′ counterpoise and the single core 77 mix 9:1 UnUn. I got the following readings from my Rig Expert Prostick with 6′ of RG316. As a control I also tested my Sparkplug transformer.
Band SWR (17′)—–SWR (65′)——Sparkplug 65′
160 – 2.4 ———— 4.2 ————– 5.6
80 – 5.4 ———— 1.1 ————–8.3
60 – 1.7 ———— 2.3 ————– 12
40 – 2.9 ———— 3.5 ————– 1.7
30 – 6.9 ———– 4.5 ————– 16
20 – 3.8 ———– 4.0 ————— 1.5
17 – 5.2 ———– 5.7 ————— 9.7
15 – 4.1 ———– 4.3 ————— 1.1
12 – 6.2 ———– 6.9 ————— 10
10 – 4.5 ———– 4.6 ————— 2.6
6 – 5.9 ———– 5.8 —————-14
Fiddling with the counterpoise length could make things a little better, but overall the SWR’s are low enough to match with a good tuner. I realize that running a short feed line would affect the Sparkplug so in another test I added a counterpoise and it did bring down the SWR on some bands. However, to me the winner is still the single core 77 mix 9:1 UnUn.

Another antenna that I like is a random wire antenna I call the K4SWL antenna https://kk4z.com/2022/06/05/k4swl-antenna-plus/. I call it that because it was Tom K4SWL who I got the basic design form. It’s a 29.5′ antenna with a 17′ counterpoise. I built an UnUn based upon a QRP Guys design but wanted to try to get a little better performance on the lower bands. In this case I used a two core 77 mix 9:1 UnUn and got the following results.
Band – SWR
160 —- 2.0
80 —- 1.7
60 —- 1.5
40 —- 1.5
30 — 1.5
20 — 1.4
17 — 1.3
15 —- 1.3
12 —– 1.2
10 —– 1.2
6 —— 1.2
Realize that this is a small antenna and will not be as efficient as a full half wave dipole (on 160 meters, that is 270′). However, it would be fun to see if you can make a contact on 160 or 80 meters in a park with a small antenna. So get out there and play radio! 73 Scott

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