Friday, October 27, 2017

Test: End fed wire versus AlexLoop on 20m

Recently I did some tests with my two WSPRLite beacons. I started testing my AlexLoop against a 20m long end fed wire on 40m. The wire beat the loop quite dramatically.

One of the comments I got was that the loop should do relatively better on higher bands. That is why I ran a test on 20m as well. I collected the data about 2 weeks ago but due to other commitments I only got around to analysing it today. 

So what was the set-up? As in the previous article, I set up the AlexLoop in the garden with the center of the loop at about 2 meters high. The end fed wire this time was 10 meters long and ran from the back of my house into the garden sloping from about 7m high to about 2,5m high. I ran the beacons on 200mW for 2 consecutive days. 

The WSPR data shows:

  • 514 spots from 49 spotters were received for the beacon on the wire 
  • 436 spots from 29 spotters were received for the beacon on the loop 

This already gives you some impression about the difference. More stations were able to pick up the signal from the wire. 

Looking at the spot map below (distance in km vs SNR) you can see the orange profile of the wire is slightly shifted to the right (higher SNR) as compared to the blue profile of the loop. It is not as big a difference as on 40m though. 
More prominently you can see that the odx is again much higher for the wire as the signal was picked up across the pond in East Coast US (orange spots on the top).

This time the overlap is bigger, which makes it interesting to zoom in on a single spotter to see the actual signal strength over time. I selected one spotter that generated the most spots (EA8) but did check if the profile was any different at other spotters. This seems like a good sample for those stations that heard both. The orange line shows the SNR of the end fed wire, while the blue one shows the loop. On average (also looking at other spotters) the loop is 3 dB down across EU.

There are not enough spotters to make further assumptions about performance differences at specific distances or directions. What you can see is that for DX the signal from the wire is received within a 6dB range of SNR. The loop is not reaching the lowest end of that SNR. So it seems the wire is beating the loop everywhere but more so on DX.

1 comment:

  1. Hallo Lars, interessante test maar de uitslag is wel wat ik al verwachtte. Ik heb zo vaak ge-experimenteerd met diverse hf-antennes en de draadantenne deed het toch altijd beter dan een loop. Een loop is een fantastische antenne als je geen andere mogelijkheid hebt. B.v. in een flat. Daar is een loop zondermeer een uitkomst. Je kunt zelfs de QRM wegdraaien. Ook met vakantie gaat de loop mee en zelfs afgelopen jaar was het een uitkomst dat ik hem bij me had. Bij ons nog onbekende vakantiehuisje was geen mogelijkheid om iets weg te spannen en alleen een MP-1 op een nepveranda deed het redelijk maar had geen vrij zicht. Toen was de loop een uitkomst. Een magnetic loop is een prima antenne om erbij te hebben en bied vaak de oplossing maar een goed weggespannen draadantenne zal altijd beter werken. 73 Hans, PE1BVQ