Comparing QRP vs 100 Watts CW on Multi-Band Fan Dipole

Had a comparison of pickups on CW at Reverse Beacon Network (RBN) skimmers today morning around 7 am local time between low power and full power of my FT-710 radio. My antenna was a multi-band fan dipole inverted V antenna with elements for 40, 20 and 10 meters, with apex height of about 10m from the ground. Feed line was 15m of RG213 and there is a 1:1 current balun at the feed point. Antenna elements are parallel to each other, stacked vertically with PVC separators. For low power, I used 10 Watts on 40 and 20m and 5 Watts on 15m and 10m. The antenna works on 15m as it is the third harmonic of 40m (7 MHz vs 21 MHz). You may be aware that center fed dipole antennas work well at odd harmonics of the fundamental frequency as well.

You may wonder why 10 Watts at lower bands and 5 Watts at higher bands. The most popular QRP radio in this region currently is the uBITX, which has lower power on higher bands. That is why lower power was chosen on higher bands, to simulate the effect of uBITX. In my earlier days on ham radio, the popular QRP radio in this region was VU2VWN QRP, of which I had also homebrewed one and used for quite a long period. We all miss VU2VWN who became silent key over a decade back.

For the low power test, I got picked up by the RBN skimmer at VU2PTT at 171 miles with a signal to noise ratio of 8 dB on 40m. CW speed was set at 20 wpm in the keyer on my FT-710 radio. There was no pick on RBN on any other bands. I am planning to continue similar tests at other times to study propagation from QRP setups for the benefit of QRP users in this region. Many of the QRP users in this region are on SSB and these tests may not reflect their on air performance. But I am aware of some who have worked much more DX with uBITX on higher bands than me with my FT-710. That may be due to better antenna setups, location and most important, sheer dedication to listen and work stations in a radio without a waterfall display. May I request my ham friends to plan similar studies so that we can get an idea on QRP propagation from this region.

In the 100 Watts test, I used the same CW speed, but it was done after the tests on lower power and there would be have been a time delay between the two tests of about 10 minutes. There was pick up only on 20m and that was at OH6BG, at a distance of 4445 miles, with a signal to noise ratio of 19 dB. I am not sure why the 100 Watts call was not picked up on 40m at VU2PTT. May be there is a setting to reject same callsign within a gap of few minutes. Another possibility is that the skimmer would have been engaged with a call from another station at that time on 40m. There were a couple of strong stations on air from this region at that time. Looking forward to hearing reports of similar comparative studies from ham friends.