We recently got ourselves a BigIR mechanically adjustable vertical primarily intended to be used on the 80m band. We have long been relying on a low-hanging dipole for 80m, which has two drawbacks. One is that the narrow bandwidth only lets us tune it to either the CW- or the SSB-part of the band and the other is that the antenna pattern is directed upwards. High take-off angles are great for NVIS and short-range communication but suboptimal for long-range QSOs.
Our purchase of a BigIR antenna in 2018 was supposed to solve both of these issues. A vertical antenna will have a lower take-off angle than a low-hanging dipole, and the mechanical adjustments would solve the issue of small bandwidth. The problem that appeared instead was the problem of ground. We only had a roof to mount it, and it proved difficult to make a functioning ground plane with the relatively uneven and unpredictable “ground” that Studentersamfundet is.
In 2018 and 2019, we worked under the hypothesis that many short radials were better than a few short ones. According to various sources, it is preferable to have many short radials to just a few long ones for the same length of wire. This worked for the higher bands, but not for the 80m band. There is a substantial amount of metal in our building, and there is a rumor that an old metal roof is under the current roof. Thus, we also tried improvising a counterpoise by connecting to gutters and ventilation shafts. Neither this was successful.
We ended up using it as a backup antenna for higher bands, e.g. on 20 m when our array was QRT. Then, in 2022 we tried a new approach. Instead of using the roof as bad ground, we tried to use it as bad air. This meant that we tried to make radials as if they were elevated radials, even though they were physically lying on the roof. We cut up 4 quarter wave radials, approximately 20m each. These radials would by design only work on the 80m band, but that was also our priority.
We found that the insulation of the control cable had rubbed against the not-used ground bolt for Bigir without the 80m coil. This caused arcs to form between the ground bolt and the now-exposed copper in the cable. The controller seemed to survive, but this gave us bad SWR and a good night’s work. We also managed to break the brass ground bolt on the 80m coil, which we were supposed to use. This would later be fixed with a stainless steel bolt, but we temporarily made a fixture for connecting the radials to the connection point for the coax.
All of this did produce some limited success. We were able to find a resonance dip in the SWR, it was just not at the frequency that the BigIR was tuned to. We did not consider that too discouraging, as we had not calibrated it. The discouraging part was the noise. We could not hear anything, not even with wspr.
Our success was on the transmitter side. Despite not hearing anything, we were heard in both northern Canada and southern Australia. This indicated that the antenna worked, but that we picked up prohibitively large amounts of noise. Noise is a difficult issue to solve, and it would take a few more years before the next serious breakthrough.
This winter, 2025, we were all a little older and thus wiser. The idea was to simply try the same approach as 3 years ago and see if we could iron out the difficulties. Thus we used the same “elevated” radials as 3 years ago, but we shortened them in a little bit. It is quite typical for us to factor in a quite generous velocity factor when making antennas, as it is easier to cut them shorter later than elongating them after they have been cut.
After slowly rediscovering how to connect everything, we attempted to connect the antenna directly to a radio on the roof. After finding the resonance dip, we found that this time we could both hear and be heard on SSB. This setup got us our first 80m QSO from Bigir, which was very encouraging. We tried using a temporary cable down to the shack, bypassing the original cable laid out when we first got the antenna. This worked and got us another QSO, LB2DK’s first. We concluded that the old cable was somehow broken and that the noise issues from last time either were caused by the cable or had resolved themselves.
We ran CQ WPX RTTY with Bigir using the temporary cable, while still being QRV on our 80m dipole. We tried using both of them, and we anecdotally did not notice a large difference. We got 1 QSO with Morocco, 2 with Asiatic Russia, and 10 from the Canary Islands, the only DX we got on 80m. In total, we got 108 with Europe, mostly using Bigir. Before the contest started, we calibrated the SDA100 controller box to the resonance dip on our antenna setup and found that we had to shorten the element quite far compared to the default settings. This implies that we still have overestimated the velocity factor of the radials and that we should shorten them further.
The following Monday, we tried to test the antennas a bit more quantitatively. The idea was to send on both antennas approximately simultaneously with WSPR, and compare the received signal strengths. After some fiddling to make it work we managed to get a comparison using the antenna comparison tool at wspr.live. Unfortunately, we found that the dipole worked better for nearby (<2000 km) contacts and equally well for far long-distance contacts. (The longest we got was approximately 4000 km).
This gave an indication that the Bigir is not as great as we hoped, even for DX. However, this simple test is not conclusive. It could be that Bigir had compared more favorably if the conditions had been better for even longer contacts.
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