Bombastik vertical antenna

Here is a quick review of the Bombastik clone of the Wolf River Coil multiband vertical antenna

I have been following a few of the US POTA activators and quite a few of them are using the Wolf River Coil vertical antenna for 80 to 10m with good results. Most of their QSO's are local but I decided it would be worth investigating the antenna for potential POTA/SOTA and portable use. The main advantage I see compared to my current EFHW antenna that I use for these purposes is the fact that you do not need a mast, the antenna is ground mounted.

When you setup a station where there are trees this is not important but a lot of my "away from home" operation if from areas without trees.

I found a local company, "Bombastik" who sells a copy of the Wolf River Coil antenna so I ordered one. It arrived a few days ago but I only managed to set it up yesterday as part of my "back yard field station" for our local Field day contest.

I ordered the complete antenna consisting of the adjustable coil, telescopic whip antenna and radials. I also ordered a mounting bracket to allow me to attach the antenna to a peg driven into the ground as well as an attachment point for the radials and coax.

When I started setting it up I noticed a few issues. Firstly the antenna was not complete, there was no way to attach the whip to the coil, fortunately I had a spare male to male adaptor I could use.

The chrome piece in the middle was not included with the antenna.

 I also found a few problems with the construction of the antenna.

The caps on the coil were both loose, the one so loose it kept on falling off, I had to epoxy it on.

Loose end-caps on the coil, the one just fell off!

The U-bolts supplied with the mounting bracket did not fit, the hole spacing on the plate was out by about 3mm to I had to enlarge the holes.

The coax fitting on the plate did not fit correctly, the way it was the radials would not actually be connected to the antenna! I again had to drill out a hole to make the fitting seat correctly so that the shield of the coax is actually connected to the plate.

The slide on the coil that is used to adjust the length is too tight, even when fully loosened you cannot slide it up all the way on the coil, the result is that the antenna cannot be tuned for 30m and if you want to use it on bands higher than 30m you have to actually remove the coil, a rather painful operation! The slide is to tight it actually dislodged some of the turns on the coil. when I tried to move it all the way to one end. I also found some glue on the coil making movement difficult. I still need to find a solution for this.

The sliding clamp is way too tight even with the bolt completely loos, the edges also catch on the turns of the coil and it is easy to displace them if you try to force the slide.

The telescopic whip is very difficult to extend, I could not extend the last section at all!

The radials have crimped connectors on them but the crimping is done do badly a few radials detached the first time I unrolled them! Some of the radials have been damaged during the assembly and crimping. The radials are also rather short and all the same length, fewer radials cut to different bands actually work better. As it arrived it was not possible to adjust for a SWR of better than 1.8:1 or 2:1 on most bands. As a quick test I cut extra radials of length 1/4 wave for 40m and 20m and then it was possible to get an SWR of 1.2:1 on both bands.

Radial attachment points, some radials just fell out. I soldered these connections and they are now far more secure.

I wonder if the production kit was ever actually assembled and tested?

Once I had solved most of the issues I used the antenna during the Field day, I also put up my usual EFHW antenna on a 8m portable mast to use as a comparison.

Conditions were not great and I ended up only working local stations on 40m and 20m with a few DX stations on 20m. Direct comparisons between the antennas showed that sometimes the vertical was close to the EFHW but in most cases the EFHW was between 1 and 2 S points better in receive and transmit.

I did some work sorting out the problems with the Bombastik copy of the Wolf River Coils vertical antenna. Adjusting the coil for 80m to 30m is still a pain but it works, I ended up taking the slide off and filing the edges that caught on the coil a bit and then polished the inside of the clamp with fine sandpaper, this helped a bit. I think replacing the slide fitting with something more suitable would be the only way to get it to work well.

Coil set to the 40m position with a lot of effort.

I have also tried the antenna on 20m to 10m without the coil. By adjusting the length of the whip it is easy to get a low SWR (around 1.2:1) on all the bands.

I did do direct comparisons between this antenna and my dipoles as well as my EFHW. In a few cases the vertical is just as good as the other antennas but most of the time signals are quite a bit weaker on the vertical. When conditions are great this does not matter as much but you still loose out on weak signals and if you are running QRP or low power people struggle to hear you on the vertical where the higher EFHW or Inverted V your signal will be quite a bit stronger. I have tested this many times with the same result every time, I always get weaker signal reports on the vertical.

In conclusion I would not recommend it unless you do not have a tree around or cannot put up a basic support of a EFHW or Inverted V antenna as it seems to perform really badly compared to a basic wire antenna. And then there are the problems with the construction and design as well, you have to accept that you will have to make a few changes to get the antenna to work.

Update 16/9/2024: I have done more tests, and made some modifications to the Bombastik vertical antenna. Results are still mixed, on the higher bands (20m and above) it does work reasonably well for DX but 90% of the time the EFHW is still better. On 80-30m it is still rather poor, maybe I need to look at more radials. Unfortunately it can be quite a pain to put out lots of radials as the want to tangle all the time. It then becomes quicker and easier to just put up a field mast and use the EFHW. The main reason I looked at the vertical was that I was hoping it would be quick and easy to put up in the field, that is not really the case!

Other than the problems I mentioned above the main issue I had with the antennas was the difficulty (Even impossible!) to adjust the coil especially for 40 and 30m. After looking at the setup carefully I could see that the problems was that the bold used to tighten the clamp was getting stuck on the inserts in the clamp. The result was that even if you loosened the butterfly nut on the clamp it would not release making adjustments almost impossible.

The bolt was catching the inserts in the round sections of the clamp and not releasing.

I removed the bolt completely and removed one of the inserts, they are not needed when the clamp is only used to tighten the connection on the coil.

The insert that caused the trouble, the bolt was catching on the rough edges that can be seen on the lower part of the hole.

Once I had done that the bolt now releases correctly and the coil adjustment becomes easy!

I used the antenna for a day this weekend, mostly chasing DX and SOTA and I managed to make quite a few contacts. When signals were a bit weak I had to revert to the EFHW a few times as it was still out performing the vertical but at least the vertical is now useable. I will test it a bit more on 40 and 80m when DX conditions on those bands are better.

 (c)R Venter 1996-2024