Mod-Bob vs. DX Engineering DV-40-P

My DX Engineering DV-40-P 40M phased array just gave up the ghost (SWR went high and there is no directionality), and while its most likely a gopher who has chewed on a wire, the two elements are really too close to the Mod Bob. It is possible (but much less likely) that transmitting on the Mod-Bob has fried a component in the DV-40-P. 

Since one of the two 40M elements is less than 10′ away from the Mod Bob its in the near field of the Mod Bob which means it no doubt distorts the patterns of both antennas, which makes both less effective than what the models say.

The broadsided direction of the Mod Bob right now is E-W, pretty much 90 and 270 degrees.

That’s great for ZS, but the broadsided direction for Bouvet is 130 degree-ish, and the 40M broadsided direction is perfectly aligned for Bouvet.

The plots in the DX Engineering DV-40-P manual show that both the broadsided pattern is not as good as the Mod-Bob on 40M, and that its also 1 dB less gain wise. What is really interesting is that the Mod-Bob is only 1 dB down from the DV-40-P’s end fire direction (Mod-Bob in broadside):

In fact, if I move two of the Mod Bob’s elements – which means they replace the 40M vertical elements, I pick up 1 dB and get a better pattern and direction for Bouvet.

The Mod-Bob has become the only antenna that I use much any more, and its very easy to maintain. My only DX hope these days is working the last 13 on 160M and Bouvet, and since 40 and 30M could be the “godsends” for the West Coast, the Mod Bob has become even more important than my 40M array – which I have really loved.

I am quite confident that I will work them on at least two of the low bands, and also on 20M with my 2 element 20M home brewed yagi.

I think I know what I’ll be doing one of these weekends soon. I have to take down the 40M array and move two Mod Bob elements. Doing this will knock out my great ZS LP path, but Bouvet is the only game in town for me now. On 160M the Mod Bob pattern is omni directional, and on 80M there is the same pattern as the DV-40-P, so the little that I give up taking down the 40M array means I gain so much more with moving the two Mod Bob elements.

Dilemma solved.

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