2 x MBM48 elm. or 1 x homemade MBM 92 elm


Jannes van Bergen:
I recently bought myself a second Jaybeam MBM48 this is a 48 elm 70cm antenna. (And there used to be a MBM88 aswell with a gain of just 19 dBd !! not dBi)

Now I can either stack them (2x48elm) or homebrew an extra long 92 elm beam .
Gain of 48 elm =   15,7 dBd   open.  26 degrees
Gain of 92 elm = > 19 dBd     open. <19 degrees

Stacking (+ 2dB?) should hardly effect the horizontal open. angle of 26 degrees but there will be some loss due to extra connectors and cable.
( boom approx. 6')

Homebrew a 92 elm will give me open.angle of just 19 degrees which makes it a very narrow beam but it will also provide me with
a wacking >19 dBd gain.  ( boom approx. 12' )

Should I go for the stack or gain........

What is your expert opinion  ?????????

Steve Fletcher:
That's an interesting question !

I think stacking would realise 2dB overall (including harness losses), maybe a bit more. So pretty close to the expected 92ele gain.

How many QSOs do you lose at the moment because the other guy can't hear you ? Would the extra 1dB from a 92ele make the difference ?

On the other hand, how many QSOs do you have now (on the single 48ele) where you have to tweak the rotator because the other station is a few degrees off ? Would you lose these contacts with an ultra narrow beamwidth ?

I think the old Jaybeam 88ele had a 'trombone' type support because of the weight/length of the aerial. You would have to make something similar if you go the 92ele route.

On balance I would probably stack. It's easier to do mechanically and in a location such as yours where contacts could be coming from almost any direction the beamwidth would be worthwhile . . . on the other hand there would always be the odd one that got away where that extra dB would have clinched it  :-)

I'll point my own Jaybeam 48ele over to PA and look out for you.

73 Steve, G4GXL


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