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OZ5ACI Denmark flag Denmark

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See also OZ0FT...

The picture above shows my current antenna system as of October 2012: A Tennadyne T6 LPDA and a F/B optimized LFA for 6M from Justin, G0KSC.

Below is the antenna setup from 2000 to 2012 - Home brew Open Sleeve fed 20-6M system, 6M is a 4 element cell - the rearmost element was picking up the RF and can't really be seen on this image. The 6M cell had about 8.2dB gain and about 18dB F/B, the rest of the antenna performed pretty much like a 2 element full size system on the resonant bands.

My antenna system from 2000 to 2012 - Open sleeve 20-6M

 

Below is antenna position while testing various feed methods for the LPDA - I tried them all, no choke, choke at feedpoint with drooping coax (which I intuitively assumed would be the best) choke at the point of descent down the mast both grounded and ungrounded. Results with good chokes were similar irrespective of where the the choke was fitted. Ended up with a W2DU style choke where the coax starts it's descend down the mast which in my case presents the best overall SWR - in a reactive load such as this the SWR varies with the nodes on the coax and thus a compromise length of coax was found. There is NO choke at the feed point up front, it is obviously redundant in the system as it is a 50 Ohm design and no transformation is required. The antenna performs pretty much as expected, F/B 9-13 dB, F/S about 25dB and SWR is less than 2:1 on the HAM bands. Gain is very apparent when compared to my elevated Butternut vertical - gain usually 12-18 dB over that antenna on long haul contacts - the LPDA is in a tower at 14.5 mtrs with the feed point, about 10-11 mtrs higher than the Butternut feedpoint - I am guestimating gain is equivalent to what can be found in a 2 element system or an HB9CV style antenna. The afore mentioned 12-18dB difference is about the same as I saw between the open sleeve 2 element system and the Butternut.

 

My mobile setups:

My current ride with a Hustler mobile whip on the roof and my previous ride with an Ameritron screwdriver antenna on the edge of the deck.

 

No, this antenna is NOT fitted on the truck ;-) It is the "Radio Arkala", OH8X, Mammoth 80/160M system as you can see with yours truly next to the truck. The mobile antenna with a 20M resonator is just visible on the sun screen on the right photo.

 

Another seriously big antenna system which is NOT fitted to the vehicle. Note the red truck under the tree next to the base of the dish. This dish is part of former "Tanum Tele Port" in Sweden used for worldwide sattelite links dating back to the 70's I believe. Imagine the gain on these babies on any HAM band above, say, 50MHz! Next picture is another view of that vehicle, as you can see it's a pretty ordinary loaded whip I use for my travels - a vintage (1980's) RSM system from Yeasu, for which I have resonators for all bands from 80 through 2M, very light and performing way beyond my expectations :-) None the less, imagine the negative gain incurred on 80M on this little baby, at least the same amount of loss as the dishes has gain (I have calculated roughly -27dBi) and yet I communicate routinely on 80M from all over Scandinavia to OZ-land, on 20 and 15M I even manage to reach the other side of our planet - not too bad for a vintage "hand-me-down" poorly designed mobile antenna!

 

And finally a view into a busy "Ham Work Station" Anno 2010... SDR's abundant :-)

73

Frank

6137476 Last modified: 2015-07-16 00:18:17, 4575 bytes

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