Thread: DIY Db8
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Old 19-May-2015, 1:16 PM   #38
Retired A/V Tech
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,516
Originally Posted by kojo View Post
I have a db8 from Antennas can yesterday in the mail. I haven't done much with it. But I guess it's different then yours and it will only get UHF signal and not vhf. I might have to start from scratch and build one like yours.
The new bowtie antennas don't pick up VHF as well as the older bowtie antennas because the baluns (4:1 matching transformers) now being used by the manufacturers are printed circuit board baluns. The older bowtie antennas used ferrite core baluns that were good for UHF and VHF signals.

DB4e and DB8e use PCB (Printed Circuit Board) Baluns, which are VERY lossy in Hi-VHF Band

To use this antenna for VHF, I recommend replacing the feed harness with two baluns and a splitter (in reverse as a combiner).
scroll down about 1/3 of the page to just before The 4228HD balun images.

When you use two baluns, one for each 4-bay, you must reverse the wire leads on one of the baluns as a test, to see which way is better. This is so that the two 4-bays are fed in phase so that the signals from each are added together.
If you can not measure it, you can not improve it.
Lord Kelvin, 1883

Last edited by rabbit73; 19-May-2015 at 1:42 PM.
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