Not knowing the history of Jeff's DB408D(B), it is possible that the previous use was for 2 separate rpt's. or base stations, each using 1/2 of the antenna(DB404) on different portions of the 450-470 MHz. band. I have one similar to Jeff's that i recently picked up, with the 2 separate feedline connections but haven't swept it to see what SWR is yet. Jeff's mismatch may also be a problem with the harness (defective, corrosion or wrong one) as he mentioned or he didn't check to see if the dipoles on the upper half measure the same as the ones on the lower half.
The length of the dipoles should determine the approx. portion of the band it was deigned for (ie: 11-3/16" OA for 450-470 MHz.) Though apparently there were some other length's used for special antennas in the same range). Also 10-1/2" for 470-488, 10-1/8" for 488-512 and 12-1/2" for 406-420. These OA dim's. are all +/- 1/16". Doug N3DAB --- In [email protected], "Gary" <n6...@...> wrote: > > Yes, I noticed. That's why I asked about similar test data on the 404B. I > look forward to you next test results on the other 408's in hopes that they > will accurately represent what my omni directional 404B's can offer for > reasonable bandwidth below 14dB RL. > Thanks Jeff. > Gary > N6LRV > > -----Original Message----- > From: [email protected] > [mailto:[email protected]] On Behalf Of Jeff DePolo > Sent: Sunday, September 27, 2009 10:09 AM > To: [email protected] > Subject: RE: [Repeater-Builder] Antenna sweep - Decibel S420-440-450 > > > > > Jeff, > > Do you have any similar test data available for the DB404B? > > Thanks, > > Gary > > N6LRV > > In the doc is a DB408D (B range) which is two DB404-B's on the same mast, > one above the other, with separate feedlines to each of the two antennas. > However, the one that I swept looks a little suspicious; the plots aren't as > good as I would have expected as I commented on. I have a couple more of > those that I can test. All of the ones I have, including the one I swept, > are new; I don't know why that one swept poorly. I'll try to sweep another > one when I get the chance. > > --- Jeff WN3A > > > > ------------------------------------ > > > > Yahoo! Groups Links >
