> 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.
The DB408D-B's that I have, four or five in all, are all new (well, they've
been in the warehouse a few years, but have never been outdoors), still with
the original stickers on them. They're definately B-range models, 450-470
MHz, per the labels. The plots for the one I swept make it appear that it's
tuned for that range, but the return loss just isn't as good as it should
be. There was no visible damage to it. I re-cal'ed the Sitemaster just to
make sure that wasn't the problem after I saw the sweep wasn't stellar.
I'll have to try one of the other ones to see how it looks..
> 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
I've seen other special-order DBxxx dipole arrays for other frequency
ranges. For example, I have one that is marked 450-482 MHz if I remember
right. It seemed strange that they'd spec the antenna for that wide of a
bandwidth, but after seeing how wide this S420-440-450 swept, I guess it's
plausible that it passed under the 1.5:1 mark across that range. I might
even still have the plot of that one in my Sitemaster, but I probably swept
it from the end of the hose, not at the pigtail. I'm not using it for ham
purposes, so I never really paid much attention to how it swept out-of-band.
--- Jeff WN3A
