Good day again, Doug, I will not be able to measure the SWR for a few
weeks as it is raining now and I will be out of town for a couple of
weeks, but I did measure the dipoles. Here is what I measured. The
two meter dipoles are 35 inches centerline to centerline top to bottom
per dipole, with the spacing between the bottom of the top dipole to the
top of the bottom dipole being 31 inches. The 440 dipoles are 11.25 CL
to CL and the spacing between the top dipole and the third dipole
directly under it is 38 inches. Remember the 440 is two dipoles at the
top of the pole, the second pair of dipoles is rotated 90 degrees with
respect to the top pair, then the third pair is directly under the first
pair and the fourth pair is directly under pair number 2. Hope this
helps in identifying your antenna. I will forward you the swr plots
when I return and can set up to do so. I will also take photos...
Regards
Curt
n3dab wrote:
Hi Curt,
Yes, that is the way I recall seeing the Dual Band antenna in the old DB products catalog. Have you
tried checking the upper and lower halves to see what kind of SWR you have at the operating freq. ?? If
it is convient, measure the end to end length of the upper and lower dipoles. The UHF diploes should be
about 11-3/16" for the 450-470 MHz. The VHF dipoles should be 37" for 138-150 or
34-3/16" for 150-160 MHz. 155-165 MHz is 33-3/4" and 164-174 MHz is 31-3/4".
For some reason the UHF 450 -470 versions are very broad banded but the VHF
versions seem to be more critical pobably due to the harness construction more
then the dipole length.
Thanks for the input.
Doug N3DAB
=====================================================================
--- In [email protected], Curt Seaton <seat...@...> wrote:
Good day Doug. I have a DB dual band antenna similar to what you are
describing, it has 4 folded dipoles for two meters, and 8 folded dipoles
for 440. These are two on each side of the pipe for two meters and four
on each side of the pipe for 440. The diameter of the pipe is slightly
smaller for the 440 section. The exact model number is not readable
(scraped during mounting or dismounting) but it sounds like what you are
looking for. IF this is the same as you desire, mine does have TWO
different feed lines coming down to connect to your VHF and UHF radio
systems. The pipes are concentric with a wedge shaped mount and held in
final position with gravity and hose clamps. Keep us all posted on your
endeavors as we are looking for the same scenario for D star here....
starting with the B module and adding C later... gotta recover
financially first...
73
Curt
W1FSM
n3dab wrote:
I know DB made a dual band 150/450 folded dipole antenna (bottom half was either a DB-222 or the bottom half of a DB-304 and the top half was a DB408 or top half of a DB-420), which is no longer available. Does anyone recall whether it was fed with one feed line or two ? I think it was 2 but, I can't recall the dipole configuration (singles on opposite sides going up, or pairs at each level).
I would like to combine a DB-224E (138 -150) with a DB-408 or DB-420 (450-470) on a single mast, or split the antennas at the mid point and make 2 antennas with the VHF on the bottom and the UHF on the top, and the reverse on the second antenna. Has anyone tried this ? What were the results ? The numder of feed lines (1 or 2) to the antenna is not an issue at this time.
The combined antenna would be for a 2 Mtr./440 D-Star application becuase of
limited tower space available.
Comments appreciated
Doug N3DAB
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