The SSM antennas have a very narrow angle of
radiation, hence all that gain. Close-in performance,
or stations under the umbrella, don't do too well. I'm
using a PD455 cut for 440-450 on my repeater on
444.xxx and at my end of the 500ft of coax there's 55
watts forward and about 0.3 watts reflected. The
antenna is up 1100ft ASL and the surrounding terrain
is in the 100-300ft ASL range. Portables within a
couple of miles can be noisy at times.
I went with the SSM because I knew it worked well, but
didn't have the time to consider down-tilt. The other
antennas on the tower were the same thing. If I ever
have to do it again, I'll probably consider a 4 or 8
bay DB224-style antenna. I don't need the 45 mile
radius; I'd rather be able to make the repeater from
my house 6 miles away at 70ft ASL.
While I haven't had to deal with RFS for antenna
parts, they've been very responsive for technical
info. So try calling them and ask about the adapter.
Bob M.
======
--- kk2ed <[EMAIL PROTECTED]> wrote:
> Good Evening;
>
>
> I just installed a repeater at a new site, and am a
> little
> disappointed in the performance. Plots using
> Radiosoft, which has
> been damn close to predicting the coverage on my
> other repeaters, led
> me to expect more performance than I am seeing from
> this site.
>
> I have been waiting for RFS to deliver a 440-450
> PD455, which has
> been delayed yet again. So while the tower guys were
> doing their
> thing, I threw up a PD1151 cut for 450-460.
>
> The site seems to cover a wide area, but the signal
> is never strong,
> even close in. The transmitter is on 440.xxx. I
> have used one of
> these PD1151 450-460 antennas in the past on a
> 449.xxx repeater, and
> it plays quite well.
>
> Is it possible that while the 449 system is close
> enough to the
> design range of 450-460, the 440 system is
> experiencing the effects
> of being too far from the design frequency range?
> THe SWR, while not
> perfect, is about 1.5:1 at 440MHz.
>
> Does the radiation pattern start to distort that
> severely when almost
> 10MHz from the design/cut frequency of an antenna?
>
> I know a lot of you are using DB420's down in the
> 440 band with good
> results. Are the dipoles that much more broadband,
> and less
> suceptible to radiation pattern distortion than the
> co-linear type
> antennas?
>
> As an experiment, I'm tempted to stick a spare
> 449.xxx box on the
> antenna over the weekend to see if it plays any
> better than the
> 440.xxx box to confirm or deny this suspicion.
> Hopefully, I'll
> receive the ham cut PD455 sooner than later.
>
> Eric
> KE2D
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