OK - I put 3 pictures in the photos section at Yahoo Groups - repeater
builders.
its at the end of the pictures because the album is W6CBS - Spirit
Antennas in Snow...
Bill - W6CBS
--- In Repeater-Builder@yahoogroups.com, "Bill Hudson" <[EMAIL PROTECTED]>
wrote:
>
>
> I guess I'm going to have to post the picture to the group... it's
relevant
> to good repeater building in rugged ice conditions...
>
> W6CBS - CBS Bill
>
>
> -----Original Message-----
> From: Repeater-Builder@yahoogroups.com
> [mailto:[EMAIL PROTECTED] On Behalf Of Bill Hudson
> Sent: Saturday, June 07, 2008 2:30 PM
> To: Repeater-Builder@yahoogroups.com
> Subject: RE: [Repeater-Builder] Re: antenna suggestions for 440mhz
>
> Jeff
>
>
>
> Thank you - you did an excellent job of explaining / writing the
answer.
>
>
>
> Now save it, so you can cut and paste it next month when someone asks
> the question again.
>
>
>
> I am a Spirit Dealer, and at New-Tronics (the parent company for
Hustler
> Antennas too), we actually make the antennas after you order them, cut
> and stamp the frequency on them, and ship them out, including custom
to
> the ham band frequencies. They are end fed (what you call series fed),
> like the old Stationmasters.
>
>
>
> Frankly, I became a Spirit dealer because I could buy them cut for any
> frequency including the ham band from 420 - 450 in 10 MHz segments,
(the
> last antenna manufacturer that I know of that will do that) and the HD
> models held up as good as Stationmasters. I have never had one fail
> through a winter. They radiate as well (all personal perception of
> signal strengths, but real piece of mind with almost zero reflected
> power in the ham frequencies) so I am a happy camper. The radial ice
on
> the fiberglass sometimes falls off if the fiberglass will whip enough,
> but the HD and EXTRA HD models just don't bend enough.
>
>
>
> I don't know if the picture will come through or not - but it is the
> close antenna on 441 MHz, with the 420 MHz Kathreine radomed yagi at
the
> bottom.
>
>
>
>
>
>
>
> Note the radial ice on the exposed element antennas. Imagine what's
> happening to a "short via water" with that radial ice all over it.
>
>
>
> Bill - W6CBS
>
> Well said. Thank you Jeff.
>
> Chuck
> WB2EDV
>
> ----- Original Message -----
> From: "Jeff DePolo" [EMAIL PROTECTED] <mailto:jd0%40broadsci.com> >
> To: Repeater-Builder@yahoogroups.com
> <mailto:Repeater-Builder%40yahoogroups.com> >
> Sent: Saturday, June 07, 2008 9:25 AM
> Subject: RE: [Repeater-Builder] Re: antenna suggestions for 440mhz
>
> >
> >> First off you will definitely loose some of the gain from the
> original
> >> "rated specs". About 1.5 - 2 Dbd. is what I'd expect...Maybe a
little
> >> worse depending on where the antenna was originally "cut for"...
For
> >> example, If the antenna was originally built for say a 454.xxx freq
> >> (center freq) the loss would be less at 442.xxx than one that had
> been
> >> built for 467.xxx. The antenna typically has a 20Mhz. bandwidth,
+/-
> >> 10Mhz each side of center freq so you can see that one cut for the
> >> upper 460-ish range would be a little worse than the 450-ish freq.
> >
> > DB404/408/420 antennas were never "cut to frequency" - they were
sold
> in
> > frequency ranges. For example, a DB408-A is 406-420, DB408-B is
> 450-470,
> > etc. So the closest one to 440 would be a DB4xx-B. If you ordered an
> > antenna for 454.575, you would get a -B series antenna. In the
wayback
> > days, sometimes they would even stamp the label with the exact
> frequency
> > you
> > ordered, but the antenna wasn't "cut" for that frequency, they just
> marked
> > it to identify the requested frequency. Nowadays they don't even
> bother
> > to
> > do that, the sticker will just say "450-470 MHz" and it will come
with
> a
> > return loss sweep showing its performance across the entire band.
> >
> > The more bays, the worse the VSWR will be (speaking in very general
> terms
> > here) as you operate these types of antennas out of band. For
example,
> a
> > 408-B will likely have better return loss than a 420-B when used at
> 440
> > MHz.
> >
> >> The next thing that would change would be the "downtilt" rating.
> >
> > No, parallel-fed antennas do NOT suffer uptilt/downtilt as frequency
> is
> > varied unless the harness was special-ordered for factory downtilt.
If
> > the
> > antenna wasn't ordered with downtilt, all of the elements are fed in
> > phase,
> > and they will always be in phase regardless of frequency. The peak
> gain
> > will be reduced as you operate them away from their design range as
> more
> > power ends up in the usually-undesired sidelobes, but the main lobe
> will
> > still be on the horizon.
> >
> > Series-fed antennas (like Stationmasters) will have the elevation
> pattern
> > (downtilt/uptilt) affected as frequency changes, because the further
> up
> > the
> > antenna you go, the more and more the radiating elements end up
being
> out
> > of
> > phase compared to the lower ones, thereby creating the
> uptilt/downtilt.
> >
> > This issue comes up so many times, and is so misunderstood, that
there
> > should probably be a FAQ about it on the web site...
> >
> >> > I like the DB's but unsure how bad the 450mhz matches when trying
> to
> >> > use it down at 440.000mhz.
> >
> > I have 404's, 408's, 411's, 413's, and 420's in stock, all in the B
> > version,
> > a few A version, and a few "S-440-450" ham-band versions which they
> don't
> > make any more. I can sweep one if you want (please don't make me
drag
> all
> > of them out of the warehouse to test). Email direct if you're
> interested.
> >
> > --- Jeff WN3A
> >
> >
>
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>
>
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