> I would agree the Sinclair Antennas are well built and
> very broadband, but I had a horible time with a number
> of 4 bay vhf broadband units installed (and removed)
> in 2005. We bought a large number of VHF SLR-235
> units new. The part number has changed but the antenna
> is the same current 4 dipole current model.
>
> The performance stank, with wild patterns and imd
> generation from all the brand new antennas we bought
> and installed at different locations. What a let down
> vs the good performance of other Sinclair antennas we've
> purchased in the past.
Geez Skipp, that's pretty unusual. I've never had anything but good luck
with Sinclair's dipole arrays, both on highband and UHF. I'm not a big fan
of their whitesticks though. As I'm sure you know, most of their antennas
are available in "low PIM" versions, though I've never had any IM problems
with even their older, standard models.
> I figured it might be something we did, so I had a number
> of people check everything at least twice over. Yes
> we checked the harness phasing, element spacing yadda,
> yadda. But the same problem with 6 brand new antennas
> at 3 different locations?
The only thing that comes to mind is maybe a "quality control" issue at the
factory that resulted in one or more of the dipoles being assembled
upside-down resulting in severe cancellation. I know they usually mark one
side of each element with a band of red tape to ensure they are properly
phased, but somebody could have screwed this process up (or maybe they
marked them after assembly instead of before). If you have nothing else to
do (hi), maybe you could do some tests to ascertain whether or not this is
the case, perhaps by transmitting a few hundred mW into the input and using
a scope to look at the relative phase between elements (i.e. check to see
that the upper side of the feedpoint is in-phase between each of the
elements).
--- Jeff
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