You guys are missing something... no one asked
him what size cavities he's using. If they are the
smaller TX/RX units... the reported lower power
output values are probably normal when using the
higher insertion loss settings with smaller
cavities.
cheers,
skipp
> "Jeff DePolo WN3A" <[EMAIL PROTECTED]> wrote:
>
>
> > The other thing.... All of the RF power being produced at
> > the 200 watt
> > level may not be on the operating frequency. Remember that a
> > watt meter
> > reads total power, not just the power on the repeater
> > frequency. If the
> > transmitter or PA or both are spurious or dirty to some
> > degree, you may
> > actually have less power (on your transmitter frequency) than
> > you think,
> > even though the power 'reads' higher. Since the duplexer provides
> > filtering, the power leaving the duplexer may show less due to the
> > removal of the spurious energy.
> >
> > Kevin Custer
>
> And to add to that, bear in mind that if you only have one wattmeter
and you
> use it to first measure the input power to the duplexer, and then
disconnect
> it and move it to the output of the duplexer that you've changed the
> electrical length of the cabling between the devices. Unless
everything is
> tuned and operating at exactly 50+j0, changing the effective length
of any
> of the cables is going to change the Z that the transmitter sees.
To get
> around this problem you have two options:
>
> 1. Make up a short patch cable with the same connectors as your
wattmeter,
> and substitute it in place of the wattmeter to maintain a constant
> electrical length when moving the wattmeter between devices in the
system.
> The cable must be the same electrical length as the wattmeter's
effective
> electrical length. For something like a Bird 43, the length is
known (and
> published by Bird) making this easy. For other wattmeters, particularly
> non-thruline types, this becomes more difficult.
>
> 2. Use two wattmeters, calibrating the differences in readings by first
> connecting the two back-to-back (preferably without an jumper cable).
> Transmit through the wattmeters into a dummy load and record the forward
> power readings of both wattmeters. Determine the error between the
two in
> dB. Then put the wattmeters into the system at their appropirate
locations,
> determine the measured loss based on their readings, and then
correct that
> value by the difference you originally recorded.
>
> --- Jeff
> --------------------------------------------
> Jeff DePolo WN3A - [EMAIL PROTECTED]
> Broadcast and Communications Consultant
>
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