[TenTec] Jupiter swr

[Mark Erbaugh]

Larry,

One of the limitations of the Pegasus (and I assume the Jupiter) is that the
forward and reflected power can only be read to a  whole watt (i.e. 0, 1,
2 - nothing in between). With lower forward power readings (such as in tune
mode),  there may not be enough reflected power to get an accurate SWR. For
example with a forward power of 20 watts and reflected power of 0 watts, the
SWR is 1.0:1 (naturally), with a reflected power of 1 watt, the SWR is
1.6:1.  At 20 watts output, there is no way to get an SWR reading between
1.0 and 1.6. As the output power increases, the SWR resolution becomes
better.

Another way of putting it: Assume that the SWR is 1.4:1. With that SWR, the
reflected power is about 3% of the forward power. With 100 watts out, that
would be 3 watts. With 20 watts out, that is only 0.6. Since the Jupiter can
only read to the nearest watt, that 0.6 watts gets reported as 1 watt, which
gives the swr of 1.6:1. As you increase the power to 100 watts, the SWR will
appear to drop to 1.4:1

Also, any additional line loss that the Jupiter sees that your analyzer is
not seeing will tend to reduce the SWR. Are you connecting the analyzer at
exactly the same place in the feedline?

Mark


----- Original Message -----
From: "Larry" <w5wlb at gbronline.com>
To: "Ten Tec" <tentec at contesting.com>
Sent: Wednesday, January 29, 2003 12:35 PM
Subject: [TenTec] Jupiter swr


> I notice after building my 40m dipole that the swr as seen by the jupiter
is lower than the swr as seen by my analyser.The jupiter also shows a lower
swr when speaking into the mike than it does when in the tune position.Its
not really important to me since its quite a bit below 2to1 but I asumed all
these readings would be some what closer than what they are.Is there a
simple answere for these differences ?
> W5wlb Larry
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