[TenTec] Paragon II and SWR meter reading

[Tommy]

Pat and Allen and Denton....

What you are seeing is pretty normal, with the exception of the AGC 
or the (rcvr) RF gain affecting the readings.

First it's helpful to realize that you are using ham equipment and 
not commercial test equipment. The most accurate reading should be 
the one in the rig, provided it was calibrated over the ham band 
frequencies and you had a known good 50 ohm load connected directly 
(and NOT through a piece of coax) to the rig's output coax connector.

Ham SWR meters are, in general, relative indicators, not absolute 
indicators. Even the 'standard' Bird watt meters are spec'ed at +/- 
5% and that is only with the meter indicating in it's mid-range. Most 
hams connect the SWR bridge to their rig by using coax cable, which 
definitely affects the accuracy of the reading. Even 'good quality' 
coax cable have some inductance and some capacitance associated with 
it's length. So even if you just use one foot of 'good quality' coax 
between your rigs output connector and the SWR bridge, the rigs 
indication, in most cases will certainly be different from the  SWR 
bridge's indicated reading. The other part of the equation is what do 
you have as your load when your are measuring SWR? If you are using 
your antenna for the load, the all accuracy bets are off, simply 
because you really have no clue what impedance you are presenting the 
SWR bridge and your rig.

The important thing is that you tune your tuner, or in the case with 
no tuner, you adjust your antenna length, for minimum reflected power.

I think it would not be worthwhile to expect ham SWR bridges, no 
matter who makes them, to read identical, in the same set up. Before 
you get concerned that different SWR bridges do not read the same, 
see if you can find any manufacturers specification for accuracy. IF 
you can find those spec's, do they tell you at what load and at what 
frequency are they giving you the specs.

What your after with ham gear is a reasonablly accurate (say, +/- 20 
to 30%) SWR indication. I've never seen a 'precision' 50 ohm load 
(meaning they cost around $600 bucks) for ham use, however they are 
available for commercial use. Precision meaning 52 ohm +/-j0 
certified across the frequency range of interest. And they are only 
guaranteed to maintain their precision as long as they are never 
overheated. Most ham test equipment will give you a good relative 
indication, which is normally 'good enough' for ham use. Some 
commercial and most microwave applications is where true accuracy is 
required and that 'true accuracy' cost as much as ten times more that 
ham test equipment.

Tom - W4BQF


At Wednesday 11:03 AM 8/9/2006, you wrote:
>Alan,
>
>Hello again.  I have similar symptoms on the SWR meter on my OMNI VI+.
>With the RF gain at max the SWR meter will not go to zero but rests at
>about 2:1 SWR even though my 238 reads zero reflected.  If I back the RF
>gain back to about 2:00 o'clock position it goes to zero as it should.  I
>would like for it to read zero but don't know if there is an adjustment
>that would affect only that symptom without upsetting other ones.  I just
>got the rig back from Ten-Tec last fall after repair and calibration. (I
>bought it in an estate sale and it had some problems.)  I would have
>expected the service guys at T-T to have zeroed it if it was easily done.
>
>
>73,
>
>Pat
>
>
>On Wed, 9 Aug 2006 10:45:43 EDT ARDUJENSKI at aol.com writes:
> > I noticed that not in all cases will the meter (set to SWR) in the
> > Paragon
> > II read exactly the same as that is the 238 ATU. By the way the 238
> > and the
> > Paragon are connected by an 18 inch quality jumper (Belden 8214).
> >
> > I found a discussion on the topic in the ARCHIVES at
> >
>_http://lists.contesting.com/archives//html/TenTec/2003-01/msg00663.html_
>
> >
> >
>(http://lists.contesting.com/archives//html/TenTec/2003-01/msg00663.html)
>
> >
> >
> > Basically this section in short says to believe the meter in the
> > rig.
> >
> > SITUATION: I did notice that if I turn the  AGC button to OFF the
> > meter will
> > match the ATU meter. (By the way I use a MFJ 249 Analyzer to find
> > the
> > settings for the ATU but find in some cases it still needs to be
> > tweeked when I
> > push TUNE.)  Is this normal? I could not find anything in the manual
> > that  even
> > mentions the AGC in conjunction with operation of the SWR/TUNE set
> > up.
> >
> > Is this normal or do I have a problem I need to look into?
> >
> > Thank you
> >
> > Alan  KB7MBI
> > Woodinville, WA
> >
> >
> >
> > _______________________________________________
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> > TenTec at contesting.com
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> >
> >
>
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