[Elecraft] [w2/K3] High SWR

[Jim Wiley]

It is my understanding that the original G5RV design is a 20-meter only 
antenna.  If built according to the designer's specification, meaning 
antenna length, feed line length, height above ground, etc. it should 
show a reasonably low SWR on 20 meters.  Many hams use it on other bands 
with a greater or lesser degree of success (depending on band) by 
feeding it via some sort of antenna matching unit, either internal or 
external to the rig.  But, and again, if built according to the original 
design, it will naturally show high SWR a on any band except 20 meters.  
If it shows a high SWR on 20 meters too, it may have been assembled 
incorrectly or there may be some sort of fault.  A common misconception 
is that a G5RV antenna will automatically match with a low SWR on all HF 
bands.  This is incorrect. All this being said, keep in mind that there 
is no rule anywhere that says an antenna has to be resonant to be an 
efficient radiator.  That's where the antenna matching unit comes into 
play. And, you are correct in stating that there is nothing the antenna 
matching (tuning) unit can do to change the SWR on the line between the 
antenna and the shack.  All the antenna matching unit does is make the 
transmitter happy (low SWR) and enable the efficient transfer of power 
between the antenna and the transceiver.


- Jim, KL7CC


On 11/8/2012 5:29 PM, Don KA1KU wrote:
> I built a new W2 today and added the coupler in-line with my G5RV, which
> recently replaced a 40M dipole.
> Both my K2 and K3 have internal tuners, and I understand that the internal
> tuners match inside the K's and cannot change the antenna so therefore can
> not effect the SWR seen by the W2.
> My MFJ 259 analyzer shows 1.1 to 1 at some point in most bands from 80 to 6
> meters.
> For example, on 40m the SWR reads 1.0-1 at 7.17MHz.  Similar points on other
> bands.
>
> Also, since the W2 is newly built, I checked the W2 out with a dummy load
> attached.  On 40m, the internal tuner shows a match of 1.0-1, and the W2
> reads SWR of 1.1.  With K3 power set at 1.0 and 5.0, the W2 reads 1.1 and
> 5.0.  On 20m, SWR (internal, W2) reads 1.0 , 1.1 and power at (1.0 and 5.0)
> reads 1.2 and 4.  I think this rules out problems with the W2.  My K2
> readings match the W2 almost exactly.  The K3 seems off a little but I have
> not tried to calibrate it.
>
> With G5RV connected, I get a much different picture.  On every band from 160
> to 80 I get a SWR reading full scale, 5.  On 6m the reading is 3.  The
> internal tuner matched each band to 1.0 or 1.1 hto 1.  Again, I understand
> this means nothing in regard to W2 reading.  What I don't understand is why
> I have such a high SWR, especially since the antenna analyzer indicates a
> close match, 1.0-1 at 7.17MHz, which I used as my test frequency on 40m.  I
> also get SWR of 5 when ATU is in bypass.  This is repeated on every band,
> using the frequency of lowest SWR indicated by the antenna analyzer.
>
> I also see odd power readings.  For example, on 40m, with K3 power set at
> 1.0 the W2 shows 4 Watts.  At 5, the W2 shows 14.  This too is similar
> across all bands.
>
> The G5RV has only been up a few months and seems to work great on receive.
> I've mostly been on 80, 40 and 20.
> I thought I had a basic understanding of this but just don't understand what
> I'm seeing.
>
>
>                         
>
>
>
> -----
> 73,
> Don KA1KU
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/w2-K3-High-SWR-tp7565299.html
> Sent from the Elecraft mailing list archive at Nabble.com.
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