[K3] SWR - Numerical Indication

[Dick Dickinson]

Hi John,

 

Per your suggestion, I ran a sweep of my 40 meter vertical with the K3 /
K3EZ software.

I then measured at ~20 kHz steps with my MFJ-259B.

Both sets of measurements were taken from the PL-259 that plugs into the rig
or 259B.

 

Conditions were ~60 degrees F, ground nearly saturated.

 

Attached is an image of the results.

 

 

Kindly,

Dick - KA5KKT

----------------------------------------------------------------------------
-----------

Hi Dick,

 

An EZNEC and SimSmith model of the on ground 1/4 wave vertical:

https://www.kn5l.net/images/SS-KA5KKT-vertical.png

 

SimSmith R1 represents ground loss, the value set to establish a 50 ohm load
at the transmitter, G in SimSmith.

 

According to the models, the 7 to 7.3 MHz SWR is a little below 1.3.

 

A flat measurement using the K3 SWR meter seams reasonable. My suggestion is
to use a Antenna Analyzer to measure the antenna and system.

 

John KN5L

 

On 12/2/18 12:16 AM, Dick Dickinson wrote:

> I have a full-size monoband vertical for 40 meters.  Simple

> architectural aluminum tapering from 1 ¼” (?) in 6’ telescoping

> sections.  The radial field is designed to provide a 50 ohm match at

> the feed point…12 – 13’+ radials.  It is fed directly…no matching

> device with RG-213 from the remote antenna switch about 50’ away at my

> tower.  The coax from the rig to the remote antenna switch is

> estimated to be ~ 50’ in length.  A lot of the time running K3EZ to

> sweep the band (typically 20 watts), it will indicate a

> 1.0:1 SWR from 7.0 MHz to 7.3 MHz in 20 kHz steps.  Occasional

> deviation from one K3EZ run to another might be due to variations in

> moisture content of the ground or less than perfect connection to the

> vertical…an uncommon situation.  The K3 shows the same readings.

>

> Is this 1.0:1 SWR across the entire 40 meter band curious or remarkable?

 


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[John Oppenheimer]

Hi Dick,

The Elecraft list does not accept attachments. Send to me directly.

John KN5L

On 12/2/18 4:14 PM, Dick Dickinson wrote:

> Hi John,
>
> Per your suggestion, I ran a sweep of my 40 meter vertical with the K3 /
> K3EZ software.
>
> I then measured at ~20 kHz steps with my MFJ-259B.
> Both sets of measurements were taken from the PL-259 that plugs into the rig
> or 259B.
>
> Conditions were ~60 degrees F, ground nearly saturated.
>
> Attached is an image of the results.
>
> Kindly,
> Dick - KA5KKT
>
> ----------------------------------------------------------------------------
> -----------
>
> Hi Dick,
>
> An EZNEC and SimSmith model of the on ground 1/4 wave vertical:
> https://www.kn5l.net/images/SS-KA5KKT-vertical.png
>
> SimSmith R1 represents ground loss, the value set to establish a 50 ohm load
> at the transmitter, G in SimSmith.
>
> According to the models, the 7 to 7.3 MHz SWR is a little below 1.3.
>
> A flat measurement using the K3 SWR meter seams reasonable. My suggestion is
> to use a Antenna Analyzer to measure the antenna and system.
>
> John KN5L
>
> On 12/2/18 12:16 AM, Dick Dickinson wrote:
>> I have a full-size monoband vertical for 40 meters.  Simple
>> architectural aluminum tapering from 1 �� (?) in 6� telescoping
>> sections.  The radial field is designed to provide a 50 ohm match at
>> the feed point�12 � 13�+ radials.  It is fed directly�no matching
>> device with RG-213 from the remote antenna switch about 50� away at my
>> tower.  The coax from the rig to the remote antenna switch is
>> estimated to be ~ 50� in length.  A lot of the time running K3EZ to
>> sweep the band (typically 20 watts), it will indicate a
>> 1.0:1 SWR from 7.0 MHz to 7.3 MHz in 20 kHz steps.  Occasional
>> deviation from one K3EZ run to another might be due to variations in
>> moisture content of the ground or less than perfect connection to the
>> vertical�an uncommon situation.  The K3 shows the same readings.
>>
>> Is this 1.0:1 SWR across the entire 40 meter band curious or remarkable?

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[ANDY DURBIN]

"Do you find a high degree of correlation between your (assumed) K3 and KAT500 SWR readings across various levels of SWR? "

I don't have a K3.  I do have loads of recorded data that would allow comparison of KPA500 SWR and LP-100A SWR and a more limited set of data that would allow comparison of KAT500 SWR with LP-100A SWR.  I have not performed either comparison but, as a general observation, it's obvious that the LP-100A is far more useful at low power levels or for mismatches that would give low reflected power.  At high power levels there is quite good agreement between the LP-100A and the KPA500 for power and SWR.  Since I know that, I look mainly at the LP-100A data.

I did a quick test on 20 m.  For an antenna system load that my LP-100A reports as SWR 1.09 with  Z of 52.7 ohm at 4.3 deg it took about 70 W output power for my KAT500 to change from 1.00 to 1.11 SWR.

To look at this another way - until the meter moves off the peg it isn't telling you much about the signal being measured.  All it's telling you is that you need a better meter.

I'm not saying there is anything wrong with the KPA500 or KAT500 SWR metering.  You just need to know how it behaves and what it is useful for.  I expect the same applies to the K3 SWR meter.

Andy, k3wyc

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