NA3DX Field Day Using KX3's

[Doug Ellmore Sr.]

The Explorers Radio Club (NA3DX) will be operating again this year from
Maryland (www.ellmore.net/na1dx) using Elecraft KX3 radios on the primary
stations.  We also have a local reporter and photographer attending
Saturday for a story.  I'll wear my new blue Elecraft hat I got in the mail
last week.  Good Luck and Be Safe!

Doug, NA1DX
Elecraft K3 #7232
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[wayne burdick]

Hi all,

Here some tips for getting the most out of your KX3 at field day:

1. BATTERY OPERATION: To conserve battery power, use 5.0 watts or less when running from a 12-V source, and 3.0 watts or less when running from an 8-10 V source (including internal batteries). At these levels, the KX3 automatically switches the power amplifier to a more efficient setting. You can tell that power-saving mode is in effect by a decimal point after the 'W' in the power value (e.g., "5.0 W."). To reduce supply current in receive mode, use headphones rather than the internal speaker, and if lighting conditions permit, turn off the LCD backlight (MENU:BKLIGHT).

2. ANTENNA SPACING: If you're using more than one transmitter, try to keep the antennas as far apart as possible. This is a good practice with all FD stations, because it can prevent receiver de-sensing and intermodulation distortion. If you have no choice but to have the antennas close together, and you hear artifacts (such as SSB signal bleedthrough) in your KX3 while another station is transmitting, try setting MENU:RX SHFT to 8.0 rather than NOR on the affected band. You could also turn the preamp off, or reduce preamp gain on affected bands using the PREAMP menu entry.

3. OSCILLATOR ISOLATION: The KX3, like other radios with a quadrature direct-conversion architecture, uses a VFO (local oscillator) running at or very close to the operating frequency. If you have another radio on the same band as the KX3, and the antennas are close together, the other radio may be able to hear the KX3's oscillator when they're both tuned to the same frequency.

To prevent this, the KX3 includes an isolation amplifier that keeps the oscillator from radiating back through the mixer. Normally this amplifier is turned off to save about 15 mA of receive-mode current drain. To turn on the isolation amp, set MENU:RX ISO to ON. This has no effect on performance.

Have fun!

73,
Wayne
N6KR




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[Mark Goldberg]

I have an issue to report and it seems this thread as good a place as any.
It might help someone else trying the same thing.

On 6 meters only, it seems the LO leaks out on the outside of the antenna
connector. I can hear it in another radio on the same frequency and the RX
ISO has no effect.

I am using the KX3 as a second receiver to provide I and Q outputs, with
the KX3 antenna connector connected to the output of a buffer amp installed
in the other radio
after that radio's preamp.

If I connect only the shield of the coax the LO is heard. The RX SHFT
corrects the problem, a the radios are synced in frequency. I have no other
issues with this setup
and both receivers provide good results with no obvious anomalies. I have a
guy two blocks from me and there is no obvious receiver desense when they
transmit.

Mark


On Tue, Jun 18, 2013 at 8:45 AM, Wayne Burdick <[hidden email]> wrote:

> Hi all,
>
> Here some tips for getting the most out of your KX3 at field day:
>
> 1. BATTERY OPERATION: To conserve battery power, use 5.0 watts or less
> when running from a 12-V source, and 3.0 watts or less when running from an
> 8-10 V source (including internal batteries). At these levels, the KX3
> automatically switches the power amplifier to a more efficient setting. You
> can tell that power-saving mode is in effect by a decimal point after the
> 'W' in the power value (e.g., "5.0 W."). To reduce supply current in
> receive mode, use headphones rather than the internal speaker, and if
> lighting conditions permit, turn off the LCD backlight (MENU:BKLIGHT).
>
> 2. ANTENNA SPACING: If you're using more than one transmitter, try to keep
> the antennas as far apart as possible. This is a good practice with all FD
> stations, because it can prevent receiver de-sensing and intermodulation
> distortion. If you have no choice but to have the antennas close together,
> and you hear artifacts (such as SSB signal bleedthrough) in your KX3 while
> another station is transmitting, try setting MENU:RX SHFT to 8.0 rather
> than NOR on the affected band. You could also turn the preamp off, or
> reduce preamp gain on affected bands using the PREAMP menu entry.
>
> 3. OSCILLATOR ISOLATION: The KX3, like other radios with a quadrature
> direct-conversion architecture, uses a VFO (local oscillator) running at or
> very close to the operating frequency. If you have another radio on the
> same band as the KX3, and the antennas are close together, the other radio
> may be able to hear the KX3's oscillator when they're both tuned to the
> same frequency.
>
> To prevent this, the KX3 includes an isolation amplifier that keeps the
> oscillator from radiating back through the mixer. Normally this amplifier
> is turned off to save about 15 mA of receive-mode current drain. To turn on
> the isolation amp, set MENU:RX ISO to ON. This has no effect on performance.
>
> Have fun!
>
> 73,
> Wayne
> N6KR
>
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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[wayne burdick]

The K3 is a proven performer at Field Day, whether running QRP or QRO. While the K3 doesn't have the ultra-low current drain of the K2 or KX3, its current requirements are still quite low compared to other high-performance desktop rigs. At QRP levels, it can typically operate for the entire field day period from a fully charged car battery.

To extend battery life, you can reduce the K3's current drain using any of the following methods:

1. If you have a KPA3 installed but plan to run QRP, set the KPA3 menu entry to PA BYP. This will limit the range of the power control to 12 W.

2. Turn off the preamp and attenuator when possible.

3. Turn off the subreceiver when not in use.

4. Turn off the LCD backlight (use the "DAY" setting).

5. Use headphones rather than the internal speaker.

The use of all of these techniques should keep RX-mode current drain well under an amp.

Regarding antennas: Always keep the antennas for different radios as far apart as possible. If you're using directional antennas, orient them at right angles to each other. If desense or other artifacts occur, turn the preamp off. If the antennas are *really* close together, there's always the 20-dB attenuator.

73,
Wayne
N6KR


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[alorona]

To add to this: In the case where you have a horizontally-polarized antenna and a vertical, it might feel like the vertical should be placed off the end of the dipole, but in fact that's where vertically-polarized response of the dipole is maximum, so the vertical should actually be placed broadside to the dipole where the dipole's vertical polarization is minimum! This seems weird, but it will make for the maximum isolation between the two antennas.

If the two antennas are both horizontally-polarized, then the usual "off the end" rule does apply.

Al  W6LX
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