[Elecraft] [K3] KRX3 Antenna Flexibility

[Bill W4ZV]

Reposting this since the Elecraft list on qth.net was down earlier:


Bill W4ZV wrote:
> 
> I believe many are now receiving their KRX3s and are about to discover the
> amazing benefits of True Diversity with the K3.  As some of you know, I
> love to chase DX on 160 and will only say Diversity is something I will
> never be without.  I typically use a directional 3-el vertical array on
> transmit and a Beverage in the same direction on receive.  In Diversity
> mode, I use my TX antenna on Main and the Beverage on Sub.  Sometimes it's
> absolutely amazing to hear signals switching back and forth between ears
> in <1 second!  I'm sure these signals would exhibit extreme QSB if
> listening on one antenna by itself.
> 
> Although the K3 has an effective switching system for most use, there's
> one situation which I've run across which needs an external solution. 
> This is the (somewhat unusual) case when a signal will be present on only
> one of the antennas being used in Diversity.  I found I wanted a quick way
> to switch out of Diversity, so that either the TX or RX antenna alone
> would be applied to both ears.  Otherwise I'm feeding extraneous noise
> with no signal to one of my ears.
> 
> A simple solution to this is to use an external splitter for the Beverage
> input.  This should be a Magic-T splitter (not just a T-connector) which
> preserves impedance and isolation between the two receiver channels.  You
> can either build one yourself (using two ferrite cores and a resistor) or
> buy a commercial unit (Mini-Circuits ZSC-2-2 or DXE RSC-2 are both ~$50). 
> The Mini-Circuits unit is available in either 50-50 ohm or 75-75 ohm
> versions and the DXE is 75-75 only.  If you make it yourself, you can make
> one which will match a 75 ohm antenna to the 50 ohm RX inputs of the K3. 
> See W8JI's website for details to roll your own:
> 
> http://www.w8ji.com/combiner_and_splitters.htm
> 
> So how does this work?  I feed my Beverage to the splitter and then
> connect its two outputs to RX ANT and AUX RF.  When I want Diversity, I
> use my TX antenna (ANT1) on Main and the Beverage on AUX RF (the KRX3
> allows you to choose either the same antenna as Main or AUX RF).  Here are
> the two cases to switch from Diversity to either the TX array or RX
> antenna using a splitter.
> 
> 1.  When I want my Beverage on both ears, I simply "tap" RX ANT.  To go
> back to Diversity Mode, I "tap" RX ANT again.
> 
> 2.  When I want my TX array on both ears, I "hold" RX ANT which switches
> the KRX3 to the same antenna as Main.  When I want to return to Diversity,
> I "hold" RX ANT again.
> 
> One tap or hold and you instantly can go out of (or back into) Diversity
> with either your TX or RX antenna in those rare cases when a weak signal
> may be on only one antenna.
> 
> There's of course a ~3 dB loss when you use a splitter, but this isn't
> significant on the low bands since the external noise floor is so far
> above the noise floor of the K3 (...even if ATT is on).
> 
> True Diversity in the K3 is a remarkable achievement compared to other
> rigs costing much more (neither the IC-7800 or Orion has True Diversity). 
> In my configuration, I have it in a rig which cost me ~$2.8k including 6
> filters (2 of which are unnecessary for non-contesters, i.e. a 1.8k and
> 200).
> 
> If you want to hear some recordings using Diversity, listen to EI6IZ's CW
> and SSB pileups here:
> 
> http://ei6iz.com/  (Audio links at the bottom of his KRX3 article, and you
> really need stereo headphones for the full effect.  BTW, I never use
> anything but headphones for DXing or contesting.)
> 
> 73,  Bill  W4ZV
> 
> 
> 

-- 
View this message in context: http://n2.nabble.com/-K3--KRX3-Antenna-Flexibility-tp1499595p1500426.html
Sent from the Elecraft mailing list archive at Nabble.com.