Monday, October 11, 2010

Elecraft KRX3 review

KRX3 installed
My KRX3 was shipped on the 8th September from Elecraft and arrived on the 22nd , I began the install the weekend of the 25th and am going to post a separate blog posting with regards to the assembly along with pictures. Here the purpose is to report on how the KRX3 has preformed up to this point. For those of  you who are unfamiliar with the KRX3 it is a completely separate high performance sub-receiver for the Elecraft K3 transceiver. My KRX3's filters are the same as the main receiver. The stock 2.7 khz 5 pole crystal filter along with 8 pole Inrad 250, 400 and 500 Hz filters ordered from Inrad International Radio.  After configuring the K3 to recognize the KRX3 and using the K3 utility to upgrade the software to the most recent for the KRX3 (which went very smoothly) I then set up the head phones so the left ear is the main receiver and right ear sub-receiver and when the sub is not being used I would have the main receiver in both ears.

                                Receiving two separate signals on the same band
Click on each image to enlarge

I wanted to try some simple stuff with the new sub-receiver at first as I had not yet dove into the manual to learn the details of the KRX3. With the two receivers on the same filter (Dual pass band) on the main receiver I found one CW signal in a QSO with another station at 7.013 (in my left ear). Then with sub-receiver I found another station at 7.034 in a QSO (in my right ear). It worked and sounded great I was even able to use different filters and depending on noise conditions at either end of 40 meters use separate NB, NR, ATT, or other filter settings. I recorded an audio sample this is from my 20 meter dipole in the attic. At first you will hear both signals then just the sub receiver (7.034)  then both and the the main receiver (7.013). Both of these signals I used the dual bandpass filter.
The audio clips are best if listened to with stereo headphones. 

Same band separate QSO's audio sample

This feature is useful in contests when a station I want to work (a multiplier) is involved in a pileup. I can keep them on the sub receiver  and work other stations with the main receiver. The sub and main have independent volume controls. The sub-receiver can be lowered and checked in on now and then to see how the pileup is going.   When the pile up thins down I am able to hear it and then take the opportunity to work the multiplier.

                                                   Working a DX-pedition

PJ4B DX-pedition
If your not a contester this feature comes in very handy when making contact with a DX-pedition. With the main receiver you tune in the DX-pedition set the sub to their offset. You are now able to listen to both sides of the DX-pedtion. In one ear you can hear the DX-pedtion calling and answering as well in the other ear you can hear those who are calling. You will know what the DX-pedition is hearing and when to fit your call in so they can hear you and not a large pileup of calls being sent at the same time.   This is a great advantage to getting through the large pileup that is trying to make their contact all at the same time. In the audio clip the DX-pedition is in your right ear and the pileup in your left ear.

DX-pedition audio sample. 

                                   Receiving two signals on separate bands

Now because the KRX3 is a totally independent receiver you are able to listen to two separate bands at the same time. The main receiver was on 20 meters and the sub was on 40 meters. (using the same antenna) Again in contesting this can allow me to check another band to see if it is open or closed for action. You also could set the sub for your weekly 80 meter skid. While waiting for it to start make some contacts on 40 with the main receiver. In the audio example you will hear 20 meters on the main VFO then the sub were a station is calling CQ on 40 meters. The audio goes back and forth as well as both bands at the same time.

Two separate band audio sample

                                                          Diversity receiving 
 I consider having two independent receivers to be a great asset, but then there is the  ability to listen on one antenna and transmit on another this is called diversity receiving.  In my case I have a 20 meter attic dipole and a High Sierra Sidekick outside at the side of my deck. Not a super station but along side the Elecraft K3 it's getting my signal out there. I use the dipole as my receiving antenna as it is horizontal and quiet, the Sidekick is the transmitting antenna. If I was just using the vertical I found I missed out on signals that were close to the noise floor. The dipole was able to pick these up and I was therefore able to work more stations. On Thanksgiving Monday I was giving the diversity mode a workout, at this point I don't understand it well enough to go into any detail. I will dedicate more time to this mode next weekend. I will blog on the diversity mode then I just want to make sure I understand it fully so I can give this mode it's due credit.


  1. Thanks for the great posting, Mike - a real eye-opener.

    You made me realize something that I'd never considered before. I was always imagining the main advantage of the sub-rx to be the fact that when working a pile-up split, no toggling of the A/B VFO would be necessary - just twek the sub-rx tuning know to stay with the DX's rx freq based on who he responds to. But as you mentioned, you also hear what he's likely hearing as far as lulls in the activity which allows you to place your call not only on the correct freq but at the best time as well.

    No question in my mind now regarding the recent query I made to the Elecraft reflector on whether the sub-rx or the pan adapter would be the most beneficial.

    Your posting and sound files provide greater clarity than everything else I've read combined.

    John AE5X

  2. Good morning John, my plan all along was to some how bring forward the KRX3 the best way I could. I felt audio was much more to the point, to write about how good it was just not the same as hearing it. Had to do some fishing around on the internet to see how to post audio on Blogger but it seemed to work. I am very happy it helped you make your mind up. This is the type of exposure I wanted to create. Well I think I have the diversity mode down and that is something amazing. I hope to blog about that mode along with audio this weekend.