Saturday, April 2, 2016

The K3S must be working alright on 475kHz!

Having done the K3S upgrades for 475kHz see here it was time for DX.  I was duly rewarded with my First transatlantic WSPR decodes of the year using the K3S and the PA0RDT whip in the loft:-

Timestamp           Call MHz         SNR Drift Grid          Pwr  km
2016-04-01 23:52 G3XIZ     0.475785 -24 -1 IO92ub 0.5  137
2016-04-02 03:56 DK7FC     0.475682 -26 0 JN49ik 1  827
2016-04-02 04:42 WG2XJM  0.475761 -28 0 EN91wr 5  5732
2016-04-02 05:10 WG2XJM  0.475761 -29 0 EN91wr 5  5732

Not band with the takeoff in that direction!

Worcestershire Beacon

Monday, March 28, 2016

Upgrading the K3S for 475kHz

Having had the initial try of the K3S on 475kHz here It was time to properly implement the low frequency bands on the K3S. The first step was to convert both KBPF3 to KBPF3A (one on the main RX one on the SUBRX). It is a simple process requiring the removal of 2 inductors from the board and adding 3 capacitors in parallel with existing capacitors. To make it look neater I actually replaced the existing capacitors. While the KRX3 was open I also added the electrolytic capacitor specified across the 9V rail. The whole process took 30 minutes

While the box was open I also added the K3EXREF 10MHz lock board and the K144XV (with K144RFLK)

I hooked up the RX antenna port to the PA0RDT active antenna in the loft and was pleased to see some DX:-

 2016-03-28 00:04  G0MRF  0.475770  -13  0  IO91tk  5
 151  300 
 2016-03-28 00:00  DK7FC  0.475682  -20  0  JN49ik  1 827  295 
 2016-03-27 23:50  DH5RAE  0.475755  -28  0  JN68qv  0.5   1161  294 
 2016-03-27 23:16  PA3ABK/2  0.475785  -24  0  JO21it  0.5
 481  277 
 2016-03-27 23:14  F1AFJ  0.475703  -27  0  JN06ht  1
 625  341 
 2016-03-27 22:26  DJ0ABR  0.475665  -30  0  JN68nt  0.2  1148  294

Friday, March 11, 2016

Initial 475kHz use of the K3S

The one big improvement in the K3S, mainly due to the new synthesiser, is the ability to tune it down to 100kHz. The original K3 hardware only went down to 479kHz.  Using the K3S properly at these frequencies requires the installation of a KBPF3A. The original KBPF3 does not go down low enough in frequency, but can be easily modified.

As the filter board was not available we stuck a 40dB amplifier between the low 80m dipole and the RX Ant input, to make up for the loss in the normal K3S 1.5MHz highpass filter. The results on WSPR using the K3S internal soundcard were impressive:-

Date                    Call         SNR   Drift Grid             dbm   km
 2016-03-09 04:56 WH2XND -21      0 DM33xt      +43 1431
 2016-03-09 04:52 WH2XGP -25      0 DN07dg      +40 2499
 2016-03-09 04:50 WG2XIQ       +10      0 EM12mp     +37 60
 2016-03-09 04:48 WG2XXM +0      0 EM15lj      +37 258
 2016-03-09 04:44 WD2XSH/15 -23      1 EM34rt      +33 422

Monday, March 7, 2016

The new K3S arrives

Having had K3 for a while now I was interested to see the arrival of the "upgraded" model the K3S. While it is possible to buy the modules to upgrade a K3 to a K3S having done the calculations it was cheaper to buy a K3S in kit form and transfer the "option" modules across.

The K3S/100 kit, with the new 100W FET PA module was ordered.

It all went together easily enough despite some issues with K3 photos/figures appearing in the K3S manual (eg Figure 91).  It powered up fine and the VCO passed self test, so time to hook up an antenna. Nothing could be heard despite putting the RX on the TX7EU pileup.  As a check an HP signal generator was hooked up to the antenna port. It couldn’t hear -50dBm. Neither could this level be heard through the rx in port or the Xverter port. The radio was dismantled, all connectors checked, EEinit done, no improvement.

Time for more coffee, during which an inspiration. When I put the subrx into the k3 I remembered I had to remove a link in the KRX3 back connector. (J64A) So I searched the K3S manual. It appeared not to need the link as it was not shown in "Figure 31. RF Board Partially Assembled." or on the photo of the main rf board on Page a-14  or on "Figure 94. Installing the KBPF3A Option Board." BUT I noticed a link still shown on the legend on the PCB and its removal is still shown in fig44 of E740126A installing the KRX3A subrx. "Nothing ventured nothing gained", so I stuck a resistor lead in  the W4 link and the K3S burst into life. Sensitivity returned and the K3S was back to full health

The other issue was the top left screw holding the bezel to the font panel would not bind. Close examination revealed that there was insufficient threading in the hole. After talking to Elecraft Support they shipped a replacement front panel, which solved the issue.

Saturday, February 13, 2016

Replacing the USB Connector on a Nexus 7 (2013 version)

Getting the charging cable to actually charge my Nexus 7 (2013 model) has been becoming Increasingly difficult. Having to balance the unit on a coffee jar and hang a weight off the USB connector at exactly the right point was a challenge. Searching the Internet I am not the only one to experience this issue. The recommended solution was to change the connector, as it becomes sloppy over time. I managed to find a connector for 1.49 off Ebay. Note the connector on the 2013 version is very different from the 2012 Version.

Guided by a Utube video I managed to get the Tablet apart, at a cost of broken finger nails, revealing the Innards..

The USB connector is on the lower edge. To remove the connector, first, using a sharp scalpel cut the 5 pins sticking out the back of the connector. If you do not,  you run the risk of lifting the tracks in further activities, The four lugs can then be desoldered and the connector removed. It is then a simple task to solder the new connector in place using a fine tipped soldering iron and thin solder. 

The Tablet can then be tested for correct operation before re attaching the cover. Mine charged fine and still produced video. Task completed

Tuesday, January 26, 2016

BARTG RTTY Sprint 2016

Having missed the ARRL RTTY contest earlier I was looking forward to a RTTY contest. The next one was the BARTG Spring Sprint.  The contest times are very civilised; noon start on Saturday, noon finish on Sunday (none of this 2am start of the BARTG March RTTY contest!!). Being a Sprint the contest exchange omits a report, only serial numbers are exchanged.

Looking in the loft I found the two Atom DG945CLF2 computers we last used in RTTY contests which ran Writelog under WinXP. Having now converted to N1MM software under Windows 7 a new computer with a more powerful processor and more memory was needed. I had built a media center in the USA using a DG41MJ motherboard. The case was also tall enough to acommodate the Delta D44 high performance stereo soundcard. Windows 7 32 bit  was installed with N1MM+ and the D44 drivers located. A stereo sound card is needed as the K3 supplies audio from the main receiver on the stereo left channel and audio on the stereo right channel from the sub receiver allowing two instances of MMTTY to be used to decode both frequencies. As usual FSK modulation was used.

The K3, KPA500 and KAT500 were assembled along with the newly established computer. The antennas were a good match so the KAT500 was not needed to match the antenna, but it does provide an easy way of automatically switching between the beam for 20/15/10, the 40m dipole and the 80m dipole.

The only issue experienced was that N1MM would go away and not allow anything to be done for periods up to two minutes,but would complain "K3 not responding" when it did come back and then work normally. This happened a dozen times on the Saturday evening, losing some QSOS. Changes were made, changing K3, closing N1MM windows, ferrite chokes, running without the amplifier but nothing changed, The same issue was also experienced with N1MM and a different K3 on a 432MHz afs a year ago which was never solved.   Then I remembered a similar issue with the TS950 and N1MM, The solution to this was to lower the polling rate in N1MM to 50%. This was tried with the K3 and the issue never happened again.

Conditions were poor for the contest and only 756 QSOs were had. All 6 continents were had for multipliers. At times it was slow that Practical wireless and the CDXC Newsletter were read!

Tuesday, December 29, 2015

Using RCFOrb On a Nexus 7

Having Used RCFOrb for a while on my laptop as mentioned in my blog I was keen to try the Android Version to control the K3. The Christmas holiday gave me the opportunity.

Download and installation was easy. Setting up the server information in the app was just like the windows version. HF bands were a bit quiet but there was a 4m contest on so used it to have a couple of QSOS.