SPE-1.3KFA Amplifier Efficiency

As the BARTG HF RTTY contest does not have different power sections I thought it would be a good time to try the new SPE 1.3KFA Amplifier on RTTY.

Originally I used the 4 band data lines from the K3 to steer the amplifier to the correct band, but experience showed it was better to use the CAT data giving the exact frequency to steer the internal ATU quicker. This was easy with the K3 but the K3S was a little harder to engineer as described at K3S to SPE.

Due to band conditions there was a lot of  CQing. From cold, after 8-10 CQ with the amp switch set to "max" at 750W  output a "PA overtemp" error would be shown and the amp switch to "mid". with the switch set to "max" again and backing off the amp to 500W output the error would reappear after 12-15 CQ

I continued running with the amp on "mid" for a while,  then, after a series of CQ the amp switched to "low" and complained of overdrive. I backed off the drive to give 400W and continued running and had no more issues for  the rest of the contest.

Explaining my findings to G4BVY after the contest he said that G4CLA had similar issues at P44K  when running an SPE amp on FT8. He found the efficiency of the SPE amps on "low" is much higher than on "mid" or "max" hence less overheating so less alarms.

Previously we had used the Elecraft KPA500 on rtty contests. This had no issues running 500W output for a 48 hour contest, apart from the noise of the cooling fans.

From the results the amp seems to have worked fine, 1st in EU, beaten only by a Californian!

K3S "HI SIG" WARNING

While testing before the IOTA contest at G8X the K3S came up with the error "HI SIG" warning

From the manual:-

"An extremely strong, sustained signal (e.g., a broadcast station’s carrier) may be causing
excessive post-mixer amplifier current when operating on the present band. The K3 will automatically turn the preamp OFF, and in extreme cases will also turn the attenuator ON"

After disconnecting the antennas and turning the rig back on again the same error was displayed, and all controls were sluggish. At this point the K3 was used as a replacement and survived the whole contest without issue.

An Internet search suggested that the IF amplifier following the mixer consisting of Q8 and Q9 had now got shorted devices. Elecraft support were contacted and quickly responded confirming this theory. The devices used for Q8 qnd Q9 were discontinued, but some were found on EBAY. These took 24 hours to arrive and when fitted resolved the issue. The IF amplifier in the sub receiver had escaped unscathed. As a note Q8 and Q9 were easy to replace as you just have to remove the front half cover underneath the K3S, they are soldered to the underside of the motherboard

Elecraft support also mentioned that for a time the K3S was shipped  with R66 in the IF amplifier as 10 ohm

"On K3S, make sure R66 is 15 ohm  E500610 not 10ohm. We briefly shipped with it 10 and reverted back, **AND at the same time changed R60 & 75 so if R66 is 10 ohm, change it to 15 E500610 and R60 to 150 ohm E500251 and R75 6.2 ohm E500265"

My K3S was one of these radios so having replaced Q8 and Q9 and checked it worked, I changed the values of R60, 66 and 75.

70MHz Trophy

Enthused about 4m from previous outings we decided to visit British (IO81KR) again. We were late starting by 30 minutes by eating cake and coffee before departing to the site!. There was mist/rain/drizzle for the whole contest. Again we used the K3S and the Anglian transverter to drive the I0JXX dualband amplifier. The antenna was the 5 ele Powabeam at 6m,

The only equipment issue was computer related. The K3S just has one USB connection to the computer (no audio leads). For the first 30 minutes on every speech peak the virtual serial port and the K3S soundcards would be removed from the computer and reappear on receive. After a while there was a warning that the device was disabled as it was unstable. Not having had this issue on previous 4m events I took a look at the USB lead. I had taken the first one from the bag; a thin black lead. Looking further I found a thicker lead with clear cover that showed a decent braid. Changing to that cable, the issue went away!
In a change to  normal, there were numerous stations QRV up north, in IO84 and 94. This activity allowed us to confirm that the site is good to the North, we dont normally work much up there as there is no activity! The loudest signal was from GM4ZUK/P in IO86. Although two stations were worked in GU, there was not even a hint of a GJ station or GD. Being called by GI4OPH in the last hour was a welcome surprise/ 98 QSOs were had with the best DX being PA4VHF in JO32 at 640km

June 70MHz UKAC

After the success during the previous Sunday's 4m contest, thoughts turned to the 4m UKAC the following Tuesday evening. Blorenge is much more hospitable at this time of week and it was much easier to get to directly after work than British Mountain

This time we used Rogers Van to support the 5 ele Powabeam at 20' Again the K3S drove the Anglian transverter then the I0JXX amplifier module, all operated from the Honda Jazz.

There was some DX heard while setting up from EA and IC8, but it disappeared as the contest started. Conditions on tropo were poor, but we ploughed on, listening around between qsos. We found EA6SX who we worked at 1442km as the best DX. After this excitement the search for multipliers continued. No continental DX was worked. Northern English squares were well represented but despite calling a lot that way, there were no sign of GM stations. 109 QSOS were made in total

Nice Sunset

Postscript
The results have been published very speedily... within 12 hours of the entry deadline, AND the writeup contained more details than "the next contest is on xx/xx/2016! Looks like only our station worked the Sporadic-E

Pos	Callsign UBNs	Loc	QSOS	Score	Mults	Total	Norm	ODX	Kms	Power
1	GW4FRE/P	IO81LS	107	19,874	34	675,716	1,000	EA6SX	1,442	150
2	G4FZN/P	IO94JF	101	17,875	32	572,000	968	G3VXM	381	160
3	G3TCU/P	IO91RF	84	13,577	32	434,464	935	GM4NFC	530	160

70MHz Cumulative Contest

Having finally  finished integrating my I0JXX dual band 50/70MHz amplifier it needed trying out. The contest calendar showed a 2 hour 4m (2nd cumulative) contest so we decided to give it a try. Blorenge is no place to be on a Bank holiday Sunday so an alternative was needed. Roger suggested British Mountain which was a bit more remote. I had never been there so I went there via his house, so i could follow him. The route was challenging for both vehicles. As we neared the destination we noted a vertical antenna and a tent, which caused concern, Dropping by and introducing ourselves we found they were CBers so we should have no trouble to us on 70MHz. We moved 100m along the road and setup the station. The 5 element Powabeam was put on 25' of pole with guys. The rest of the station was the K3S (on its first outing) and my G4DDK Anglian Transverter. We also got to try the audio boxes I had made which allows the operator and logger to choose any combination of main and sub RX audio

When the antenna was connected the band was full of wideband signals. Sporadic-E was in progress, the band was occupied by FM broadcast stations from Eastern Europe. SQ8EP was worked before the contest, but during the contest, despite the broadcast SP-E signals there was no SP-E dx available, the best dx was PF7M. The Northern English squares were well represented but despite calling a lot that way there were no sign of GM stations. 71 QSOS were made in total.

Postcript:

A friend of a friend stumbled across a youtube video from visitors to the CB station wondering what was going on at the white van up the road from the cb station! The video is here  https://www.youtube.com/watch?v=jJ5Bs29CXGY   The marauding sheep timestamp the recording time

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

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:-

Timestamp	Call	MHz	SNR	Drift	Grid	Pwr			km	az
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

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

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. Perhaps someone should have checked that when the K3 manual was converted to a K3 it was correct.

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 arrived three days later and resolved the issue.