Remco.org

In my previous post I reported a succesfull try wih LinuxPPS in conjunction with ntpd’s NMEA, ATOM and SHMPPS drivers. However, as far as I could ascertain, the PPS signal from the CIROCOMM G100/300 (I still have not heard anything from them..) can not be locked to the GPS signal due to the relatively large offsets and jitters.
I borrowed a Rockwell Jupiter unit, which Bas PE1JPD bought on a HAM-radio flea market a few years ago, to use it with his PDA and TomTom Navigator.

It seems that the Jupiter PPS signal is locked onto the GPS signal and the datasheet mentions that the rising edge of the TMARK pulse (i.e. PPS) is synchronized with the UTC one second epochs to within ± 1 μs. Other information states that the TMARK output is 10 – 40 ns accurate.
I interfaced the Jupiter using a 74HC00 to invert the TxD (mandatory) and PPS (not mandatory ; -).

Click on the image right to enlarge.

I placed the Jupiter into ‘Zodiac Binary Protocol mode’ (pin 7 HIGH and pin 8 GND, 9600 bps mode) first, and when I connected the receiver I could not see a GPS fix at all. I suspected the small patch antenna from Bas and remembered that I had an ‘official’ GPS antenna somewhere. To minimise errors, I placed the Jupiter into 4800 bps NMEA mode (pin 7 GND and pin 8 HIGH), and connected the GPS antenna to the Jupiter. Within a few minutes I could read the UTC time from the NMEA output. A few minutes later the receiver had a fix.

The relevant lines in my ntp.conf are:

#NMEA 4800 bps on ttyS0 (falling edge PPS, flag2 1)
server 127.127.20.0 minpoll 4 prefer
fudge 127.127.20.0 stratum 0 flag2 1 flag3 1 refid GPPS

#ATOM (falling edge, flag2 1 )
server 127.127.22.0 minpoll 4 maxpoll 4
fudge 127.127.22.0 flag2 1 flag3 1 stratum 0 refid PPS

After six hours:

remco@helium [/home/remco]> ntpq -p

remote            refid   st t when poll reach   delay   offset  jitter
=======================================================================
+GPS_NMEA(0)      .GPPS.   0 l   11   16  377    0.000    0.008   0.001

oPPS(0)           .PPS.    0 l   10   16  377    0.000    0.006   0.002

I could not run ntpd with the Jupiter in ‘Zodiac mode’ because I receive errors in clockstats:

54513 26640.110 127.127.31.0 unknown message id 1003
54513 26640.310 127.127.31.0 pulse: jupiter_parse_t: Unknown gweek
54513 26640.874 127.127.31.0 gpos: Navigation solution not valid
54513 26640.982 127.127.31.0 unknown message id 1002

However, driver31 is not patched for LinuxPPS yet. Unfortunately I am more into hardware and did not succeed patching refclock_jupiter.c without gcc errors ; -(

You can monitor ntp.remco.org (helium) if you like : -)

As many of you know, I run an ‘open access’ stratum 1 NTP server (ntp.remco.org) for almost four years now.
In fact, ntp6.remco.org is one of the few open access IPv6 NTP servers worldwide. During this period ntpd was disciplined with a DCF77 radio module, keeping the time within a few milliseconds of CET/UTC.

One of the problems I encountered was that Linux lacked a for me understandable PPSAPI, and still has no easy nano kernel implementation. Recently Rodolfo Giometti started writing a PPS implementation for the Linux kernel. He wants it to be inserted into the 2.6 kernel officially. For now patching existing kernels and software is the only way to go. His wiki tempted me to ‘try this at home’. Richard PA7FA, donated a few CIROCOMM G100/300 GPS-receivers and found out that besides 4800 bps NMEA, also a PPS signal was present. I mailed CIROCOMM for the datasheet of this OEM module, but I still heard nothing from them. Therefore I don’t know the accuracy and/or usability of the PPS signal.
The GPS module is fed by the USB port (+5V) and the 4800 bps NMEA data is inverted with a transistor and fed to pin2 of the DB9 of ttyS0 while the PPS signal (active positive) is fed directly into pin1 of the -same- serial port. Thus, no ‘level’ converters are required as both pin1 (DCD) and 2 (RxD) are inputs. The modern 16550A-chipsets have no problems detecting TTL input levels. This picture shows the first VERY experimental setup.
Traffic on the serial port can be monitored with minicom -s and/or cat /dev/ttyS0:

remco@helium [/home/remco]> cat /dev/ttyS0
$GPRMC,083057.198,A,5314.6975,N,00510.7342,E,0.00,,140208,,,A*71
$GPVTG,,T,,M,0.00,N,0.0,K,A*13
$GPGGA,083058.198,5314.6975,N,00510.7342,E,1,08,1.0,48.2,M,,,,0000*39
$GPRMC,083058.198,A,5314.6975,N,00510.7342,E,0.00,,140208,,,A*7E
remco@helium [/home/remco]>

I encountered some difficulties getting the LinuxPPS contrapsion to work. I will submit these difficulties to the LinuxPPS mailinglist soon.
Anyway, after some hacking I received the desired ‘o’ from ntpd:

remco@helium [/home/remco]> ntpq -p remco.org
remote refid st t when poll reach delay offset jitter
=======================================================
+GPS_NMEA(0) .GPS. 1 l 22 16 377 0.000 0.060 0.336
oPPS(0) .PPS. 0 l 5 16 377 0.000 -0.177 0.550
remco@helium [/home/remco]>

Initially I did not understand from Rodolfo’s wiki that the patched NMEA driver also handles PPS requests. Therefore I configured ntpd for the ATOM driver (driver 22) too. Below are some significant ntp.conf lines:

#NMEA 4800 bps on ttyS0
server 127.127.20.0 minpoll 4 prefer
fudge 127.127.20.0 stratum 1 flag2 0 flag3 0 refid GPS

#ATOM __| |___ (rising edge, flag2 0)
server 127.127.22.0 minpoll 4 maxpoll 4
fudge 127.127.22.0 flag2 0 flag3 1 stratum 0 refid PPS

I learned from Philip that the (patched) NMEA driver handles PPS too (flag3 1).
I will experiment with these several setups, i.e. NMEA + seperate PPS, NMEA + PPS and DCF with separate PPS, e.g.:

#NMEA 4800 bps on ttyS0 and use PPS (flag3 1)
server 127.127.20.0 minpoll 4
fudge 127.127.20.0 stratum 15 flag2 0 flag3 1 refid GPPS

#ATOM __| |___ (rising edge, flag2 0 )
server 127.127.22.0 minpoll 4 maxpoll 4
fudge 127.127.22.0 flag2 0 flag3 1 stratum 0 refid PPS+

#SHMPPS (falling edge) shm_splc2 -d /dev/ttyS0 -s -l DCD -u 0 -c
server 127.127.28.0 minpoll 4 prefer
fudge 127.127.28.0 flag3 1 refid PPS-

#PARSE Conrad RAW DCF77 (mode 5) no PPS
server 127.127.8.1 mode 5 minpoll 4
fudge 127.127.8.1 time1 0.0 flag2 0 flag3 0 stratum 14 refid DCF

You can track my experiments at ntp.remco.org.

OK, here is the picture: the CQWW 160m contest and my recent experiments with K9AY-loops, of which Gary K9AY (also active during the contest!!) himself wrote:

“The changes are good ideas. I also stopped using an autotransformer and do not use the +/-/AC control voltage. When I added a 3-relay termination adjustment, separate control wires were required, and I also put the direction control on that cable. This allows me to use a preamp that is powered via the coax. There will be a product review in QST soon, describing the Array Solutions product that uses my design. The information on RF chokes is very useful. I have seen the power supply problem before, but it is usually fixed with a good EMI filter on the AC input. However, in the past, I have needed a larger RFC as PG0A has discovered. With DC control voltage, this is not a problem, and I typically use a 220 uH RFC. 73, Gary K9AY”

Richard PA7FA and Remco PG0A wanted to test their 160m setup, strategy, and ideas during this contest. That is, not fully participate, but experiment, and see how we can learn. Our goal was to beat Dutch stations in pile-ups, and to ‘DX’, i.e. to work DXCC countries and experience the propagation during a fully saturated band. Nice aspect is that you can sleep during the day ; -)

We prepared the following (Google Maps overview here) setup (click on the picture to enlarge the shack ; -) :

- inverted L TX-antenna with a few radials, and 10000 sq. m. of aluminium greenhouses
- 250m US Beverage, made of welding wire, 4 bamboo sticks, a tree at the other end, and stretched with a bucket of stones.
- K9AY-loops
- ICOM PW-1 amplifier
- ICOM IC-756 pro 3 (I think .. ; -)
- N1MM logging software
- headphone (<- mandatory!!)

The setup functioned very well and we think we were the first Dutch station that evening to work into the US (VY2KM not included ; -) with K1LZ @ 22.21 UTC. Our ‘competitor’ PC5M logged their first US station for that evening (W2YE) @ 23.34 UTC, one hour later (!)

Experiencing this contest, I think it must be possible to work your 160m DXCC within one weekend.
Nice contacts were MD4K, UP0L, T77C, OH0Z, CU8A, CT9M, 4Z4DX, EA9EU, ER5GB, TF4M, 7X0RY, CN2R, C4M, VP9I, KP2M, TA3D, and XE2S.
Statesside we worked about 50 stations including K9AY himself. (Sorry Gary, you were louder on the Beverage ; -)
HK1X and C6ANM were actually the only two stations heard that couldn’t be worked before I fell asleep @ 02.30 UTC.
We did not hear Japanese stations that evening but worked JT1CO (!) easily.

The next evening we gathered a few new ones like 4L2M, JH4UYB (!), IS0OMH, a lot of EU and some new US stations.
Our score will not be high but N1MM showed 204/27/63, i.e. 204 contacts, 27 ?? and 63 mulitpliers??, resulting in a 116820 points claim.

We considered the experiments to be very promising and perhaps we will participate in the 160m SSB contest too.

9:1 transformer
During my preparations for the PACC contest I made some K9AY loops. It is generally recognized that galvanic separation of the loops and the receiving system is highly recommended to decrease interference, noise, and other strange phenomena. The original K9AY design used an 9:1 autotransformer, and voltages to switch the two relays are fed through the coax. Both on the internet and in ON4UN’s Low-band DXing book, usage of a galvanic separated 9:1 transformer seems to coincide with the loss of the initial, and elegant solution to switch the relays via the coax cable.

Noise/interference from the control box
Reported noise/interference when positioning the controlbox in the ‘NW’ position may be the reason for this. In this position an AC voltage is superimposed on the coax instead of a DC voltage. What actually occurs, is that the mains power supply (220V here), with a lot of ‘superimposed’ interference from connected equipment, is almost directly ‘transformed’ into the receiver when the switch is in the NW position (!) In the SE (+V) and SW (-V) positions rectification with subsequent derippling shortcuts this mains power interference.

I also experienced an increase in noise/interference with the switch in NW position initially, but as far as I could ascertain it disappeared when using the ideas below.

AC/DC blocking choke in control box
I think that the inductance of the original choke (in the original K9AY-article 100 μH) is insufficient for the range 0.5 – 3.5 MHz. In my control box I use a 22 mH (Farnell) choke I had ‘in stock’. Its reactance @ 1.8 MHz (XL = 2*pi*1.8E6*22E-3 = 250 kΩ) is of insignificant influence compared to the original 100 μH choke (which reactance is -of course- 220 times lower).

PG0A’s Law: Listening is feeling
I think that a 1 mH choke will eliminate interference/noise most cases. However, I have not experimented with this. To assess the noise/interference, put your receiver into AM mode, dismount the coax towards the loops from the control box, and place the switch into the NW position. Compare it with the SE (+V), SW (-V), and NE (0V) positions. Besides some clicks (AGC effects due to the change of super imposed voltages which (dis)charge the DC-blocking capacitor in the control box) no (significant) increase of interference/noise may occur.
If you feel this is not the case (PG0A’s Law: listening is feeling ; -) increase the inductance of the choke significantly. With my 22 mH choke, all four positions (NE, NW, SE, and SW) sound equal. This was not the case when I used a 100 μH choke.

Another idea, which I haven’t tried yet, is to use a mains AC filter (e.g. from an old computer -switch mode- supply) in series with the power supply transformer.

LEDs on the switch box
Experiences from last year, while building and testing the loops, urged to have some kind of indication which of, and in what direction, the loops are pointing or to assess ‘remotely’ if anything switches at all. So, I replaced the (rectifying) diodes with LEDs, assuming that the relays draw between 15 – 25 mA of current (well.. they do and so do yours ; -).
By the way, I use DPDT 5V relays to compensate loss of voltage when using large lengths of coax as the loops have to be placed far away from the TX-antenna. And.. I have some ideas to create more than four states on a single coax to switch the Rterm value too in order to ‘optimise’ the nulls.

Pictures!
Below you’ll find the schematic diagram. I also made detailed pictures of the contrapsion, controlbox, switchbox-v1, and switchbox-v2. The difference between v1 and v2 of the switchbox, besides the Rterm switch, is the transformer used.
Switchbox v1 used a toroid and v2 uses a binocular version with teflon isolated wire.

Control box
I have been asked to publish the diagram of the control box. My implementation, depicted below, is identical to the original K9AY version except that the ‘AC/DC’ blocking choke is 22 mH, and I don’t like fuses.

Rocket science?
My initial feelings concerning the aforementioned were that it was not ‘rocket science’ but ‘handy’.
However, my ex-collegue, friend and 160m guru Kees PA0CLN was really surprised with my LED ‘invention’.
“You really should inform Gary about this”, he said. I told him about the galvanically separated transformer, the enormous loss of interference, the single coax solution, and that everything really worked well and so on.
“But how to you feed the relays via the coax cable then?”, he asked.
I promised him to mail him my contrapsion but I thought it would be a nice idea to publish it here : -)

Does it work for you?
Please find out if the above is reproducable, and leave your feedback here.

This week I upgraded my firewall and, inherently, this site Rembl.org. The old site was running on WordPress 2.0 and an AMD K6-2/300 with 96 MB memory and 4 GB harddisk. I bought a surplus Compaq Evo D500 – P4 1.7 GHz with 512 MB memory and 20 GB harddisk from www.2dehands.nl for a nice price and upgraded to WordPress 2.3.
Below you see a picture of this machine.

Jurgen PE1LWT (see right, click on picture to enlarge), bought a second AM6154 for me in Friedrichshaven last June. It looked like a virgin and the first challenge was to power it up. The first result was that we did not experience a big bang with corresponding flashes, also not after powering up the 2.4 kV plate voltage. Because this amplifier was originally designed for aeronautical AM (amplitude modulation), the amplifier was immediately set in ‘idle’ mode.
While approaching the amplifier, we saw that the plate current was ‘ticking’ as well as the screen voltage. We first thought it was the electrolytic capacitor in the screen power supply. It turned out that the screen (G2) glass overvoltage protector was arcing. My philosophy is, remove as much protective devices as possible because they cause and create more damage than they protect!
So we did.The amplifier was left into idle mode during a coffee break and my cat jumped on it, almost got electrocuted because his tail was hanging in the high voltage power supply. Besides the activity of the cat, we did not hear strange noises, nor could we smell strange odours from the amplifier.

So, the next step would be to apply some drive. We applied a little drive to the amplifier, tuned it and soon measured 100W output.

After tweaking and tuning we reached 300W with almost 12W (!) of drive (see right, click on picture to enlarge). We expected a bit more output, but, we left the amplifier ‘key down’ at 300W during the evening. This resulted in a VERY HOT Spinner dummyload. But also it demonstrated that the amplifier was stable with this output and… it is a quick way to recondition a tube!

My other amplifier, with a GS-36B inserted, delivers almost 3 dB of output more. So, it was time to modify the amplifier and make it ‘contest ready’.

The input circuit was completely modified according to the FYM-tetrode match. Perhaps for reasons of (in)stability, but I cannot understand why the standard input circuit of the AM6154 is designed so inefficiently. After this and some other modifications, the amplifier delivered a stable 500W with 2.2W of drive power. A good backup amplifier for the contest!!

Richard PA7FA wanted to become active on 160m during the 2007 PACC contest. Being mostly active on 144 MHz and higher contests (see www.pa6.nl), 160m is a grey area for me. Fortunately, my old collegue and friend Kees PA0CLN revealed some of his 160m secrets to me and this is how I discovered the real expert information on K9AY loops.
Now I understand why Kees was so late at work sometimes in the late nineties ; -)

DXing on 160m is a actually contest towards the (man made) noise. In my opinion the challenge is not to transmit, but to receive. Reading the internet, the K9AY loops, discovered in the late nineties, are considered to be at least one of the holy 160m DX grails.
So, Richard and I made two loops, directing towards NE-SW / NW – SE.

Click on the image to enlarge the picture.

Listening for the first time to the K9AY loops is really a special experience!! Although the loops have an attenuation of >20 dB, the S/N ratio is incredibly better than our transmitting antenna, which is an inverted L with 8 radials. The first evening we worked JA, 9M2, V51 and other stations, all not audible on the TX antenna due to heavy QRM and/or QRN.

During the 2007 PACC contest PA7FA made ca. 150 QSO’s on 160m with 33 multipliers.

Note/update: with a solid mains power supply, undistorted 700W can be achieved!

In 1992 I bought a surplus AM-6154 amplifier from departing US-forces in Darmstadt (Germany).
The amplifier was intented to serve as a backup during 144 MHz IARU-contests of PE0MAR/p, now PA6NL.
And, it did for one contest. The second contest the amp delivered only 200 Watts and died quietly, and was subsequently stored for almost 15 years with the mark: “To be repaired”.

My intention was to revitalize the amplifier. Not because of the power (only about 400 Watts output if I remember it correctly) and/or urgent needs. No, it is because of the fact that having 25 kg of worthless iron scrap is of no use at all. This year I found the time and patience to investigate the AM-6154 amplifier and got it running again.

This blog entry is not supposed to be an extensive story about all the modifications I made on this amplifier. However, I will try to describe some experiences during the repairement of this nice (and heavy!) amplifier.

Normally AM-6154 amplifiers are equipped with an Amperex DX393, an equivalent of the Eimac 8930, which is a ruggedized version of the well known 4CX250B. After several ‘reconditioning’ experiments I had to conclude that my DX393 was really beyond reconditioning and had to be discarded.

It was my intention to use the Russian GS36B tetrode as an alternative for the DX393. Although publications on the net suggest that a 1 on 1 replacement is possible, this cannot be true due to the physical dimensions and electrical characteristics of the tube. The anode diameter of the GS36B is ca. 1 mm smaller than that of the DX393.
I compensated this with several layers of copper foil around the GS36B anode until the tube fitted well into the silver fingerstock anode ring of the AM-6154 cavity.

The control grid voltage (Vg1) had to be modified. I replaced the original 100V/1W zener diode VR1 with two 39V/1W zeners in parallel. I determined from the datasheet that with Va=2000V and Vg2=390V, the GS36B needs about -45V to draw 50 mA of anode current.

The GS36B tube draws more screen (G2) current than the DX393 (which may have non linear negative screen currents at certain stages). The Vg2 dropped significantly (390 -> 350V (!)) at larger output levels. I shortened one of the 100K/100W resistors in the HV power supply to increase the zener current to ca. 16 mA (2000 – 390 / 100000 = 16 mA). This eliminated the Vg2 dropping almost completely and increased the output considerably.

I considered the G1 input circuit far to complicated and modifications, as proposed on the internet, too ‘sloppy’ and chose for a brute force approach. I substituted the original 1/4 wave inductor for a 1/2 wave contrapsion.
For further information look here.

With ca. 3.5 Watts of drive the amplifier draws about 450 mA anode current (idling current = 50 mA) and produces solid >550W output, as measured with a Bird 43 and both a 1000C and 1000D slug. Here you can see and hear me tuning the amplifier (.MOV, 19.2 MB).

Download the manual of this AM-6154 amplifier.

Internettelefonie (VoIP) is helemaal HOT.

Ik kan me nog herinneren dat Ton aan de Stegge (toen directeur bij Ericsson) in ca. 1999 in het Mediapark meedeelde: “Dames en heren, we zijn er uit. Op de vraag of het ATM of IP wordt, luidt het antwoord: “Het wordt IP”. Ik kreeg toen de indruk dat het merendeel van het aanwezige publiek geen flauw benul had wat hij bedoelde. Daarna kwam een forumdiscussie, voorgezeten door Victor de Koninck, die over de toekomst van de telecom ging. Convergentie was toen een thema. Evenals de voorspelling dat ‘wireless’ de toekomst had, daarom was ik uitgenodigd.

Maar goed, ik heb nu dus ook integrated VoIP en kan lekker (gratis!) overal naartoe bellen. Het mooie is dat mijn bestaande infrastructuur intact is gebleven. Ik kan dus gewoon met mijn bestaande telefoon- en faxapparaten bellen en gebeld worden op zowel de VoIP- als KPN-nummers. Daarnaast verzorgt het kastje mijn internetverbinding want er zit een ingebouwd ADSL-modem in, een analoge en digitale telefooncentrale en een WLAN-accesspoint (!)

Samenvatting in nijntjestaal: dit kastje vervangt vier of vijf andere kastjes ;- )

Afgelopen weekend de meicontest gehad. Net voor het begin van de wedstrijd horen we LA3EQ op 432.200 CQ roepen. Hij is zich niet bewust dat er een contest aankomt en er is kennelijk tropo op 70 cm en hoger. Hij buldert binnen, evenals zijn baken LA5UHF op 432.441 MHz. Op de hoge toren horen we het baken op 10 GHz ook op 10368.885 MHz.
Hier een filmpje, opgenomen met mijn Nokia 6230i. NB: Realplayer heeft een codec voor .3gp