mandag den 1. januar 2018

Yaesu FT-920 no transmit

I was surprised when my Yaesu FT-920 HF transceiver suddenly stopped transmitting. RX was ok, but no TX in any mode.

I began checking the backup battery and performing a master reset. This advice was given on by KB5UBI: "A full reset did not solve the problem, but a button battery replacement followed by a full reset solved the problem".

I removed all power and all cables from the transceiver. Then I removed the bottom cover. I located the backup battery and measured the voltage to 2.32 volt. Then I switched off the Backup switch (next to the yellow capacitor) and replaced the battery (CR2032). Then I swithced on the Backup switch. The voltage of the new battery when fitted was 3.13 volt.

Yaesu FT-920 backup battery.

My Yaesu FT-920 now performs normally. Replacing the backup battery and performing a master reset did the trick!

Happy new Year 2018 from OZ1BXM Lars


fredag den 1. december 2017

Adding Sidetone for Winkeyer Lite

I am the happy owner of a Winkeyer Lite. This electronic keyer is excellent for contest use, and many contest programs support it. The Winkeyer sends perfectly timed CW regardless how busy the PC's CPU. The picture below shows how the Winkeyer is connected.

How the Winkeyer is connected
When the Winkeyer is connected to the transceiver, you will hear the transceiver's sidetone. But sometimes the keyer is not connected, and the Winkeyer is now silent. I decided to add a sidetone, and make the circuit as simple as possible. The diagram is shown below:
A buzzer generates the sidetone.
Transistor Q2 is controlled by the Winkeyer's PTT line (default off). You have to activate PTT in the Winkeyer to make Q2 work. This can be done with the WKdemo test application.

The buzzer generates a 2,3 kHz tone (square wave). I can live with a high-pitched sidetone since the more pleasant sidetone of the transceiver is heard 99% of the time.

Winkeyer Lite with sidetone added.
73 from OZ1BXM Lars

lørdag den 18. november 2017

QSL-card for EME

When I began EME operation, I decided to confirm QSOs with a QSL-card related to Moonbounce. I had a picture of my EME-antennas pointing at the Moon. The picture was taken at dawn, and both the 4 antennas and the Moon were clearly visible.

There are many websites, where print-shop owners offer QSL printing service. I selected UX5UO
due to his fair pricing and great design flexibility.

My new QSL looks like this:

New QSL for EME contacts.
Vy 73, OZ1BXM Lars

mandag den 16. oktober 2017

144 MHz EME: First QSO

I worked my first initial yesterday morning. I answered the CQ of EA8DBM, and he came back to me right away! It was a wonderful feeling getting a response from the Moon! The protocol was JT65B. The signal reports were exchanged using short hands. This means the report O is given as two tones rather than a decibel value. The reply is sent as RO, which is also a two-tone signal.

First EME QSO with EA8DBM.
Interpretation of messages:

0946 EA8DBM calls CQ
0947 OZ1BXM answers EA8DBM
0948 EA8DBM reports "OOO" to OZ1BXM
0949 OZ1BXM confirms reception (R) and reports an O: "RO"
0950 EA8DBM has received all info and sends "RRR"
0951 OZ1BXM sends "73" (this confirms that "RRR" was received)
0952 EA8DBM sends "73"

After this maiden contact followed DL8II, RX1AS, and OH4LA. I am happy for these QSO's and hopefully many more will follow!

My setup was 4 x 6-element yagi and 800 W from a homebuildt SSPA (version W6PQL).

Same news on Facebook: link

My homepage:

73, OZ1BXM Lars

mandag den 18. september 2017

144 MHz EME: New 4x6H Array

I've tried different antennas for EME on 144 MHz without much success. The antenna gain was 11-12 dBd. Sometimes an antenna received few signals from the Moon, but most of the time it received nothing. That was quite frustrating! I tried a sked with a big station (HB9Q) in order to get my first QSO, but the sked failed. He could not hear me, and I could not hear him.

To solve the problem, I decided to build a new antenna array with 15 dBd gain. This gain is generally considered as minimum for reliable EME communication on 144 MHz. LA3EQ Jan has succesfully used this antenna type for several years.

4 x 6-element yagi at OZ1BXM
My new antenna is 4x6H which is 4 stacked 6-element yagi-antennas with horizontal polarization. Each yagi is PA144-6-2 from Dual (YU1CF). The stacking distance is 2.40 m horizontal and 2.20 m vertical. All four antennas are mounted on an H-frame made of 1½" galvanized steel tubes. The 4-way power splitter was fitted using a homemade clamp. The box below the rotator contains a 1 kW coax-relay. The other box contains a HA8ET Extra-2 preamp (NF 0.5 dB). The horizontal rotator is Yaesu G-600 and the elevation rotator is Kenpro KR-550.

With this array, I hope to get my first EME QSO soon. Stay tuned!

Vy 73 from OZ1BXM Lars

søndag den 30. juli 2017

144 MHz EME: Antenna problems

My elevation rotor KR-550 was repaired and remounted last month. So far, so good.

My next step was replacing the 2 x 6 vertical yagis with an 8-element horizontal yagi (Wimo WY208). The reason for this change: I wanted horizontal polarization. I heard only a few stations with the vertical yagis.

8-element yagi with elevation.
I had a sked with HB9Q yesterday. He called me, and I called him. But there was no QSO, not even a trace on the waterfall. I was disappointed, because HB9Q is probably the biggest station in Europe transmitting a very strong signal with his 15 m dish. I tried with another big station, and he shifted between horizontal and vertical polarization. No trace at all on my side.

Some time ago I received signals from the Moon using my 2 x 6 yagis. So there seems to be a problem with my 8-element yagi since nothing is received. I'll do some troubleshooting, and hope to find out what is wrong.

73 from OZ1BXM Lars

torsdag den 22. juni 2017

Repairing my Kenpro KR-550 elevation rotor

My Kenpro KR-550 rotator was "frozen" and could not move in any direction. I searched for advice (Google is your friend) and found instructions from PA1IVO on how to disassemble and repair the rotor.

Disassembly of the rotor cabinet was tricky! The 8 bolts holding the cabinet together were completely stuck. I had to apply a dismounting technique, which I learned from a Youtube video: Heat the bolt and apply candle vax to the thread. That surprisingly worked!

The bolt can be loosened after treating it with candle vax.
Next step was to spot the error. The motor and gearbox were in good condition, and they operated normally when power was applied. However, the big gear wheel, which is fitted on the boom shaft, had chunks of clotted grease between the teeth. This was the core problem, and it prevented the big gear wheel from rotating. I removed the chunks and cleaned all gear wheels.

Clotted grease was found in the gear wheel.

Finally, I replaced the 500 ohm potentiometer inside the rotor. The new potentiometer was purchased at UKW-Berichte in their webshop (item 01999-KR-Poti). The spare-part cost me 27 EUR plus shipping from Germany to Denmark.  

The new 500 ohm potentiometer.
Now it was time to assemble the rotor. The gasket between the two halves of the cabinet was renewed. I applied Loctite 243 to the 8 cabinet bolts. Loctite 243 prevents loosening due to vibration, and it permits disassembly with hand tools for servicing.

The elevation rotor is now back in operation. I am eager to resume my EME project, and I will report my progress here.

73 from OZ1BXM Lars