As some of our members will be aware, I have been building an Elecraft K2 kit radio, and I completed construction this Easter weekend.
When I ordered the kit, I didn’t order the internal ATU or the 100W amplifier option, as I already have an Elecraft KXPA100 amplifier with KXAT100 ATU. However, this amplifier is designed to work with the KX3 radio, and so to get it to work with the K2, I would need to build up a keying circuit.
Fortunately, Elecraft published on their website a neat solution for this. It consist of a couple of transistors mounted on some perfboard, which slots into a PCB header socket intended for the K2′s transporter interface module. Because I don’t have this option, my radio didn’t have the required header socket, but luckily the local electronics store sells suitable headers as part of their Arduino range. I picked up one of these headers, together with the other requisite parts.
The article on the Elecraft website provides a schematic, and some photos of the finished board, but they didn’t provide detailed information about how to build the circuit onto the perfboard. Fortunately, the circuit is quite simple, and wasn’t too hard to work out, but I decided to draw up a diagram which provides a better view of how the components are laid out and the physical connections are made.
The dotted lines show connections running under the board (except the gate lead of the 2N7000 JFET — that runs under the transistor, but along the top of the board).
I built the circuit in the following sequence:
1. put the 8 pin male header under the board on the left side, and solder one leg of the 2.2k resistor to the pin sticking out the top of the board at position A8. This then holds the header in place. The other leg on the 2.2k resistor goes through hole B5.
2. Sit the 10k resistor sitting up on end in hole C5, bend over the top leg and stick it through hole D4. Bend the legs underneath the board to hold the resistor in place.
3. Put a piece of hookup wire (eg. a component lead off-cut from when you built your K2) through hole D3. On the top of the board, bend the wire so it reaches the header pin 2 sticking through hole A2 and solder it to that pin.
4. Mount the right-angle molex receptor on top of the board through holes E1 and F1. Under the board, bend the hookup wire you installed in the previous step so it reaches the receptor pin sticking through hole F1, and solder to the receptor pin and trim. This will hold the receptor in place.
3. The Gate and Source legs of the 2N7000 JFET are the left two legs, if you hold the transistor with the flat face towards you. Bend those two legs backwards, and put the remaining leg (the Drain) in hole C1. Bend the Drain leg under the board down towards the resistors to hold the transistor in place.
4. Solder the Source leg (the left one you bent back) to the header pin 2, which sticks out of hole A2, and trim. Careful not to dislodge the hookup wire that is also soldered to that pin. Trim both the transistor lead and the hookup wire.
5. Solder the Gate leg (the middle one you bent back) to the header pin 1, which sticks out of hole A1, and trim.
6. The drain of the JFET which goes down through hole C1, and the resistor legs sticking through holes B5 and C5 should be bent so they all meet up. Solder the three leads together and trim.
7. The Emitter leg of the 2N2222 BJT is the left-most leg, if you hold the transistor with the flat face towards you. Bend that leg backwards, and put the middle leg (Base) through hole C4 and the right most leg (Collector) through hole C3. Solder the Emitter leg that was bent back to the header pin 4 sticking up through hole A4.
8. Bend the Collector leg sticking through hole C3 so it reaches the molex receptor pin sticking through hole E1 under the board, and solder the leg to the receptor pin.
9. Bend the Base leg sticking through hole C4 so under the board it meets the 10k resistor leg sticking through hole D4, solder the two legs together and trim.
10. Make up a short cable (3″ or 4″) with the molex plug on one end. Solder the side of the cable that connects to the pin closest to the side of the board, going through hole F1, to the ground lug on the RCA connector.
11. Install the RCA connector in the hole on the bottom chassis labelled “XVTR IN”. Solder the other side of the molex plug cable to the inner conductor of the RCA connector.
12. Plus the keying circuit board into the J13 header socket on the RF board. Connect the molex plug to the molex receptor on the keying circuit board.
And that’s it. Plug one end of the RCA-RCA cable into the new RCA connector on the back on your K2, and plug the other end of the cable into the “PA KEY” RCA socket on the back of the KXPA100. Connect up a patch cord between the K2 ANT OUT and the KXPA100 RF IN, and you are good to go.
Here are some pics of the completed circuit, from above and from beneath.
On Wed 19th Feb Nick VK2DX gave a technical lecture on the 630m band (472-479kHz). His lecture covered suitable transmit and receive antenna options (they are different!), as well as hardware and software for scanning the band visually. He also spoke of propagation characteristics, usually this band propagates via ground wave with a path loss advantage over higher bands however sky wave propagation can and does happen!
On Wed 15 January 2014, Matt VK2RQ gave a lecture on packet radio, which provided an overview of what is packet radio and how it works, and described some of the applications for which packet radio is used. Here is a link to the presentation slides in OpenOffice or PDF format. A video recording of the lecture is available here.
MWRS operated portable during the Sunday morning segment of this year’s Summer Field Day, from the oval behind our club rooms. This oval is at a high point in Terrey Hills and provides a good outlook in all directions. Operators were Nick VK2FS, Geoff VK2MIA, Matt VK2RQ and Carlo VK2MXC. In addition we had several club members turn up to say g’day and see how we were going.
Weather was warm and sunny, quite humid as it had rained overnight and the residual moisture was evaporating out of the ground.
For 6m, we used a squid pole supporting an inverted V, with the peak about 7 metres above ground level. FT-897D radio running on 2 x 12V 7Ah SLA batteries.
For 2m, 70cm and 23cm we used high gain Yagi antennas on a portable mast, rotated by hand. Unfortunately the coaxial relay for our 23cm equipment was playing up so we didn’t make any contacts on that band. IC-7000 radio running on large blue SLA battery.
Total contacts 19, with a great 6m opening to VK5, VK4 and ZL. Due to the nice opening, our score for 6m was almost our best category!
We had some carefully calibrated inserts to make the U-bolt bite down on the mast
2m, 70cm, 23cm Yagi setup
7m squid pole, with 6m inverted-V dipole
DX on a squid pole! Dom VK2JNA was highly entertained
I was excited when the 555 contest was announced to recognize the most used Integrated Circuit ever.
After considering for a while what I could do for the competition, I started thinking about how best to celebrate the 40 years that the device has been around and the 10s of billions produced.
I have often admired home built computers that use discrete components so I though, I will make a 555!
This 555 project recreates an operational 555 timer using discrete transistors, resistors, diodes and capacitors.
It may not strictly conform to the competition rules, but I thought it would be fun and original anyway.
I downloaded a few 555 datasheets from various manufactures only to find that the circuits often have subtle differences. Eventually after some Googling I located a scanned copy of the original Signetics datasheet from dapj Circuits, Including the Equivalent Circuit below.
After inspecting the circuit, I noticed Q19 is rather unusual and has 2 collectors. How can I implement this using discrete components? I decided to simulate the circuit using the brilliant and free Java app from falstad.com to make sure it worked and to quickly experiment with different arrangements for Q19.
This is the simulation. You can run the simulation yourself by clicking the link .
Arranging the resistor on the base of Q19 as in the simulation works perfectly. If I used 2 transistors to replicate the original Q19 design, the circuit did not oscillate.
ConstructionIn order to simply construct the circuit to show its operation and at the same time preserve the original authenticity, I photocopied and enlarged the Philips schematic, glued it to some card and inserted the components through the card and used point to point wiring on the rear of the card.
Component side of card.
Rear of card using soldered point to point wiring. Drawing pins are used to secure the input and output pins. Much ice cream was consumed during the construction of this project.
A pin was used to poke holes in the card to insert the components. This was a surprisingly quick method of building the circuit. For prototypes of simple circuits I may use this technique again.
the only thing I might do differently is to paste a reverse image of the circuit onto the wiring side of the card in order to avoid wiring errors.
In order to test it works, I attached an LED to the output and suitable timing components, Ra, Rb and C to give an approximate 1Hz flash rate.
Making it presentable
The final thing to do is to make the project presentable. I decided the inside of an old data book would be appropriate. I found a copy of a suitable book on the ‘free’ table of my local ham radio club, the Manly Warringah Radio Society.
This was the first time I have used a book as an enclosure. It works well if you are not in a hurry, which I wasn’t. I followed the guide by Bre Pettis from Make Magazine. (Cool guy who I had the pleasure of meeting at a Maker Faire in Austin, Tx.)
One half of the book was cut to accommodate the circuit, while the other half was to house a battery, the 555 timer data sheet and memorabilia.
JOTA time already?? MWRS has hosted activities for the Scouts and Girl Guides for several years and this year was another busy and fun experience! We had around 180 kids come through the hall over the weekend of 19th-20th October. … Continue reading →
As the dust settled and the flags were packed away for next years activities I collected the logs, photos and evidence for review at a casual club meeting. Firstly I have to say for our first comp things went really well, we had contacts from across the land in conditions that were difficult to say the least.
By popular vote points for flags, setup and effort were awarded and the I am happy to announce that the winner is …… Geoff VK2MIA with 152 points.
Not only did Geoff have a flag pole station, he also had a pirate hat, pirate dreadlocks, a sea location, made SSTV contacts and emailed through photos that he had a random by passer take. If that wasn’t enough he also had to deal with someone telling him he couldn’t do “what ever it was he was doing”…
Special mention goes to VK3BQ for his awesome efforts in getting the word out in VK3 about our comp and his great sstv images. VK3YE and VK3BQ for the YouTube video and everyone else who participated in this fun event.
If you know of anyone missing please let me know asap..
The trophy was handed out on Wednesday night (Thanks Greg!) and now we look forward to next years INTERNATIONAL Flagpole Comp which will be held on Saturday 20th September 2014.
This is a fun and as you can see not too serious contest that will promote Amateur Radio and portable operations. So dust of your rig, get your antenna in the air and try out some new modes with friends.
Geoff (VK2MIA) procured a Flagpole for mobile operations and tweaked the interest of the wider club when he brought it up to the clubhouse one wednesday night. Upon inspection a group buy was in planning, with Shaun (VK2XPP) taking the lead. The club procured almost 2 dozen flagpoles (From here). Once shaun picked up the shipment the club members get right to business, with some great results.
So with all these flagpoles ready for field operations the idea for this contest was born and the point structure was decided upon around the club fireplace with more than a few laughs.
The winner of the competition will be the person who collects the most points during the day of the competition. The goal of the event is to exercise your ability to operate using a portable antenna across multiple modes and perhaps to get you out of your normal operating comfort zone.
Non-flagpole stations are welcome to participate, but will have to work a little harder to get points.
Rules are as follows
1. The Flagpole station must make up part of the antenna or antenna support.
2. The contest will run all day on the 21st of September 2013.
3. The President / Vice-President’s of the MWRS will be adjudicators.
4. This is a fun event, keep it fun and positive.
5. This event is open to all Amateur Frequencies and Modes.
6. A contact will be the exchange of Callsign, Signal Report and a quick report of your flagpole setup!
7. Log’s are to be submitted using the Competition spreadsheet. (See below)
Make a contact with a non-flagpole antenna 1 Point
Make a contact with a flagpole antenna 2 Points
Make a contact with another flagpole station 5 Points
Make a contact with D-Star 10 Points (Maximum of 100 Points)
Huge thanks goes to Mark and Chris for giving up their Saturday in the name of Amateur Radio. They have helped 5 new Amateur Radio operators get licensed, and held exams for 2 others to upgrade. Club member Lionel who … Continue reading →
Geoff Van der Wagen, Roger Hynes and Ben Menge. Photo courtesy of News Limited
This weekends International Lighthouse and Lightship weekend is a great opportunity to promote Amateur Radio, and with that in mind Club Publicity Officer Richard has done a great job working with the Manly Daily to get us some local press. A journalist from the publication visited the shack to meet with Roger, see first hand the restored Barrenjoey Radio and get some snaps of the guys in action.
I know everyone has their own favourite, but for me Lighthouse is the event of the year so keep an eye out for VK2MB / Lighthouse Portable on the airways!