Homebrew | KC9QQ

Using a Modified SignaLink™ for FSK Transmission

Posted on February 23, 2014 by fjkFebruary 23, 2014

KC9QQ
Ready for NAQP RTTY Contest

After the CQWW WPX RTTY contest I decided to modify my RTTY setup so that it could operate FSK instead of AFSK. I wanted to do this because in the CQ WPX RTTY contest I had experienced several cases where the SSB filters (the only filters available during AFSK operation) didn’t provide the desired selectivity. In a previous post (SignaLink™ USB Not Transmitting) I talked about the modifications made to my SignaLink™ for FSK operation. I decided to tryout the modification in the NAQP RTTY contest on Saturday.

I didn’t have a lot of time to operate because I needed to take several hours off to attend our monthly astronomy club meeting. However, I was able to spend enough time with the new setup to realize that being able to use the RTTY filters in the Icom 756 Pro III resulted in a substantial improvement over the SSB filters.

The RTTY filters were able to do a much better job providing error free copy of stations adjacent to other strong signals. In a few instances, I used the Icom 756 Pro III’s dual peaking filter to pull weak stations out of the noise. I was impressed. There were a couple of stations that I was only able to copy about 50% of their transmission, but after I activated the dual peaking RTTY filter I copied them error free. I limited my use of the dual peaking filter because it did make it a little more difficult to tune in stations, but it was just a click away when I would run across a weak station that needed a little boost to be pulled out of the noise.

A Lesson Learned

I want to thank the station that took the time to tell me that I was off frequency. I was about 50 contacts into the contest, but seemed to be having problems being heard on the first or second call. Several stations had sent Agn? Agn? after I made my call. After I called one very busy station at least four times he came back and told me that I was off frequency. I looked at my radio and realized that I had left the RIT on! I turned the RIT off and stations quit asking me to repeat my call and report! Murphy is alive and well. I didn’t plan on setting any records; I just wanted work a new mode, hand out a few contacts and have some fun. All three objectives were accomplished.

Here is a summary of my results:

NAQP RTTY February 2014: Low Power, All Band

Band	QSOs	Points	Sections
80m	24	24	18
40m	43	43	22
20m	15	15	12
15m	30	30	13
10m	24	24	9

Total	136

Final Score: 10,200

SignaLink™ USB Not Transmitting

Posted on February 19, 2014 by fjkFebruary 23, 2014

If you have ever had trouble getting the SignaLink™ to go into the transmit mode perhaps you may find this article helpful.

After I operated in the CQ WW WPX RTTY contest I decided to modify my setup so that I could run my Icom 756 Pro III in the RTTY mode, in order to take advantage of the 756 Pro III’s nice RTTY filters. This meant I had to switch from AFSK transmission to FSK transmission. Since the SignaLink does not support FSK output I started searching for a different interface which that would allow me to operate FSK. While I was searching for other interfaces I came across an article written by K7SFN describing how to modify the SignaLink™ for FSK transmission.

Here is a link to Frank’s nice modification: http://www.k7sfn.com/projects/signalink.html.

SignaLink FSK Modification for Icom 756 Pro III

I made the modifications to the SignaLink™ described in Frank’s article. I also made a serial cable to connect between my shack computer and the FSK keying jack I had installed on the back of the SignaLink.

I reconnected the SignaLink™ to my computer and radio and setup MTTY to work with the new FSK setup. I fired up the rig and MTTY and was receiving RTTY as I expected. I then connected my Icom 756 Pro III to a dummy load to test the FSK keying circuit I had added. When I tried to transmit, the SignaLink™ would not go into transmit (the PTT led would not come on). I then spent two frustrating hours trying to figure what I might have messed up making the modification. I even fired up Fldigi to see if I could transmit PSK-31 and it would no longer transmit. I was concerned that I might have damaged my SignaLink making the modification.

Rather than lead you through my whole trouble shooting process I’ll just cut to the chase. I followed the troubleshooting guide in the SignalLink manual and could not correct the problem. I then went to their website to see if they had any other solutions. On the website they had the following statement:

My SignaLink™ USB was working perfectly but now will no longer Transmit – This is the most common problem we hear about and it is virtually **always** due to the software volume controls being reset by Windows. This can happen if you unplug the USB cable, change the default sound card in Windows, or accidentally mute the SignaLink’s output. Other things can cause this to happen as well, so please check your Windows software volume controls carefully. Note that they will most likely be reset exactly opposite of how they should be set, so they can look correct at a glance.

I then repeated Tigertronic’s audio setup procedure and the SignaLink™ started transmitting again. I don’t have any idea why windows behaves this way, but beware if your SignaLink™ will no longer transmit, be sure to go back through the audio level setup described in the SignaLink™ manual. Had I known this could occur I would have saved myself several hours of troubleshooting.

I can now continue to use the SignaLink™ to receive RTTY and use FSK instead of AFSK for transmitting. I plan to try out the new setup during the North American QSO Party RTTY contest this weekend.

73,

Fred, KC9QQ

Homebrew Portable Power Pack

Posted on December 13, 2013 by fjkDecember 13, 2013

Completed Power Box

I recently constructed a portable power pack that would serve a dual role: operating our telescopes during observing sessions and running my ham equipment on camping trips. By coincidence, ham radio transceivers and telescopes have similar power requirements (12V @ 1-10 A). Most amateur astronomers use either car or motorcycle batteries, auto JumpStart devices or expensive power packs sold by telescope manufacturers.

The power packs sold by telescopes manufacturers are basically automotive jump starters having one or more female cigarette lighter plugs that are used to power the telescope and accessories. Not only are these power packs expensive they sometimes do not have enough capacity to run a telescope and dew heaters for a whole night of observing in the humid midwest.

Motor cycle and automotive batteries have sufficient capacity, but pose a significant safety risk when stored and charged indoors. A safer alternative is the sealed AGM lead acid battery often used to power security systems and uninterrupted power supplies (UPS). After a bit of research I determined that a 28 amp-hr AGM (absorbed glass mat) battery would provide enough energy to power our telescope for a weekend of observing and that the same battery would easily power my Elecraft KX3 for several days of QRP operation.

RigRunner4005

I made the decision to utilize Anderson Power Poles for connections because of the reliability and flexibility they provide. I purchased a RigRunner Power Pole panel to provide a connection point for the telescope and its accessories.

For a case, I considered the Pelican cases, but was turned off by their high price and weight. I didn’t need a case that was 100% waterproof or one that could survive the airport baggage handler gorillas. I considered using an RV battery box, but they are awkward to handle. While walking through the Walmart fishing section the other day I stumbled across the perfect box or my application. It is made by Flambeau Outdoors. It is ( 15″W x 9″H x 8″D ), water tight, has a strong handle, a hinged top and a large lockable latch. The box was large enough to hold the 28 Ah battery, charger and the charger power cord. There was some room left over to hold other accessories: female cigarette lighter plug to power pole adapter, a power pole Ah meter, spare fuses and a power pole extension cable.

BatteryTender

I used a Battery Tender Plus 1.25 A charger to charge the battery. These chargers are the ultimate trickle chargers for lead acid and AGM batteries. They have a number of features:

Temperature compensated to ensure optimum charge voltage according to ambient temperature.
Automatically switches from full charge to float charging mode.
Battery Tender® at 1.25 amps will charge as fast or faster than any 3 amp charger available.
Reverse Polarity Protection to ensure user safety. Red & Green Lights Alternately Flash in this condition.
Complete 4-step charging program (Initialization, Bulk Charge, Absorption Mode, Float Mode).

Completed Power Box

Here are some photos of the finished power pack. The first photo is of the exterior of the power pack. Some of the features are the integral voltmeter which shows the current state of the battery charge. The case has a very strong handle which is important because the finished power pack weighs in at nearly 25 lbs. I incorporated a three position switch which selects the Operate, Off and Charge positions. During Charging I the switch disconnects the Power Pole panel from the battery to eliminate any chance that a failure of the charger could result in a over voltage condition on the Power Pole panel.

The next photo shows the interior of the Power Pack. The battery is a 28 Ah AGM battery. The Battery Tender charge is attached to a Aluminum “L” bracket with a heavy duty wire tie. I used the “L” bracket to support the Battery Tender for two reasons: so that it was flush with the top of the case so that it is easier to see the charger LEDs and to provide a space below the charger where I could wire tie the extra Battery Tender wiring. The AGM battery is held in place by 4 pieces of Aluminum “L” channel (3 around the base of the battery and one which captures the batter at the top. The brackets hold the battery snuggly against the back of the case. All of the fasteners are stainless. I also placed 4 rubber feet on the bottom of the case so that the fasteners inserted into the bottom of the box would not scratch any surface the box is placed on during storage.

This photo shows the small compartment in the top of the power pack case which can be used to store cables, spare fuses and the Volt/Amp/Watt-Hr meter I use to check each device I connect to the power pack.

Power Pack with Amp-hr Meter attached

The Amp-hr meter can also be used to monitor the total Amp-hrs consumed from the battery by placing it inline between the input to the RigRunner and the Power Pole connection coming from the battery (shown at right).

After building the first power pack I have since built two additional power packs–one for a friend and another to run my wife’s Celestron telescope. I think my Power Pack will also see a lot of use running my new KX3 on summer camping trips.

Best 73,

Fred

An Arduino Project for the Link Telescope

Posted on April 19, 2013 by fjkApril 19, 2013

Top view of the Hour Angle Calculator in Operation — note the rotary encoder has an internal RED led.

I have been continuing to work with the Arduino single board computers. One of the tasks required at the Link Observatory is to align the Argo Navis (digital encoders) using two well spaced stars. My wife and I have found that the easiest way to pinpoint the alignment stars is to use the telescopes German equatorial mounts setting circles. One of the challenges we had using the setting circles was having to continually recalculate the Right Ascension Hour Angle as we are moving the telescope into position–it takes a bit a time to accurately position a 36″ telescope that weighs over a ton. Therefore we would have to keep recalculating the hour angle which is calculated by subtracting the stars Right Ascension from the current local Sidereal time ( which is obviously changing).

I decided to use an Arduino to continuously calculate the RA Hour Angle using equations to calculate the sidereal time and the Hour Angle given the selected alignment stars Right Ascension. This project involved building a circuit which included a real time clock, a rotary encoder ( to select the star from a lookup table) and an LCD display. I assembled the circuit in a plastic 3″ x 5′ card box I found at Office Depot.

One of the more challenging aspects of the design for me was getting the rotary encoder to accurately count. I used a 24 pulse per rotation encoder which I purchased from Sparkfun (http://sparkfun.com). In the initial circuit the software would count extra pulses and sometimes miss pulses. After I tried several different software schemes to resolve the problem I finally used an oscilloscope to examine the waveforms coming out of the rotary encoder. Once I attached the scope I immediately saw the problem. When the encoder is being rotated It would frequently have high frequency wiping noise on the encoder A and B pins. After I attached a couple of .01 uf capacitors between the pins and ground the encoder began working flawlessly.

ChronoDot Realtime Clock Module

The next challenge was to interface a realtime clock to the Arduino. This turned out to be very easy using a ChronoDot clock module. This little gem interfaces to the Arduino using the I2C serial interface. It will run over 8 years on a single battery and will maintain the time with an accuracy 1 minute a year. The module requires four connections (5V, Gnd, SCL and SDA). SCL and SDA are the serial interface connections. The neat thing about the I2C interface is that many devices can share the same interface. In this project I also used the I2C interface to interface a 4 line by 20 character display.

I spent quite of bit of time developing the software–mainly because I was also learning how to program in ‘C’ at the same time I was developing the code to for the project.

The software to interface to the realtime clock, rotary encoder and display were developed by modifying examples readily available on the web.

I also had to develop the software to calculate the Sidereal time from GMT using one of several algorithms I found on the web. One problem I experienced was an error of about 5 to 30 seconds in the Sidereal time because of floating point round off errors in the Arduino software. This occurs because the Arduino software does not support double precision floating point calculations. This did not present a major problem in my application since the resolution of the mechanical setting circles on the Link Telescope only have a precision of around 1 minute.

The following photo shows the internal circuitry of the Hour Angle Calculator. The circuit board at the top of the photo is the backside of the 4 line by 20 character display. The four wires connect the display to power and the I2C interface. The circuit board shown in the 3 x 5 file card box is the prototyping shield attached to the top of the Arduino. This board holds the realtime clock, the pull-up resistors and bypass capacitors for the rotary encoder and other wiring to needed to interface to the Arduino. The circuit can be powered for several hours using a 9V battery.

73,

Fred

Arduino Experiments

Posted on January 22, 2013 by fjkJanuary 22, 2013

I don’t know how many of you have heard about the Arduino single board computers, but they make and excellent platform for developing gadgets for the ham shack. Here is a brief description of the Ardurino board.

Arduino Uno

Arduino is a tool for making computers that can sense and control more of the physicalworld than your desktop computer. It’s an open-source physical computing platform based on a simple microcontroller board, and a development environment for writing software for the board.

Arduino can be used to develop interactive objects, taking inputs from a variety of switches or sensors, and controlling a variety of lights, motors, and other physical outputs. Arduino projects can be stand-alone, or they can be communicate with software running on your computer (e.g. Flash, Processing, MaxMSP.) The boards can be assembled by hand or purchased preassembled; the open-source IDE can be downloaded for free.

I have been playing with an Arduino board in order to learn the basics of interfacing it to real world objects and developing simple programs that can gather information from and control these objections. So far I have developed a simple program which reads a digital temperature sensor and display the sensor temperature on a small LCD display called a shield. The Arduino can be accessed over a LAN using a LAN Shield.

Once I get a bit more experienced with the Arduino, I am going to try using to control some things around the ham shack.

Fred

KC9QQ

Adventures in Ham Radio

Category Archives: Homebrew

Using a Modified SignaLink™ for FSK Transmission

SignaLink™ USB Not Transmitting

Homebrew Portable Power Pack

An Arduino Project for the Link Telescope

Arduino Experiments