Category Archives: Featured

This category is for featured articles that we want to include in the sidebars and other areas on our website.

First Homebrew Contact on my Scratch Built BitX20 SSB Transceiver

About a year ago I decided to build an SSB transceiver for making contacts with other amateur radio operators on the HF bands.  I was given good advice from both Bill and Pete from the SolderSmoke Podcast to start out with a direct conversion receiver then go with the BitX20 as a first SSB rig.  I am very happy that they gave me that advice and I would agree that the BitX is not a good first project.

After getting all the proper adjustments made and confirming proper operation with a dummy load it was time to put this rig on the air (I don’t need a case)!   I tried calling CQ using SSB voice but no one came back.  I then decided to add some relays and other modifications to allow digital modes.

On January 15, 2017, at 21:46z I answered a psk31 CQ from Josh K1JOG in Kissimmee, FL.  Little did he know that he would be making history (maybe just for me) in my first home brew QSO.  Below is his eQSL card to me.

BitX20 First Contact QSL
Thank you, Josh K1JOG for the contact!

If you are interested in scratch building this rig you can follow the photo link  below:

BitX20 Homebrewed Transceiver
BitX by Ashhar Farhan, VU2ESE

Ashhar Farhan also sells a BitX40 at http://www.hfsigs.com/

The units he has built in India are almost ready to put on the air.  You build the case/box or just go open board style!  You can’t beat the $59 price for a rig!

Below are some photos of my project:

BitX20 Mic amp on the left LM386 audio amp on the right
Mic amp on the left LM386 audio amp on the right

A good place to start is the Audio “end”.  I built mine using perf prototype board.  FYI the 10k ohm resistor on the mic amp needs to be 39k ohm for proper bias.

BitX20 Balanced Modulator
Balanced Modulator

On the balanced modulator, I used a mystery toroid core because I have a bunch of them and they did not cost much!

BitX 10 MHz crystal filter
10 MHz crystal filter

In this photo, you can see some transmit and receive amplifiers and the crystal filter.  I built some test equipment and used a frequency counter to make a matched set of crystals.

BitX20 Mixer circuit
Mixer circuit

The mixer circuit is shown here with some coax to the left that is from the VFO.

BitX20 VFO
Original VFO design on the left. Filtered SI5351 clock generator on the right

You can see the benefit of building small modules.  With SMA connectors, I can quickly swap out the VFO “soul” of this rig!  No more drift with the SI5351 chip! I ordered mine from Adafruit. I added a small LC filter to the output to make a nice sine wave.  I am not sure it is needed.

BitX20 Bandpass Filter
Band Pass Filter by Pete N6QW

Now I had trouble with the original band pass filter.  I’m not sure why but a quick google search on 20m band pass filter and I found a replacement circuit on his website.  When I told Pete about this he sent me a new updated design to try.  My PTT relays are 5v so the small heatsink is for the voltage regulator.  I also included diode protection for the replays.

BitX20 Power Amplifier
Irf510 power amplifier

The IRF510 is more of a switch and not designed for linear RF amplification but it is cheap and works great for QRP.  They have different bias requirements from one unit to the next.  That is why you carefully set the bias level with a trim pot.  The large heat sink was part of an old high power LED driver that died.  I used T37-6 toroid cores for the low pass filter on the right. The 2nd relay was needed to prevent the output of the IRF510 feeding back into the original PTT switch and back into a nasty loop.

I am not sure if this rig will ever get a case or future modifications but I do know that I would like to see if I can make more contacts with it.

I would like to end this article with a quote I very much like from a video with Rev. George Dobbs, G3RJV

“Radio construction is rather like a pilgrimage where the journey is often more important than the destination”.

73,

Mike,  AB1YK

Time to Prepare for Field Day 2017

On Christmas morning, it always amazes me how the kids can rip the packaging off all their gifts in mere minutes.  The smile on their faces and their pure joy and excitement makes it all worthwhile.  What took months of planning, shopping, hiding, wrapping is over before you know it.  As they say, you get much more out of giving than receiving.

As you might imagine, there is a parallel here to field day.   Sure, you could just show up at Field Day on Saturday morning, and everything would be setup and ready to go.  However, much of the value comes from all the strategy, planning, preparation and setup activities.  Despite the large investment the club has made in towers, antennas, generator, etc., It takes a small army of volunteers to get this right.

This is my first year as field day chairman.  Truth be told, I only attended my first Nashua Area RC field day last June, and was truly impressed.  I was reluctant to volunteer last year, as I just didn’t quite know what I would be getting into.  I suspect many of you are feeling the same way this year.  Whatever the excuse; I haven’t been a ham long enough, don’t know if I can devote the time, I don’t know anything about field day, etc.  Trust me, you can and will add value to this event.  Like Uncle Sam used we say, we need you!

Now that it’s the new year, we are going to start having a regular series of meetings to plan for Field Day 2017.   The first meeting will be centered around what we learned from field day last year.  I’m looking for some early ideas about new things we can do to make field day more interesting and relevant for each of you.  Please feel free to contact me at [email protected] anytime with your ideas.

Some of the preliminary feedback I have received is tactical in nature.  It includes the following:

Current Field Day electrical distribution setup
Current Field Day electrical distribution setup
  1. The Electrical distribution system needs help. The current system consists of a Honda ES-6500 Generator with 240v distribution lines to step-down transformers at the tents.  The main distribution panel needs to be completely rebuilt and reduced in size.  Additionally, the whole setup isn’t currently weatherproof.  The existing distribution “cables” are single-conductor THHN wires taped together which certainly isn’t optimal.  Ideally, we should start with a clean sheet of paper and rebuild this properly.  Perhaps a small transfer switch so we can run two generators (so one can be serviced while still operating), with twist-lock plugs on the distribution cables and transformers, and proper SJOOW cable.  This effort alone would exceed the club budget for field day, so we could use donations of time and materials.
  2. The club owns a significant amount of coax cable. However, much of it is quite old and the connectors have seen better days.  I will look to schedule a tech night to put on new connectors and weatherproof using head-shrink with adhesive-lined backing.  We also need to make-up some short patch cables to connect to the club’s bandpass filters.  We should also label all club cable with the club call.  Finally, we need to determine the best strategy to coil up and store the coax without kinks.
  3. The iron anchor stakes for the towers need to be modified to have a sharp point at one end. Someone with a grinder could do this in relatively short order.  We could also benefit from having a large hammer drill on-site with a ground rod bit to drive them in.
  4. We need to review the hardware and storage containers used to assemble the towers. There was a recommendation to use shoulder bolts that are smooth and unthreaded through the tower to prevent crushing. Also, many of the storage containers are cracked and need replacement.  Need to inventory and rebuild these kits.
  5. We have a trailer, affectionately referred to as BOB (the Big Orange Box) at the Nashua Wastewater Treatment Center. I understand this could use some reorganization.  We need mount some brackets to the wall to get things up off the floor.  Also, we should group each of the tower kits together.

So what should you expect from me?  I will be looking to divide the work up into a series of teams and assign leads for each.  The teams will include a site readiness team, electrical, tower and antenna construction, safety, transportation, food, and potentially others. Many hands make light work, and there’s something here for everyone.

The preparation begins now.  Who said it can’t be Christmas in June?  Let the excitement begin!

Dave, K1DLM

Hashtags: #ARRLFD #N1FD

The DX Alarm Clock – Part 1: Raspberry Pi Software

I have been an Amateur Radio Operator for 5 years and my favorite thing to do is chase DX. As a new Ham, it was always a thrill to work a new DXCC, but now that I have over 280 DXCCs and over 1000 band points, it is a little more difficult to find a new one. Add to that the fact that I am trying to get a DXCC in 80m and 160m., which are usually open when I am asleep. I created the DX Alarm Clock as a way to get notified that there is something new on the air when I am not down in the shack.  This article will talk about how I developed the software for the DX Alarm Clock.  Part 2 will talk about building the Raspberry Pi-based Hardware and loading the OS.

DX Alarm Clock Architecture

The DX Alarm Clock is a Python software program running on a Raspberry Pi that gathers data online about my log and what is on the spotting network and uses that data to alert me when there is a “new one” on the air.

Ham Radio Raspberry Pi Project - DX Alarm Clock Architecture
DX Alarm Clock Architecture

The ClubLog website provides a light DX Cluster website called DXLite, which has an XML Interface. The DX Alarm Clock uses this interface to get the current spots. The software uses the Developer API from ClubLog to get a JSON matrix of all DXCC entities by band indicating whether I have worked, confirmed, or verified each band entity. The software loops through all of the spots returned by DXLite and looks each DXCC up in the JSON ClubLog matrix. I also use the QRZ.com XML Interface to get additional information for each callsign that is spotted, like the state.

User Interface

Ham Radio Raspberry Pi Project - DXCC Configuration Screen
DXCC Configuration Screen

The DX Alarm Clock uses Tkinter/TTK for the GUI.  I used the Notebook widget to create a multi-tab GUI.  There is a tab for configuring filters for DX Entity. The user can choose all New DXCCs, as well as specific bands and nodes to provide alerts for.

Ham Radio Raspberry Pi Project - WAS Configuration Screen
WAS Configuration Screen

There is another tab for configuring filters for WAS. ClubLog has no log look-up capability based on US State so the WAS filter lets you create a list of States and associated bands to provide alerts for.

Ham Radio Raspberry Pi Project - Notification Configuration Screen
Notification Configuration Screen

The Notification tab allows the configuration of what notifications the user would like to receive. The user can specify a separate email address for New DXCCs, New Band Points, and New US States. This allows alerts to be sent to email accounts or as SMS texts. You can also configure the sounds the DX Alarm Clock itself makes to “wake you up” when that ATNO or new Band Point is spotted.

DX Alarm Clock Alerting

The DXAlarm clock wakes up every 5 minutes and gets the latest spots from the DXLite Cluster. It checks each spot against the ClubLog log and if there is a match based on the configure filters, it sounds the alert, and then speaks the alarm, giving you the Callsign, DXCC Entity, Band, and Mode.   A simple text-to-speech package called flite (festival-lite) was used to implement the speech on the Raspberry Pi.

Ham Radio Raspberry Pi Project - Alert Screen
Alert Screen

It also puts a message with these details and the Frequency, UTC Date/Time, Spotter and Comment on the display.

Ham Radio Raspberry Pi Project - Text Notification to iPhone
Text Notification to iPhone

Additionally, it sends this information as an email to the configured email address, which results in a text or email.

 

Ham Radio Raspberry Pi Project - Apple Watch Alert
Apple Watch Alert

I can even get the alert on my Apple Watch.

Ham Radio Raspberry Pi Project - Filtered Spots Display
Filtered Spots Display

Once all spots are processed, it keeps a running list of all spots that resulted in alerts on the main screen. Spots are aged out if they do not recur over time.

Ham Radio Raspberry Pi Project - DX Alarm Clock Hardware
DX Alarm Clock Hardware

The DX Alarm Clock just alerted me that ZC4SB is on 20m – that’s an ATNO!  Got to go down to the shack and work him!    Stay tuned for Part 2 of this post on the DXAlarm Clock Raspberry Pi-based hardware and on setting up the Raspberry Pi OS.

Anita, AB1QB

Radio Amateurs Developing Skills Worldwide