Category Archives: Homebrew

Curt builds an Icom IC-705 control interface for his Elecraft T1 ATU

November 26, 2020 Thomas Witherspoon 12 Comments

Many thanks to Curt (WU3U) who recently contacted me and mentioned he had built an IC-705 control interface for his Elecraft T1 ATU. This is a homebrew project based on others’ work and uses the FT-817 control port on the side of the T1 tuner.

I asked Curt if he could share a little more about his tuner to post here on QRPer:

Hi Thomas, I can’t take credit for the interface, as a guy in Japan designed it. When I built mine the entire instructions and notes for code for the PIC controller were in Japanese. I used Google translate to translate all of the information and I was able to successfully program the PIC chip and build the circuit. He has since released the details and code in English.

There are two designs: one with an on/off switch, and a newer version without an on/off switch that has auto power save. Both circuits are the same but the software for the PIC chip is different. If you build the one without the on/off switch there is a very specific sequence of connecting and disconnecting the device and it’s my opinion that the one with the on/off switch is the version that makes more sense to build. It shouldn’t matter which order you connect everything up and you simply throw the on/off switch to turn the device on and off.

Building the interface takes an understanding of a fairly simple electronic schematic and acquiring the parts. You also have to have a PIC programmer and the software to write his .hex file into the PIC controller chip.

The parts for the interface are all very common parts. The resistors are standard values. My build cost me about $30 in parts but I had to buy many of them in bulk from Amazon like the enclosures, switches and 3.5mm jacks and circuit boards to name a few. Individually the parts were $30 but my bulk order cost me much more. I also had to buy a PIC programmer for $25 and figure out what software I needed to download to program the PIC chip with the author’s code. It takes an experienced builder about two hours to build the device but it’s not out of the realm of a semi-novice as long as they can get the PIC chip programmed.

Here is the original code using the on/off switch. Everything is now in English:
https://amateur-radio.cocolog-nifty.com/blog/2020/11/post-1eb3cf.html

Here is his newer version with the same circuit design eliminating the on/off switch by using a different PIC program allowing the interface to have auto power shutdown (low power standby) but there is a specific order for connecting and disconnecting the interface. With this version there is still drain on the battery but the designer thinks that drain is less than the normal self discharge of the battery. I feel that any discharge combined with the self discharge of the battery will be more discharge than using the design with the on/off switch.
https://amateur-radio.cocolog-nifty.com/blog/2020/11/post-591d17.html

Video

I think this is a brilliant project and certainly one worth considering for those of us who already own an Elecraft T1 ATU and would like full control from the IC-705.

Thank you for sharing these details, Curt!

Homebrew, Kits, News, QRP

Guest Post: Steve builds a DC30B QRP Transceiver

October 13, 2020 Thomas Witherspoon 1 Comment

Many thanks to Steve (KZ4TN) who shares the following guest post:

DC30B QRP Transceiver Project

by Steve Allen, KZ4TN

I wanted to build a lightweight backpackable transceiver I could take hiking and camping. I chose the 30 meter band as it is specific to CW and the digital modes. I am also in the process of building Dave Benson’s (K1SWL) Phaser Digital Mode QRP Transceiver kit for the 30 meter band. Also, a 30 meter antenna is a bit smaller than one for 40 meters and the band is open most anytime of the day.

I sourced the DC30B transceiver kit, designed by Steve Weber KD1JV, from Pacific Antennas, http://www.qrpkits.com. It appears that they are now (10-11-20) only offering the kit for the 40 meter band. The following information can be used for the assembly of most any kit that lacks an enclosure.

Lately I have been finding extruded aluminum enclosures on Amazon.com and eBay.com. They come in many sizes and configurations. I like to use the versions with the split case which allows you to access the internal enclosure with the front and rear panels attached to the lower half of the enclosure. Most of these enclosures have a slot cut into the sides that allow a PCB to slide into the slots keeping it above the bottom of the enclosure without having to use standoffs. The one requirement for assembly is that the PCB needs to be attached to either the front or rear panel to hold it in place.

As the enclosure is anodized, I didn’t want to rely on the enclosure for common ground. I used a piece of copper clad board that I cut to fit the slot width of the enclosure and attached it to the back panel. I was then able to mount the transceiver PCB to the copper clad board with standoffs. This basic platform of the enclosure with the copper clad PCB provides a good foundation for any number of projects. All you have to do is mount the wired PCB on the board, install the components on the front and rear panel, then wire it up.

I wanted to have the choice of a few frequencies to operate on so I searched eBay for 30 meter crystals and found a source for 4 different popular frequencies. I installed a rotary switch on the front panel and added a small auxiliary PCB with two, 4 pin machined IC sockets. This allowed me to plug the crystals into the sockets. I wired the bottom of the socket PCB first using wire pairs stripped from computer ribbon cable leaving extra length. I marked the wires with dots to indicate which sockets each wire pair went to so I could solder them onto the rotary switch in the correct order. It was tight but I always work with optical magnification so I can see exactly what I’m doing. I have used this crystal switching method in the past with good success.

The rest of the assembly was straight forward. I find that most kits are well designed and documented, and if you take your time and follow the directions carefully all should go well. The two most common speed bumps seem to be soldering in the wrong component or bad soldering technique. I double check all component values and placements prior to soldering, and I always use optical magnification while working. I inspect each solder joint and look for good flow through in the plated through holes, and make sure there are no solder bridges.

The finished product. I bought a Dymo label maker and it works very well for projects like this. I love using these enclosures and they are a leap forward from the old folded aluminum clam shells I used in the past. I could stand on this without causing any damage. Power out is 1-3 watts depending on the DC power in. The receiver is sensitive and the ability to choose from four frequencies is a real plus.

73 de KZ4TN

Steve Allen
Elizabethton, TN

Wow, Steve! What a top-shelf job on this build! I’ll have to look for those aluminum enclosures as well. Beautiful little rig you’ve made there and I think it’s fantastic you’ve a few crystal frequency options! Thank you for sharing!

Homebrew, Morse Code, News

Alex builds a simple sideswiper

October 5, 2020 Thomas Witherspoon 1 Comment

Many thanks to Alex (W3AVP) who shares this photos of his homemade cootie/sideswiper originally posted on the POTA Faxcebook page. Alex notes:

I didn’t want to lug my Begali key to the parks so I made my own using the plans from KA8VIT. Worked great! I had a little QRP key but my fat fingers would make so many mistakes. The DIY aspect of this hobby is extremely entertaining!

And I bet your “cootie” serves you well in the field! I love the simple design and the fact it even has an adjustable action. At the end of the day, keys are merely switches so are perfect for homebrewing!

If you have a sideswiper/cootie or any other key you’ve built and would like to share it here on QRPer, contact me (K4SWL at QRPer.com).

Thanks for sharing, Alex!

FT8, Homebrew, News, Software Defined Radio

The Hermes-Lite SDR: an open source QRP transceiver based on a broadband modem chip

May 16, 2019 k4swl Leave a comment

Note: This is a cross-post from the SWLing Post.

Many thanks to Pete (WB9FLW), who shares the following:

Don’t know if you are familiar with this project, a full blown 5 watt HF SDR Transceiver for less than $300!
No sound cards, DUC/DDC architecture.

Here’s the project description by Steve Haynal via YouTube:

The Hermes-Lite is a low-cost direct down/up conversion software defined amateur radio HF transceiver based on a broadband modem chip and the Hermes SDR project. It is entirely open source and open hardware, including the tools used for design and fabrication files. Over 100 Hermes-Lite 2.0 units have been successfully built.
The FOSSi Foundation is proud to announce Latch-Up, a conference dedicated to free and open source silicon to be held over the weekend of May 4th and 5th in Portland, Oregon, USA. Latch-Up: a weekend of presentations and networking for the open source digital design community, much like its European sister conference ORConf. Produced by NDV.

Click here to view this presentation on YouTube.

Fascinating! Thank you for sharing, Pete!

Homebrew, Kits, News, QRP

How To Convert QRP Labs QCX Transceiver to SSB

May 9, 2019 k4swl 3 Comments

Many thanks to Pete (WB9FLW) who shares the following:

This is truly amazing, Guino PE1NNZ has converted the QRP Labs $49 CW Transceiver to SSB.

Not much to add, a ATMEGA328P plus some firmware and a few component value changes and you’ve got a $50 SSB Transceiver!

(Source: GitHub)

This is a simple and experimental modification that transforms a QCX into a (Class-E driven) SSB transceiver. It can be used to make QRP SSB contacts, or (in combination with a PC) used for the digital modes such as FT8. It can be fully-continuous tuned through bands 160m-10m in the LSB/USB-modes with a 2400Hz bandwidth has up to 5W PEP SSB output and features a software-based full Break-In VOX for fast RX/TX switching in voice and digital operations.

The SSB transmit-stage is implemented completely in a digital and software-based manner: at the heart the ATMEGA328P is sampling the input-audio and reconstructing a SSB-signal by controlling the SI5351 PLL phase (through tiny frequency changes over 800kbit/s I2C) and controlling the PA Power (through PWM on the key-shaping circuit). In this way a highly power-efficient class-E driven SSB-signal can be realized; a PWM driven class-E design keeps the SSB transceiver simple, tiny, cool, power-efficient and low-cost (ie. no need for power-inefficient and complex linear amplifier with bulky heat-sink as often is seen in SSB transceivers).

An Open Source Arduino sketch is used as the basis for the firmware, the hardware modification bypasses the QCX CW filter and adds a microphone input in-place of the DVM-circuit; the mod is easy to apply and consist of four wire and four component changes and after applying the transceiver remains compatible with the original QCX (CW) firmware.

This experiment is created to try out what can be done with minimal hardware; a simple ATMEGA processor, a QCX and a software-based SSB processing approach. It would be nice to add more features to the sketch, and try out if the QCX design can be further simplified e.g. by implementing parts of the receiver stage in software. Feel free to experiment with this sketch, let me know your thoughts or contribute here: https://github.com/threeme3/QCX-SSB There is a forum discussion on the topic here: QRPLabs Forum
Click here for full project details via GitHub.

73, Guido pe1nnz@amsat.org

Wow! What a brilliant modification, Pete! Thank you for sharing.

Homebrew, News, Product Announcements, SOTA

New Product: Kev-Flex Stealth Kevlar Antenna Wire

April 4, 2019 k4swl Leave a comment

My good friend David Cripe (NMOS) has recently informed me about a new product he’s offering to the radio community via his eBay store: Kev-Flex Stealth Kevlar Antenna Wire. Kev-Flex looks like a superb option for field antennas of all stripes especially since it has an incredibly high tensile strength. It’s available in 75′ bundles, but Dave can also cut custom lengths. NM0S is also a trusted retailer in the ham radio world, so you can purchase with confidence.

Here’s the product description and link:

Kev-Flex is a unique antenna wire manufactured exclusively for NM0S Electronics. The lightweight center core of the wire is made from Kevlar fiber, giving the wire its incredible strength. The Kevlar core is wrapped with six tinned strands of 30 AWG copper. The effective surface of the wire creates an effective skin area capable of handling well over 100W.

The cable is protected from the elements by a coating of UV-resistant black polyethylene. With a total diameter of only 1/16″ (incl. insulation) and a weight of just 16 feet per ounce, the tensile strength 125 lbs allows lengthy unsupported horizontal runs. Kev-Flex is ideal for extremely long LW-antennas and Beverages and is great for balloon or kite-supported antennas. Its low weight and high break-load makes it most suitable for SOTA activations and other field operations.

The outer insulation makes the wire kink-resistant, and its slippery finish makes it ideal for stealth antennas that must be passed through trees or other obstacles without snagging.

This antenna wire is sold in 75 foot long bundles, which is enough for a 40M dipole or EFHW. Two 75 foot bundles would make a great 80M dipole. Custom lengths are available on request.

Specification

– Kevlar fiber core wrapped with six 30 AWG copper strands
– Weather-proof black polyethylene (PE) insulation, 1/16″ O.D.
– Weight: 16 feet per ounce
– Breaking-load: 125 lbs
– Velocity factor 0.97

Click here to view on eBay.

FT8, Homebrew, News

A Simple and Low Cost FT8 Transceiver

March 24, 2019 k4swl 5 Comments

Many thanks to Pete (WB9FLW) who writes:

Adam Rong BD6CR has designed a simple DSB Transceiver for FT8. Crystals are available for 7.074 MHz. and 14.070 MHz (which can be “pulled” with a trimmer to 14.074 MHz).

Using only 4 Transistors, 2 IC’s, 3 Toroids, 5 Diodes/LED’s and a handful of resistors and capacitors this one watt wonder will get you on the air in no time.

One could build this on Perfboard (see above), or use Ugly/Manhattan style construction. There are no plans for a circuit board.

Adam posted this on groups.io crkit:

“I built this 7074 DSB 1-watt radio and made 6 FT8 QSO with JA stations in 15 mins last weekend. It is fun to operate by switching PTT manually to keep it simple and lower current consumption.”

For more info check out crkits groups.io.

Wow! Thank you for sharing this Pete. I’ll have to give this a go myself!

Homebrew, News

Bill’s 1 Watt Wood Box QRP Beacon

August 20, 2018 k4swl Leave a comment

Many thanks to Bill (AA0RQ) who writes:

I’m running an attended beacon on 7041.8 kHz–the ID is VVV de AA0RQ/B AA0RQ/B AA0RQ/B 1 watt…

Often after running the beacon I plug the beacon crystal into the little 6L6 single tube transmitter.

Been having a number of QSOs with the bread boarded radio…

Below is the 40 meter 6L6 transmitter:

Thanks for sharing, Bill–I love the wooden box enclosure as it reminds me of early 1900s wooden box homebrew radios.

We’ll be listening for you on 7041.8 kHz!

Homebrew, News

micro-BITX: a homebrew general coverage SSB/CW QRP transceiver

March 16, 2017 k4swl 6 Comments

Many thanks to Pete (WB9FLW) who shares the following:

Farhan VU2ESE Does It Again!

http://www.phonestack.com/farhan/ubitx/ubitx.html

A compact 10 watts, easy to build, general coverage SSB/CW transceiver for HF bands

Homebrewers have traditionally avoided making multiband transceivers as they can get extremely complex and difficult to make. There have been some remarkable successes in the past, the CDG2000 (designed by Colin Horrabin G3SBI, Dave Roberts G8KBB and George Fare G3OGQ)is one such design. The SDR route as followed by several designs offer some simplification at the cost of bringing digital signal processing and a PC into the signal path.

On the other hand, many of the homebrewers do need a general coverage transceiver on the bench as well as as a base transceiver for bands beyond the HF. I ended up buying an FT-817ND that has been a reliable old warhorse for years. Two years ago, I attempted a high performance, multi-band architecture with the Minima transceiver. The KISS mixer of the Minima, though a very respectable receiver front-end, had serious leakage of the local oscillator that led that design to be abandoned as a full transceiver. Over months, I have realized that the need for a general coverage HF transceiver was wide-spread among the homebrewers. Most of us end up buying one.

While achieving a competition grade performance from a multiband homebrew is a complex task as evidenced by the works like that of HBR2000 by VE7CA, it is not at all difficult to achieve a more modest design goal with far lesser complexity. The uBITX shoots to fulfill such a need. It is a compact, single board design that covers the entire HF range with a few minor trade-offs. This rig has been in regular use on forty and twenty meters for a few months at VU2ESE. It satisfies for regular work, a few trips to the field as well.

A key challenge for multiband transceivers has been to realize a local oscillator system with such wide range. Silicon Labs has now produced a series of well performing oscillators that solve this challenge trivially : You connect the oscillator chip over a pair of I2C lines and it is done. The Si5351a is one such a part that provides 3 programmable oscillator outputs in a small 10 pin TSSOP package. We will exploit this chip to build the multiband transceiver.

Having exclusively used homebrew transceivers all the time, I get very confused whenever I need to use a commercial radio. There are too many switches, modes and knobs to twirl around. The uBITX use an Arduino to simplify the front panel while retaining all the functionality in a simple menu system that works with the tuning knob and a single â€˜function’ button. The rig supports two VFOs, RIT, calibration, CW semi break-in, meter indicator, etc. In future, more software can be added to implement keyer, SWR display, etc.

Click here to read the full description of this project and download diagrams/schematics!

This is brilliant! Thank you for sharing, Pete!