Tag Archives: FT8

Guest Post: QRP POTA Activation During the CQ World Wide Contest

QRP POTA Activation During the CQ World Wide Contest

by Joshua (KO4AWH)

I had an opportunity to activate Fort Yargo State Park (K-2177) during the CQ WW DX contest.

Fort Yargo is my local park, about 30 minutes away. The park features a great playground for the kids to play on and many tall trees which are perfect for deploying a wire antenna. There really is not much more I could ask for in a POTA location. Even the noise floor is very low, about S0, so I typically turn on the pre-amp which brings it up to S2-S3 on my Discovery TX-500.

This was very much a last minute plan. I knew the contest was going on which may present some difficulty activating QRP. I knew I would not be calling CQ on 20m where I normally activate and hunting stations could be difficult but likely doable.

There was a bit of rain at the house in the morning, then a promise of drizzle the rest of the day. Not too sure what I would find at the park, but hopefully the rain would hold off and I could get the activation in using the TX-500 without too much worry about it getting wet. I threw in a picnic blanket with a water barrier that promised a bit of protection from the rain if needed it.

I have a go-box setup with my TX-500 and IC-705, as well as several antennas, an ATU, and all cabling and power needed to run FT8 either on my Raspberry PI4 with the TX-500, or on my iPad through the IC-705.

I was taking my wife’s vehicle as she had the car seats needed for the 3 kiddos that were coming along. So, I had to be sure I had everything I needed. There are quite a few additional radio items I keep in the back of my car that I would not have available. But everything should be in the go-box, right?

Go-Box with two full stations, TX-500 and IC-705

After a bit of mist and some rain on the drive over, I planned to setup the TX-500 knowing it would get a bit wet. I tossed the throw line in the tree and pulled up my Tufteln EFHW QRP cut for 20m. In retrospect I probably should have pulled up the EFRW for a bit more band agility.

I tuned around for a few minutes.

Yup, there was not a single free place across 20 meters where I could start calling CQ in the clear. In fact, the stations I listened to for more than a few seconds had someone else start calling right on top of them. 20 meters was indeed crazy.

I could try to hunt some DX with my QRP signal, it would be a fight no doubt, and a nice challenge. After another DX station I tuned to had someone in the States start calling right over top of them, decided not to hunt. Continue reading Guest Post: QRP POTA Activation During the CQ World Wide Contest

How Joe keeps his Icom IC-705 cool during long FT8 sessions

Many thanks to Joe (KD2QBK) who writes:

Hi Thomas:

I’ve recently discovered QRP FT8, which I’ve been working with my Icom IC-705. I run with an end-fed sloper that runs out of my 2nd floor shack window using a 49:1 unun and a length of RG-58. I’m also using an Emtech ZM-2 tuner between the antenna and the radio when needed.

The set up works really nicely, except for the way FT8 heats up and overtaxes the radio after a while. Searching around a bit, I’ve found just the right solution for that issue. The AC Infinity MULTIFAN S1 USB-powered table fan.

https://amzn.to/3DvqemJ (affiliate link)

It’s basically just a 3-inch square fan like you’d find in a computer or some other electronic devices, with rubber “feet” attached. It can stand upright or lay flat depending on your need. it’s stated purpose is to cool or ventilate routers, game consoles, audio equipment, etc.

The AC Infinity MULTIFAN S1 includes a speed control switch and an inline USB socket to daisy-chain other devices. One caveat with the inline socket: because it’s placed in the line between the fan and the speed control switch, the switch must be set to high speed else the socket won’t have adequate power for the attached device.

All I do is plug the fan into a USB socket and place it at the rear of the radio, sans battery, to keep it cool. I have it set up to blow onto the radio. Obviously I need to power the radio with an external source when the battery isn’t attached. I’ve not tried to use the fan with the battery attached, but I don’t think it would help much. The ventilation slots next to the battery compartment don’t seem wide enough to let much air in. Continue reading How Joe keeps his Icom IC-705 cool during long FT8 sessions

FT8 Portable: Steve takes his Phaser Digital Mode Transceiver to the field!

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

FT8 QRP Portable

I recently finished my Phaser digital mode QRP transceiver kit and have had a hankerin’ to take it portable, and today was the day.

Temps were in the upper 60s with clear blue sky. About fifteen minutes from home is the Watauga Point Recreation Area on Watauga Lake in Carter County, Tennessee. It’s a day use area and is not an official POTA site, though it is in the Cherokee National Forest, which is. I opted to not make this a POTA activation as it was more of a first time “proof of concept” trip.

The Phaser is a small digital mode transceiver designed by Dave Benson, K1SWL with the enclosure the design of AA0ZZ, Craig Johnson. Phasers were available for most all of the HF bands, put out between 3 to 5 watts, and in addition to FT8, have the ability to program a second frequency to operation other digital modes such as PSK-31. They were sold and supported through Midnight Design Solutions, but unfortunately are no longer being offered. Occasionally I see them coming up for sale on the QRZ.com swapmeet forum.

In addition to the Phaser, I brought an FT-891, an LDG Z-11Pro 2 tuner, a netbook computer, and two batteries; a small AGM for the Phaser and a deep cycle lead acid power pack for the FT-891. I brought my W2LI magnetic loop antenna and a homebrew “NorCal Doublet” that sets up as an inverted V on a 20 ft kite pole as a backup antenna. The whole kit (excluding the batteries) fits in two wooden ammunition crates which make it really easy to drive, set up, and operate.

One note on using the W2LI mag loop. You need to first tune the antenna using the radio and listen for an increase in the background noise level. Using the Phaser while connected to my computer made that not possible. If I had brought a small set of earphones I could have plugged them into the audio out jack on the Phaser and tuned for max background noise. So, instead I connected FT-891 to the loop and used it to tune the antenna to 30 meters. Next time bring earphones.

After about fifteen minutes I had the station set up. The waterfall on WJST-X showed that the Phaser was receiving transmissions but no displayed text. Unfortunately I had neglected to synchronize the computer clock before I left the house. The netbook is pretty old and the internal battery needs to be replaced. What to do? First I tried to manually sync the clock to WWV but Windows 10 won’t let you set the seconds in the clock to 00. As I had cell service I figured I could use my cell phone as a hotspot. Never having set it up before I have to say that it was pretty easy. Thank you 21st century tech! This allowed me to sync the internal netbook clock, but it also let me log contacts on QRZ.com, and check my propagation on PSK Reporter.

The Phaser puts out around 3.5 watts, so I didn’t respond to a CQ that was less than -5 dB. While PSK Reporter showed reception of my signal up and down the East coast, contacts were scarce. I seemed to have a window open up into New England as I worked PA, MA, and CT. I was right in the middle of my fifth contact when the computer battery died so that was it. WSJT-X reported these stations on the +dB side for reception but my signal strength was always reported at < -10 dB.

The 30 Meter band was up and down with band conditions being reported as only Fair on the Solar-Terrestrial Data report on QRZ, and at one point for about a half hour there were no signals displayed on the waterfall.

With a loop antenna on a tripod and 3.5 watts I can’t complain. I’m thinking of building an RF amplifier to boost the output up to 10 watts which should help. My next step is to load WSJT-X on my tablet and see how portable of a kit I can assemble. As FT8 was designed as a weak signal mode, it’s perfect for QRP portable operating.

Steve Allen, KZ4TN

FT8 transceiver kit: CR Kits taking orders

The CR Kits DSB Transceiver prototype (Source: CR Kits)

Many thanks to Pete (WB9FLW) who writes:

Adam of CR Kits is now taking orders for his FT8 Transceiver Kit and the price is very reasonable.

From Adam at CR Kits:

FT8 transceiver kit

I start to take email order now. The introductory price is 39 USD for kit including shipping to worldwide. As in the introductory period, you will get audio cable options for free. The earliest possible shipment date is now improved to May 13.

You can directly PayPal to [email protected] and let me know 40m or 20m (80m not ready yet). I will ship based on the sequence of receiving your payment. I may delay shipment for one week or two due to workload.

This is the spec so far:

Summary: Crystal controlled single frequency DSB transceiver for 20m (14.074MHz), 40m (7.074MHz) or 80m (3.573MHz), other frequencies could be added per requestPower supply: 10-14V DC regulated power supply or battery pack, 12V is recommended, center positive, reverse polarity protection availableCurrent consumption in RX: about 15mA at 12VCurrent consumption in TX: about 300mA at 12VRF output: about 1W for 40m band at 12V, and a bit less for 20m bandSpurious suppression: no worse than -50dBcAntenna connector: BNC connector, 50 ohmAudio in connector: 3.5mm mono, at least 600mV to activate VOX, connects to headphone connector at PC sound card, no dedicated PTT connector is requiredAudio out connector: 3.5mm mono, connects to microphone connector at PC sound cardAmber LED: TX statusGreen LED: RX statusFrequency accuracy: -600 Hz ~ + 200 HzFrequency stability: Okay for FT8 mode per test. If the optional heater resistor R20* is added, after warm up, long term frequency stability in 10 min will be improved at the cost of acceptable short term frequency stability sacrifice in 30 sec.
Thanks, Adam

Click here to check out the FT8 DSB Transceiver via CR Kits.

The CR Kits FT8 DSB Transceiver: Some preliminary information

Many thanks to Pete (WB9FLW) who notes:

Adam BD6CR of CR Kits is getting close to releasing the FT8 DSB Transceiver. Below is some preliminary information:

D4D: A simple QRP transceiver for FT8

Adam Rong, BD6CR

D4D stands for DSB transceiver for Digital modes. It is a Double Sided Band transceiver kit designed for digital modes, especially for FT8. If have chance to try FT8, you will be amazed by the strong decoding capability offered by the communication protocol, digital signal processing and software. I still remember clearly a YouTube video by W6LG who communicated with bulbs. I started to think how much the transceiver could be simplified if you have a moderate antenna like a full sized dipole or EFHW.

A DSB transceiver is much simpler than a usual SSB transceiver, however it was never used for FT8 as far as I know. I did some experiments on my Choc perf board. I started with a direct conversion receiver for FT8 and it worked okay. Then I made a DSB transmitter and the transmitted signal can be decoded. By referring to the designs of AA7EE, VK3YE and ZL2BMI, I combined them using only one NE602 and a PTT switch and it gave me success to make a few FT8 QSO’s.

Personally I really enjoyed it because a manual PTT switch will save power consumption and circuit complexity, but you will need to well sync with computer, although it was not really a problem for me. Per request from a few hams, I found a VOX control circuit and modify the hold time to be compatible with FT8, and I put them together and made a few improvements on the signal purity and frequency stability, and it became our D4D. Do we have to worry about the unwanted Lower Side Band? Maybe, but for a transmitter of 1-watt, it is not really a big problem. Is it just a toy for a transmitter of 1-watt and only half of the power will be effective? Not really, as I can easily make a few QSO’s as far as 1500 miles range for 40-meter band.

Here is the brief specifications I have measured (subject to change without notice):

Summary: Crystal controlled single frequency DSB transceiver for 20m (14.074MHz), 40m (7.074MHz) or 80m (3.573MHz), other frequencies could be added per request
Power supply: 10-14V DC regulated power supply or battery pack, 12V is recommended, center positive, reverse polarity protection available
Current consumption in RX: 15mA
Current consumption in TX: about 260mA(?) at 12V, and about 300mA at 13.8V
RF output: about 1W for 20m band at 12V, a bit more for lower bands like 40m and 80m
Spurious suppression: no worse than -50dBc
Antenna connector: BNC connector, 50 ohm
Audio in connector: 3.5mm mono, at least 600mV to activate VOX, connects to headphone connector at PC sound card, no dedicated PTT connector is required
Audio out connector: 3.5mm mono, connects to microphone connector at PC sound card
Amber LED: TX status
Green LED: RX status
Frequency stability: Okay for FT8 mode per test. If the optional heater resistor R20* is added, after warm up of about 3 min, long term frequency stability in 10 min will be improved at the cost of acceptable short term frequency stability sacrifice in 30 sec.

Let us briefly go through the circuit: The input audio will activate the VOX circuit of D2 (1N4148), Q5 (2N3906), Q6 (2N3904), Q7 (2N3904) and Relay. The relay is a DPDT type and controls both antenna and power supply. The LPF consists of L2, L3 and surrounding capacitors, and it is switched to either transmitter output or receiver input. The power supply is polarity protected by D1 (1N5817) and switched to either receiver circuit or transmitter circuit. The receiver circuit is only for audio amplifier consists of Q1 (2N3904) and optional heater resistor R20*, while the transmitter circuit is for RX muter Q8 (2N3904), TX driver Q3 (2N3904) and TX final Q4 (BD139). X1 is a filter in the receiver front end to help eliminate strong broadcast interference, and X2 is the crystal for the built-in oscillator in U1 (NE602). U2 (78L05) is the 5V regulator for U1, and Q2 (2N3904) is a buffer amplifier in the TX chain.

Thanks for sharing this, Pete! What a simple transceiver concept!

We’ll post updates as they become available.

Click here to view CRkits.com.

New digital mode: Joe Taylor (K1JT) has announced FT4

(Source: Southgate ARC)

Joe Taylor K1JT has announced a new digital mode, FT4, which is 2.5 times faster than FT8 

FT4 is an experimental digital mode designed specifically for radio contesting.  Like FT8, it uses fixed-length transmissions, structured messages with formats optimized for minimal QSOs, and strong forward error correction.  T/R sequences are 6 seconds long, so FT4 is 2.5 × faster than FT8 and about the same speed as RTTY for radio contesting.  

FT4 can work with signals 10 dB weaker than needed for RTTY, while using much less bandwidth.

FT4 message formats are the same as those in FT8 and encoded with the same (174,91) low-density parity check code.  Transmissions last for 4.48 s, compared to 12.64 s for FT8.  Modulation uses 4-tone frequency-shift keying at approximately 23.4 baud, with tones separated by the baud rate.  The occupied  bandwidth (that containing 99% of transmitted power) is 90 Hz

Further information on FT4 is at  

A Simple and Low Cost FT8 Transceiver

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.

Click to enlarge.

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!

FT8 growing in popularity, fueled by poor propagation

(Source: Southgate ARC)

ARRL report on a survey by Club Log’s Michael Wells G7VJR that shows significant growth in the use of WSJT FT8 during 2018 

Wells reported that operators from some 270 DXCC entities were active on FT8 in 2018. “It’s quite a showing for FT8,” he allowed, pointing out that the figure is close to the computed 287 active DXCC entities.

Wells posits that FT8 may be the only way to stay in the hobby for operators living on small lots and confronting stringent zoning regulations.

Read the ARRL story at 

Proportion of modes used on the air – 2018 update G7VJR