Skip to main content

June 21, 2024. Happy Summer.

Summer brings all sorts of wonderful opportunities. Some involve ham radio and some focus on the food consumed in the summer months. Things like watermelon and corn on the cobb or the tons of burnt burgers cooked on a charcoal grill. 

This definitely would not get Mary Jo into the back seat of the 57VW Bug!

I mention foodie stuff because non-contest ham radio this weekend will be a bust with Field Day. So, if you just want some friendly QSO's forget it until next Monday.

This might be a good time, if not participating in Field Day to think about station accessories. I am often surprised that many stations do not have an in line SWR bridge. If you were smart enough to ditch EMRFD and acquire SSDRA, you can find some nice designs for homebrewing a SWR bridge. 

For those who do not fear the Arduino you can do some code modification to include a Tune Up functionality built into the code. Typically, all of the code I develop has a Tune capability.

So why would you need a Tune function in your homebrew rig? One of the primary reasons is to provide a bit of RF to the antenna to assure you have the lowest SWR. Another is to determine if the rig is operating properly. Still another reason is that you are one of the cool guys who has this capability.

[For those forever welded to the Bitx design, I have always been surprised that a Tune Tone was not in the original design. In a Bitx40 I modified so that it does both LSB and USB (for FT-8), it also has the Tune Function.]

The theory of operation is simple. The Arduino is capable of generating tones using the Tone library. One of those tones is 988 Hz. So, firstly we generate a tone at that frequency, and next we set the code so that it is on for a certain time period and the off for a certain time period. 

We ask the code to do this for so many cycles using a loop counter. We now have essentially created a pulse train of so many cycles, typically about 10 seconds. This pulse train is then introduced into the microphone circuit. Unless you add some isolation, you unplug the microphone and use the MOX switch as you don't want to back feed audio tones into the microphone. 

Now a bit of a sewer backup. The Arduino output is like a square wave, so we need to set its level (trim pot for just a few watts) and add an RC Filter to turn those square waves into a sinewave. I think there might be some issues with harmonics of the generated sound wave if they are left as pure square waves.

Essentially an engagement of a momentary push button starts the tune sequence. Now in several of my rigs this also trips the PTT switch while in others I simply engage a MOX (manual switching of PTT in addition to the PTT on the microphone) and then hit the Tune button. The MOX approach also offers a way to have the transmitter on without having to use the Mic like for troubleshooting.

Once the 10 second sequence is over the rig goes back to receive. Now to be totally Kosher you need to station identify your station once the test is complete. OR as I did in a couple of rigs simply extended the code after the 10 seconds to send my call in CW. This also opens up the possibility of an automated station identifier as in a CW beacon.

OK wasted enough of your time so I will end this. If you want the code snippet for a Tune Tone, email me at my QRZ.com email address.

Happy Summer and Happy Burger cooking.

73's
Pete N6QW

Popular posts from this blog

January 26, 2024. A simple CW Transceiver/Transmitter

Cruise through the lower part of the ham bands bands and what do you hear? Well, FT-8 and CW. Often you will not hear any SSB stations yet go to the lower part of the bands, and it is a cacophony (I love that word) of bad sounding signals and some high-speed keying. Fast is not so much of the issue as is bad, run together and jerky keying. But none the less our hobby started there.    So, you could crank down your ICOM 7300 and watch the waterfall on CW or you could homebrew a radio. Actually, to do CW right you need more thought up front than you do with a SSB transceiver. Often, I will state that a CW Transceiver is much more difficult to build than a simple SSB rig. I published two articles in QRP Quarterly on CW transceivers and all I got was a yawn so maybe history will repeat itself.  Yawn!   30M CW Transceiver with RIT!   Of interest is that the LO is a Varactor tuned LC oscillator using a NE602. Look closely at the RIT circuit which is only activated on ...
Read more

August 30, 2024. A PNP 20M SSB Transceiver

Shown below is the Block Diagram for the 20M PNP SSB Transceiver steered in the  Transmit Mode . The components shown in the dotted block are relay steered so that the block module is single pass and amplifies in a single direction. The Block diagram show steered in Transmit.  Essentially the steering process works so that the IF Module input follows the Balanced Modulator on Transmit and then the input side follows the Receive Mixer on Receive. All done with some relays and a bit of RG174U coax. For those who count things in detail, this block diagram is not unlike what was used for the PSSST Transceiver which can be found on my website . Yes, a warmed over P3ST only using PNP devices. TYGNYBNT. 73's Pete N6QW
Read more

March 31, 2024. Happy Easter to those who celebrate this day.

What a great day to Binge on Chocolate and experience the pain of that filling that has been leaking.  I would be in that category with the leaking filling(s) had I not just spent an amount equivalent to one of the fancy new uptown appliance box transceivers on two filling repairs. Well at least I can binge on the Chocolate bunnies without fear of pain. Regrettably everything appears to have jumped in price including the price of parts. Well not so much the parts as the shipping costs.  That notably is seen in the eBay treasures. I spotted a nice heathkit DX-20 for about $50 and the shipping was $65. Likely it is a twofer with part being a way to in effect charge a higher price by inflating the shipping and in part by increased shipping costs. Shipping with insurance across the US was about $150 for this jewel and that was three years ago. 6AM on the Left Coast ~ 20M Easter Sunday! My only hope is the cost of Chocolate Bunnies remains steady although a pound of See's Candies f...
Read more