The Mighty Little Rockmite XCVR
WRITTEN BY: DARRON SANCHEZ | PUBLISHED BY: K9YA TELEGRAPH
Volume 11, Issue 7, July 2014

 

Dad_cover Rockmite Collection
80m, 40m, 30m, 20m - These are all QRPp radios

 

Let me tell you a story about my Rockmite transceiver. I bet your story is just about the same as mine, except the ending. Originally available from Dave Benson, K1SWL, of Small Wonder Labs, Rockmite kits are now offered by Rex Harper, W1REX (http://www.qrpme.com/). The rigs are available for 80-, 40-, 30- and 20-meters.

 

MY ROCKMITE


It was a joy to receive my easy to build and hassle-free Rockmite from Small Wonder Labs. The building instructions are great and the features the completed rig offers are amazing for a low-cost radio.

 

  • RF output 1/2 watt at 12 volts

  • Automatic offset, reversible

  • Built-in Iambic keyer, 5-40wpm with a 700 Hz sidetone

  • Two frequencies from a single crystal at the touch of a button

I wonder if you did the same thing I did after building my radio, worked five or six stations at 1/2 watt and put it on the shelf; that was about six years ago. Every time I sat down to do some CW I would see the little rig sitting there. It finally got the best of me, so on 11/09/2012 I dusted it off and powered it up. Wonder of wonders, it still worked.

 

I made up my mind that the time had come to really wring this thing out and see what it was made of. On 20-meters my Rockmite has a 14.060 crystal, with a reverse sideband of 14.059.5. I started out slow, at first running 1/2 watt.

 

Using my Cushcraft three-element beam, at 60 feet and fed with Heliax(R), my confidence with the little rig skyrocketed after I worked 91 stateside stations. Wow, that’s pretty good QRPp.

 

I figured let’s drop the power and see what happens. Here’s what I achieved.

  • 300 milliwatts, four stations
  • 200 milliwatts, eight stations
  • 100 milliwatts, one station
  • 50 milliwatts, 18 stations
  • 40 milliwatts, five stations
  • 30 milliwatts, three stations
  • 20 milliwatts, two stations
  • 10 milliwatts, two stations

 

RUNNING QRPp

 

qrpp quote
With one milliwatt, an amazing story. During a QSO with Gary, N2ESE, in Stanhope, N.J., a distance of 1,160 miles from my Greenwell Springs, La. QTH, we started at 30 milliwatts. Gary asked how low could I go and I told him one mW.

 

He said try it and then stated he was copying enough to make a valid QSO. Wow, one milliwatt, made my day, month, and year. Thanks Gary. I had no idea I could make a valid QSO at one mW–the beam did all the work. How much power did the antenna radiate after feedline and SWR losses?

 

I found it takes some time to make contacts at QRPp power levels. On 20-meters, where I have made all of my contacts, what seems to work is getting on around 5 pm local time. There is always more activity on the bands when people get home from work and sit down at their rigs. If you try to time your activity around the gray line this helps a great deal.

 

You can also listen for your signals on the reverse beacon network, see which stations are receiving you, and point your beam in their direction. The time of year is also a factor; I think winter months, when QRN levels are lower, are better for QRPp.

 

I can’t wait to see what the winter months bring to improve conditions. All this helps, but time and determination are what pays off.

 

QRPp is not easy, but it can be done. A lot of hams do QRPp with attic antennas–talk about a challenge.

 

To get to QRPp power levels with my Rockmites I drop the voltage to 9V–RF output will be 3 mW, add an attenuator to the antenna line to drop power output to 1 mW.

 

I built each Rockmite breadboard style on its own finished board. This way each transceiver can be used individually. The complete setup is built to hold the WM2 wattmeter, the Rockmites, and the Bencher paddle, as seen in the photo.

 

ROCKMITES TODAY

 

When I started this project I bought all my Rockmites from Dave Benson, K1SWL, at Small Wonder Labs. Dave was always helpful and did his best to make things work for your build. He has now retired and is no longer kitting. Small Wonder Labs is shut down, but Dave stated he would keep the Web site open for a year.

 

Thanks Dave for your help and devotion to the QRP community, I hope you have a long and enjoyable retirement.

 

Rex Harper of QRP ME, W1REX, worked a deal with Dave Benson to continue selling Rockmites.

 

TROUBLESHOOTING


I was having trouble with my 20-meter Rockmite and by chance found Chuck Carpenter, W5USJ, on the QRP-L reflector.

 

I sent him an e-mail telling him of my problem with the Rockmite 20; he replied, send it to me. Chuck has a thorough understanding of Rockmites. He can fix most we mess up. However, Chuck is retired and, at his discretion, accepts only a limited number of repairs. His fix-it prices are very reasonable. Thanks for your help, Chuck.

 

After finding out that Rex Harper of QRP-Me would continue the Rockmite line, I wanted to read the write-up on his Web page. I was surprised to find that Chuck Carpenter and Rex made changes to the Rockmite and changed the one surface mount component to an easy to solder chip. It seems the SM chip was troublesome for many hams. That’s why Chuck has the know-how to fix the little transceivers; he knows them like the back of his hand.

 

I don’t know where all of this is going, but I am having a great time chasing stations with low power. It truly is a challenge and you have to stick with it. When you make the longest contact the thrill is worth the effort.

 

Now, time to work some DX.

 

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A MOMENT IN TIME

EDWIN HOWARD ARMSTRONG 1890-1954

Armstrong

 

 


He was called the most prolific and influential inventor in radio history.

 

Armstrong was responsible for inventing the Regenerative Circuit in 1912, the Superheterodine Circuit, in 1918, and the Superregenerative Circuit in 1922.

 

These circuits are the basis of all radio to this day.

 

The regenerative circuit (or regen) allows an electronic signal to be amplified many times by the same active device.

 

Regenerative Receiverone-tube Regenerative Shortwave Radio set with headphones

It consists of an amplifying vacuum tube or transistor with its output connected to its input through a feedback loop, providing positive feedback.

 

This circuit was widely used in radio receivers, called regenerative receivers, between 1915 and World War II.


Regenerative Receiver InsideRear view of the above radio,

showing the simplicity of the regenerative design

 

Armstrong was granted 42 patents that most are still in use today.

 

In 1921 a challenge was issued to the American hams, to their counter parts in the United Kingdom.


As a result of this challenge on November 27,1923 the first Transatlantic two way contact between American Amateur Fred Schnell 1MO, and French radio amateur Leon Deloy F8AB on 110 Meters 2.72 Mc was made.

 

SUPERHETRODYNE RECEIVER

 

Heterodyne Receiver

Superheterodyne receivers, built in 1920

A superheterodyne receiver (often shortened to superhet) uses frequency mixing to convert a received signal to a fixed intermediate frequency (IF) which can be more conveniently processed than the original radio carrier frequency. Virtually all modern radio receivers use the superheterodyne principle.