Saturday, March 19, 2011

Der Nauen Crosses the Pond

I'm pleased to report that a pair of passive, Epstein-Joly-Arco (EJA) frequency-doublers are currently producing an output power of 100mW on the 20m CW band. The saturable reactors for these multipliers employ four, 1960's-era, magnetic computer memory core ferrite toroids.

The excitation for these multipliers is presently provided by a BUL128 bipolar transistor that I once salvaged from a compact fluorescent lamp. Some of you may recall my use of this transistor in my Das DereLicht transmitter and receiver projects. While this low-gain, high-voltage/current transistor was never intended for use at RF, I found that it worked reasonably well at frequencies below 4MHz. At 7MHz and above, the working efficiency of this transistor is impractically low. In fact, that's the reason I chose to use it in the transmitter of this 20m radio. 

An oscillator drives a power amplifier made from a BUL128 transistor to produce an output of 1.0 watt at 3.5MHz. This energy is delivered to a tandem pair of EJA frequency-doublers. The first doubler produces 360mW of RF output at 7MHz. The second doubler delivers 100mW at 14MHz. The total passive frequency-multiplier conversion loss is 10dB.

Last week I paired this 20m transmitter with a straight, two-transistor regenerative receiver to form a rig that I've named, Nauen.

My first contact with the Nauen came on Tuesday evening, when W3HZZ answered my CQ from Atlanta, Georgia. When I went up to the house later in the evening I found that receivers in the Reverse Beacon Network had captured a good many of my calls. The most distant receiver that heard me was PJ2T's station in Curacao!

The DX propagation was considerably worse the next day. However, on Thursday evening I was pleasantly surprised to hear G3NWR reply to my CQ on 14.059kHz. The conditions were such that we only managed to exchange signal reports, nevertheless, my little Nauen prototype had crossed the pond! 

G3NWR is the call sign for the Wirral Amateur Radio Society club station. MØATZ was at the key for our QSO. Colin later wrote

"Your RST was indeed a 559 – it was a lovely signal and I was surprised to hear the /QRPp at the end of your call as it was moving the meter quite well this end! 

Later, when I checked the Reverse Beacon Network, I noticed that both a half-hour before, and twenty minutes after my UK contact, the receiver at OL5Q in the Czech Republic had picked up my calls.

These photos of my prototype transmitter were taken shortly after my QSO with G3NWR.The second photo is a close-up view of the tandem EJA frequency-doublers.

W4OP and NØUR both kindly made an audio recording of my 100mW signal. Please click here to listen to my signal as received by NØUR at a distance of 1642km.
Nauen Log 

W3HZZ       559/569      Atlanta, GA        1520km     5w to G3RV
W4OP         589/579      Glenville, NC      1329km    12w to Optibeam
W7CNL      549/549      Boise, ID            3445km     90w to 5el Yagi
K9FO         549/539      Momence, IL      1266km     AT Sprint at 5w
W6EOD      459/559     Swansboro, NC   1106km    Elecraft KX1 at 2w
W4OP         599/589     Glenville, NC       1329km    200w to Optibeam
N4HS          569/589     Lanet, AL            1649km    2w to 3el Yagi
N4HS          559/559     Lanet, AL            1649km    2w to 3el Yagi
G3NWR      559/559     Wirral, UK           5005km   80w to 3el Yagi
KØIIS          569/?         Davenport, IA       1478km
NØUR         559/559     Ellendale, MN        1642km    2w to 3el Yagi
W3HZZ      559/549     Atlanta, GA           1520km    10w to G5RV
KO1U/M    569/449     Abbeville, SC         1381km     50w mobile
NU8S         569/449     Loveland, OH        1097km    5w to Yagi
WA9ETW  559/319     Monticello, WI      1362km     ATS-3 @ 3w
WA9BXB  599/339     Brookfield, IL        1253km     500w to Yagi
N1KW      569/549     Homer Glen, IL       1270km    DX60 & invee
N1ZX        569/599    Stuart, FL               2000km   

I would like to thank everyone who listened for my signal. A special note of thanks is due to DL3PB. Peter returned home from work on two evenings and set up a temporary 20m antenna in order that he might hear me.


  1. Congratulations, Michael! Quite a feat using century old technology. BTW, I found a 1.8 degree/step motor in my junk box and interfaced it to a small 1800 RPM synchronous motor (this just to characterize the motor). With no load, it produces a 400V P/P sine wave at 1500 Hz. The other coil produces a similar voltage in phase quadrature. I will have time to take more data later this week.
    Paul W2IOG

  2. Cool setup Mike! Where did the inspiration for this project come from?

    Steve w6eod

  3. Hello Michael,

    Great to see the Nauen. Thank you for the pictures in the Blog. I very like the set-up with bread boards. It great fun to experiment this way. It gives a lot of freedom.

    I studied the schematics of the oscillator in the lamps, via the links on your site. This BUL128 is no Bul.... With it's very high Vce and it's power it's an excellent deivice for a HF amplifier. hi.

    It's amazing that the frequency doublers give only 10 dB attenuation.

    The 14 MHz is excellent for 100 mW signals. And with 100 mW you breach the 1000 Miles per Watt boundary more often than one would think.

    It's great fun to see this unconfentional setup. The Telefunken engineers could not have thought, that the Grossfunkstation Nauen should lead to this amazing Kleinfunkstation at AA1TJ.
    The Nauen Log is impressive.

    Good luck with the Nauen.
    Bert, PA1B

  4. Gentlemen,

    Thank you for your very nice comments.

    Paul, my plan to use a 400 pole stepper motor, (working as an alternator) as did these fellows

    I'll be spinning my alternator at 3360RPM.

    Steve, I take inspiration from the indomitable radio pioneers themselves. The thought of what these men accomplished with simple tools and great ideas still makes my head spin. Their imagination and determination paved the road upon which we so effortlessly travel.

    Many thanks, Bert. Speaking of inspiration; reading about your amazing microwatt contacts adds "rocket fuel" to my own aspirations. Congratulations, OM!

    Mike, AA1TJ

  5. Hello Michael,

    These 1 milliwatt QSO's are great FUN. The QSO with more than 1 Million Miles per Watt with RT6A could only be made by their kindness to make TWO Dupes. hi
    Three QSO's in the same contest with: 410 mW, 4.1 mW and 0.85 mW is an example of extreme changes in the propagation. hi

    Bert, PA1B

  6. Hello Michael,
    Very cool and impressive projects you have worked on.

    In fact you work reminds me of a Mike Rainey I worked with at a Medical Ultrasound manufacturing company back in the early 80’s.

    After a little research I am quite convinced you are the same person. I am not sure you will remember me, but I learned a lot from you and we had a lot of fun.

    Please send me a PM.

    Brian Stewart