Pebble Crusher 40m XMtr

Building this transmitter was a bit of a comedy of errors. Bill Meara, N2CQR, recommended this circuit in my hunt for a transmitter on 12v with a RF amplifier in tow. Bill sent me the schematic, but it took me several weeks to get started. After deciding that I'd like to build this using the Manhattan Technique, I had to find some PC boards. I had a few, but they were cheap--they really shattered when I attempted to cut them down. I was also missing a few parts, of course. And there's also the fact that my time is not my own.

I also credit some delay to trying to visualize the enclosure that would contain this circuit and vice versa. I never solved that last step instead opting to keep the circuit exposed for now. If I get the right performance, I might re-envision the circuit and squeeze it into a circuit for a SOTA outing. I then saw this short vid by the veritable Paul Taylor (VK3HN) which further cemented my plans to spend time to layout the circuit before I melted any solder. 

I started by redrawing the layout several times. Doug DeMaw's book, W1FD's QRP Notebook, includes a PC board layout, but I was purposefully trying to layout the circuit mentally and as close to the schematic as possible, limiting my circuit flips and inversions. 

Before

After Re-layout

I was then all ready to begin when...who grabbed my crazy glue? Another delay.

To be honest, working with the circuit Manhattan Style was nice. I drew a small grid on the board with pencil in an attempt to keep the circuit aligned during the build. 

I spent the week of 21-25 Jun checking and rechecking my layout against the schematic. I even melted some solder here and there. I finished the circuit on Sunday, 27 June. I plugged in the antenna jack and key. I added power and...nothing. Darn. I checked continuity of the ground, transistor pin outs, everything. 

I emailed Bill Meara who had these thoughts:

Jack: First, try to isolate the problem by stage: Disconnect the amplifier from the power supply and from pin 3 on the transformer. Now, does the oscillator oscillate? Listen on a receiver. Fiddle with the variable cap C1 as you listen. Also C5.
Check the voltages on Q1. Collector should be high, close to 10 volts. Base should be lower and emitter should be about half a volt less than the base.
Is the ferrite bead shorting to ground?
Some of the connections to the copper clad board look possibly cold. I would re-heat all of them and let the solder flow onto the board.
Make sure you have good contact with the enameled wire on your transformers and chokes. It can be tough to get those wires clean. I usually burn off the enamel with a cigarette lighter, then follow up with some sandpaper.
Let me know if any of this helps. 73 Bill

As suggested, I separated the RF amplifier from the oscillator. And, boom, we had oscillation. But it wasn't on 7.015. It was on 7.0135. I found that my filter was too narrow and I wasn't looking far enough away from 7.015. I reconnected the amp and the signal moved to 7.014. No problem. We were back in business. 

I checked voltage across the dummy load which indicated 2.038v. Given that:

P(watts) = (V + 0.25)2 /25 where V= volts and 0.25 is the RF voltage drop across the diode.

P(watts) = (2.38v + 0.25)2/25

P(watts) = (2.63v)2/25

P(watts) = 0.27w

A quarter of a watt is a little lower than I thought. I hoped to get 1/2 watt out of this. NP. But the signal was very clean. I checked on the scope and found only one small harmonic. A near perfect sine wave.

Here's the video:

Here's what it looks like on the Reverse Beacon Network:

14db into NY; 7 db into OH (270mi)

Final board. Note cardboard under the ferrite bead to prevent shorting to ground. Alligator clip on transistor as a heat sink...but I can still smell that I'm roasting the transistor....

ARRL VHF Contest Fun

 

I had such a great time participating in the ARRL VHF Contest this past Saturday and Sunday. As was my habit, I headed out to Hogback Mountain on the Skyline Drive. Hogback Mountain stands at a little over 3000 feet and has a good view of New England to the N/NE and Pennsylvania to the N/SW:

Hogback Mountain, FM08

My approach to this contest is laid back. In fact, the June VHF Contest is the only contest series that I participate in. (There is also a September and January segment. September starts to get in the way of hunting and, well, January is pretty cold on a mountaintop.) Since I'm casual about this, I really only use one Yagi and the FM vertical on my Jeep. Also new this year was a significant amount of QRM from neighboring operators. We'd step on each other every time we were operating the same band. We then decided that we'd not call CQ and hunt/pounce instead. Hunt/pounce worked, but it did reduce log entries.

Spring on the Skyline Drive

The Shenandoah Valley, Virginia

Equipment. My equipment was a little different this year. I blew out my IC-7000 to years ago; I replaced the same with an Elecraft KX3 using a Dual Band VHF/UHF Transverter made by
UR3LMZ. All my SSB contacts were at 8W. (Note: next time I'll reduce power further to 5W and go for the QRP category.) I also used my vehicle mounted Kenwood TM-D710GA for most of my early FM VHF contacts. I then used the KX3 for both VHF and SSB. I know, I know: my Yagi is clearly horizontally polarized. Still, I made plenty of FM contacts with little degradation of signal. Besides, the FM contacts were local.

Elecraft KX3 with Upverter

My setup on Hogback. Flagpole holder, MFJ-1910 mast...and cooler.

• Challenges/Observations.

• I heard very little CW on the bands. I heard none--zip, zero--on the designated frequencies of 144.000-144.100 and only scant QSOs in the 144.200-144.300 range. I only made  two or three CW QSOs myself. 
• Once I started operating primarily from the KX3, I found that moving between bands/freq tiresome. Next time I'll add the following to memory before going to the field and make sure I know the procedure for doing so in the field:
• 144.100 (2M CW Calling/start of band)
• 144.200 (SSB 2M Calling Freq)
• 146.520 (2M Simplex Calling Freq)
• 420 (70cm CW Calling/start of band)
• 432.10 (SSB 70cm Calling Freq)
• 446.00 (70cm Simplex Calling Frequency)

• Future Plans/Expansion
• I normally operate as a limited Rover. This means that I must transmit and make contacts from more than one grid. I normally spend all afternoon on the first day of the contest on Hogback Mountain. I leave soon after dark so that I can see the sunset:

Sunset from Hogback

Illuminated Clouds from Hogback

 

On day two/Sunday, I go to Mass then normally park on the top deck of a parking garage in FM18 for a few calls to qualify. But this plan was impossible this year. The amount of RF pollution and new buildings invalidated this plan. I made a few contacts on FM, but that was it. For future contests, I will forgo parking garages and go a little farther to either Bull Run Mountain or Mount Weather. 

•  If I feel ambitious, I may add a 430 MHz Yagi similar to my 2M Yagi. I can stack the two on the same fiberglass mast and use a switch to go between the two.  I also have a 6M Moxon that I built that I could press into service, but this might need it's own mast. It also doesn't breakdown so easy for the back of the jeep.

Nice photo, but made zero QSOs on SSB with KX3 and Yagi. Made two QSOs on FM using Kenwood
TM-D710GA mounted in my Jeep. Remainder of the QSOs made from my home.

• Results. At the end of the day, I made 55 QSOs from FM08 and FM18. All but four QSOs were from Hogback Mountain. Best QSO: W1VD, Burlington, CT (363 mi) on 8 watts USB. A personal best. Hogback Mountain (elev. 3000') sure helps.

QSO Map

Get Ready, Get Set....

The ARRL VHF/UHF Contest is next weekend. I'm reading my equipment in between chores. Crimped some shorter LMR-400 Max (started with 2', down to probably 19' now that I screwed up a section). I'll probably operate as a "rover." Like the last few years, I'll spend a majority of my time in FM08 on the top of Hogback Mountain along the beautiful Skyline Drive. Nothing like pulling an all-nighter hammering out some Morse Code like the fate of the free world rests with me and my trembling fingers. I'll follow up the next day from home after Mass (grid FM18) to fully qualify as a rover.

Since I fried my IC-7000 last year, I'll be operating FM using my Kenwood TM-D710G in my Jeep. It will beacon my position via APRS. New this year: I will operate a VHF/UHF using transverter on my Elecraft KX3 by Alex Shatun (UR3LMZ). Will also have a small VHF Yagi with me as well. This should be plenty fun.

Newly crimped LMR-400 Ultra