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Saturday, January 10, 2015

"Gentlemen, We have Oscillation!" Jacob's California Mighty Mite


Bill and Pete,

I bring news of the California Mighty Mite as Bill dubbed it.

I repeated the steps as documented in version two with Pete's parts. I had one hiccup. I was winding L1 with Pete's red wire when, on turn 42, I ran out. Luckily a search of the workroom revealed the last two coils of radio shack magnet wire that I bought with the Gold wire. I checked the thickness of the Green-coated wire and found it to be one gauge smaller than Pete's wire. To be ready in time for the podcast, the green wire would have to do. It was fussier that the larger gauge wires, but with my trusty electrical tape, the L1 coil stayed on the coil-form quite neatly. Using a scrap of gold wire, I wound L2 making sure to tape it evenly spaced.

Next I remeasured each of the parts to be soldered and arranged them in according to the Schematic. With the Soldering iron hot from warming while I would the coil, I detached the 365pf varicap from the MMv2. I strapped on the heatsink to the 2N3058 transistor and soldered the 27Ohm resistor to the Emitter. I attached one pole of the Colorburst crystal to the solder tab on the varicap along with the stripped end of L1 coil. I soldered the Collector to the Tap-2 of the L1 coil, then the Base to the other pole of the crystal. I then attached the 10k resistor to the base and attached another red-magnet wire to the side of the varicap. Almost done I looped a 47nF ceramic capacitor to the  2 power posts of a DC connector, then wrapped the Tap-1, 10k, and the lead from the varicap into the pin (positive) solder tab of the DC connector. I took a second red scrap and stripped the ends, stuck it in the sleeve (negative) solder tab.

Two applications of solder later, the multimeter was back out for a final continuity check. After checking across every joint, I plugged in my power supply to the Mighty Mite. Reaching over to the shortwave I leaned in the power button and tapped in the Colorburst frequency, 3-5-7-9. Static filled the room as I made sure the radio was how I left it earlier that week. SSB mode, attenuator off, and volume up. My finger tingled as caressed the straight key, now wired to the resistor and negative line. I was scared something would melt or flame up when I keyed down. Well no way to find out, except to do.

 The key spring resisted, but I felt metal below as the key bottomed out. The radio let out a sound like rubber going down a slide and faded as I held down the key.

Gentlemen, we have Oscillation.

Revision 3 was a success. Version 1 being breadboard and Version 2 being Bill's crystal and what I had on hand.

I tried tapping out CQ, but was faced with the chirping fact that I haven't practiced in a year. I don't even know TEST let alone CQ CQ KK6JTL TEST. I turned the varicap to see if the sick squeal got any better with adjustment. It did and the pitch out of the radio changed after a bit. I must be changing frequencies! I spun around and fired up the computer. The RTL-SDR would show me what I was doing and who may respond, along with who I might be interfering with.

With the waterfall display zoomed in, showing about 5kHz around 3579kHz, I went back to the Mighty Mite. I saw one CW QSO going on in 3575kHz and two other spikes at 3576-3578kHz. Any guess at what those are? I knew since Sunday night I had been listening to JT65-HF. I reached over and held the key down. A big red spike went up at 3576.5kHz

I waited for quiet and keyed down. I turned the varicap to lower the capacitance. The spike moved to a higher frequency. When the varicap was half out, the squeal began to sound like a tone again. Problem was I was still at 3578kHz and still stepping on the JT65 signals. I called my wife in in excitement to show her and asked her to help me tune the circuit to the official frequency. I'm going to leave the varicap there for now. So I start it at 3577 and have to dial it back to 3579 to operate. I can almost go to 3580 with this little Mighty Mite.

Finally I was curious. I had forgotten to check the output of the transistor Pete sent me on my LC meter. So I got the datasheet from the Internet. The BC547A I had used in Versions 1 & 2 were rated for 325mW. The 2N3058 is rated for 5W. Pete, how much power does this put into an antenna when fed with 12V? Apparently not enough to wake my Radioshack SWR/Power meter. But that thing is hungry. It needs more than 2 Watts for it to function correctly.

Pictures attached. The transistor heatsink looks like it it touching the varicap in the pictures but I made sure there is plenty of gap. Too bad none of the pictures of that gap turned out. The wiggle in the waterfall picture is due to me turning the varicap to show range. Pete left a grounding wire on the case of the crystal. I chose not to remove it, but did not attach it to anything.














Congratulations Jacob!  You really hung in there, overcoming obstacles including the US Postal Service's Crystal-Crushing Steam Roller.  The rig looks great! 



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Friday, January 9, 2015

Irish Mighty Mite



Hi Bill and Pete,

I couldn't stand it any longer, listening to you guys on the podcast and seeing all the Mighty Mites being built I had to have a go myself.  Concerned that I might plunge Soldersmoke into receivership if I asked for a free crystal to be posted to Ireland I used a 3.560MHz one, recently purchased from the GQRP club store.

2 amazing things happened when I was building it.

1) for the first time ever I had all the parts I needed in my junk box.  Since getting my licence in 2012 I've been gradually collecting and buying components.  It's so much easier when you find everything you need.

2) for the first time ever it worked straight away.  When I finished the last component I heard this voice from over my shoulder, it was Pete saying "Now go and noodle through the circuit and check your work"  Sure enough I'd missed one of the connections and everything else checked out ok.

So I plugged it in, hid behind the shack chair and turned it on.  Success!!!

Keep up the good work both of you!

73 de Chris EI6KH
Licensed since November 2012
Fists UK Member #15966
G-QRP Member #13730
Phoenix Radio Club Member
IRTS Member
MLS: IO63jk


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Thursday, January 8, 2015

W5RST's Mighty Mite + CQ article on Super Mite


I think Mike's MMM looks fine!   The CQ article he refers to has some very interesting ideas.   Here it is:  http://soldersmoke.com/SuperMite.pdf

Hi Bill (and Pete),

Well, mine is not as pretty as Chuck’s, but I put one together last weekend, too.  Before I added the lowpass filter, the output looked pretty ugly on the scope, but afterwards it was OK.  Mine puts out about 200 mW on 80 M. I’m thinking of trying the power modification from CQ to boost the power a bit (attached):  when you’re competing with W1AW on 3.5815, it can’t hurt! Sorry for the iPhone quality pictures...

73,
Mike

Michael McShan W5RST
Oklahoma City, OK




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W5USJ's AMAZINGLY BEAUTIFUL Mighty Mite


More beauty and technical details at his site: 

http://www.w5usj.com/mmmassytest.html

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Wednesday, January 7, 2015

Goats, a Paraset, and a QSO with a Mighty Mite! (Video)



This is a really wonderful video, made even more wonderful near the end by the appearance of a Michigan Mighty Mite!  Thanks Steve!  Thanks Nick!  

Our book: "SolderSmoke -- Global Adventures in Wireless Electronics" http://soldersmoke.com/book.htm Our coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmoke Our Book Store: http://astore.amazon.com/contracross-20

Tuesday, January 6, 2015

Nick's BITX


Good Evening Gentlemen,

Pleased to report that, inspired by Pete’s help before Christmas, and innumerable comments by Bill over the last few months, I have a working BitX receiver strip – first light about 30 minutes ago on a short length of random wire but still heard a couple of Italian stations.

Followed Pete’s example and built each stage as a module, I used MePads, having noodled the layout, which is far from optimum, but did mean that I could tinker and, more to the point, test each section before I connected it together, so that starting from the amplifiers (Pete’s design), I was able to test the mixer after a bit of thought and then slowly work my way back through the filter, via the amplifier blocks, DBM, and back to the BP filter … Came together surprisingly quickly working as you suggested Pete, and nice manageable chunks too. I think about 2 hours for each module to noodle the layout, test it and document what I’d done.

Still lots to do, using a semi commercial BP for now as I need some bits that I’ve ordered to build a homebrew BP filter, the crystal filter isn’t optimised and just uses Fahran's suggested values, nothing is properly tweaked so far, but, it does work – thanks guys !!

I’ll follows Fahran's suggestion and tinker with it on rx for now, might build a VFO so it’s ALL discrete devices. Currently all 2n3904s except for the 2n3906 in the audio stage, and of course the Chinese DDS with an Arduino so I have followed the path that Bill set out a while back – it’s a little deaf against my FRG7 so far but tweaking the filter to match the impedances a little better will probably help, and the filter has a lot of ripple.

Next stage will be to build a microphone amp and test it on the Tx side, then tackle a small linear amplifier for it, I’ll stick to around 5 watts for now, and inevitably, I can see it being tinkered with in the course of time.

VERY pleased – thank you both for your help and inspiration

73s

Nick, G8INE



Hi Nick,
 
Congratulations – very nice looking and the other bonus of building it large the 1st time through is when you build the 2nd one –you 1) know the circuit works and 2) you can optimize the layout. I frequently said that I often build two of the same, learning from the 1st and applying to the second. See below. Version 1 was a larger board in comparison to the whole radio in version 2.
 
Bravo – in short order you should be making lots of QSO’s
 
Pete N6QW


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25% off On SolderSmoke Book (and on "Us and Them") through Jan 8


You can find all the books on this Lulu site: http://www.lulu.com/spotlight/soldersmoke
Just plug in the code FLASHY15 when checking out. 

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Sunday, January 4, 2015

Who is this earnest young radio amateur?


Name that ham!  Here are his comments:

This is vintage early 1960’s and my call sign at that time was K3???.   One of my favorite rigs was the Johnson Adventurer which I built and had a 6AG7 driving an 807 –50 watts input. On the top shelf near the lamp is the screen grid modulator for the Adventurer. I was in tall clover.
 
On the bottom opening is a 40M CW transceiver I built it had a 6CX8 MOPA—about 5 watts. The RX was a two tube regen.
 
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Friday, January 2, 2015

A Thatched Roof, Some Palm Trees, A Dipole, and a Homebrew Rig

 

Look at the drawing above.  That is the banner logo of Rod Newkirk's column in QST magazine.  For many years Rod regaled us with exciting reports on the activities of intrepid foreign radio amateurs, transmitting from exotic locations using ingeniously devised homebrew radio equipment.  Look at the picture on the left side.  See the palm trees?  See the thatched roof shack with the dipole antenna?  Well, that's pretty close to what it was like for me out on the Samana Peninsula in the Dominican Republic last month. 


I set up the station under the thatched roof in this picture:


The red pins mark the spot:



Here I am, tuning the rig while looking across Bahia Rincon: 


The rig was my Azores-built, oft-modified, NE602-based, ceramic resonator DSB transceiver with a recently added India-designed BITX IRF510 RF amplifier chain.  A little article I wrote about the ceramic resonator VXO was featured in SPRAT 127.  My antenna was a half wave dipole strung up in the thatched roof. Power came from 10 AA Batteries.  So this was the Double A, Double Sideband, Dipole DX-pedition.   

I had given some thought to building an SSB rig for this trip, but because of the efforts of Peter Parker, VK3YE, I felt compelled to take a DOUBLE Sideband rig with me to the beach. 

Here is an old (2006) video on the rig.  The power amplifier has been significantly modified: 




Here is some more information on the rig, including a schematic for the receiver and the SPRAT article on the Variable Ceramic Oscillator:

http://www.gadgeteer.us/PORTABLE.html
 
Here is the log book for my contacts.   

17 DECEMBER 2014
W1JPR PAUL MT. DESERT ISLAND MAINE
8P6AE (BARBADOS) COULD BARELY HEAR ME, BUT GOOD QSO

18 DECEMBER 2014
N4USA DAVE IN FLOYD, VA. FAIRS NET. (KK4WW.COM)
KE4UGF DON ALSO FAIRS, NICE GUYS. FUN CONTACTS!
KA4ROG ROGER NORTH OF ORLANDO

19 DECEMBER 2014
WB2HPV GUIDO TALKING TO ITALIANS EVERY MORNING FROM WAYNE NJ.  HE HAD TROUBLE HEARING ME.   
CONDITIONS SEEMED POOR, BUT I WAS HEARING AUSTRALIAN STATIONS
W8GEO GEORGE IN THE INTERCON NET.  HEARD ME.  ALSO ON INTERCON: KA4AOQ AND 6Y5MP (JAMAICA) ALSO HEARD ME.
N4PD PAUL
W3JXY/4 NAT IN KEY WEST
N1FM TOM, NORTH OF MIAMI SOLID QSO.
KM4MA PAUL IN ORLANDO WITH MARITIME MOBILE NET.

20 DECEMBER 2014
NA2LF LLOYD IN NY
WB8YWR JIM IN DALLAS 
KM4MA.
W1AW/3 IN MARYLAND (TOOK ME A WHILE TO GET HIM)

21 DECEMBER 2014   NICE 4 WAY SPANISH LANGUAGE QSO:
KI4PZE MIGUEL
CO8OT JUAN IN SANTIAGO DE CUBA
WA4RME RAFA IN CHARLESTON S.C.
C08KB MARCO IN CUBA


Here is a short video showing the station and the location.  Note the little birds (Golondrinas or Swallows) flying by.  They nest in the thatched roof.   They often got confused and flew inside the house.  Billy and Maria rescued many of them.  Whales breed in this bay in January and February.  There are also  manatees.  It is really a beautiful place. 



There were obviously other attractions (!) so I didn't spend a lot of time on the radio -- just a half hour or so every now and then.  But it was really very satisfying to carry this little homebrew device with me, set it up in this amazing place, and use it to send my voice across mountains and hundreds of miles of ocean.   I built this rig in the Azores and have used it in the UK, France, Italy and the Dominican Republic.  It contains circuits devised by members of the British QRP club and by my friend Farhan in India.  The ceramic resonator circuit is something I cooked up on my own.  The microphone is from my old Sony Walkman and the pen that serves as its support is from that wonderful magazine "Electric Radio."  In short, there is a lot of soul in this little machine.  And it was a lot of fun to take it to the beach.  

Thanks to Elisa for finding us this wonderful place.  And to Rod Newkirk and QST for the DX inspiration. 


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N2HTT's MMM Makes Contacts (the little rubber feet are important)


Hi Bill and Pete,

Some further adventures of the Michigan Mighty Mite - I have added several amenities since first oscillation:
- a low pass filter on the output
- bnc connections for antenna and a rcvr, and a tx/rx switch
- coaxial connector for power
- stereo jack for the key
- LED tx power indicator, and
- little rubber feet

Of all of these, I cannot sufficiently emphasize the importance of little rubber feet. A project just cannot be considered complete without them.

More pictures and details of the low pass filter are on my blog at http://n2htt.net

I've been heard on RBN on 40m several times, but haven't gotten any replies to calling CQ. This weekend was the December SKCC Sprintathon, and I pretty conclusively proved that if there are any other signals on the band the MMM is not likely to be heard.
After the contest ended, I posted on the SKCC sked page, and two stations, KC9W and KT4TN agreed to listen for me. We made successful contacts on 7059 kHz. Both stations are in Tennessee, and coincidentally both ops are named Randy.
As Bruce KK0S observed in his report, the rig seems to operate about 1 kHz above the nominal crystal frequency, as confirmed by both Randys.
I've had a lot of fun with this little rig, it's a keeper.
Keep up the great work with the podcasts, and Happy Holidays

73
Mike N2HTT



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Thursday, January 1, 2015

Larry's Mighty Mite



Larry's rig looks like it is almost ready to go for Straight Key Night!   FB.   I was glad to heat that the crystal survived the rough treatment dished out by the US Postal Service these days.  Apparently all envelopes are sent through a steam roller!  Who knew?

Hi Bill and Pete,

As usual life has intervened in my plans, but after a delay for professional and personal reasons I can now report success in yet another additional the the CLA.  I was able to successfully transmit into a dummy load yesterday with my new transmitter.  It is not the prettiest device I have ever built but it is functional.  I tried the home made mepad construction and it works fairly well.  I did discover a few things while building and testing this unit.  First, I need a new soldering iron with a little better temperature control.  Second, before using this transmitter on the air (currently on a dummy load), it needs a low pass filter.  I can see several harmonics imposed on the generated signal.

The first picture show how everything is mounted to piece of scrap wood for stability.  I even screwed down the old key for stability during testing.  The alligator clips are for the dummy load connection (the dummy load is also home built from 20, 1K ohm resistors which is located just on the right edge of the picture).  

Even without an antenna I was able to receive the transmitted signal on my IC-7200 in the shack.  

The signal on the scope is messy but the tome received on the IC-7200 sounds good.

Next steps are the additional of a Low Pass Filter and better matching to the dummy load (currently I'm only at about 49 Ohms).

Thanks again for the encouragement.  I plan to do a little more tweaking on this unit and will keep you updated on any progress.

Have a great holiday and a Happy New Year,
73
Larry
AE7TM

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Mac's Mighty Mite



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Designer: Douglas Bowman | Dimodifikasi oleh Abdul Munir Original Posting Rounders 3 Column