Ham Radio Exam Day in Ireland: October 4

OK gang, it is time for us to do what we can to help a worthy Short Wave Listener transition into the world of amateur radio.  Chris will be facing the Irish radio examiners on October 4.  So please try to send some positive vibes in the direction of Ireland.  Cross your fingers (especially the ones with the soldering iron scars!)  Maybe melt some sacrificial solder. C.F. Rockey might suggest sacrificing a chicken to Papa Legba.   Say a prayer if you are so inclined.   Good luck Chris!  

Hi Bill,

Just wanted to say thanks for the great podcast and keep up the good work.

I’ve been listening for a good while now and following your subscriptions advice on things like Tim’s “Hot Iron” Constructors club and QRP/Sprat magazine.

I’ve got my Amateur Radio licence test in 2 days time (4^th Oct) over here in Ireland (Dublin’s Comreg Offices) so please give all the candidates a mention and wish us luck.

Great book as well…  When I’ve had my fill of studying I switch over to your book for a while to relax a bit and read your thoughts on getting to grips with it all.

There’s only one licence here in Ireland so it’s Full or nothing  so it’s going to be tough! My brain is well and truly fried!!

I’m determined not to be a (can’t even remember what you call them in your book ha ha) “User” and go out and buy everything I need so I’m looking forward to lots of construction projects when (IF!) I get my licence J

Best Regards (I don’t think I’ve earned my right to use 73’s yet),

Chris

(EI1628 SWL/qrz.com)

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How to Get Ready to Build a BITX-20

Continuing with our workshop inspiration theme, I spotted this in the BITX-20 mailing list this morning.  The response is from Farhan: 

blake,

i would suggest a different route. a long and winding one, that will
finally lead to a bitx.

the idea is to learn. you do this by understanding what you build and
building what you understand. by 'understand', i specifically mean, being
able to measure. here is what i suggest, buy yourself a bunch of 2N3904s
from the local radio shack and some resistors and caps. then build this :

http://www.phonestack.com/farhan/testosc.gif

this is an oscillator. if you plug a coil between the open ends, it will
become a vfo, if u plug a crystal, it becomes a crystal oscillator. you can
use your frequency oscillator to check the frequency it is oscillating at,
etc.

with this, you would have mastered the first of the three blocks that make
up almost every radio circuit. but next, you must make another test
instrument. a power meter. most of us ham start out with a simple RF probe.
while that was fine and dandy for its day, now we can do much much better.
we can make a very accurate power meter that enable you to measure things
as finely as anybody in this business. W7ZOI has designed a super simple
power meter. it is available as a kit.
read about the power meter here :
http://www.kangaus.com/Documentation%20files/Power%20Meter%20Documentation%20May%202011.pdf
you can purchase the kit at www.kangaus.com
(I have no business interest with kanga or any other kit manufacturer)

with the power meter in place, you can now measure the power levels coming
out of any circuit with great accuracy.

now, you can build a single stage feedback amplifer (there are six of them
used in the bitx) on a copper clad board. using the test oscillator as an
input, you can measure how much gain the amplifer has (measure the
oscillator output, then connect the oscillator to the amp and ,measure the
amp output. the, amp output - oscillator output = amp gain).

of course, while building both these blocks, you will discover what
voltages to expect at which junction of components in both these blocks.

next, you can build a step attenuator. which is a really simple thing and
of immense value in the home lab. here is a design
http://www.arrl.org/files/file/Technology/tis/info/pdf/9506033.pdf
or you can now buy it in a kit form from
http://www.qrpkits.com/attenuator.html

finally, you can build a simple signal generator like this :
http://www.phonestack.com/farhan/siggen.html  . this will allow you change
frequencies and measure what a circuit does at different frequencies. you
can use this to test how the filters are doing and get them to 'spot' where
you want them to.

so, there it is, a signal generator, a power meter, step attenuator, test
oscillator. four, very simple test instruments that you  can build
yourself. they will give you one helluva education in radio. and within
weeks, you will understand and start building on your own!!

- farhan

> Quoting bfabman :
>
> Hello Everyone, I have been watching the group for a few months now
> with interest. I have no electronic experience to speak of, but I have
> a burning desire to make one of these, and I am wondering what all of
> you think of someone like myself building one as my first real radio
> project, to be used for qrp mountain topping. I don't have any
> electronic test equipment for the final alignment, other than a
> standard DIG vom meter. (I am willing to buy some equipment if
> necessary) I think that this would be an awesome winter project just
> don't know if it would be over my head. If I got it all built, could I
> actually get it aligned and working properly. I did make a Norcal
> frequency counter project last year and it turned out very well. Thanks
> for your opinions before I spend the money. Blake
>
> Paul Daulton K5WMS
> beacon WMS 185.302 khz qrss30/slow 24/7
> Jacksonville,Ar 72076
> em34wu
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

Science Fair Light Beam Communications in 1960s

Hi Bill!  This Bob Schubert, KC4FNE in Blacksburg Virginia just wanting to say hello and taking the opportunity to say "Thanks" for the SolderSmoke Series.  I have to let you know your podcast accompanies me as I do my early morning exercise regime.  Before SolderSmoke, I would begrudgingly get out on the track every other day.  Now I'm out there just about every morning listening to a new episode.  I'm not sure what I will do once I exhaust all of the episodes?  Normally I would cover my obligatory 2 miles in 45 minutes, now I'm looking for excuses to stay on the track so as to complete a one-hour or so episode.  When I'm listening to it in the car, I find myself circling the block just so I can finish a podcast.  It has also prompted me to purchase the SolderSmoke book.  I'm thoroughly enjoying the book as we seemed to have both grown up close to the same timeframe and our early lives led as "geeks."  If you interetsted in what an "old geek" is up to now, point your browser to http://www.lumenhaus.com/  This is a solar powered house done by a team of architecture and engineering students/faculty I was involved with.  If you ever find your way to Blacksburg and are interetsed in our Lumenhaus, I would be happy to provide a tour.

I've included a photograph of me taken at Orange County High School in the mid-60's with a science fair experiment "Talking on a Light Beam." While not quite in the 478THz range of the high-power LEDs it was up there!  While modulating the filament on a flashlight I would be hard-pressed to go 95ft much less 95 miles.

Best, Bob Schubert KC4FNE

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

Video Model Rocketry

Our plan is to strap a key-chain video camera to the center of gravity on this mean green machine.  Using Duct Tape (of course).  Kind of like this guy did:  

http://www.teamten.com/lawrence/projects/video-camera-on-model-rocket/


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

Bell Labs: Similarities in Wave Behavior

John N. Shive rocks the universe with his 1959 wave machine.  We saw this device some time ago in a video in which Dr. Shive explained standing waves.  Thanks to Armand WA1UQO for alerting us to this gem.  

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

Real DX: Hubble's EXTRA Deep Field

http://www.clarksvilleonline.com/2012/09/26/nasas-hubble-space-telescope-takes-deepest-image-of-the-universe-to-date/

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

SSB Generation: Ideas from Around the World

I liked this thread on the EMRFD mailing list.  The question of how best to generate SSB is very interesting, and I also liked the global scope of the Q&A:  Peter in Hungary asks the question, Farhan in India and Allison in the U.S. respond.   

 On 9/25/12, ha5rxz wrote:
When generating an SSB signal from audio and a 9 MHz carrier which would be
the best mixer to use?
a) A high-level ring bridge mixer such as the SRA-1H
b) An H-Mode mixer using an FST3125 chip
c) An H-Mode mixer using a 74HC4016
d) Something else
Note that this mixer will not be used to demodulate.
Peter HA5RXZ
...................................
Ashhar Farhan wrote:
In my experience, if you keep the audio level low enough, it is
difficult to beat a simple two diode mixer.with a 10 db attenuator in
the output. Having just two diodes makes balancing of reactive as well
as resistive differences of the two diodes quite trivial. Schottky
diodes are best.
One thing, I did discover though is that the balance should be to
minimize the harmonic distortion, rather than just the carrier
suppression.
What we are shooting for is to keep the In-band IMD down. Carrier
suppression is just hygiene. So, you will want to tune in to the
signal, modulating it with two tones and see it on a audio spectrum
analyzer (freely downloadable from the net) and try getting the third
spike down.
Though the 'packaged' mixers don't give you the needed control for
hi-fidelity, for trivial usage, NE602 is pretty good. Just drop it
into the rig and live with what you get (which is not bad at all).
The best resource is the chapter on phasing receivers and transmitters
in emrfd. Rick is the guru. I hope he joins this thread.
 
- Farhan
............................................
FROM KB1GMX: 

I'll weigh in..

Yes, they all work. You need a provision for adjusting carrier balance on some but anything over 40db will be good.

I've used 602/612s, SBL-1, SBL-1H, diode rings, and even varicap
diodes (there is a design using them in capacitively balanced 
a modulator from many years ago. They all work if the levels are correct.

These days I use the sa612 for simple designs, SBL-1 with a 50ohm 
pot added for balance for better radios and the 4 diode ring I've 
used many times as its uncritical, needs only one untapped 
transformer and easy to make. Most of those are listed in the 
older 1975 through current handbooks and EMDRFD.

If needed I can post to the files section a few designs but 
they are all textbook and all are capable of good results.
In just about all the diode modulator cases a fairly strong 
carrier (5mW or more) is needed and the audio will be about 
10db lower for very good result. The active devices like the
ca3028(and friends), SA612, MC1496 the levels for the carrier 
and audio must be matched accordingly for the device. You can 
look at the output with a scope and get a first order eyeball 
call on quality (no carrier and no clipping or limiting) and a
receiver (any your ears) will tell you if its right.

Allison

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