PROJECT 14: THE WORLD'S SMALLEST TRANSMITTER
Jeff Herman
If there was a contest to come up with a xmtr containing as few
parts as possible, this would be the winner: 10 parts if you include
the key, battery, and antenna!
In the CODE/NO-CODE debate on r.r.a.policy some pro-coders will
mention the simplicity of CW xmtrs as opposed to those of other modes;
this circuit really drives that point home (that's why I'm posting this
on .policy)
On r.r.a.misc we've heard talk about how costly ham gear is today - all
this rig will cost you is the effort to find an old color TV chassis -
that's the parts source for all my QRP transmitters (and this is why I'm
also posting this on .misc).
Normally I post these xmtrs only on r.r.a.homebrew and on the QRP
mailgroup; so if you've missed the first dozen xmtr circuits email me
and I'll send them off to you.
I built this for 80M only because I've got so many 3579 kHz crystals
from old TV sets, but this can be used on any HF band - just choose
L and C to resonant at the crystal frequency.
For peace of mind you might want to add a bandpass filter to the
output.
--------------------------------*---------*--------*----||---ANT
| | | | 10pf
| | | |
- | ) ---
XTAL | ) --- C
- | ) L |
| | / c ) |
*----------------------------|/ | |
| b |\ | |
| 2N2188 \ e *---------
/ or any PNP | |
\ 100K that'll work | |
/ GND |
\ |
| |
*-----------------------------------------*
| |
| |
| ---
| --- .01uf
| |
---------*KEY*----*1 to 4 volts +*--------*
|
|
GND
Again, choose L&C to resonant at the desired frequency; one of the two
should be adjustable. I got both from the chromatic board of a TV -
both were sitting next to the 3579 kc xtal; easy, huh? I didn't use
a 2N2188 transistor; rather, I used a x-sistor right off the video
board (of the TV).
So, don't you dare buy one component for this - just dig through your
junk box (or your neighbor's trash for an old TV). With a good antenna
(those are the magic words in QRP work) this little peanut-whistle
will provide hours of pleasurable QSO's.
Oh, 3579 kc has become a national QRP frequency due to the easy avail-
ability of these crystals.
.... .- ...- . ..-. ..- -.
72,
Jeff NH6IL
Myron A. Calhoun
>parts as possible, this would be the winner: 10 parts if you include
>the key, battery, and antenna!
Several years ago I saved a similar (but different) 9-part
(counting a 2-winding tapped inductor as one part!) xmtr from either
73 or Ham Radio magazine. The design was "Thanks to WB6OMV" and
supposedly (I've NOT built one) ran about TWO WATTS output:
fund. Antenna
+------xtal-----------+------------+ |
| | | |
| 365pf ) |
| | ) +----+
| +----)------------) |
| | | ) (
| 2N3053 | / c | ) (
+-------------|/ | ) (
| b|\ | | |
| \ e +-----+------+ +----+
10Kohm | | | | |
| | | | | |
| 22ohm | | |+ |
| | | 0.02uf battery |
| key | | |- |
| | | | | |
| +----^-----+------+-------+
| | |
+---------------------+ ground
--Myron.
--
# We preserve our freedoms using four boxes: soap, ballot, jury, and cartridge.
# Myron A. Calhoun, PhD EE; Assoc. Professor (913) 539-4448 home
# INTERNET: m...@cis.ksu.edu 532-6350 work, 532-7353 fax
# UUCP: ...rutgers!depot!mac Packet radio: W0PBV@N0ARY.#NOCAL.CA.USA.NA
--
# We preserve our freedoms using four boxes: soap, ballot, jury, and cartridge.
# Myron A. Calhoun, PhD EE; Assoc. Professor (913) 539-4448 home
# INTERNET: m...@cis.ksu.edu 532-6350 work, 532-7353 fax
# UUCP: ...rutgers!depot!mac Packet radio: W0PBV@N0ARY.#NOCAL.CA.USA.NA
Dana Myers
>Gang,
> If there was a contest to come up with a xmtr containing as few
>parts as possible, this would be the winner: 10 parts if you include
>the key, battery, and antenna!
I can beat this.
> I built this for 80M only because I've got so many 3579 kHz crystals
>from old TV sets, but this can be used on any HF band - just choose
>L and C to resonant at the crystal frequency.
Try using a 4049 or 74C04; use one inverter as a crystal osc (two
caps + crystal) and the other five in parallel as a buffer. Use a small
cap to couple the antenna, maybe 100pF. It'll run off 3-15V. Lessee..
xtal+74C04+caps+battery+key+antenna = 8 parts.
The 74C04 was invented in something like 1973.
> For peace of mind you might want to add a bandpass filter to the
>output.
or maybe a lowpass filter; that adds at least three more components.
The 74C04 approach would really benefit from an LPF, too.
Oh, is this a CW issue? :-)
--
* Dana H. Myers KK6JQ, DoD 466 | Views expressed here are *
* (310) 348-6043 | mine and do not necessarily *
* Dana....@West.Sun.Com | reflect those of my employer *
* This Extra supports the abolition of the 13 and 20 WPM tests *
John Welch
> In article <CK0o0...@news.Hawaii.Edu> jhe...@uhunix3.uhcc.Hawaii.Edu (Jeff Herman) writes:
> >Gang,
> > If there was a contest to come up with a xmtr containing as few
> >parts as possible, this would be the winner: 10 parts if you include
> >the key, battery, and antenna!
>
> I can beat this.
Me too.
> > I built this for 80M only because I've got so many 3579 kHz crystals
> >from old TV sets, but this can be used on any HF band - just choose
> >L and C to resonant at the crystal frequency.
>
> Try using a 4049 or 74C04; use one inverter as a crystal osc (two
> caps + crystal) and the other five in parallel as a buffer. Use a small
> cap to couple the antenna, maybe 100pF. It'll run off 3-15V. Lessee..
> xtal+74C04+caps+battery+key+antenna = 8 parts.
>
> The 74C04 was invented in something like 1973.
Try using a 28.322MHz oscillator (or a14 or 7 meg that I've
seen occasionally that are still in the Ham bands). Low-pass filter
this as well, and you need battery+key+oscillator+3xLPF components.
Note that these oscillators are usually not a 50% duty cycle, so a
bandpass filter would be better.
> > For peace of mind you might want to add a bandpass filter to the
> >output.
>
> or maybe a lowpass filter; that adds at least three more components.
> The 74C04 approach would really benefit from an LPF, too.
Of course, taking that approach to extremes, use an Alinco
DJ580. It is all one 'piece', including the battery, key and antenna
;-)
--
John Welch, N9JZW
mark.a.mccuistion
> Try using a 4049 or 74C04; use one inverter as a crystal osc (two
> caps + crystal) and the other five in parallel as a buffer. Use a small
> cap to couple the antenna, maybe 100pF.
I hate to be an idiot (what a leading phrase!!!) but could you draw
a simple diagram of this? I follow instructions real good, but an
not an electrical engineer.
> For peace of mind you might want to add a bandpass filter to the
>output.
>
> or maybe a lowpass filter; that adds at least three more components.
> The 74C04 approach would really benefit from an LPF, too.
More diagrams, please. I love building these simple circuits!!!
Randy
Here are some mods to make it run 50 ohm Z ( as original, it would want
Hi z ants...1/2 wave etc direct connected)
:
: 1.5C
: --------------------------------*---------*---)(---*---------ANT
: | | | |
: | | | |
: - | ) ---
: XTAL | ) --- 3C
: - | ) L |
: | | / c ) |
: *----------------------------|/ | |
: | b |\ | |
: | 2N2188 \ e *---------
: / or any PNP | |
: \ 100K that'll work | |
: / GND |
: \ |
: | |
: *-----------------------------------------*
: | |
: | |
: | ---
: | --- .01uf
: | |
: ---------*KEY*----*1 to 4 volts +*--------*
: |
: |
: GND
:
: Again, choose L&C to resonant at the desired frequency; one of the two
: should be adjustable.
Adding to Jeffs info.....
Knowing the freq and the inductance, do this formula to find C
25330
--------------
F^ * uh F = mhz ^ is 'squared' ( F x F )
Now multiply C by 1.5 and 3 to get the 2 caps values...and BINGO! you
will be close to a 50-75 ohm Z output
Diddle the coil to get cleanest keying.
The coil will want to be a value between 3 and 20 uh for 80 mtrs, for an
absolute min/max workable value.
===
Jeff.. I tried the ckt out and 15 uh , 180 uuf and 330 uuf worked with
a 3579kc xtal....but I had to place a bit of ferrit slug by the
coil to make it key nice into a 68 ohm resistor load ( I'm a tek
so, I can't air the thing )
I used a 2N3053 ( NPN ) so I had to turn battery umop apisdn .
Hey...where is that zillion volt spark thing I was hearing about?
Can't find it in homebrew....
--
Randy KA1UNW If you get a shock while
servicing your equipment, "Works for me!"
ra...@192.153.4.200 DON'T JUMP! -Pete Keyes
You might break an expensive tube!
Grover Cleveland
Are y'all forgetting the Fireball transmitter?
Battery, key, dip relay, xtal oscillator at 29.060, antenna.
I think this about as minimalist as anyone could go.
Grover
WT6P