Comments are moderated before they will appear on the website, this is a manual process and may take some time. Please be patient.
Author Name is a required field.
Email Address is optional, but without one I won't be able to contact you back. It is never shown or linked on the website. You can always just email me if you'd rather not post a public comment. I generally reply in-line with a comment rather than email you back, unless I want to discuss something in private or off topic. Please check back to see when I reply.
Website URL is optional, if supplied the Author Name will be hyperlinked to this URL.
You may use wikitext in the body, preview may be handy here. Don't worry if you can't figure them out, just give me a hint what you want linked to what and I'll do it during moderation. Wikitext is not BBcode!
Spammers: Please don't bother wasting your time scripting up posts to this form. Everything is moderated, your post will never be seen on the web even transiently, there is no way to even view it by its internal ID, it will never be indexed. I will simply delete your post in the moderation interface. If I'm your target audience you're really on the wrong track; I'll never click on a URL in your garbage. The post content is not emailed to me (and I don't use a Win32 mail client anyway), I view the posts in plain text in the moderation interface so no clever tricks of any kind will make anything you type be interpreted by anything other than me, a human. Just give up and go elsewhere please!
29th May 2012 22:25
Reminds me of an AM B/C band transceiver I made when in high school in the late 60s. The active device was a 1S5 valve running on a used battery from a CPRC26 set (I was in the army cadets). On RX it was a regen and for TX it was put into oscillation. It used a carbon mic and disposals headphones to interface with people. It was built into a square metal icecream tin with a length of wire hanging out which could be connected to a longer antenna. It received B/C stations and could be heard on radios for 10s of yards.
31st August 2011 13:37
Hey, this is a great idea to build a pair of watch-intercom to my son. I´ll try to use the small components that come in tv tuners like the smd fets and caps. Thanks!
17th September 2010 23:26
Wel Alan, I didn't try it either, way to high frequency but I have modified your design here a little bit so that the source resistor on TX gets replaced with a carbon microphone. Works quite well but nothing like gate modulating via a carbon mike and step up transformer,you even overmodulate sometimes than. I'm going to give this a try with a bigger FET like the VN10KM. And then put this thing on air for serious. I'm working CB by the way, no antenna or contacts so far. Hoping to make the cross into 10 meters soon with license.
16th August 2010 16:36
Thomas,
Interesting circuit, emitter modulating the oscillator on TX simplifies the switching. Not sure how linear the result will be, but I'll have to give that a try.
Regards,
Alan
19th June 2010 04:02
I'm going to build a minimal rig like a converted this one (has been build but not functioning yet because of lack of crystal). I'm wondering what a five transistor rig(2x LF amp extra) in RX and TX mode could do. Indeed reducing the number of poles of a standart walkie talkie by building both amps seperate. Something like this design http://ok1ike.c-a-v.com/soubory/tipy/Porto1.gif. I'm also wandering what a converted walkie talkie circuit could do with a good antenna and crystal. It would indeed be the Minimalist rig. About to find out...
Greetz
11th June 2008 21:06
Hue,
Indeed, adding more transistors is "cheating" in some sense. Three is a good minimum for a practical device, it gives you the much needed AF gain on both TX and RX with some switching. I've always toyed with the familiar three transistor walkie-talkie circuits, but I've longed to reduce the switch poles required.
My best DX ever has been on 10 or 11 metres. I had AM QSOs over thousands of kilometres using hand-held < 1W radios with barely any antenna. Like 6 metres it can be quite magic when it is open, but most of the time it is completely dead.
Tunnel diodes are something I haven't really played with that much. While interesting they seem to be problematic to achieve any significant power from because of their very low voltages of operation and relatively delicate nature. Michael's tunnel beacon projects are very impressive though!
Regards,
Alan
2nd June 2008 06:36
If you go to 3 transistors, then your rig
is not really different from the millions of
3-transistor toy talkies in the toy departments, the ones for $10-15 the pair.
I have been interested in a minimal rig like
a modified 3-transistor CB talkie but hooked
to external antenna and telephone handset and
see what it can do during a 10m opening, but-
the stumbling block is ordering 10m overtone
crystal.
Years back P-E magazine, sometime around the
early 1960s, had in the 'reader's circuits'
sectiion a tunnel diode broadcaster. The text
said the interesting thing was, it could be
changed from transmit to receive just by changing the bias on the diode. Maybe with the
bias just right it went into quenched oscillatio - superregen - mode. -H M
24th December 2012 01:42
siva wrote...