transmitter(FM) section is good, i build it non of the component is critical, and zero error. but stuck at reception the transmission is around 100meter in normal receiver. but in this Transceiver its 30cm after that its dead.. low sensitivity & range can you make an RX with BC548.

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.

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!

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.

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

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

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

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