Look what neigbours kids did!

[EFR]

Hah, click bait topic hits better

But, as topic says, boys from neighbour did built an small FM transmitter! And they are 11 and 14 years old! When I was 11, my transmitters didnt look that neat!

And it even works, sort of...
Then they had an idea, if that friendly "radioamateur" living edge of town would fix it.

Its simple free running VFO using 2N2219, and 2N4427 as amplifier. Output seems to be about 400mW, 2N2219 runs hot as hell, measured on 13.8VDC. 2N4427 seems to be ice cold.

They did built it using that schematic: https://electronics-diy.com/4-watt-fm-transmitter.php

Looks like they have used 27pF between stages and 2.2pF between emiter and collector of 2N2219.

Boys told that it wont oscillate when using 10pF caps.

That 56ohm resistor with burn marks should be 47ohm, but they said that 2N2219 will burn if they used it.

2N2219 has very strange date code, and is bought from shop known to sell lots of fake components.

2N4427 looks like it is genuine Motorola.

We did run it from 10V supply and look output using my R&S CRTU, after small tweaking of trimmers, it was cleaner than these chinese boxes So, looks like there is no parasitic oscillation happening.
It allso did drift only like 20kHz/30min!

Didnt take photo from CRTU screen, because my hamcall is on it.


I promised to get genuine transistor from my jubk box, and some better capacitors, maybe some coilformers if I have some.

They are very happy about that small transmitter

Btw, is there still any good and "cheap" kits?
I dont want anything like Kemo and that Greek kit factory did sell, something better for boys, max like 5W, someone promised to build them an dipole (and there might be 50ohm resistor in it).

But Im happy to see young kids to built transmitters!

[yellowbeard]

Our Dutch buddies are still selling the stentor 5 Watt from the '80s for €35 yoyos:
https://www.amateurradioshop.nl/webshop ... uwkit.html

If you think they are up to it or you're willing to help, there is a PLL 6 Watt with display and all for €62
https://www.amateurradioshop.nl/webshop ... -bord.html

These are good quality non Chinese kits, and build them a fat J-pole - they'd love it...

[EFR]

That 35€ one might be nice to start.

I think that aluminium tube dipole would be best choice, easiest way to hide one cheap 100W 50Ohm resistor. We all live very near of very active military base/airport, I dont want that these kids get busted.

[1608cc]

Wow Really, really, really... nice first build

[87to108]

If hoping for people to tune in, even a stable VFO with 20kHz drift is too much with modern receivers. The search tuning on many radios will skip over stations that are 0.02MHz off channel.

Also DSP receivers will probably reduce the volume with stations that are a bit off-channel (soft-mute). This may lead to erratic drops in volume on modern DSP receivers.

Years ago, with the dial-tuned receivers most people were using, 20kHz drift was not much of an issue. Receivers were less selective such that 20kHz did not really matter (the receivers themselves drifted and may have needed slight retuning anyway due to temperature and battery voltage changes too...

[Albert H]

These days, adding a basic PLL to the "Stentor" is simple enough to achieve. The simple 2-IC PLL (PIC and a SAA1057) works every time, and will give the rig stability similar to the reference crystal - certainly good enough for modern receivers.

[EFR]

Heh, thats just toy for them. I swapped these ceramic caps to NP0, got new transistor for them and they are happy.

[radionortheast]

I once made a transmitter using the 2n2219 back in 1998, based on 1 transistor fm microphone from electronics world? first time I was able to hear a signal a mile away quite weakly exciting with the aerial hooked up outside, silly aerial never did much good, remember listening on a black pocket sony radio the switch set to dx a wire hanging down from the battery compartment, exciting!, lucky back then nothing broadcast above 106…it was all over when white rose came on

[EFR]

Heh, my first transmitter was 3 transistor one on breadboard, I think i was able to receive it about 2-3km away. I had an cheap Chinese/Taiwanese clone of Sony walkman, it did suffer from that small RF field, and tape speed did change randomly. Worst thing was when tape ended, and motor that turned it, didnt stop automatically, had to run like idiot back to home to stop it before it destroyed that tape.

That small transmitter was inside of an small copper cartridge box, if I remember right is was old 25 box of 7.62-53R that was used. Antenna connector was RCA type, badly soldered to an 75-ohm TV-coax. Dipole was made from copper wire.

I have no idea what these transistors were, other parts were desoldered from old radios etc.

Power was from 10 AA cells, these did last about 4-6hours.

I remember that we tried to use it outdoors on winter, -20°C and it didnt oscillate.


Im not sure how old I was, maybe around 10-12?

I did notice that neighbour kids transmitter can be heard about 1km away (3 houses on that area....)

[reverend]

My first transmitter was a single transistor (BC108 if memory serves) which had its output connected to a random piece of wire slung over the roof of the shed we used as a studio. It probably reached a quarter of a mile but as we had a number of friends within that range, it was sufficient for a bit of fun.

Within a year or so, we had progressed to a 45 Watt transmitter, with pre-emphasis and a limiter, still using a free-running BC108 VFO but amplified by numerous stages each on their own board, connected with coax. I seem to remember there were at least 4 or 5 stages of amplification. This was fed into a dipole mounted on a broom handle which we jammed into the frame of a bedroom window in the house of the guy who lived furthest up the local hill. With this arrangement we were heard nearly 50 miles away.

Another year later we were 45 Watts in stereo with a two-band compressor/limiter, with a PLL transmitter and were running outside broadcasts using a couple of converted CB radios. The antenna was now mounted on a 20 ft pole on the outside of the 'house on the hill'.

All of this was 'encouraged' by a few friendly gents at the local radio amateur club, so don't be afraid to help the neighbours kids - they will learn a lot and in the process may also become better operators with cleaner gear!

[Albert H]

My first rig was a Practical Wireless 160m AM design using an 807 bottle (from Dec 1965 edition), modified to move it downwards into the top end of the MW band. The first installation used an Inverted-L aerial from my bedroom window to the bottom of our garden. It did about 12 Watts carrier, and went for miles!

That rig lasted for about 6 months, and was then impounded (on their second visit) by the authorities. It was quickly replaced with a more powerful version (using 813 valves) that did about 60 Watts carrier, and was modulated with an old valved guitar amplifier! That was operated from a nearby lock-up garage, and had a Philips reel-to-reel tape recorder feeding in the programmes. Later on, I built my first ever FM rig (just off the bottom of Band II at about 86 MHz) which was received at the garage by a slightly doctored FM receiver (moved down a bit in frequency). The "studio" remained in my bedroom!

My first FM broadcast rig used a QQV03-10 valve, fed from an ECC83 "Kallitron" oscillator, and did about 12 Watts on 88 MHz. When I finally got my vertical aerial matched, it went a long way in mono. A bit later, it went stereo. The next rig (after that one was impounded) used a QQE06-40 and did around 75 Watts. I built my first useful FM transistorised rig in the mid-70s, and it had a BLY90 final and was around 40 Watts of RF and 100 Watts of heat!

Since then, I've built literally thousands of rigs!

[EFR]

Kids asked couple days ago 4mm and 16mm coilformers, one genuine IRF510 fet and now they have cloned Jack Donios 10W MW rig with freerunning VFO... They dont even drift that much!

[Albert H]

Jack Donio is a bit of a hero! Some of his designs were quite ingenious. One clevel trick I saw him do was to use a cheap MW PLL receiver to stabilise the oscillator frequency of a shortwave rig! He's the kind of engineer that can get almost any pile of random components to work as some kind of transmitter.

My local pirates are currently trying out MW as well as their FM output. They've got a little PLL rig I built some years ago, loaded into a disused electricity pylon for their aerial. They've got about 7 Watts of carrier, with 125% positive-going mod, and quite tightly compressed (and filtered) audio. In the daytime, it goes several miles. In the evenings, they switch it off, since the noise floor rises at sunset, and their signal is lost in the general noise.

[EFR]

Its sad that Jack died 2017, https://shortwavedx.blogspot.com/2017/1 ... 1.html?m=1

We did exhange so many emails about small tube rigs.

Btw, kids promised to show me their rig, after they desolder it from table? What that ever means.