500 mW VHF Video Transmitter

At the Position from R5 to R7 and from C5 to Q2
is there a Connection of this 4 wires or is there
a Bride over one wire?

I hope anybode can help, please Post

Thanks!

100% sure its connected
otherwise Q2 qould not be polarised and the signal from the modulator part(Q1) would not be amplified...

i need to know the following:
1.what output frequency does it have?
2.please, send me the analysis of the circuit?

I always want to jam the signals of our neighbors with this circuit but sometimes I get tired of doing this crazy things...

can this be easily hacked? i guess it is not allowed to do this for it is a violation, but well, it looks fun doing this haha!

what's the maximum range can this VHF transmitter send out?

this analog tune TV antenna is fairly enough to capture VHF signals and there are designs which can be very beneficial..

Next step would be to have circuit that includes audio modulation, also. Can you post that schematic? Thanks

hi , what's what frequency output ?

maximum range depend on output of transmitter.and antinna hieght and reciever sinstivity.

Maybe its me but it does seem that getting the proper literature to build a decent TV transmitter has proven to be quite difficult these days or next to impossible in a few cases. I have personally built many homemade devices over the years ranging from a measly 250 MW to 500 watts or more.

I've already examined the circuit thoroughly on the top of the page and find it to be OK if you're expecting small results. You see the trick to building a decent broadcast device starts at the "oscillator?" It is the most critical part of any transmitter indeed. Thus, what these small circuits fail to recognize is that "modulating any video" with those reverse negative peaks tends to draw any free running oscillator quite a bit off frequency. Thus, to correct this problem the oscillator should be either crystal or digitally controlled to avoid any unnecessary drift.

Now the best transmitters require the largest aluminum heat sinks. Sounds kinda funny doesn't it? As a matter of fact, it's better to build a transmitter inside a large aluminum heat sink were each transistor can be properly mounted to dissipate that unwanted heat. What the big boys won't tell you lads is that sophistication means nothing. No, a single transistor, let's say a T. X. final from an old CB radio incorporates some amazing properties when used as an free running heavily loaded oscillator. Yes, as a professor of engineering it can produce upwards of 20 W or more, pending on the power supply feeding it. Frequency stability of this high-powered oscillator is quite satisfactory too. The trick to oscillator stabilization is using short Rf coils loaded down with some heavy capacitance. I've used this principle many times building various single transistor devices over the years. & one such device is connected to a homemade wire wound antenna with an excellent frequency range of 4.8 db at 88-108 MHZ. The single transistor transmitter that pushes this particular high gain antenna to a whopping coverage of 30 miles or more is one T. X. final mounted on a very large heat sink with a cooling fan. That's it no confusing stages just one single oscillator with a power supply of 35 volts producing roughly 20 Watts of affective PEP. Thus, by using an FM stereo exciter it makes an affordable pirate transmitter indeed.



Television transmission is no different. A single T. X. final operating in the low VHF range of 55.250 MHZ = CH # 2 can be easily collector modulated to produce a superior vivid color picture complete with 4.5 MHZ sound.