Quote:
Originally Posted by luRaichu
There goes the briefcase transmitter...
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Someone either hasn't seen the dimensions of an AM-60 or has already bought an extra small briefcase....My AM-60 is 14.5"D x 1.75"T x 19"W....It can be 17.5"W if you cut off the unnecessary rack mounting ears. There's definitely briefcases out there that can fit an AM60 and a thin battery, power inverter and media player underneath it.
A BAVMz can transmit about 3/4 block (AM-60 is one block) with only a good antenna (dipole cut to frequency), and a BAVMz is about 9" less deep than a AM-60. Most briefcases should be able to fit 4 BAVMz family modulators...Now the BAVMz is fixed channel (unlike the agile AM60s), but you can buy ones built for any VHF channel and all cable channels (some of which overlap UHF TV channels).
Another thing to consider is what channels you want to use and how big your antenna must be to be decent as a TV transmit antenna. The best solution for simplicity and Omnidirectional operation is a dipole cut to 1/2 the channel wavelength...For channel 2 that's a nearly 10 foot long wire with a coax connection in the middle! It gets smaller the higher the channel though... Channel 13 is about 26" (you could build a couple of telescoping rods that retract into the briefcase), and a standard 1970s era UHF bowtie antenna (so far my favorite for UHF receiving and transmitting) is about 13".....
Generally using an unnecessarily high power level to get a certain amount of coverage from a bad antenna doesn't yield as good of results on the receiving end (or for the reliability/life span of the transmitter) as using a good antenna with sufficient power. If the transmitter antenna isn't tuned for the channel you can have almost all the RF power not radiated into space and instead reflected back into the output stage where components will see ~2x their designed power level (the power their sending now plus the full power they sent a fraction of a wavelength ago) and rapidly burn up....In some cases TX life expectancy under those conditions can be measured in seconds. Also if almost all the power is being reflected a 2W TX can have worse signal coverage than a much smaller 100mW transmitter.
I think your project is doable and interesting, but it requires sound engineering effort....If you brute force design it you'll be building a glass jackhammer that works worse than a steel carpentry hammer.