Quote:
Originally Posted by tvcollector
Thanks!!
I recapped the other mod, and replaced the bigger rectifier diodes, it's noticeably better, and able to program it for UHF frequencies now, but it still has issues with reception, it's still weak, not as weak as it was before but still much weaker than my second mod.. I did order up the three transistors, and the smaller rectifier diodes, I'll try replacing those tomorrow to see if it makes a difference..
With the bowtie I'm able to get reception about a block radius with an area where it's completely dead.. I thought it would go a bit farther with UHF..
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About a block with the unit on the second floor is what channel 7 gives me....I always figured VHF (especially low band) would give better range since the lower the frequency the less a TV signal behaves like light/FM radio (line of sight transmission), and the more it behaves like AM/SW signal (sky waves and skip)...I hear tales of people with just a few trees between them and the towers loosing DTV signal when the wind blows the trees, so if there is something like a brick or metal wall, vent ducts in the walls, a fence, or something of that nature between your transmitter and and your receiver in your UHF dead zone odds are it is the cause of your dead zone.
Two other things to consider: All antennas are directional to some degree (google radiation pattern of antenna in question, in your case UHF bowtie dipole, to see it), and dipoles have the weakest reception at an angle at which the transmit antenna is pointing at you*. Also the RF power of the BT seems to vary from channel to channel (which is not too surprising given is is hard to make wide band tuned circuits and reflected wave traps completely flat over the whole TV spectrum).
*Another side effect of directionality is what IIRC is called polarity mismatch....If the TX and RX dipoles are oriented to face 90 degrees different from each other then minimal signal transfer for the other given conditions will be minimal.
I took an antennas elective last year, and despite it being the first time the class was offered and the professor diving way to deep and spending way too much time on the maths of infinitesimal dipoles I did take some useful stuff away from it.