I finally went up on the roof again and into the attic to satisfy our curiosity. Similar to the diagram that you provided: THere was a transformer right at the antenna contacts; this was connected to a coax cable hooked on the other end to another transformer that went in the opposite direction into the pre-amp/transformer (evidently the pre-amp/transformer two wire cable was not long enough to reach the antenna contacts); then the cable from the pre-amp/transformer went into a powered box inside the attic; the signal from the powered box went to a four way splitter that had cabling to the two TV's and an unused jack.
So, I disconnected everything as directed. I bought a new transformer at the Shack and hooked it directly to the antenna contacts. The cable from the new transformer goes directly to the 4-way splitter in the attic now.
The results are that my reception and signals at the TVs are pretty much the way they were before with the pre-amp, which is kind of interesting. I guess the pre-amp was not doing a whole lot. I repositioned the antenna while I was up there and most stations are acceptable at around 30db. The worst stations are local channel 2 (24 db) and local channels 39-1, 39-2 (variable at 12-18db); so the latter fades repeatedly.
Another hardware item I noted is that one of the long horizontal spokes on the side of the antenna facing away from the transmitters is missing. I am not sure how big an impact this has as it is a fairly large antenna.
Quote:
Originally Posted by GroundUrMast
There are several variations of this concept... Generally, the part(s) inside the building are power related, and are designed to send power up to the mast mounted amplifier unit.
The mast mounted unit may have one or two inputs. If two, one is usually for VHF and the other for UHF. There can be any combination of 300 ohm twin-lead or 75 ohm coax input and output. It sounds like you may have a short section of 300 ohm twin-lead from the antenna to the amplifier and the output is 75 ohm coax.
I would be very curious to know how your system performs when you remove the amp and power supply. If there is a short section of twin-lead between the antenna and amp now, a matching transformer will be needed.
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