Only getting VHF-HI channels -preamp problem?

chabunga · 27-Mar-2012, 1:51 AM

We have a roof top antenna that used to get a lot of channels. Now it only gets two. From the signal analysis it appears that these two channels are VHF-HI. Does this indicate that I need to replace the preamp. Thanks if advance!

GroundUrMast · 27-Mar-2012, 2:11 AM

Please post a link to your TV Fool report.

How old is the antenna? Has there been any reason to suspect recent damage?

Thanks

chabunga · 27-Mar-2012, 2:22 AM

Here is the analysis report: http://www.tvfool.com/?option=com_wr...0b86702d88a04d

It's an old antenna, probably 20+ years old. But it has worked like a champ until recently. We live in south central Wisconsin. Until the recenly we could pull in stations from Milwaukee, Rockford, and Madison. Once in a while I could even get Channel 5 from Chicago. Money is tight, so I don't want to replace more than I absolutely need too.

I don't know a lot about the analysis. I apologize for not educating myself first. But I just happened to notice that the two channels I can still get are VHF-HI. And the preamp seems like a easy to replace part, out side of climping upon the roof

Thanks!

Electron · 27-Mar-2012, 3:33 AM

What antenna looks similar to the one you have?? http://www.kyes.com/antenna/pointing/pointing.html. How many tv's are/will be connected?? Is the antenna you have mounted on a antenna rotator??

GroundUrMast · 27-Mar-2012, 5:18 AM

The common enemies of all parts of an antenna system are the elements and time. Broken or bent parts are usually obvious. Corrosion in connectors is not as obvious but in most cases, fairly easy to spot if you disconnect the connector to inspect. Water in the coax and matching transformer is difficult to see, often the most practical test is to replace suspect coax and transformer. (If I left you out in all types of weather for twenty years, you'd be ready for replacement too.)

I would test the viability of the antenna first, by connecting the antenna directly to one TV, all parts of the preamp removed and no splitters or splice connectors. Use a known good coax and matching transformer. (If you find terminals corroded so badly that you can't disconnect the old transformer or reconnect the test unit, it's time to consider a new antenna.) With the antenna connected to a single TV, do you receive more than the two H-VHF signals? If so, that would tend to vindicate the antenna.

Once you have proven the antenna good, then add the preamp back into the mix, still with only one TV connected. If the trouble returns, the preamp is highly suspect, time to consider it's replacement. If things work this way, the coax and/or transformer could well have been the trouble. Add the splitter and inside coax into the mix to be sure...

Bottom line, start at the beginning, the antenna, then add more complexity... you'll be able to prove the failed part or parts.

chabunga · 27-Mar-2012, 2:52 PM

Electron: My antenna looks like a All-Band UHF-VHF-FM. It was connected to two YV's and it has a rotor.

chabunga · 27-Mar-2012, 3:04 PM

GroundUrMast: Thanks for all the info. Before I can try your suggestions, I have one more question. I don't know if you can help on this next question, but here goes. The antenna is on top of a two story farmhouse. The antenna is mounted on a tripod. The tripod has cross members. Are those designed for climbing? I might have to climb up it or lean a ladder against it, in order to reach the preamp and route around it. How heavy are antennas? Perhaps I could unbolt the antenna from the tripod and take it down to work on it? My wife doesn't want me to go up on the roof. I not real excited about it my self, but there is a shed type garage roof about 4 feet below the house roof edge, so it wouldn't be a killing fall :-) I should probably just hire someone, but I have more time than money... Thanks Again!

Electron · 27-Mar-2012, 3:20 PM

To prove out , the reception of antenna , connect a known to be good matching transformer balun , (a transformer/balun connects the antenna to the coax) , and a known to be good RG-6 coax direct to the Tv , No splitters , No amplifiers , No preamplifiers , No nothing. The coax will go from the antenna through a open door or window direct to the Tv. Aim the antenna at about 309 degree magnetic compass . What is the reception like now??

Electron · 27-Mar-2012, 3:21 PM

Can you get a make and model number off the amplifier inside unit in the house?? Antennas do not weigh much and a rope will lower the antenna to the ground. And the rope will bring the antenna up again.

GroundUrMast · 27-Mar-2012, 5:22 PM

I have to presume the tripod is not designed for climbing. I would look for a safe way to loosen bolts so I could lift the mast and antenna free from the tripod, then lay it over carefully to work on it.

An antenna alone is usually quite light, made of aluminum. A 10' mast section and antenna might weigh between 15 & 30 lbs. The challenge may come when the assembly is long and cumbersome to maneuver. This may be a two person job.

Please don't get hurt.