JER

tommymc

The multi-path issue is an interesting factor. It gets confusing trying to discuss stations performance before and after the digital switch because the frequencies changed but not the numbers.... But I'll try to add some info.

Before the switch, UHF 22 (ABC) was unwatchable because of a strong double image. I assume this was due to multi-path? It is now 22.1 broadcasting on VHF 13 and is our strongest channel.

Before the switch, VHF 3 (CBS) was usually strong with no double images. It is now 3.1 broadcasting on UHF 22. It is usually watchable but with some dropouts.

Before the switch, VHF 5 (NBC) was snowy but watchable with no double image. It is now 5.1 broadcasting on UHF 14 and is only occasionally watchable. It pixelates and drops out.

Before the switch, UHF 44 (FOX) was so snowy as to be not worth watching. It is now 44.1 broadcasting on UHF 43 and is so weak that the converter box shows "No Signal".

Before the switch, UHF 33 (PBS) was watchable, but we watched duplicate programming on UHF 41 which was our strongest signal. It is now 33.1 broadcasting on UHF 32 and is usually watchable.

Before the switch, UHF 41 and UHF 31 were very clear. They are broadcasting from 4x farther away but without as much obstruction. Since our rotator broke last winter, I have had the antenna pointed away from them. During maple sugaring season, I put a homemade DB-4 upstairs in the garage and was able to watch 41.1 while boiling sap out there. So I assume (but haven't tried) that if I rotate my roof antenna in the correct direction, I can pick up 41.1 and 31.1

All of the networks have their towers within a few hundred yards of each other, so if I can just get a little stronger signal, I won't have to mess around with a new rotator.

I thought that my style of antenna was very directional and less prone to multi-path problems. Is that not so? Is there a better choice that will also allow me to recieve VHF? Thanks.

Trip

As notoriously bad a signal as WVNY-DT 13 (22-1) has, whatever you end up with needs to have very good upper-VHF performance.

- Trip

__________________
KJ4IEA

Comments are my own and not that of my employer or anyone else.

tommymc

The mast mounted part of the unit is actually piggybacked on the bottom of the antenna. Here's a link to the manual. There is a 50ft run of coax to the power unit which also has an FM trap which has been set to "out".


With our current antenna, WVNY-DT 13 (22-1) is now our strongest signal. I was looking on Google Earth, and note that the WVNY tower is located about 500ft away and 167ft lower than the other towers.

WCAX-DT22 (3.1) and WPTZ-DT14 (5.1) are the two stations I would like to improve reception on. WFFF-DT43 (44.1) would be an added bonus but I have little hope for that.

JER

Sorry, I haven't looked super hard at your particular station config so I can't help there.

If I were you I'd set the FM trap to "IN" unless you absolutely need to get FM from this antenna.

You may also want to look at the gain setting. It depends on how they designed the amp but usually the NF goes up as you decrease gain. On the other hand, if you're getting hammered with some strong signals (even out of band) decreasing it may still help.

The other thing to look at is how well shielded your amp is. If you're in a strong signal environment (FM, etc) the ones that are just a ckt board in a plastic case tend to have pickup direct into the amp. This can cause all kinds of problems. If you decide to get a new one look for one that's sealed up tight in a metal box. Those types have done better in strong signal areas on my test bench.

This is my last post here for a while until the owner and moderators can figure out what kind of forum they want. Some here are worried that I just tried to sell you something.

Good luck in resolving your problem!

tommymc

Here's an update and more questions. I bought a Winegard HD7697P antenna and have installed it on my old (but refurbished) chimney mount. I replaced all the cable with new RG-6, except for a few feet of old RG-59 that runs through the roof and chimney flashing....it was just too hard to try to snake the new cable.
Masts:
I've removed the broken rotator and just aimed the antenna toward the nearest towers. With the rotator gone, I had to connect two mast sections. They have tapered ends which slip inside the next section. How are these supposed to be secured? I put a bolt through, and braced the joint with a piece of steel strapping and U bolts.

Pre-amp:
My old pre-amp was made for a 300 ohm input, and the new antenna has a 75ohm connection. So that isn't going to work. The good news is that the new antenna works better than the old one, even without using the pre-amp. If reception remains steady, I may decide not to replace the pre-amp. There is still one channel that I can't pull in. It is FOX 43uhf. It shares towers with other stations I receive, but apparently is lower power. The meter on my DTV converter shows a very low signal 4-5 out of 100. I need a threshold of 35-40 for steady reception. I know that a pre-amp can't pull in signals that aren't there, but I have to wonder if one would boost the existing signal to the threshold of reception?

Grounding:
This is the only piece left to do. Since the grounding terminal block is supposed to be mounted where the cable enters the house...in this case, the chimney flashing....I mounted it to the bottom of the mast. I intend to run the ground cable along the ridge to the end of the house, then down the side to where the power lines are grounded. What's the best way to secure the cable to the ridge? I have a plastic/asphalt shingle ridge vent and the best I've come up with is to use zip-ties to attach it to the edge of the ridge vent.
Thanks for all your help and great info.

Don_M

You can try a Channel Master Titan 7777 pre-amplifier for its really low noise factor and find out. That would negate signal loss in the cable, particularly if it's more than 50 feet long. Still, I can't offer too much hope. Your suspicion is on target: The Fox station puts out only about 10 percent of the power of the other UHF stations broadcasting from that location. TVFool shows a WFFF signal strength of -105 dBm. That's so weak that under normal circumstances, it's barely detectable above the radio noise floor, which is what the signal-level meter indicates.

Can't think of a better plan, myself. Use black zip ties; they'll last longer because they withstand UV degradation better than the white/translucent ones do. Also, be sure to curve the ground line very gently, both below the mount and at the edge of the roof. A "square turn" in the line increases the chance that a discharge might jump to something else on the roof or nearby.

tommymc

The black zip ties did the job. So everything is working pretty well, but the signal on the UHF channels does seem to fluctuate and a few nights ago, 3.1 (CBS) started breaking up. Since my one VHF signal is strong (it measures 60-65 on the converter box meter) I wonder if I should consider a UHF only pre-amp? I'd like to boost the UHF but don't want to over amplify the VHF. Does that make sense?
Is the Winegard 4800 so much noisier that it wouldn't work for half the price of the Channelmaster?

One more question....I have a total of just shy of 50' cable. Eight feet on the mast, 3 ft through the roof and 35ft into the basement and over to the TV. I know the preamp should be placed as close to the balun as possible...mounted on the mast. If I don't get this resolved before the snow flies, how much noise would 11 ft of cable introduce? Until it's safe to get up on the roof, I'd put the preamp in the eaves just below the chimney.
Thanks again for all the good advice.

Don_M

Post by jodi moved to its own thread in the Comcast forum.

Don_M

You can use an AP-4800 -- it's not significantly noisier than the 7777 -- but amplifying UHF signals only adds complexity to the coax wiring at/near the antenna/pre-amp. To do this, you'll need two UVSJ band separator/combiners and additional short lengths of coax to separate the VHF signals from the downlead ahead of the amp, and then combine them with the UHF signals again after the amp. Here's how:

• First UVSJ, above the pre-amp: Connect the in/out port to the antenna balun and the UHF port to the pre-amp input.

• Second UVSJ, below the pre-amp: Connect the in/out port to the downlead going to the splitters/TVs, the VHF port to its counterpart on the first UVSJ, and the UHF port to the pre-amp's power-injector output. You read that right: The power injector needs to be installed in the coax wiring before the second UVSJ for the pre-amp to work properly. (Did I mention this was going to be complex?)

The first UVSJ acts as a separator; the second is used as a combiner.

None. A longer cable ahead of the pre-amp introduces additional signal loss, though, which means that much less of a margin between the signals and the radio noise floor. Eleven feet isn't significantly longer than three feet on a temporary basis. It'll still be a good idea to move the pre-amp up to the antenna next spring after the snow melts off the roof.