Attenuator killed reception? CM4221+7777

www.Tvfool.com/?option=com_wrapper&Itemid=29&q=id%3dbc27ac90e1f998
I have big trees about 50 feet away in line of sight.
Reception degrades when it rains. Stations are
about 13 to 25 miles away.

Installed CM 4221 recently with CM7777 amp,
about 24 feet up on top of gable. Cable goes
to a splitter near the antenna, runs about 60
feet, then splits near TV to accommodate
digital tuner. Splitters were not a problem
with the big old RS combo antenna (trashed).

Got no reception, so I disconnected the amp.
Got halfway decent reception; had to rotate
antenna every time I changed the channel.
Some weaker channels stayed pixelated.
Called Solid Signal; they said an attenuator
would definitely solve the problem, so I ordered
one and installed it. Now I get no signal.

Any ideas?
Thanks

Your problem is multi-path and signal loss due to the trees. You need a chainsaw, or a tower, or a clean line of sight through the trees.

I did a lot of research before I bought the
CM4221, and especially found hdtvprimer.com
to be helpful. From what I read there, multipath
should not be a problem, and the 4221 is the
best kind of antenna to use with trees. After
all my investigation, I came to the conclusion
that it would be better than my old antenna.
So far, I have better luck with rabbit ears.

The man I talked to at Solid Signal said that
the only reason I couldn't get a signal with
the amp installed was because it was too
strong. This has nothing to do with trees
or multipath.

Where was the attenuator installed? How many db?

It "maybe" should have been between your VHF antenna and the pre-amp. The 4221 should be connected to the UHF side of the pre-amp. The amp should be set to separate and the FM trap should be in.

Multi-path is ALWAYS a problem when there are trees in the line-of-sight.

Your statement that your "Reception degrades when it rains" must be considered at face value. That condition, by itself, is NOT due to excessive signal strength alone - it is due to the effects of the water accumulating in the foliage of the trees. The increased water both blocks and deflects more signal than the trees would under drier conditions. When combined with the predicted strength of several of your stations, the multi-path is likely severe.

Several of your stations are strong and are likely causing the 7777 pre-amp to overload. There may be FM transmissions present so switch in the FM trap as suggested. If you MUST amplify to overcome distribution losses, get rid of the 7777 (which overloads easily) and use a CPA19 or HDP-269 along with an external FM trap.

Amplifying a jumbled mess of multi-path is about the worst thing you can do. Go passive and search for a better antenna mounting location - i.e., "walk the roof" like a pro would do it.

... You need a chainsaw...

Agreed...
But Solid Signal doesn't sell chainsaws :D

From what I see you have basically what could be a single aim install, at ~245 degrees. This should get you everything on that general aim, and possibly picking up ch 17 off the back.

...the 4221 is the best kind of antenna to use with trees.
I disagree here, and am of the understanding that a 4-bay has a wide beamwidth, thus actually making it more susceptible to multipath, and I agree with projectsho89 that is the prob. And Sam's advice is spot-on as to the amp - if you're using a separate VHF antenna...

However you didn't mention one, so I assume you're trying to use the 4221 for everything, which isn't very strong on VHF. (But since 8 & 10 are pretty strong this is a crap shoot.) A DIY mclapp or the
http://cgi.ebay.com/Tune-A-Tenna-UHF-VHF-HDTV-TV-Antenna-USA-Channel-Master_W0QQitemZ180413666554QQcmdZViewItemQQptZLH_ DefaultDomain_0?hash=item2a017e14fa&_trksid=p3286.c0.m14
would serve you better for VHF, and may help with the multipath a little due to the curved reflector/swept forward elements making the beamwidth a bit narrower.

I can only guess SS thought you were overloading the 7777, which seems unlikely since the only strong channel is 8 and the antenna's relatively weak there - so I don't see an attenuator helping. (I could be wrong here, but then why didn't the atten help? What is the value BTW?) The old CM4228 would've been a better choice, (If one could even be had) since it had a narrower beamwidth, and the reflector did it somewhat well for VHF.

I'll throw this out there, since you're dealing with all 1 & 2-edge signals and trees, maybe a 43XG (or even a RS U-75) & a YA-1713 may do you better, hooked into the amp as Sam recommends. (And with the atten between the 1713 and the amp.)

Or we're back to the chainsaw...:D

I agree with Sam Spastics comments.

Are you sure you are getting power to the amplifier on the mast? If not its just acting like an attenuator as well....thus the bump in signal when removed from the loop. Maybe one of those splitters isnt passing DC?

The 4221 and an amplifier is likely to get you everything in yellow and green.

... Maybe one of those splitters isnt passing dc?

Good catch EV!

http://www.solidsignal.com/pview.asp?mc=03&p=1296F&d=20dB-Variable-Attenuator-for-VHF-UHF-HD-OffAir-Reception-1296F&c=Signal%20Variators&sku=853748001293

Above is the attenuator. It is inside,
near the TV.

Thanks for all your advice and clarification.

I have no other antenna installed.
Channel 8 is strong. Ch 10 has trouble
with rain.
The trees are in my yard and my neighbor's.
Chainsaw is not an option.

I was psyched up to build a mclapp or
maybe a GH, since I am unemployed,
but feared failure;
and seriously considered the 43xg
before settling on the CM4221HD.
I did not want to spend 50 bucks on the
amp, but figured I would take the plunge
and buy a good one, esp after reading all
the bad things people had to say about
RS equipment. I have a RS 15-1108 amp
from my old antenna setup. Is this thing
worth fooling with?
http://www.radioshack.com/graphics/uc/rsk/Support/ProductManuals/1501108_PM_EN.pdf

Looks like the 7777 was a bad idea.
Know anyone who needs one?

When I bought the 4221, I thought I might
end up stacking another one on top if
the reception was not good enough. Not
ready to go down that road right now, but
should I keep that option open?

By not doing anything more then just looking at your TV fool report, my analysis of your situation is that you bought the wrong antenna for the job.

You do not buy a 1/4 ton pick up if you haul coal for a living and need to move a 1,000 ton pile of coal. You buy a 25 ton tri axle and you put 50,000 pounds of coal in it and you make as few trips as possible.

Trying to use a small antenna and a UHF antenna to receive VHF signals and low UHF and putting a amplifier on it to compensate for a lack of antenna is like the guy with the `1/4 ton truck.

You can load and load as much coal into it, but the engine is not strong enough to haul the load and the frame and suspension is not heavy enough to withstand the weight for any period of time.

If you would have came here first, I would have said you needed a Winegard 7498P antenna or even a 7496 and left it at that.

Depending on what is in the first and second fresnel zone, you may or may not have reception. At 20 miles - with nothing more then trees in the way. I would suspect that you would always get something. I would not recommend that you use any type of pre amplifier.

The only station in your service area that would be a little hard to get would be WPXA - Ion channel 51, and even it is only 46 miles away.

You are definitely using the wrong antenna and the wrong pre amplifier.

I would run one RG 6 wire to the bottom of the house and then I would put in a lightning arrester and then run it into the house and split it as many times as you need - to provide service to as many rooms in the house as you feel you need to have a television in.

The 224, 237, 245, 287 should all come in with one point of aim.

You would have to turn the antenna to watch WUVG because it is in a opposite direction, you would also have to turn the antenna to watch WPXA because it is in a opposite direction.

As you have found out, when living in a fringe area, and having the wrong antenna set up, unless you have the antenna pointed directly at the station, you will get no reception.

For reliable reception, you will need a 70' tower to get above the trees and stay above the trees for the life of the antenna. With a raise of 70' - you should still have enough signal that a small pre amplifier would be all the more you would ever need to get reliable reception.

At 80' HAAT - you would have more stations then you could shake a stick at.

Mast mount CM 7777 input set to combined VHF+UHF on one line in (which uses the UHF input) plus FM Trap switched on. Make sure you are getting power to the mast module through the splitters. Try replacing the splitters with DC passing splitters.

Should solve most of your problems.

JB
I don't see a 7496 or 8 anywhere.

EV
I get most local stations without the amplifier.
So the splitters are not blocking current,
right?

Hey space Ranger,
Don't think of it as "current" Sure the splitters are passing TV freq's.

The current that powers the amp (traveling from the power injector to the amp itself) is 14-18volts DC and your common run of the mill splitter doesn't pass DC - it starts passing signal at around 40-50MHz.

Most amps without the DC voltage to power it becomes an attenuator.

For a quick check move the power injector upstream of the splitter(s) and see what you get. This is the recommended placement in the instructions, btw.

If you need that power injector location you can replace the splitters with a DC passing type splitter(s)

And JB meant a HD7696P, 7698P

From what I understand, you will want a voltage blocker for the other side of each splitter to keep the DC current from going to the other tuner/tv, when you replace the splitters with DC power passing splitters.

Like this...

http://www.pacificcable.com/Picture_Page.asp?DataName=201-500

Hi EV,

It is my understanding that the dc blocks are required if the splitter is power passive in all ports. here is one example: http://www.solidsignal.com/pview.asp?mc=03&p=PV23-602&d=Perfect-Vision-PV23602-Wide-Band-2Way-Splitter-52300-Mhz-%28PV23602%29&c=Signal%20Splitters&sku=PV23-602


However, they are not required if one gets say a 2-way that is power passive on one side only. Here is an example: http://www.solidsignal.com/pview.asp?mc=03&p=PV23-222&d=Perfect-Vision-PV22222-Wide-Band-2Way-Splitter-52300-Mhz-%28PV23222%29&c=Signal%20Splitters&sku=PV23-222

Best,

Rick

I agree that the 7777 amplifier is too powerful for the location. This is demonstrated by the improvement that was apparent when the amplifier was removed from the equation, even though you still didn’t have a great signal. Pre-amplifiers have a certain amount of signal input that they can handle. Too much input signal and you can overload the amplifier, which can affect all frequencies being received. The CM4221 gain on the VHF band is not great, but still could be enough to overload the amplifier given the close proximity of the station.

The Antennas Direct 1296F is not power passive, so it cannot go between an amplifier and the power inserter. They are used to attenuate amplification, though, and would defeat the antenna’s capability if installed between the antenna and the amplifier. Any splitter installed between the amplifier and power inserter must be single port power -passive on the port that carries the current. Amps do not improve your antennas range, they can only amplify signals that the antenna receives by itself.
Multipath is an issue given the wide beamwidth of the CM4221 and the trees 50 feet away from the antenna. Those trees will kill UHF reception through multi-path and reduced signal. I agree that in this situation, to continue using the CM4221, you’ll likely have to ‘walk the roof’, as projectsho89 said, in order to find the best spot for reception. The trees may be creating a null where your antenna is placed, making signal strength much weaker in one spot, whereas it may be strong enough in another location. The ‘right’ spot may not be where you would expect.

Any time you are testing an antenna’s capabilities, ideally you would use an OTA signal meter, or if a signal meter is not available you connect the antenna to the television that is closest to the antenna with no splitters or amplifiers between. This will give you the strongest idea of the capabilities of the antenna. A larger directional antenna, like one of the Winegard HD769 series mentioned by aka.Hooper, would be a better choice for the location to reduce multi-path and increase gain across the channels you’re trying to receive if you cannot find an acceptable spot for the CM4221. (I would use, at smallest, the HD7696P) If rain causes reception problems even in your best location, there isn’t much that you can do other than trying a directional antenna or placing the antenna above/away from the trees. Before considering changing though, I would try the antenna in a few different locations to see where it might work best.

Since you’re getting most local stations without the preamplifier, and you find that you can get all your stations to come in reliably connected directly to the antenna, your only remaining issue would be signal strength when splitting the signal. To overcome loss from splitters, you need a distribution amplifier and not a preamplifier. I would suggest the Winegard HDA200 or some other adjustable strength distribution amp in this situation.

Feel free to call us if you would like to discuss your situation.

Ron H.
Solid Signal
866-374-4625, x. 7441