Attenuator killed reception? CM4221+7777

space ranger · 11-06-2009, 08:10 PM

http://www.Tvfool.com/?option=com_wr...bc27ac90e1f998
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

projectsho89 · 11-06-2009, 08:38 PM

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.

space ranger · 11-06-2009, 09:04 PM

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.

Sam Spastic · 11-07-2009, 03:55 AM

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.

projectsho89 · 11-07-2009, 06:37 AM

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.

aka.Hooper · 11-07-2009, 08:06 AM

Quote:

Originally Posted by projectsho89

... You need a chainsaw...

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

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.

Quote:

...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...d=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...

EscapeVelocity · 11-07-2009, 09:21 AM

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.

aka.Hooper · 11-07-2009, 09:35 AM

Quote:

Originally Posted by escapevelocity

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

Good catch EV!

space ranger · 11-07-2009, 10:16 AM

http://www.solidsignal.com/pview.asp...u=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/u...1108_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?

JB Antennaman · 11-07-2009, 12:02 PM

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.

EscapeVelocity · 11-07-2009, 06:38 PM

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.

space ranger · 11-09-2009, 11:39 PM

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?

aka.Hooper · 11-10-2009, 06:45 AM

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

EscapeVelocity · 11-10-2009, 09:04 PM

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_...taName=201-500

IDRick · 11-10-2009, 09:23 PM

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...s&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...s&sku=PV23-222

Best,

Rick

11-06-2009, 08:10 PM	#1
space ranger How can anyone watch standard def? Join Date: Feb 2008 Location: Atlanta metro area Posts: 17	Attenuator killed reception? CM4221+7777 http://www.Tvfool.com/?option=com_wr...bc27ac90e1f998 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 Last edited by space ranger; 11-06-2009 at 10:12 PM.

11-07-2009, 06:37 AM	#5
projectsho89 How can anyone watch standard def? Join Date: Oct 2009 Posts: 24	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. Last edited by projectsho89; 11-07-2009 at 06:42 AM.

11-07-2009, 12:02 PM	#10
JB Antennaman Marvin the Martian rules! Join Date: Jun 2009 Location: In the Suburbs of Punxsutawney Pennsylvania - ground hog country! Posts: 568	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. __________________ Where is the Kaboom? There is supposed to be a earth shattering Kaboom!

11-10-2009, 06:45 AM	#13
aka.Hooper "Babe" 2002-2009 Join Date: May 2009 Location: Eastern Suffolk, LI, NY Posts: 292	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 __________________ Some details on my DIY antenna builds: http://mysite.verizon.net/res11d41p/ Last edited by aka.Hooper; 11-10-2009 at 06:50 AM.

11-06-2009, 08:38 PM	#2
projectsho89 How can anyone watch standard def? Join Date: Oct 2009 Posts: 24	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.

11-06-2009, 09:04 PM	#3
space ranger How can anyone watch standard def? Join Date: Feb 2008 Location: Atlanta metro area Posts: 17	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.

11-07-2009, 03:55 AM	#4
Sam Spastic High Definition is the definition of life. Join Date: Jan 2008 Location: Just south of Normal Posts: 119	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.

11-07-2009, 09:21 AM	#7
EscapeVelocity High Definition is the definition of life. Join Date: Jun 2008 Posts: 59	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.

11-07-2009, 10:16 AM	#9
space ranger How can anyone watch standard def? Join Date: Feb 2008 Location: Atlanta metro area Posts: 17	http://www.solidsignal.com/pview.asp...u=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/u...1108_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?

11-07-2009, 06:38 PM	#11
EscapeVelocity High Definition is the definition of life. Join Date: Jun 2008 Posts: 59	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.

11-09-2009, 11:39 PM	#12
space ranger How can anyone watch standard def? Join Date: Feb 2008 Location: Atlanta metro area Posts: 17	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?

11-10-2009, 09:04 PM	#14
EscapeVelocity High Definition is the definition of life. Join Date: Jun 2008 Posts: 59	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_...taName=201-500

11-10-2009, 09:23 PM	#15
IDRick High Definition is the definition of life. Join Date: Oct 2008 Location: Eastern Idaho Posts: 1,106	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...s&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...s&sku=PV23-222 Best, Rick