LA CA preamp antenna questions

[James]

Advice requested on preamp for antenna.

It took me a long time from the advice on what to install (see this thread: New Antenna in Hemet CA http://forum.tvfool.com/showthread.php?t=3014) to finally select and setup my antenna.
That advice is appreciated.

Now I am getting reception of most channels out of LA on my Winegard HD7084 High Definition VHF/UHF Antenna. Signal strength on my Panasonic GT50 Plasma varies from a high of 86% down to 14% and even zero. When I fall below 40% on some channels and mid thirties on others it will start to break up then seriously and completly drop out when it drops to the 20s and teens.

This has all been great given that I was advised I would only get a few channels and not all the time on those at this 70 mile distance.

When I was watching the Olympics it would drop out intermittently on channel 4. This would happen at completly random times both day and night with early evening being more and more intense drop outs. These would last from seconds to a several minutes. Channel 13 would also drop out with 4. Rarely channel 2 would fail during that time and when it did channel 4 would usually show strong signal with occasional drops. This reception pattern was consistent in both sunny, windy and rainy weather and at night.

Recently we have had a cooling trend here in the Southern Calif region. Also the days are getting shorter and I notice that I get more drop outs and loss of channels in the evening hours lasting till after sunset. Last night, the 24th of August was the worst. I lost 2, 4 while 7 came in strong. I had 11, can't remember if 9 and 13 came in but I also had drop outs in the PBS channels 22, 24, 28 and 30 which has been rare. Another odd thing has been that when 2, 4 and 7 have strong signals the UHF channels are weaker signals and vice versa.

Bottom line, currently I can watch most channels just fine all day long and until last night in the evenings as well. Still losing several minutes at a key play in sports or the peak of drama hurts.

I have read a bit on preamps and am confused what to choose or if one will even resolve the problem. If the signal goes away completely obviously I will receive nothing. But last night it would log on just enough to pixelate the whole screen and freeze image or judder for minutes at a time. Not watchable.

Here's the specs on my setup; The antenna is on a mast at a height of 19' pointed at or a few degrees south of 299 ° . I have a 15' quad 6rg cable running from the antenna 75 ohm down lead to a groundblock splitter. It is a two out splitter at 5 - 1000Mhz. The open side of the splitter is not capped. I am running a cable that I think is rg11 dual shield because of it's thickness compared to rg6 at approx 50' along underside of metal carport roof and in through a metal sided window to a coupler and then 6' of the rg11 into a splitter for cable/antenna (Mhz unknown. It came from the dollar store. It works). Finally I have 6' of quad rg6 plugged into the TV from that. That comes to 77' of cable run with two splitters.

My estimation of signal loss lead me to think I should get the WInegard preamp ap8275 with it's29db boost. Guidelines say that the TV has AGC and that makes me wonder if it won't negate the boost signal enough to overcome the weakness. Also when I have an excellent signal will the boost be a risk to my TV electronics? I have attached a pictures of the antenna as well as the skyline it is pointed at. You will see a tree approx 100' away partially in the path. It seems to me it is not having an effect on signal quality.

Channels I get: 2,4,7,9,11, 11.2 FoxSD, 13, 20*, 22, 24, 28, 30, 46, 50, 51
*lists but no reception.
Channels I'd like to add KTLA 5, FSFV 6, KFLA 8

Feedback on what might be causing the signal loss when it happens as well as suggestions on my preamp choice invited.

[rabbit73]

James:

I looked at your tvfool report from the other thread:
http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3d60b5a214cc43dd

It looks like there is not much chance of overload, so a preamp would help a lot.

Checking your local FM signals, the strongest is KLYY at -28.9 dBm, so it probably will not cause a problem; see attachment. If it does, then use an FM trap.

I have a 15' quad 6rg cable running from the antenna 75 ohm down lead to a groundblock splitter. It is a two out splitter at 5 - 1000Mhz. The open side of the splitter is not capped.Are you using a 2-way splitter for a groundblock with one port unused? That gives a loss of about 3.5 dB. If you don't need the splitter there, then use a regular groundblock.

If you do need a splitter there, then it must be a powerpassing splitter for the preamp at the antenna.
I am running a cable that I think is rg11 dual shield because of it's thickness compared to rg6 at approx 50' along underside of metal carport roof and in through a metal sided window to a coupler and then 6' of the rg11 into a splitter for cable/antenna (Mhz unknown.Are you using a splitter to combine antenna and cable signals? That's not a good idea; use an A/B switch. The cable company and the FCC would not be happy that your antenna is radiating cable signals.

RG11 does have less loss than RG6, so it helps with long coax runs. With a preamp, it's overkill.
Guidelines say that the TV has AGC and that makes me wonder if it won't negate the boost signal enough to overcome the weakness.The AGC adjusts the gain of the tuner for the channel selected. The AGC is your friend because it adjusts the tuner gain to compensate for changes in signal strength.

With very weak signals, the AGC doesn't compensate because the tuner is being run at max gain. That is why you see intermittent pixelation and picture freeze when you are at the "digital cliff." See attachment #2 for my noise margin diagram, as defined by Andy Lee. Andy has an interesting post with two diagrams of signal reception and his explanation of Noise Margin:
http://www.avsforum.com/t/841787/tv-fool-discussion-thread/390#post_15700679 #397
Also when I have an excellent signal will the boost be a risk to my TV electronics?No; even if overload happens, it shouldn't damage your preamp or tuner with OTA signals.

There are three types of preamp overload, in order of increasing signal strength:

1. The strong signals cause enough IM distortion to interfere with the reception of weak desired signals. This is the point that holl_ands uses in his preamp charts (http://imageevent.com/holl_ands/files/ota) to obtain max SFDR (Spurious Free Dynamic Range). No damage will happen.

2. The strong signals cause overload to the preamp or tuner that makes it impossible to receive any signals. No damage will happen.

3. The signals are so strong that the input transistor is toast. You are not likely to encounter OTA signals that strong.

I used to favor the CM7777 preamp until they changed the design. They should have called it 7777A after making such a drastic design change to keep it from being confused with the original. At this time there is not enough feedback to know how it compares with the original.

I haven't tried the AD CPA19, but a lot of people like it.

[James]

Rabbit:

Thank you. I saw your posts in another thread and you show a great deal of knowledge. This somewhat technically challenged guy who likes hands on sure appreciates it. Regarding my stating that I had a splitter for the antenna and cable I, with that tech challenge issue misspoke - it is an a/b switch (physically similar to splitter but with two in and one out and a slide switch on top. I don't know if this device bleeds any Mhz but the switch slides over from cable to antenna. My perfect signal under what are the ideal conditions of a clear warm temp day shows a percentage of signal mirroring my test setup with no splitters or switches.

I bought the ground block because it is what was on the rack at Fry's Electroincs. I rent from my landlord next door I may end up splitting the signal to them when they return in the fall.

I am unclear on how the power to the preamp will be affected by the splitter. I envision that the coax from the power cable will connect to where the coax now exits that splitter to my TV (a/b switch actually). Then I thought the preamp dc converter would have that feed out to the TV from a second cable. Is this right?

Also your reply Rabbit reminded me that I did not mention that Accessing the inputs at the antenna is extremely difficult if not impossible. They are above the center of the carport roof, an aluminum siding type material that will not bear weight. I don't have a ladder that will get me to the 19'. I had thought I would connect the preamp just above the ground block using the 15' rg6 quad and then jump to the ground and complete the rest as needed. I figure that the rg6 quad should not lose much signal at all. Is this right in your opinion?
I did come across that antennas direct AD CPA19 while checking on the Winegard AP8275. The Winegard does have an fm trap.

I came back over here to check for replies when the Saints and Texans game lost the signal completely at around 6:30 PDT. I checked and all the channels up through 28 were gone as well. I did not have this drop out blitz when the Olympics were on which was the first week it was up.

[rabbit73]

- it is an a/b switch (physically similar to splitter but with two in and one out and a slide switch on top.Good, then no problem there if the switch keeps working OK.
I bought the ground block because it is what was on the rack at Fry's Electroincs. I rent from my landlord next door I may end up splitting the signal to them when they return in the fall.I have a 15' quad 6rg cable running from the antenna 75 ohm down lead to a groundblock splitter.It's still not clear to me what you have there. There is no such thing as a groundblock splitter. A groundblock connects the coax shield to ground to satisfy the NEC for safety; it has very little loss. It is similar to an F81 coax coupler connected to ground. A conventional 2-way splitter can be used as a groundblock, but because the signal is divided in two there is a loss.

If you have a conventional splitter at that location just below the antenna it will not pass the DC power to the preamp. The coax between the preamp near the antenna and the power supply indoors carries the RF signal and the DC power at the same time. The DC goes up to the preamp and the signal comes down the coax to the power supply and then to the A/B switch and then to the TV. You need to replace it with a splitter that passes the DC power to the preamp in addition to splitting the signal in two. A conventional splitter will not pass the DC for the preamp.

For purposes of making a test with a preamp, I suggest you mount the preamp, without the splitter, as close to the antenna as you can without climbing; there will not be too much loss in the 15 feet of coax to make it worth the trouble of climbing.

antenna > 15 ft coax > preamp > real groundblock > coax to indoor power supply > power supply > A/B switch > TV

When it comes time to send some signal to the landlord:

/ landlord's TV
ant > RG6 > amp > DC pass splitter >
\ coax to p s > power supply > A/B > TV

If you can put the splitter indoors after your power supply to send some signal to the landlord, then you can use a conventional splitter and eliminate the special splitter outdoors.

Thread about DC pass splitter:
http://forum.tvfool.com/showthread.php?t=9235
http://www.antennasdirect.com/store/2-Way-DC-Pass-Splitter-SPT2.html
http://www.antennasdirect.com/cmss_files/attachmentlibrary/Using_A_Preamplifier_With_A_Splitter_Opt2.pdf

Grounding thread:
http://www.avsforum.com/t/1333059/grounding-antenna-and-dish

Grounding block in attachment. The NEC calls a grounding block an antenna discharge unit.

[GroundUrMast]

Most splitters include a connection for a ground lead and therefor can serve as a connection to the shield conductor for grounding purposes.

I would encourage anyone using a splitter in this manner to mount it adjacent to the electrical service ground, so as to minimize the length of the grounding conductor. Also, it's best to make the shield ground connection outside, before the coax enters the building, therefor all the connectors attached to such a splitter need to be waterproof.

[No static at all]

The Winegard 8275 is an excellent choice for the money. It will most certainly improve reliability of the desired stations.

[teleview]

The Following is a Teleview Recommendation for Tv Reception.

To prove Tv reception , do this test , aim the antenna at about 300 degree magnetic compass direction. Here is how to aim antennas , http://www.kyes.com/antenna/pointing/pointing.html.



Run a known to be good long RG-6 coax from the antenna through a open door or open window direct to the Tv , no couplers , No splitters , no amplifiers , no nothing.

Scan for channels.

___________________________________________

After proving reception.

Replace ALL of the Hodgepodge of coax with all new RG-6 , quad shield is not required but you can use it if you like.

The compression type coax fittings (not the crimp type) will help seal out water.

Here are High Quality Power Passing splitters.

To be used if preamp power is to be passed through the splitter.

HFS-2D , 2 way splitter.

HFS-3D , 3 way splitter.

HFS-4D , 4 way splitter.

http://www.hollandelectronics.com or http://www.solidsignal .com.

____________________________

Do not chain splitters one after the other , one splitter connected to another splitter connected to another splitter , eash time a split takes place the signal strength is reduced.

Use only one splitter and coaxes out to the Tv locations.

[James]

Hey Guys:

You are great. Thanks for the input. I have attached a picture of my splitter ground block. I don't recall seeing the straight through ground at Fry's but have seen it elsewhere. Being at Fry's and thinking I might give feed to my landlord and emmm.... assuming that the connections for coax to grnd blks were basically the same I went with it. I can go out and grab the straight one thus eliminating some of that loss. Thank you Rabbit and Ground. Ground your comment about waterproofing is appreciated. My ground block is out doors right where the feed wire runs off through the car port at about 9' high. I have the wire attached to a 6" bolt connected to and sticking above my antenna run to and thru the block (by stripping 3/4" there) and then continuing on another 8' to a ground block on my service panel. Those are not water proofed so I thought I did not need to waterproof the antenna block.

And No static thanks for recommending the 8275. I will order it right away.

Last night the system began it's breakdown of signal shrotly before sunset and just grew worse all night. Only channels I got were 9 KCAL and 30 Ion. Can of any of you tell me what could cause the reception to break down at that time of day?