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Advice for Antenna in Marin, CA

2K views 58 replies 9 participants last post by  hotsho111 
#1 ·
Comcast recently (as of Oct 1st) started blocking QAM channels in my area and I was hoping to get an OTA antenna to get some local channels.


Me neighbor has a small GE rabbit ear antenna that she let me borrow and I hooked it up but the only channel I got was 4-1. My apartment has cinderblock walls, which I imagine would be causing that.


I do have 2 south facing windows, but I have no problem throwing something up on the roof but I'm looking for some advice.


I'd like to get ABC, CBS, NBC and Fox and ideally ION (65.1). I'm not sure that is possible though


I was checking out the clearstream2 (and 4 in the hopes of getting ION), db2 and cm4220.


Is it even possible for me to get ION from where I am? That was the only reason I was considering the clearstream 4, which could be ruled out if it's not possible.


Any advice is appreciated


Here are my TVfool results:
 
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#28 ·
So I hooked up the preamp today and the signal is exactly the same.


This is how it's currently wired (from the antenna):


Antenna -> UHF/Combined input on the preamp (with the switch set to UHF/combined. Strangely the manual said UHF/combined should be the default but it was actually set to separate inputs) with the FM trap on -> 10 feet of cable -> a second fm trap (this was where I put the originally recommended fm trap) -> 10 feet of cable into the house -> RCA amp -> splitter -> 7 foot cable to first tv, 15 foot cable to second tv


Thoughts?
 
#31 ·
Wow! I'm surprised that the preamp made no change in your signal strength. All I can figure is that the preamp isn't working.


Larry
 
#32 ·
No, put it at the input! Otherwise, it's useless. Until it's correctly installed, you won't know if it's having any effect or not. This is the third time I've told you where it needs to be.


Keep in mind that "signal strength" meters in TV sets don't measure signal strength. If the reception problem is due to signal quality issues, the amp will make little to no difference. If the amp was not working, you would have seen a marked reduction in overall reception.
 
#34 ·
Yes, there is a reason I told you to try it on the input (I know how ineffective the internal one is). I specifically wanted the FM filtering doubled as you have multiple unobstructed 80K FM stations less than 5 miles away with a calculated signal differential of 30 dB-40 greater than KNTV.


There are multiple possible reasons that you're having problems with that one channel. Adding a filter (properly) that you already have in hand will take care of one potential reason.
 
#35 ·
Just moved the trap. I noticed without the trap my second TV wasn't getting NBC at all. It's picking it up again but the reception isn't that great.


The signal doesn't seem to be any different though. I'd say the two channels giving me the biggest problem, ION and NBC are slightly worse after the preamp install.


Edit: had a hunch since the separate/combined switch was the opposite of what the manual said so I double checked the fm trap. Manual said it was on by default, it was turned off. Now both traps are on. The signal strength is the same. The stability seems about the same, but I'll give it more time to see how it goes.
 
#36 ·
So after testing this out for a day or so, I don't think it's making a difference. I did confirm that I do need the fm trap to get NBC on the second tv though.


These results make me think that the NBC (and sometimes ION) signal that I'm getting is occasionally getting blocked by something (trees would be my guess), so when I get the signal, it's strong, but I don't always get the signal. The preamp wouldn't help with that though
 
#37 ·
See post # 8.


You're probably down to two possible remedies, either singly or in combination:


1) Go big. Your signals from San Bruno are likely far weaker than the math suggests. A much larger antenna will have an advantage of being more capable at picking up weaker signals at a better signal to noise ratio and will better reject multipath.


2) Continue experimenting with antenna height and location to see if you can find a better location.


Trees don't seem to have the ability to affect VHF as severely as they do UHF. However, if you can find a tree-free signal path, that might be helpful.


One other possibility is local electrical interference. The only effective way that would be diagnosed would be to get your hands on a spectrum analyzer.
 
#39 ·
So, like a madman I've given it my all today to see what I could do. I replaced all the old cable ends (they were outside from an old satellite installation and the ends were pretty corroded).


I went back and forth from the root adjusting the antenna, using the amp, not using the amp, messing with the ground, in the middle of the day it seemed to start getting significantly worse and I couldn't get it back. Felt exactly like this: http://xkcd.com/349/


After much, much trial and error I think I got the ideal direction for the antenna. To the south east of where I live there is a big mountain, if I aim the antenna way west around the mountain, I get NBC pretty good but lost ION. If I aimed it way east around the mountain I got ION ok (not great), but couldn't get NBC. The best location is pretty much pointing directly at the mountain between a gap in some trees.


Weirdly, my second TV actually seems to be handling the NBC signal better than the first. I've been testing this by having them both on and my main tv (55" plasma) seems to cut out a lot more than the second tv (26" LCD). There were times where the primary tv would cut out for a few seconds where the second tv wouldn't have any problems.


I'm still not convinced the amp is doing anything. After getting what I felt like was the ideal position of the antenna I started messing around using or not using the amp. With the amp installed the signal strength doesn't change and the picture stability (not sure if that's the right word) doesn't appear to change.


I also tried installing a grounding block with a 10AWG solid copper core wire for a ground wire but that reduced the signal strength by 8% or so. Would hooking up a ground directly to the antenna cause any signal issues?


Getting a good workout today though, I've probably gone up and down off the roof more than 30 times.


Thoughts? I know the amp at the antenna is the better choice but I might try a distribution amp just so I can be sure I've exhausted my current options (besides getting an even bigger antenna or a rotator).
 
#40 ·
Wow... you've tried just about everything. As you're finding out, TV signal reception is a crap shoot and sometimes you win, sometimes you lose.


If the amp isn't doing anything, it must not be working. Take it out of the line and send it back for a new one. An amp that doesn't increase your signal is no good, so you need to replace it. Other than that I don't have anything further to offer as suggestions.


Looks like the tuner in your smaller LCD set is better than in the larger TV. For my own curiosity, is the smaller set newer than the large one? For me, every newer TV I've bought has had a better tuner than the previous models. Our first Sony, which produces a great HD picture and is still working great, only receives about half the channels that the newer sets get. The tuner in our new DVR beats them all and receives three stations that I can't get at all on any of the other sets.


All the best in your continued efforts...


Larry

SF
 
#41 ·
The smaller tv (LNT2653H) is actually significantly older than my Plasma (a GT50). 6 years older in fact haha.


The only thing I was thinking is maybe the smaller tv could handle a worse signal better because it doesn't need to be amplified as much to fill a large screen (that was the only thing I could think of, probably way off though).


It's frusting, soooooooo close to having exactly what I'd like.
 
#42 ·
The signal strength depends on the sensitivity of the tuner in the receiver. It has nothing to do with the size of the picture. In your case, your older TV is better for receiving weak signals.


Change that preamp and I think you'll be in business.


Larry
 
#44 ·
Well this is kinda strange. I got the new amp in and when using the new amp I no longer get NBC. Switching back to the old amp I DO get NBC. I double checked to make sure the FM trap was on as well.


I literally just replaced the amp so the cable length is the same for both. The old amp is mounted on the pole the antenna is, the new one I just hooked up and let sit on the roof (no idea if that would make a difference).
 
#45 ·
Sorry, but I don't know what to tell you now. None of your results make any sense. All I can say is best of luck on your trials and efforts.


Larry

SF
 
#46 ·

Quote:
Originally Posted by hotsho111  /t/1493248/advice-for-antenna-in-marin-ca/30#post_23878715


Well this is kinda strange. I got the new amp in and when using the new amp I no longer get NBC. Switching back to the old amp I DO get NBC. I double checked to make sure the FM trap was on as well.


I literally just replaced the amp so the cable length is the same for both. The old amp is mounted on the pole the antenna is, the new one I just hooked up and let sit on the roof (no idea if that would make a difference).

You might want to move the RCA preamp power inserter closer to the preamp. The regulated voltage required by the preamp is generated in the power inserter, I think it is +10 VDC. If you have a long cable run, this voltage will drop, possibly to too low a value to power the preamp.
 
#47 ·
The cable length from the power inserter to the preamp is ~30 feet. I can't really get it much closer than that.


I did swap the preamps again today and this time the results were the same. I'm guessing it's just crazy coincidences.


I does appear that when the preamp is in I either get a clean signal or nothing where without the amp I would get some pixellation a clean signal, or nothing.


I'm not sure how much more I can do from here but I appreciate the help from everyone.


If I come across some magic bullet I'll let everyone knows (in case anyone stumbles across this in the future)
 
#48 ·
Your preamp boosts both signal and noise the same amount (somewhere in the 10-30 dB range), so even with a splitter both TVs should be getting strong signals. (A 2-way splitter takes 3 dB away from each output.) I think your problem with NBC and ION are that you are hitting the bottom end of your combined system's noise margin (the signal to noise ratio, expressed in dB). If the noise margin by the time it gets to the TV is negative or near zero, then there is no way for the tuner to separate signal from noise.


If you take the NM figure in your TVFool report for a channel, add your antenna's gain figure for that range or channel, then subtract the noise floor of your preamp, you get the real noise margin your TV will see. That part about "subtract the noise floor of your preamp" may be your saving grace: Most of the $20-$30 preamps have noise floors around 5 dB! ChannelMaster has some that come in around 3 dB, but Winegard has a brand new LNA-200 preamp for about $80 on Amazon) that has 1 dB across the entire OTA spectrum.


That extra 4 dB might make a real difference for your marginal channels. I live in North San Diego County so the nearest broadcast tower farms are 75 miles Northwest over 2 mountains (Mt. Wilson in LA) and 45 miles South over one nearby hill (Mt. Soledad in San Diego). I have a 10 element Yagi directional antenna (~10 dB gain) with Winegard's previous LNA-100 preamp pointed at Mt. Wilson. I get the VHF channels with 100% symbol quality. By the conventional wisdom of the antenna info websites, 75 miles is about the limit for Line Of Sight (LOS) signal paths, but I manage to do it over two mountains because of the high-gain antenna and low noise floor preamp.


I also manage to get very good (100% symbol quality) UHF channels from Mt. Wilson with a ChannelMaster highly-directional 8 bow-tie UHF antenna and their UHF-only preamp. That would actually get another 2 or so dB NM if I replace the preamp with a Winegard LNA-200.


You may not want to change to a higher gain antenna because they obtain that gain by being much more directional. You have some very receivable stations in several different directions, so you should probably try upgrading the preamp to see if it gets "good enough" with your "center of the mountain" position. Of course, that is if you want to spring for $80 on the hope to get both ION and NBC with one antenna setting.


Good Luck!
 
#49 ·
#50 ·
That Winegard preamp has been selling for around $50 - $57 from various online vendors. I think the noise figure may be around 1db on certain channels, and 3db on others as stated. You may also want to consider one of the Kitztech preamps, as they have a low noise figure and perform well. I have gotten by best signal strengths from the Kitztech.
 
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