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Old 2007-09-30, 04:39 AM   #181
dfex
 
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I've never seen an audio pre-amp before so I'm not sure. But it did look like a pre-amp for TV antenna's - two parts, one mounted close to the antenna, the other placed in the basement with a power source (two ports - one read ANT-IN, the second TV-OUT). They said they've used these for years so I'm pretty sure they know what they're doing.

Do you have a link to the Antec website?
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Old 2007-09-30, 06:54 PM   #182
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I also know nothing about Antec pre-amps. They may be fine, but I would stick with either CM or Winegard.
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Old 2007-10-01, 11:31 AM   #183
dfex
 
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Sorry guys - my mistake. The brand name is actually Anteco (I forgot the "o"). Anybody ever hear of this brand before?

I found this on the net:

Anteco Electronics
200 Wood Dale rd
Vaughan, Ontario, Canada

But the phone number is not assigned and the website doesn't work.

Anyway, I requested a Channel Master 7777 instead.
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Old 2007-10-12, 09:04 AM   #184
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Default Should my Preamp power source be closer?

Hi Folks,

I've carefully read through this entire thread and I understand a heck of a lot more about amps and preamps etc. Thank you! I'm generally quite pleased with my results (posted here: http://www.digitalhome.ca/forum/show...&postcount=523) but I have lost a couple of channels (CBS and NBC from Buffalo) occasionally. I also seem to have lost ABC completely. I'd like to try and rule out any problems at my end and maybe attribute the losses to environmental issues and/or my bungalo surrounded by large trees. i.e. I want to confirm that my long cable run is not hurting me.

I have a CM4221 with a 7778 preamp. Obviously the amp part is mounted on the Antenna pole. I know this part is done right because Yamon helped me install it. :-) I did the rest of the setup afterwards.

After the amp, there's an estimated 50 to 60 feet of RG6 that runs through the attic and then inside an interior wall down to my networking 'hub' in the basement. At that point I have the power source for the Preamp and then there's another 40 to 50 feet of cable that go to the TV.

Questions:
1) Does it matter that the power for the preamp is upwards of 60' away?
2) If I sometimes (but rarely) see the partially unstable channels at almost 100%, does that pretty much confirm my cable setup and distances are fine? Or is it possible to still have a less than optimal setup and still see weaker channels with really strong reception occasionally?
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Old 2007-10-12, 09:23 AM   #185
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dfex; That link is dead.

btsterli; Without me cheating and getting out my map, aren't you in the shadow of the CN tower?? Don't you guys get blasted with overload??
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Old 2007-10-12, 11:41 AM   #186
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Good question videobruce: Assuming 'shadow' just means close (vs. a specific OTA meaning) then yes, I'm just over 10 km from the CN Tower.

After reading through this thread, my understanding of overload is that certain channels start to pixelate and I would assume that would always be the close channels? In fact the channels from the CN Tower have all been around 90% and are extremely reliable. It's only the long distance channels that are sporadic.

Can overloading occur on the long distance channels too? Does overloading just pixelate a channel but still show good reception in the tuner? Or does it also cause the tuner to display it as 'bad' reception (such as with ABC at 90% immediately after my install but 0% to 10% the last couple of weeks)?

Also note that I believe a preamp is justified because of my long cable run and my future plans to split the cable at least 4 ways.
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Old 2007-10-12, 12:04 PM   #187
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Quote:
Can overloading occur on the long distance channels too? Does overloading just pixelate a channel but still show good reception in the tuner? Or does it also cause the tuner to display it as 'bad' reception (such as with ABC at 90% immediately after my install but 0% to 10% the last couple of weeks)?
It's cross modulation and it's most likely cause by analog station(s). Scan the analog all channel in analog mode and you will see/hear analog station where they should not be.
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Old 2007-10-12, 05:23 PM   #188
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Thanks Kro. I've been doing a bunch of searches on "cross modulation" and it seems to only come up with your posts. I appreciate all the info you've documented the last couple of years! However, I just can't imagine you're the only one on Digital Home who has had this type of problem and found ways to resolve it. Is it possible there's another name for this that I could use for searches to do more research?
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Old 2007-10-12, 05:50 PM   #189
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Exclamation Overload drowns weaker channels

Quote:
my understanding of overload is that certain channels start to pixelate and I would assume that would always be the close channels?
Overload as in overloading an amp wipeing out the weaker channels.
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Old 2007-10-12, 05:59 PM   #190
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You can start with:

This is a spreadsheet (By holl_ands ) and you can play with it.
Google->SF DTV_Overload_Calc_RevD.zip

Read the thread where that guy post.
Google->holl_ands Pre-Amp
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Old 2007-10-13, 12:07 AM   #191
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btsterli, the placement of the power supply does not affect the performance of the preamp.

All the power supply does is power the preamp which pushes signal gain down the coax cable.

I'm sorry that I did not see those problems when I was there.

See how reception is this weekend and let us know. As I replied before mark the pole position and if you like try and move the pole a little more east at a time while comparing the signal strength of Nbc and Fox.

When I was peaking your antenna I normally setup for equal signal strength for Nbc and Fox. Positioning your antenna more east did not give me any more signal strength for Nbc.

Remember you have some huge trees, and with the wet weather we are having when the leaves accumulate moisture it will tend to absorb some signals, just like fog affects reception.

Normally chans that overload pilexates and the signal strength on that chan jumps down and up.

Check the signal strength of Nbc, Cbs, and Abc and let me know if they fluctuate allot. If they do then you can add attenuators.

Overload does not affect only strong signals. On a Dish811 receiver that I have at home with my setup Pbs pixelates and to correct it I had to add attenuators 9db compared to the other tuners in my house just the regular splitter loss 7db. This means the dish is down 16db to get all ota chans fine. Without the attenuators all other chans comes in fine but Pbs breaks up. Four other tv's in the house is fine without any attenuators.

Question are you encountering all these problems after the rewiring you did? Are the connections at the end of cable that you used proper and if you strip the coax you did not strip away the braided ground wires.

Hope some if this info helps.
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Last edited by Yaamon; 2007-10-13 at 12:18 AM.
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Old 2007-10-13, 10:26 PM   #192
btsterli
 
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Thanks for the info videobruce and Kro. That one small clarification from videobruce is what I just didn't quite understand from all the posts I read from this thread (although it was probably right in front of me the whole time!). When a tuner is overloaded from an amplifier and one or more channels are so strong it can make the weaker channels even weaker.

Armed with this new info I did a real quick experiment. I tuned to MyTV which is always a bit weak. Even though Friday evening seemed like a decent OTA night, I could tell MyTV was just barely getting locked by my TV. It was somewhere in the 30 to 40% range. As an experiment I tried taking out the one splitter I have attached right now. The splitter has always been there but I just haven't utilized the 3 other outputs from it yet. When I took the splitter out, MyTV completely went away and was down around 20%. When I put the splitter back, reception went up again so the TV could lock it. I did it a couple of times just to prove it wasn't a coincidence.

Given what I've learned from this thread, more experiments are in order and likely one or more attenuators will be needed. I have lots of old cheap splitters which can be used as a poor man's attenuator to do testing if I read correctly. I guess the process would just be to keep adding attenuators as long as the weaker channels keep getting stronger.

Yaamon: Don't apologize. I'm very happy overall and you had nothing to do with the setup inside my house. I also think the install day was an excellent OTA day which could mask anything that was less than optimal in my setup. You're probably right about the moisture on the leaves. I've been keeping an eye out for fog days and diligently checking the signal and been impressed. However, I didn't think about the moisture on the leaves. I may have to wait until next spring to prove that theory though. ;-)

I also must note that my concerns about ABC were completely incorrect. Sorry guys. It must have had a bizarre problem when I did a full scan a couple of weeks ago. When I noticed it missing I tried to manually add it but I did it wrong! Duh! A full scan on Friday night brought it back properly and it's much stronger than NBC and CBS.
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Old 2007-10-17, 02:26 PM   #193
btsterli
 
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Default Results from further testing with attenuators

As I mentioned in the post immediately above, I'm certain that I have at least some form of an overloading problem if I don't use my 4-way splitter. When it's missing, weak signals get weaker. When it's there you can immediately see them go up as I described.

Since then I have purchased some real 3db Attenuators made by Channel Master. Adding one of those attenuators either at the TV or just after the splitter is inconclusive. At first I thought it made a difference but the signal was moving around quite a bit so I couldn't prove it 100%. I can conclude, however, that adding a second 3db attenuator will for sure cause the weaker signals to go down.

What's interesting is that despite the splitter and two 3db attenuators, I still have one distant channel (PBS) that is rock solid at 100% reception all the time. It never wavers. Even all the locals from the CN Tower aren't that strong. If a channel is still 100% all the time is that a fairly clear indication that it's causing at least some minor overloading?

In my quest to optimize, should my next test be to get a notch filter specifically for PBS? I guess the problem with notch filters is they are relatively expensive for just doing a test. Is there any way to do some kind of a test to simulate what a notch filter would do? Again, I don't really have have any significant problems (that I'm aware of) I just want to try make sure I've done everything correctly inside my house to squeeze every last db of signal for the US networks that aren't coming in quite as strong.
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Old 2007-10-17, 02:35 PM   #194
stampeder
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Default Time to talk to Tin Lee Electronics

bsterli, given the unusual circumstances you are facing I highly suggest that you either visit or call Tin Lee Electronics in Toronto and get their opinion:

http://www.tinlee.com/contactUs.php

The top guy, Philip Lee, is a genius and I would be very interested to see what he suggests.

Also if you talk to Philip please ask him if he has any new projects or products he's working on. I heard a very strong rumour that he has a design for a super-efficient preamp but hasn't produced it yet.
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Old 2007-10-17, 03:48 PM   #195
Kro
 
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Quote:
If a channel is still 100% all the time is that a fairly clear indication that it's causing at least some minor overloading?
I would be very very surprise that a distant DT signal would cause overload. It is for sure an analog station. Don't forget that those % are signal quality.

Anyway if you want to make more test:
1-Disconnect the Pre-Amp and put attenuater in it's place until you receive only one or two channel (It will most likely be an analog channel and it's the one you want to attenuate.)


2-Add the 3 db attenuator before the pre-amp and see the result (If any). You can try to add more attenuater (Up to 20db) and check result. Don't forget to scan also in analog and note the difference. By adding attenuater before the pre-amp that will help you determine the number of DB the notch should have.
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