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Old 23-Apr-2014, 11:02 PM   #1
mulliganman
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help troubleshooting

I have been having reception issues on my local ABC and its sub-channel. My setup is a two antenna setup. I have an Antennas Direct C2V pointed toward all towers except Fox (it is in a completely different direction). I am using an Antennas Direct 91XG to pull in Fox. I just recently had both antennas combined using this custom combiner: http://www.tinlee.com/PDF/AC7-custom...kup%20Info.pdf

The combined output ran to a Channel Master 3414: http://www.channelmasterstore.com/An..._p/cm-3414.htm


That is then ran out to 3 television sets. I had experienced some trouble with the new Channel Master DVR+ that I was hoping the Tinlee AC7 combiner would solve. But, unfortunately it didn't. The Tivo Roamio I have hooked up was not having any of the same problems the DVR+ has with the same setup. I began problem-solving to make sure that the tuners on the Channel Master DVR+ weren't being overpowered (which they weren't). I can't add a preamp to the Antennas Direct C2V (that's where the ABC stations are coming from) because when I ordered the custom AC7 combiner I only had DC pass built in for the Fox station from the Antennas Direct 91XG (because according to my TVFool report it is my weakest station). I had this amp laying around from an earlier setup:

http://www.solidsignal.com/pview.asp?p=sky38323


I decided then to run the combined output from both antennas into the Skywalker amp (it has a nob to control amount of amplification; I did not turn it up all the way), then from there to the Channel Master 3414 amp and split to the 3 TV's. Then voila. The ABC channels stabilized and my Fox station signal quality has jumped up to 84% signal strength and mid 90's signal quality. Unfortunately, the stabilization of ABC and its sub-channel (33.2) only lasted a couple of days. Now, the signal quality meter on the Channel Master DVR+ is back to fluctuating quite a bit. Hence, the picture difficulties on said channels.

So, I am looking for help with this situation. One TV only connected to a coaxial line doesn't have the problem. Another set connected to a Tivo Roamio hasn't had the problem. I'm not sure what to make of it. I'm wondering if there is an issue that the DVR+ is detecting because it is more sensitive but don't know what it could be.

Here is my TV fool report: http://www.tvfool.com/?option=com_wr...5b940f11af42d0

Here is Antenna Web report too: http://www.antennaweb.org/Stations.a...on=-93.1995227

Last edited by mulliganman; 24-Apr-2014 at 3:01 AM.
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Old 24-Apr-2014, 2:15 AM   #2
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I'd suggest you start at the antenna. Each antenna should be capable of driving a single tuner with no accessories. To test, connect the antenna via a known good coax, not longer than 50', though shorter is better if it's practical. Connect only one tuner, preferably one with a good signal quality/strength meter function.

Does each antenna produce a reliable signal for each desired channel? If not, you need to consider changing the antenna, it's location or it's aim... or some combination of these.

Once you have established reliable 'barefoot' (non-amplified) reception, then consider the need for amplification. In this case, I doubt the need for a preamplifier on the main antenna, but the 91XG may benefit from an RCA TVPRAMP1R at the antenna.

It's also possible that a 3 dB or 6 dB attenuator on the inputs of the AC7 combiner may help by isolating less than perfect cable impedance or antenna SWR. The resistive termination of an attenuator may help the tuned filters in the AC7 behave as designed. The CM-3414 is going to overcome enough loss that a few dB of attenuation should be quite tolerable.

Don't rule out the possibility of FM interference either. An FM trap is not expensive. The Radio Shack #15-024 is about $5.

At the risk of being 'nosey', how much does tinlee get for the AC7 these days?
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Last edited by GroundUrMast; 24-Apr-2014 at 2:18 AM.
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Old 24-Apr-2014, 2:55 AM   #3
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Originally Posted by GroundUrMast View Post
I'd suggest you start at the antenna. Each antenna should be capable of driving a single tuner with no accessories. To test, connect the antenna via a known good coax, not longer than 50', though shorter is better if it's practical. Connect only one tuner, preferably one with a good signal quality/strength meter function.

Does each antenna produce a reliable signal for each desired channel? If not, you need to consider changing the antenna, it's location or it's aim... or some combination of these.

Once you have established reliable 'barefoot' (non-amplified) reception, then consider the need for amplification. In this case, I doubt the need for a preamplifier on the main antenna, but the 91XG may benefit from an RCA TVPRAMP1R at the antenna.

It's also possible that a 3 dB or 6 dB attenuator on the inputs of the AC7 combiner may help by isolating less than perfect cable impedance or antenna SWR. The resistive termination of an attenuator may help the tuned filters in the AC7 behave as designed. The CM-3414 is going to overcome enough loss that a few dB of attenuation should be quite tolerable.

Don't rule out the possibility of FM interference either. An FM trap is not expensive. The Radio Shack #15-024 is about $5.

At the risk of being 'nosey', how much does tinlee get for the AC7 these days?
GroundUrMast,

Thank you so much for replying. I may have further questions, but for the moment I just have a couple. First off, I was hoping you could further explain how to test the antenna on a single tuner. Are you saying that I should disconnect both antennas (one at a time) from the AC7 combiner and run a coaxial cable from that antenna to a TV that has only a single tuner bypassing the CM3414 amp that is currently installed?

When you talk about the attenuator, you are suggesting picking up a couple correct? If so, can you recommend a specific one and whether 3db or 6db would be better?

Can you also share how/where to install the FM trap and if needed what would be a good replacement antenna for the C2V antenna (I think Channel Master said the DVR+ plays better with directional antennas). Also want to double check that I should still consider the Radio Shack FM trap (I noticed the RCA amp mentions something about an FM trap too).

As far as the AC7 combiner, its $125 plus shipping costs. For me, it ran about $150.

Last edited by mulliganman; 24-Apr-2014 at 3:07 AM.
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Old 24-Apr-2014, 8:51 AM   #4
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One easy test that I would do is unplug the C2V and cap the AC7 "All Channel Input" with a 75 ohm terminator, leave everything else the same and see if you can reliably get FOX from the 91XG, pre-amp, AC7 and cables and no second antenna.

If this works, you might even adjust the aim to optimize the signal before reconnecting the C2V. Notice that FOX is 2Edge and some times you can get a few more dB if instead of horizontal you aim the antenna up 5-10 deg toward the sky. Also, 91XG has a very narrow 30deg half-power beam width at higher frequencies in both azimuth (left/right) and vertically (up/down toward sky) so careful aiming could make a difference. I like to use True azimuth aim (instead of magnetic compass aim) as it is more accurate. Google map your house and get a true bearing off a major landmark like your roof line or wall and use that to calculate the correct aim to the Fox tower.

If FOX won't come in with the other input capped I'd try it without the pre-amp and/or without the distribution amp as you might be getting weird amp feedback loops with two amps in series. You could also temporarily take the C2V off the mast to see if it is interfering with the other antenna. If that fixes it the you'll need to figure out a way to get more separation between the antennas. You should also rerun your TV Fool report and see how high you need to go to get FOX as 1Edge or even LOS. You might need to go to a taller mast to get a reliable signal for FOX and get more separation between the antenna to minimize interference.

TL;DR: FOX is not too weak at 39.1 NM though it is 2Edge. You have a good antenna and system that should work but you need to tweak it for FOX and make it work right BEFORE combining. Once you get FOX reliably, if combining knocks it out you then need to troubleshoot that problem sepaately.
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Old 24-Apr-2014, 5:33 PM   #5
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Quote:
Are you saying that I should disconnect both antennas (one at a time) from the AC7 combiner and run a coaxial cable from that antenna to a TV that has only a single tuner bypassing the CM3414 amp that is currently installed?
Yes. The goal is to prove the antenna, by itself, is receiving a reliable signal. By using a short section (50' or less) of known good coax and a known good receiver, the antenna is the only variable left. Once the antenna has been proven to produce reliable reception of the desired signals, you can turn your attention to troubleshooting other parts of the system.

Here is a source for attenuators: http://www.3starinc.com/drop_in-line_attenuator.html The exact value is not critical in most cases. You don't want to add too much loss though. The goal is to isolate the imperfect input impedance of the filter from the imperfect impedance of the cable and connector from the antenna. The resistor network in the attenuator is likely closer to 75Ω than either. Try one 3 dB attenuator and if needed, experiment with two 3dB attenuators stacked end to end. The attenuator should be installed on the AC7 with no cable in between.

Be open to the idea that AC7 can be located near the antennas... Or not. If it's more convenient to run each antenna lead into a protected location and the combine, that's fine. I'm thinking of situations with a preamp at the antenna and power inserter inside the house. In these cases, I'm prone to place the combiner downstream of the preamp power insertion block. This also keeps the combiner protected from the weather while also making future service access much easier.

An FM trap needs to be between the antenna and preamp. The TVPRAMP1R has an FM trap built in... Simply verify the switch is set correctly.
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Old 24-Apr-2014, 9:27 PM   #6
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There should be enough signal with no preamp or distribution amplifier, even on FOX. I'd do as GUM suggests with the process of elimination and then try replacing the CM-3414 with a 4 way splitter.
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Old 25-Apr-2014, 12:48 AM   #7
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There should be enough signal with no preamp or distribution amplifier, even on FOX. I'd do as GUM suggests with the process of elimination and then try replacing the CM-3414 with a 4 way splitter.
You would think that. But, I have run tests on the antennas before bypassing the CM3414 and the signal drops dramatically.
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Old 25-Apr-2014, 1:19 AM   #8
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Yes. The goal is to prove the antenna, by itself, is receiving a reliable signal. By using a short section (50' or less) of known good coax and a known good receiver, the antenna is the only variable left. Once the antenna has been proven to produce reliable reception of the desired signals, you can turn your attention to troubleshooting other parts of the system.

Here is a source for attenuators: http://www.3starinc.com/drop_in-line_attenuator.html The exact value is not critical in most cases. You don't want to add too much loss though. The goal is to isolate the imperfect input impedance of the filter from the imperfect impedance of the cable and connector from the antenna. The resistor network in the attenuator is likely closer to 75Ω than either. Try one 3 dB attenuator and if needed, experiment with two 3dB attenuators stacked end to end. The attenuator should be installed on the AC7 with no cable in between.

Be open to the idea that AC7 can be located near the antennas... Or not. If it's more convenient to run each antenna lead into a protected location and the combine, that's fine. I'm thinking of situations with a preamp at the antenna and power inserter inside the house. In these cases, I'm prone to place the combiner downstream of the preamp power insertion block. This also keeps the combiner protected from the weather while also making future service access much easier.

An FM trap needs to be between the antenna and preamp. The TVPRAMP1R has an FM trap built in... Simply verify the switch is set correctly.
Thanks for the link on attenuators. Regarding installation, do you install it on the "output" of the AC7? How will I know if I need two 3ds while testing?

The only tuner I have that has both a signal quality and signal strength indicators is the DVR+. So, I may try it there (it is where I am seeing the signal quality fluctuations). If you advise against it, please share. I will say if I bypass the CM3414 when running this test, I don't think my signal strength will be high enough to get a reliable picture (past tests have shown this to be the case).

I didn't know that about the AC7 combiner. Based on the diagram, I thought it had to be located at the antennas to get the best results: http://www.tinlee.com/PDF/AC7-custom...kup%20Info.pdf

I thought it had to be there too as to make a better, cleaner combined signal. But, you are saying I could install the RCA preamp on the 91XG antenna and connect both leads from each antenna inside the attic though. Correct? I also assume by power inserter you are referring to the CM3414?

I did pickup the Radio Shack FM trap. I realize the RCA preamp has a trap also, but just in case I don't use the trap on that or need that preamp, where/how does the FM trap get installed? I know you said between the antenna and the preamp but I'm a little confused as to proper installation.

I'm wondering if the C2V may need to be moved a little and if that isn't causing some interference the DVR+ is picking up on when I see the signal quality fluctuations. Right now, the two antennas are probably a couple of feet or so apart.

If all the troubleshooting doesn't fix the issue and I find I need to replace the C2V do you have a recommendation? I am presuming if there is an issue it would be with that antenna since it is the one that should be receiving the ABC signals.
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Old 25-Apr-2014, 6:27 AM   #9
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Last question first... Let's try to make the C2V work before giving up on it. Yes, there should be a bit more separation between the two antennas. Two feet is pretty close together, enough to significantly detune both antennas. Three feet of separation would be the minimum... more is better in most cases. If I am using a 5' mast, I generally have room for only one antenna. Correct this issue first... it may be all that's needed.

Are the antennas in the attic or outside in the clear? If they're in the attic, please, test reception outside, clear of the building penetration loss and added RF noise.

But, back to the first and most important question, can the antenna, by itself, produce a reliable signal. If not, you need to experiment with changes of aim, location and elevation... If those don't provide reliable reception, then a change in antenna may be needed. If the antenna plus a preamp is able to produce reliable results, it suggests two possibilities,

(1) The antenna is collecting almost enough signal to deliver reliable reception, but there is so little effective noise margin that you may not be able to distribute it to multiple tuners due to the noise and distortion added by distribution amplifier, splitter and cabling. (The solution would be to experiment with changes of aim, location and elevation and, if all that fails, consider a different antenna.)

(2) The test tuner has a poor noise figure and the preamp is able to overcome the issue. (If this is the case, a better tuner would be able to do OK with the unamplified feed direct from the antenna, and the correct combination of antenna + preamp + distribution amp and passive losses in cable, splitters and combiner may deliver usable signal to all tuners.)

Re. the FM trap, presuming you have a preamp at the antenna, you'll need a short (1' to 3') RG-6 cable connected to the antenna matching network/balun/transformer and the other end connected to the trap. The cable that leads to the preamp input would connect to the output of the trap. If no preamp is present, then simply connect the down-lead to the output of the trap, or, locate the trap at the end of the down lead before any distribution amplifier. If you have strong FM signals close to you, you can use both the external trap and the preamp's internal trap. I expect the C2V to be more affected by FM if there are any strong FM signals present, but the UHF only antenna could be impacted also, if the FM signal(s) are strong enough.

Consider the attenuators an experiment, to be conducted once we have reliable signals at the antennas. Other than observing the results, (ie. does reception improve or not?) and the signal meter in the TV or DVR, there's no consumer grade test devise to connect. I'd simply install an attenuator on the antenna ports of the AC7... Then if I had another attenuator I might also install one on the output. Given the cost of the parts, it seems to be a fairly low cost experiment. This is not the place I would start... I'd need to know I had usable signals at each antenna first.

The AC7 does not need to be at the antenna location. It's a passive device and will not add any significant noise to the signals like an amplifier will. A preamp will add some noise, so it will do best when fed a signal that has not been attenuated by a long cable. If the antennas are receiving a signal with enough quality, amplification can be used to overcome the losses in the cable, attenuators, combiner and splitter. If the antennas are not receiving signals of sufficient quality, amplification and or filtering is quite unlikely to solve the problem. This is why I'm suggesting that the quality of the signals at the antennas be checked (with no amplification) to begin with. We need to know there's adequate signals to work with.
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Last edited by GroundUrMast; 25-Apr-2014 at 6:46 AM.
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Old 25-Apr-2014, 12:39 PM   #10
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You would think that. But, I have run tests on the antennas before bypassing the CM3414 and the signal drops dramatically.
That implies a fault in the antenna, balun, or coax. Water, corrosion, manufacturing problems, installation issues, and melted insulation are some possible causes.
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Old 25-Apr-2014, 4:50 PM   #11
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Last question first... Let's try to make the C2V work before giving up on it. Yes, there should be a bit more separation between the two antennas. Two feet is pretty close together, enough to significantly detune both antennas. Three feet of separation would be the minimum... more is better in most cases. If I am using a 5' mast, I generally have room for only one antenna. Correct this issue first... it may be all that's needed.

Are the antennas in the attic or outside in the clear? If they're in the attic, please, test reception outside, clear of the building penetration loss and added RF noise.

But, back to the first and most important question, can the antenna, by itself, produce a reliable signal. If not, you need to experiment with changes of aim, location and elevation... If those don't provide reliable reception, then a change in antenna may be needed. If the antenna plus a preamp is able to produce reliable results, it suggests two possibilities,

(1) The antenna is collecting almost enough signal to deliver reliable reception, but there is so little effective noise margin that you may not be able to distribute it to multiple tuners due to the noise and distortion added by distribution amplifier, splitter and cabling. (The solution would be to experiment with changes of aim, location and elevation and, if all that fails, consider a different antenna.)

(2) The test tuner has a poor noise figure and the preamp is able to overcome the issue. (If this is the case, a better tuner would be able to do OK with the unamplified feed direct from the antenna, and the correct combination of antenna + preamp + distribution amp and passive losses in cable, splitters and combiner may deliver usable signal to all tuners.)

Re. the FM trap, presuming you have a preamp at the antenna, you'll need a short (1' to 3') RG-6 cable connected to the antenna matching network/balun/transformer and the other end connected to the trap. The cable that leads to the preamp input would connect to the output of the trap. If no preamp is present, then simply connect the down-lead to the output of the trap, or, locate the trap at the end of the down lead before any distribution amplifier. If you have strong FM signals close to you, you can use both the external trap and the preamp's internal trap. I expect the C2V to be more affected by FM if there are any strong FM signals present, but the UHF only antenna could be impacted also, if the FM signal(s) are strong enough.

Consider the attenuators an experiment, to be conducted once we have reliable signals at the antennas. Other than observing the results, (ie. does reception improve or not?) and the signal meter in the TV or DVR, there's no consumer grade test devise to connect. I'd simply install an attenuator on the antenna ports of the AC7... Then if I had another attenuator I might also install one on the output. Given the cost of the parts, it seems to be a fairly low cost experiment. This is not the place I would start... I'd need to know I had usable signals at each antenna first.

The AC7 does not need to be at the antenna location. It's a passive device and will not add any significant noise to the signals like an amplifier will. A preamp will add some noise, so it will do best when fed a signal that has not been attenuated by a long cable. If the antennas are receiving a signal with enough quality, amplification can be used to overcome the losses in the cable, attenuators, combiner and splitter. If the antennas are not receiving signals of sufficient quality, amplification and or filtering is quite unlikely to solve the problem. This is why I'm suggesting that the quality of the signals at the antennas be checked (with no amplification) to begin with. We need to know there's adequate signals to work with.
When I have more time, I am going to read through and post a follow up to make sure we are on the same page with everything. In the meantime, I am wondering as TowerGuy has suggested about the cabling. Existing cabling was used upon setup. I know you said to bring in 50 feet for one of the tests. But, if it looks like a lot of the existing cabling is bad, how much cable do you think I need for 3 TV lines and 2 antennas? I am looking at using this probably: http://www.amazon.com/Mediabridge-Co...+coaxial+cable

It seems to have very positive reviews and is reasonably priced.
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Old 25-Apr-2014, 5:18 PM   #12
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After decades of messing about with cheap crimp connectors and cheap coax, I recently bit the bullet and bought a 500 ft roll of tri-shielded RG-6, and a compression fitting kit with cutter. I've used maybe half the roll already, rewiring much of the unreliable work I did in the past, plus new runs for TV (nearly 100 ft) and FM (another almost 100 ft), and feel that it was money well spent. The tools (cutter and fitting compression tool) will last forever, and the result is solid and (I feel) reliable. Not that you'd need 500 ft, but by the foot it's cheaper than shorter lengths, and I'll use it all sooner or later. The fittings are similarly more money than cheap crimp fittings, but the result is outstanding.

Just sayin'.
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Old 25-Apr-2014, 7:09 PM   #13
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I'd agree that the most common problem with existing cable (that's not exposed to the weather) is poor quality connections. Unless the cable is damaged or too short, replacement of the connectors may resolve the trouble... It's not a given that every cable run needs to be replaced.

By starting with a known good signal at the antenna, you can add individual runs to the system one at a time, checking for signs of trouble. If you add a section and have a problem, odds are high that the newly introduced parts or the connection to the existing system is the problem.

It's sort of like a plumbing system. If you have low pressure or dirty water at several taps, the trouble could be anywhere in the system. There could even be several problems adding to the confusion. In such a situation, you can avoid confusion by starting at the beginning... A well with just a little muddy water is going to result in poor pressure and water quality.
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Old 26-Apr-2014, 5:20 PM   #14
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O.K. I have tried to create a step by step set of instructions for myself based on your recommendations (this antenna stuff can be difficult for the average Joe). If something needs correcting, please let me know.

1. Move the C2V to approximately 5 feet or so away from the 91XG.

2. Run, new high quality RG6 cable (I'll be using the brand I already linked) from each antenna to a single tuner (bypassing the CM3414 and the use of any splitters) testing for reliable reception. If reliable reception is not obtained, try adjusting aim. If reliable reception is obtained, this could suggest some issue with the cable that needs to be replaced/fixed (because I don't recall that Fox has never been able to do that with this antenna setup without the use of a distribution amp; it seems other signals have been lower too).

3. If reliable reception is not obtained from each antenna using the new, high quality coax to a single tuner without the use of a distribution amp/splitter or after readjusting aim, consider changing out that antenna.

4. If/when reliable reception is obtained (and after replacing any cable from the downleads from the antennas) move the AC7 combiner into the attic.

5. Without the AC7 combiner being connected and after reliable reception is obtained, add the RCA TVPRAMP1R on the 91XG (C2V can't be amplified due to the specifications of the AC7 combiner). Observe results using signal strength/signal quality on the single tuner. If tuner is overpowered or signal quality/strength is negatively affected, re-evaluate after splitting the signal either though a 4 way splitter or the CM3414.

6. Add/utilize an FM trap on both antennas. If using the FM trap on the RCA preamp, use 1-3 feet of RG6 cable connected to the antenna and the other end to the trap (preamp input connects to the output of the trap and switch is turned on). If using the Radioshack FM trap, it can be connected toward the beginning of the download of an antenna or at the end of a downlead before any distribution amp.

7. Reconnect antenna downleads to the AC7 combiner. Run output from AC7 combiner to the CM3414 distribution amp. Check signal quality/strength on all tuners.

8. Disconnect AC7 output from the CM3414 distribution amp. Then connect AC7 output to 4 way splitter instead. Check signal quality/strength on all tuners.

9. If significant disparity exists for signal quality/strength between the CM3414 and 4 way splitter (particularly if much lower readings are present from using 4 way splitter) replace/repair coaxial cables running to all 3 TV's. Then recheck each way of connecting again. Compare those results to previous results. Use whichever accessory between the CM3414 and the 4 way splitter produces the best results for all TV's/tuners.

10. Finally, install attenuators on the "input" ports for each antenna on the AC7 combiner and one attenuator on the "outport" of the AC7 combiner. Check signal quality/strength on all tuners. If signal quality/strength drops or picture deteriorates remove attenuators.
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Old 26-Apr-2014, 5:38 PM   #15
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There are a couple of things I need clarification on. One is how to evaluate the addition of the RCA preamp when looking at all tuners since they each have different signal strength or signal quality readers currently. For example, the TV that is just directly connected to coaxial cable shows a signal strength in the mid to high 70's for Fox. But, the Tivo Roamio is around 50% while the DVR+ when not utilizing both the Channel Master and Skywalker distribution amp is in the 40's for signal strength. I guess I am saying it is hard to determine wiggle room when trying to check for overpowering a tuner.

The other thing I need clarification on is should the DVR+ tuner be used as the single tuner in the initial tests. It does have a signal quality and signal strength readers than no other TV's/DVR's do. But, it is the tuner that is having the intermittent issues with ABC and its sub-channel that don't seem to be present elsewhere.
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Old 26-Apr-2014, 5:43 PM   #16
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Are you testing these three tuners/TVs on the same short, new length of cable, under otherwise identical conditions (time of day, etc.)?
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Old 26-Apr-2014, 8:13 PM   #17
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You have a well organized task list / plan.

Re. #5, If the need for a preamp at the C2V was proven, simply lay the system out as follows; C2V Antenna > FM trap (if used) >preamp > preamp power inserter > AC7 > distribution system. The other antenna can be similar; 91XG > FM trap > preamp > preamp power inserter > AC7 > Distribution system.

Re. #6, An FM trap needs to be between the antenna and any amplifier. The job of an FM trap is to protect block ('attenuate' is more precise) FM signals from getting to the input of any and all amplifiers, including preamplifiers at or near the antenna.

Most signal meters are not indicating raw power level, but some form of data error rate or a combination of error rate and signal strength. The individual TV manufacturers don't make the details of their design easy to find or may even consider the information to be a trade secret. Still, I would simply compare the results of single changes... I would avoid adding a preamp and also change tuners / metering, that would leave you to wonder which change is responsible for the altered end result.

I would make notes regarding the performance of the antenna without a preamp... Then add a preamp, (without any other changes) and compare the results. If a strong reliable signal becomes unreliable after adding a preamp, you can safely conclude that either the preamp is overloaded or the tuner is overloaded. Adding attenuation between preamp and tuner will help you understand if the tuner was overloaded or not. Attenuation between the preamp and tuner would be expected to resolve tuner overload, not preamp overload. Attenuation between the antenna and preamp can resolve preamp overload, but leaves you wondering if the the problem was preamp or tuner overload... Attenuation ahead of the preamp affects both the preamp and tuner.
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Last edited by GroundUrMast; 26-Apr-2014 at 8:16 PM.
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Old 26-Apr-2014, 10:30 PM   #18
mulliganman
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Originally Posted by GroundUrMast View Post
You have a well organized task list / plan.

I would make notes regarding the performance of the antenna without a preamp... Then add a preamp, (without any other changes) and compare the results. If a strong reliable signal becomes unreliable after adding a preamp, you can safely conclude that either the preamp is overloaded or the tuner is overloaded. Adding attenuation between preamp and tuner will help you understand if the tuner was overloaded or not. Attenuation between the preamp and tuner would be expected to resolve tuner overload, not preamp overload. Attenuation between the antenna and preamp can resolve preamp overload, but leaves you wondering if the the problem was preamp or tuner overload... Attenuation ahead of the preamp affects both the preamp and tuner.
I sincerely hope the C2V doesn't need a preamp because unless I am mistaken or misunderstanding, I only had DC pass built into the AC7 for the 91XG (Fox antenna). From an email from the folks at Tinlee: "Your AC7-ch.49 will have DC power pass if you need to have a preamp installed for your ch.49 antenna". That's why I have been interpreting it that way. If I am right, a preamp for the C2V or any other second antenna would require a new AC7 combiner.

Regarding the initial tests with the preamp, you are saying I should disregard signal meter indications and just look for picture problems. Is that correct? And, if a problem does come up to try to use the attenuators to check to see whether it is preamp overload or tuner overload? Can I just check to see if it is tuner overload by inserting it on the back of the coaxial input on the test tuner and connect the coaxial downlead into that input? Am I correct to assume, that if it is tuner overload that I can continue to utilize the attenuators on the inputs and output of the AC7 combiner as planned? If preamp overload is present by process of elimination from testing the tuner, rather than removing the preamp the attenuators should somehow be attached at the antenna. Is that correct? If correct, how/where are the attenuators placed? Or if it is the preamplifier causing the overload, is it taken out of the system?
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Old 26-Apr-2014, 10:59 PM   #19
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I sincerely hope the C2V doesn't need a preamp because unless I am mistaken or misunderstanding, I only had DC pass built into the AC7 for the 91XG (Fox antenna). From an email from the folks at Tinlee: "Your AC7-ch.49 will have DC power pass if you need to have a preamp installed for your ch.49 antenna". That's why I have been interpreting it that way. If I am right, a preamp for the C2V or any other second antenna would require a new AC7 combiner.

Regarding the initial tests with the preamp, you are saying I should disregard signal meter indications and just look for picture problems. Is that correct? And, if a problem does come up to try to use the attenuators to check to see whether it is preamp overload or tuner overload? Can I just check to see if it is tuner overload by inserting it on the back of the coaxial input on the test tuner and connect the coaxial downlead into that input? Am I correct to assume, that if it is tuner overload that I can continue to utilize the attenuators on the inputs and output of the AC7 combiner as planned? If preamp overload is present by process of elimination from testing the tuner, rather than removing the preamp the attenuators should somehow be attached at the antenna. Is that correct? If correct, how/where are the attenuators placed? Or if it is the preamplifier causing the overload, is it taken out of the system?
I doubt a preamp is needed on the C2V. But, if one were needed, you don't need a new AC7. That the AC7 has the DC passing feature does not mean it must be used. You have the option to feed one or both inputs of the AC7 from the RF output of the preamp power inverters. Don't worry about it now... It's just an option if you need it.

Don't disregard the signal meter indications. Use both the observed picture and sound, together with the signal meter indications. Generally, stable signal meter indications are what you would like to see. The absolute level does not need to be at maximum in order to produce reliable viewing... If the signal meter indication increases with the addition of a preamp or other accessory, fine... but an unstable reading that's high most of the time may be accompanied by signal drop outs or picture / sound impairments.
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Old 27-Apr-2014, 9:15 PM   #20
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Modified plan according to new information. Changed/updated info is in bold.

1. Move the C2V to approximately 5 feet or so away from the 91XG.

2. Run, new high quality RG6 cable (I'll be using the brand I already linked) from each antenna to a single tuner (bypassing the CM3414 and the use of any splitters) testing for reliable reception. If reliable reception is not obtained, try adjusting aim. If reliable reception is obtained, this could suggest some issue with the cable that needs to be replaced/fixed (because I don't recall that Fox has never been able to do that with this antenna setup without the use of a distribution amp; it seems other signals have been lower too). Make notes regarding the performance of the antenna with new cable (see Step 1 A-B-C test). Then reconnect to existing cable and splitter one antenna at a time making notes regarding performance (see Step 2 of A-B-C test). Compare results to Step 1 A-B-C results.
If the need for a preamp at the C2V was proven, simply lay the system out as follows; C2V Antenna > FM trap (if used) >preamp > preamp power inserter > AC7 > distribution system. The other antenna can be similar; 91XG > FM trap > preamp > preamp power inserter > AC7 > Distribution system.


3. If reliable reception is not obtained from each antenna using the new, high quality coax to a single tuner without the use of a distribution amp/splitter or after readjusting aim, consider changing out that antenna.

4. If/when reliable reception is obtained, move the AC7 combiner into the attic.

5. Without the AC7 combiner being connected and after reliable reception is obtained, add the RCA TVPRAMP1R on the 91XG antenna (making sure no other changes have been made since step 1 other than connecting through existing cable and a splitter). Observe results using signal strength/signal quality on the single tuner. Compare results to Step 2 of A-B-C test with existing cable and splitter. Run test again with RCA amp on C2V antenna.
Side note: If a strong reliable signal becomes unreliable after adding a preamp, you can safely conclude that either the preamp is overloaded or the tuner is overloaded. Adding attenuation between preamp and tuner will help you understand if the tuner was overloaded or not. Attenuation between the preamp and tuner would be expected to resolve tuner overload, not preamp overload. Attenuation ahead of the preamp affects both the preamp and tuner.
* Check for tuner overload if this situation presents itself by attaching attenuator(s) to test tuner. If it is the tuner being overloaded, continue plan to attach attenuator on AC7 combiner in Step 10. If preamplifier overload exists, remove preamp.

6. Add/utilize an FM trap on both antennas. If using the FM trap on the RCA preamp, use 1-3 feet of RG6 cable connected to the antenna and the other end to the trap (preamp input connects to the output of the trap and switch is turned on). If using the Radioshack FM trap, it needs to be between the antenna and any amplifier.

7. Reconnect antenna downleads to the AC7 combiner. Run output from AC7 combiner to the CM3414 distribution amp. Check signal quality/strength on all tuners.

8. Disconnect AC7 output from the CM3414 distribution amp. Then connect AC7 output to 4 way splitter instead. Check signal quality/strength on all tuners.

9. If significant disparity exists for signal quality/strength between the CM3414 and 4 way splitter (particularly if much lower readings are present from using 4 way splitter) replace/repair coaxial cables running to all 3 TV's. Then recheck each way of connecting again. Compare those results to previous results. Use whichever accessory between the CM3414 and the 4 way splitter produces the best results for all TV's/tuners.

10. Finally, install attenuators on the "input" ports for each antenna on the AC7 combiner and one attenuator on the "outport" of the AC7 combiner. Check signal quality/strength on all tuners. If signal quality/strength drops or picture deteriorates remove attenuators.
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