Low signal strength or strong signal+intermod?

We need to see a TV FOOL report to make an appropriate recommendation for your situation. Your address will not appear when posting here.

Welcome to the forum Bryan88,

Thanks for the link info; my guess would have been Selkirk.

Your tvfool report looks like this:
http://www.tvfool.com/?option=com_wr...9fbe7fbc1bfde8

I don't think you need a preamp; it would cause overload.

Try inserting an attenuator or a splitter or two between the antenna and the Bravia until the strength scale reading comes down. It looks like the strength scale has maxed out; mine never gets to 100 on my KDL22L5000 no matter how strong the signal is:
http://www.avsforum.com/avs-vb/showp...ostcount=10649

You might have a problem from strong FM signals (like WQBK-FM) which would require an FM trap; see the attachment.

Do NOT obsess about the internal signal meter readings. You will drive yourself nuts trying to achieve something that isn't needed. All you need is enough signal, day in and day out, that yields dropout-free reception. It is insane to try to maximize the " signal reading" when you don't even know what the parameters for that reading might be. 80 of 100 should be fine as long as you are not experiencing defects. Besides internal "signal strength meters' really are not true meters. You are wasting time and effort trying to achieve a "score" of 100.

If you are not experiencing any audio or video defects, install an 8-port distribution amplifier (cap unused ports with terminators) and be done with it.

Agree 100%. A distribution amp is a much better choice than a pre-amp for powering 4 additional outlets in your situation.

If you are in fact experiencing reliability issues with just 1 TV connected, you will need to address that first before adding additional outlets. With such strong signal strengths, the proper antenna should easily power 2-3 sets with no amplification.

I do also agree that an FM trap may be beneficial if any of you VHF stations are problematic. You should have no overload concerns at 11 miles away from the TV stations. (Unless improper amplification is added)

I disagree 100%. Almost any amplifier will overload with that much TV signal. The strength of WQBK is even stronger.

There is sufficient signal available to split 8 ways through 100' of coax and still have more than 40 db of NM (Noise Margin) on all the major channels.

If you want ION, you'll need a second antenna, a channel 50 channel filter, a preamp, and then an A/B switch or Tinlee channel adder.

Also, the attached FMfool report is for your exact location, not the generic location for Glenmont.

With all due respect, I have used the Channel Master 34xx series with even stronger signals & great success. (91-XG & YA-1713 antennas)

I was merely suggesting that a distribution amp is a much better choice compared to a preamp if amplification is truly needed in a strong signal environment.

I agree.

Interesting; how did you do that, Tower Guy?

Bryan88:
Are you still there?

There's no need for any amplifier in a properly installed system in Glenmont, NY. Your answer avoids the real problem and suggests a solution that will frustrate Bryan even further.

The Channel Master 3418 is rated for 14 dbmv output level. The conversion between dbmv and dbm is: dbmv=48.75 + dbm. (in a 75 ohm system) The 3418 has 4 db gain. Therefore the CM3418 will overload with an input signal of -30.75 dbm. Assuming that antenna gain offsets feedline losses, there are 7 FM stations and 6 TV stations in Glenmont that are stronger than the overload rating of the CM 3418.

Now let's compare a 3418 to a HDP-269 preamp. Winegard rates it at 350,000 microvolts input capability. That's the same as +50.88 dbmv or an input level of -2 dbm. Therefore the overload resistance of an HDP-269 is far better than the CM distribution amplifier.

I'm not saying that your experience is wrong, but using your conclusion to advise others is not supported by electronic theory and math.

Well, it helps to live 20 miles from Bryan and know the specifics of the situation. But the same technique works everywhere;

Using the published TVfool report, select two stations that are roughly 90° apart. Note the two distances. Go to TVfool and select the "online TV maps" option from the top menu. Enter a location as close as you can. When the map appears, note the distances to the two stations that were previously selected. Move the push pin on the map until the data matches. Highlight the geographical coordinates from below the map, copy and paste them into FMfool.

It just so happens that I was two blocks from Bryan's house on Tuesday evening and noted the very short distance to WQBK's tower.

Thanks Tower Guy

I didn't mean to cause any confusion. I do agree that amplification should only be used when truly needed. I don't use any on my personal system, because it does in fact make things worse for the reasons you mentioned.

Does the 3414 possibly have more resistance to overload than the 3418? I was basing my comments on my experiences when comparing the HDP-269 to the 3414. The 3414 handles strong signals better in multiple sitautions than the HDP-269 has; especially VHF.

I endorse that idea.

Thanks for describing your method, Tower Guy.

3414

Operating frequency: 5 to 1002 MHz
Return path: 59 to 42 MHz
Amplifier gain: 8 dB
Noise figure (avg): 2.7 dB
Isolation between outputs: 22 dB
Output level: 18 dBmV

3418

Operating frequency: 5 to 1002 MHz
Return path: 59 to 42 MHz
Amplifier gain: 4 dB
Noise figure (avg): 2.7 dB
Isolation between outputs: 22 dB
Output level: 14 dBmV

When the gain difference is factored in, the input ratings are identical.

Good, I'm glad that we have given you some ideas to try.

A few thoughts about the Bravia signal strength meter:
As ProjectSHO89 said
Yes, they are not true meters that give the signal level in dBmV or dBm, but they are still useful for comparisons. A Signal Strength meter with an arbitrary 0 to 100 scale is much better than nothing; that is why it is on the Signal Diagnostics screen. I must admit, however, that I would be lost without my signal level meter that reads in dBmV.

The Bravia signal strength reading is derived from the AGC (automatic gain control) circuit. The AGC circuit changes the sensitivity of the tuner to accomodate a wide range of signal strengths from very strong to very weak. Without the AGC, the signal dyanamic range would be much smaller.

When the signal is very strong, a larger AGC voltage is developed to reduce the sensitivity of the tuner (inverse relationship). As the signal gets stronger, a point is reached where the AGC is no longer able to reduce the sensitivity of the tuner any further which is the maximum signal strength number (80), which you have experienced. Beyond that maximum number, with even stronger signals, the tuner eventually reaches its overload point.

With very weak signals, the ACG voltage is smaller to increase the sensitivity of the tuner. Below a certain point, the minimum signal strength reading is shown (55 on my Bravia) where the tuner sensitivity can no longer be increased. With even weaker signals you reach the "digital cliff" with SNR below 16 dB, picture freeze, and finally dropout.

My professional Sencore meter maxes out the measured SNR reading at 36 dB SNR. Above that, the SNR reading no longer really matters so it just displays "> 36 dB" for stronger signals. I can still go to the spectrum analyzer screen and measure SNR by doing my own addition and subtraction of the signal top vs the noise level, but there's no point in doing so.

Bryan88 says he is seeing "signal strength" numbers of 80 or better with a single receiver on 85 feet of RG-6 coax with just one barrel splice. His TV fool numbers tend to indicate that he could drive about a hundred receivers with no amplification at that length. He should pop in a 4-way splitter and see if he has performance problems that he doesn't have without the splitter before pursuing the alternative of amplification any further.

I have no experience with the Bravia tuner, but I have other tuners that work reliably with signal quality nuimbers of around 40%.

The published numbers for the Channel Master distribution amps cannot be used to estimate overloads because they do not include the channel load under which the overload threshold is reached. With mast-mounted preamplifiers, the published figures are usually for loads of anywhere from one to four equal strength analog carriers. With cable TV type distribution amplifiers, they may be "fully loaded", which can mean 135 channels, or they can be for fewer that that. Based on my experience 1) Winegard's preamps do not quite meet their claimed overload thresholds, but 2) they generally are about as good as anyone else's, and the 12dB gain of the model HDP-269 winds up being beneficial for most strong signal situations.

Digital Rules lives in a Hobbit Hole, so it is not possible for anyone to draw any conclusions based on his experience. Since the HDP-269 case is unshielded but the 3414/8 are shielded, there will be situations where the ingress into the HDP-269 is significant enough to more than offset the benefit of its low amplification.

If someone is in the shadow of a 103.9MHz transwmitter (WQBK), then they might benefit from an FM trap, but nearly any old wideband FM trap will do, as they nearly all start at around 93 MHz and attenuate the remainder of the FM band up to 108 MHz. There used to be a few 88-108 MHz traps available that trapped 88-108 MHz which degraded channel 6 somewhat, but those are hard to find. It would be difficult if not impossible fror someone to hand tune a tunable FM notch for 103.9 without having the proper test equipment.

Filter manufacturers like MicroWave Filter, Eagle Comtronics and C&E can probably sell you a tuned 103.9 filter for $20 to $30 if you want to keep the rest of the FM signals.

Thanks for the positive review. I assume you have used both of these models in various locations throughout the DC area as I have. If so, I'd love to see how they compared in real world situations from your experiences?

I am a strong advocate of not using amplification to solve every problem, so please excuse me for coming across that way in this thread. My sincere apologies to the OP for any confusion. Thank goodness I didn't cost anything.

Other factors besides a weak signal can cause artifacts from a reduction in signal quality (related to BER---bit error rate), like static or dynamic multipath, off-target antenna aim, overload, spurious signal interference (from IM or from a nearby non-TV transmitter), and local noise interference.

Not on the Bravia; errors have an indicator separate from strength. The error indicator is post-correction, which shows a sudden increase at the cliff because the FEC (forward error correction) has reached its limit of correction ability. A pre-correction error indicator would show a more gradual increase. The FEC sharpens the 'cliff.'

As previously mentioned by ProjectSHO89, high SNR is OK. It's low SNR that causes an increase in errors. In the BER VS MER attachment, MER (modulation error ratio) is similar to SNR. The chart is for DVB-T (used in the UK, which requires a SNR >19 dB, but handles multipath better than ATSC), but a chart for ATSC/8VSB would be similar. The FCC requires broadcast signals have an MER of at least 27 dB, as per Trip in VA.

I quote holl_ands:

TOV is threshold of visibility.
http://www.wowvision.tv/signal_strength_meters_BER.htm

Most CATV drop amps want to see an input level of ~+10dBmV. That's based on a 77 channel loading. OTA is going to have a lot fewer than 77 channels (typically), which allows it to see a stronger input level. Most drop amps have 15dB gain. Multiple output models are nothing more than a drop amp with a splitter (2, 4, or 8-way) on the output.

Thanks for the positive feedback Bryan!

73,
rabbit