or Connect
AVS › AVS Forum › HDTV › HDTV Technical › The Official AVS Antenna and Related Hardware Topic!
New Posts  All Forums:Forum Nav:

The Official AVS Antenna and Related Hardware Topic! - Page 406

post #12151 of 16112
See the two charts at the bottom? There's one for VHF and another for UHF.

It looks to me like all your major nets, CBS, NBC, PBS, FOX, CW are all UHF and the ABC channel is VHF.
post #12152 of 16112
Quote:
Originally Posted by keenan View Post

See the two charts at the bottom? There's one for VHF and another for UHF.

It looks to me like all your major nets, CBS, NBC, PBS, FOX, CW are all UHF and the ABC channel is VHF.

So it looks like all UHF with the exception of 1 station on the High VHF scale.
post #12153 of 16112
Quote:
Originally Posted by superorb View Post

So it looks like all UHF with the exception of 1 station on the High VHF scale.

That's what I see, yes.
post #12154 of 16112
Quote:
Originally Posted by keenan View Post

That's what I see, yes.

So back to my original question, what would be the most effective antenna for me to build provided it will live in the attic out of sight? Thanks for the help thus far.
post #12155 of 16112
Quote:
Originally Posted by superorb View Post

So back to my original question, what would be the most effective antenna for me to build provided it will live in the attic out of sight? Thanks for the help thus far.

At 13 miles with line of sight you're not going need much. I use a 91XG myself but that's because I'm a good 60 miles from the transmitter. Hopefully some folks here more familiar with close range antennas will give you some recommendations.
post #12156 of 16112
Quote:
Originally Posted by superorb View Post

So back to my original question, what would be the most effective antenna for me to build provided it will live in the attic out of sight? Thanks for the help thus far.

I don't know that a single aim will be possible for all of your channels, such as PBS. You might want to try a single classic bowtie near a window first. I know it is a UHF antenna, but the flat wire also acts as an antenna. I've reliably received rf 9 (Nm db 54) with a bowtie for over a month now. You've got stronger signal there than I have here. It might work. Good Luck.
post #12157 of 16112
Quote:
Originally Posted by Splicer010 View Post

Too funny. Please explain to me and everyone else Ron, just how a passive combiner itself can raise/add signal level then.

?

The -3.5db loss on each leg is if it is used to split the signal or assuming lack of phasing if used as a combiner. 3db is 50 percent loss due to the split (or incorrect phase) and .5 db is through-loss.

However, if you phase properly with two identical antennas pointed in the same direction and equal coax lengths to the combiner you'll see increased performance over a single antenna even using a common splitter. The problem is that common splitters just don't phase very well no matter what. That's the reason stripline combiners work better.

In your situation with the antennas pointed in different directions, the -3.5 db loss should be roughly accurate. Additionally, though, you generate multipath which is the reason it would be technically better to use an A/B switch and two downleads.
post #12158 of 16112
I have found the Apex DT502 to be very useful when trying to solve OTA antenna problems. It gives not only signal strength but also signal quality. It's a measurement bargain even without the coupon. But, the supply has dried up, so I wanted to try the Centronics ZAT502 HD because it has the the same tuner and dual signal bars. The Centronics is in short supply and I noticed that some Sony TVs have a diagnostics screen mentioned in the pdf manual but no screen shots of it.
I went to a local store to look at the diagnostics screen in the menu of a KDL-26L5000 and then ordered a KDL-22L5000. (The KDL-xxM3000 manual also mentions a diagnostics screen.) The diagnostics screen looks like this:



Now that I have all three units I am able to make a comparison using them, a SLM (signal level meter), and a 4-way splitter. My previous tests were done in my car to get away from the street traffic in front of my antenna at home that causes the readings to vary (but the signals stay locked when they are strong) and I was able to drive to strong and weak signal areas. I couldn't work that out because having the 22-inch TV in the car was a big logistical problem. I stayed at home, ran the tests at night with light traffic, and used preamps to vary the signal levels. I also rigged up a mic, amp, and speaker to listen for the traffic to ignore readings when cars were passing by.

The first test used two preamps; a CM7777 near the antenna and a RS 15-1115 inline preamp (one of my better RS purchases) before the attenuator to find out where the signal meters maxed out:
antenna-> 7777-> 50 ft coax-> CM power inserter-> RS amp-> attenuator-> 4-way splitter:

Code:
Attn    Apex   Centronics       Sony          SLM     Equiv
 dB    Q    S    Q    S      S   Er   SNR     dBmV     dBm
  0   100  87   100  89     79   0    25     +18.5   -30.3
  3   100  86   100  89     79   0    25     +15.0   -33.8
  6   100  86   100  89     79   0    25     +11.9   -36.9
  9   100  86   100  88     79   0    25      +8.8   -40.0
 12   100  85   100  88     79   0    25      +5.9   -42.9
 15   100  85   100  88     79   0    25      +3.1   -45.7
 18   100  83   100  87     79   0    25       0.0   -48.8
 21   100  79   100  85     79   0    25      -3.5   -52.3
"Q" is quality, "S" is strength.
Sony IF-AGC figures not listed because in all cases they were the same as strength.

The RS preamp was removed, leaving only the 7777 (my normal setup):
Code:
Attn    Apex   Centronics       Sony          SLM     Equiv
 dB    Q    S    Q    S      S   Er   SNR     dBmV     dBm
  0   100  84   100  88     79   0    25      +3.0   -45.8
  3   100  81   100  87     79   0    25      -0.8   -49.6
  6   100  78   100  84     79   0    25      -3.9   -52.7
  9   100  73   100  80     78   0    25      -7.0   -55.8
 12   100  69   100  76     76   0    25     -10.0   -58.8
 15   100  66   100  71     74   0    25     -12.9   -61.7
 18   100  62   100  67     71   0    25     -15.7   -64.5
 21   100  58   100  63     69   0    25     -18.6   -67.4
 24   100  54   100  59     66   0    25     -21.6   -70.4
 27   100  49   100  54     62   0    24     -25.4   -74.2
 30   100  45   100  50     59   0    23     -28.2   -77.0
 33   100  38   100  45     55   0    21     -32.0   -80.8
The 7777 was removed (to simulate weak signals) leaving only the coax between the antenna and the attenuator:
Code:
Attn    Apex   Centronics       Sony          SLM     Equiv
 dB    Q    S    Q    S      S   Er   SNR     dBmV     dBm
  0   100  55   100  58     66   0    24     -22.0   -70.8
  3   100  49   100  53     62   0    24     -25.9   -74.7
  6   100  45   100  49     58   0    22     -29.0   -77.8
The RS preamp was inserted between the splitter and the SLM because the meter was near the bottom of scale, and I repeated the test just above. The preamp noise figure does not affect the tuners because it isn't in line with them:
Code:
Attn    Apex   Centronics       Sony         SLM+amp dBmV corr  Equiv
 dB    Q    S    Q    S      S   Er   SNR     dBmV    for amp    dBm
  0   100  54   100  58     66   0    25      -6.1    -22.1    -70.9
  3   100  49   100  53     62   0    24      -9.3    -25.3    -74.1
  6   100  44   100  49     58   0    23     -12.1    -28.1    -76.9
  9   100  38   100  44     55   0    21     -14.9    -30.9    -79.7
 12    77  27    65  38     55   0    18     -18.1    -34.1    -82.9
 15    26V  0    20V 27     55   0    16     -21.2    -37.2    -86.0
 18   dropout   dropout     55 3099V  13F    -24.3    -40.3    -89.1
A "V" after a figure means that it varies; the Sony errors are updated about once every second. An "F" after the SNR means that the display is frozen at that value. Adding even more attenuation makes the Sony screen go black and say "no signal." At least 15.5 to 16 dB SNR is needed to maintain lock.

When aiming or comparing antennas using the signal strength meter you must keep it below the max value (where your meter doesn't go any higher) by using an attenuator. In my case, that would mean keeping it well below 86 for the Apex, 89 for the Centronics, and 79 for the Sony.

Attachment No. 1 shows a Sony "frozen screen" at 13 dB SNR.
Attachment No. 2 is the RS preamp specs.
Attachment No. 3 is the RS preamp diagram. RS used to print diagrams in the manual, but they don't anymore. I think that's a mistake, because showing the diagram encourages experimentation, which means more sales. Looking at the diagram, you can see how the RF signal and the DC power are combined on the coax using capacitors and chokes (inductors). Capacitors pass RF but block DC; chokes pass DC but block RF.
LL
LL
LL
LL
post #12159 of 16112
Yesterday, I installed two Winegard antennas - YA-1713 high VHF, and a 9095P UHF. Each has a plastic box with a PC board balun, to provide 75 ohm connections. However, the UHF one also has a connector for a VHF antenna, so I guess that is a combiner also. I am using a CM7777 preamp with dual inputs, so I don't use the combiner mounted on the UHF antenna, so I put a 75 ohm cap on that input. How does this configuration relate to the discussions above?

This appears to work well, pulling in WNJN RF 51 in New Jersey, 55 miles away fairly well. I still don't get WCBS RF 22 or WWOR RF 38 (I get all the other NYC stations, as well as some CT ones). Tomorrow, I am getting a 24 ft mast to raise this assembly (currently the VHF one is about 1 ft above my porch roof, and the UHF one is below it - my current 10 foot mast is mounted on my deck). Any suggestions? I'll post a photo of this assembly when I can get one (it's nightime now).
post #12160 of 16112
Quote:
Originally Posted by deltaguy View Post

I don't know that a single aim will be possible for all of your channels, such as PBS. You might want to try a single classic bowtie near a window first. I know it is a UHF antenna, but the flat wire also acts as an antenna. I've reliably received rf 9 (Nm db 54) with a bowtie for over a month now. You've got stronger signal there than I have here. It might work. Good Luck.

I'm only interested in the major networks like ABC, NBC, FOX, CBS.
post #12161 of 16112
Quote:
Originally Posted by superorb View Post

So back to my original question, what would be the most effective antenna for me to build provided it will live in the attic out of sight? Thanks for the help thus far.

Before you build one, you might want to try this specific model (Catalog # 15-1874) indoor VHF/UHF antenna which is very inexpensive and has worked quite well for many AVSForum members that are not very far from the towers.. You can use it indoors or (better) in the attic, with a coax extension.

The loop part of the antenna is for all the UHF channels. The dipole "rods" are for the lone VHF (abc) channel in your area. Extend each rod about 13" each and in a "V". Aim the antenna perpendicular to the towers.

If it doesn't work, just return it for a refund and come back here for more suggestions.
post #12162 of 16112
Quote:
Originally Posted by superorb View Post

I'm only interested in the major networks like ABC, NBC, FOX, CBS.

If the top 6 channels on your tvfool chart are all that you need, then you probably won't need multiple aims. I can only say probably though. If multiple aims are required, these are easier to accomplish if the antenna is not in the attic. If multiple aims are not required, then a single trip to the attic should do the trick. The RS budget antenna is both VHF and UHF and probably a good bet. You might also be able to receive those top 6 channels with a pair of rabbit ears alone. Yes, rabbit ears do pick up UHF signal as well.
I'm watching Fox on rf 40 right now with a pair.
post #12163 of 16112
Quote:
Originally Posted by Splicer010 View Post

Too funny. Please explain to me and everyone else Ron, just how a passive combiner itself can raise/add signal level then.

It's simple. A splitter is a reciprocal device. The input and outputs ports are interchangeable. As a splitter, if we apply 10 microwatts to the input port, we get (ignoring losses for now) 5 microwatts on each output port. As a combiner, if we apply 5 microwatts to each input port, we get 10 microwatts on the output port.

What is so difficult to believe about that?

http://www.w8ji.com/combiner_and_splitters.htm

Ron
post #12164 of 16112
Quote:
Originally Posted by dr1394 View Post

It's simple. A splitter is a reciprocal device. The input and outputs ports are interchangeable. As a splitter, if we apply 10 microwatts to the input port, we get (ignoring losses for now) 5 microwatts on each output port. As a combiner, if we apply 5 microwatts to each input port, we get 10 microwatts on the output port.

What is so difficult to believe about that?

http://www.w8ji.com/combiner_and_splitters.htm

Ron

Incredible. I hope you aren't really a dr and just play one on the internet. I know exactly what a splitter is and what it does. I've only used them professionally for 27+ years. Nobody here that I am aware of, including myself, has ever denied the fact that combining 5+5=10 on the output. The whole point is that a PASSIVE combiner cannot add or raise the signal. The ONLY way to raise the signal is to raise the input level. I'll say it again, it is IMPOSSIBLE for a PASSIVE combiner to raise/add signal level on its own. The key word is PASSIVE. Now if you are talking about an ACTIVE combiner (and you are not) that would be a different story.
post #12165 of 16112
Quote:
Originally Posted by Splicer010 View Post

Nobody here that I am aware of, including myself, has ever denied the fact that combining 5+5=10 on the output.

You disagreed with Colm, yet he is saying exactly the same thing. 5 + 5 = 10. I'm not sure what your point really is.

Ron
post #12166 of 16112
Quote:
Originally Posted by dr1394 View Post

You disagreed with Colm, yet he is saying exactly the same thing. 5 + 5 = 10. I'm not sure what your point really is.

Ron

Ummmm, you really should read the entire conversation before you just jump in and say to me:
Quote:
Originally Posted by dr1394 View Post

You're the one that's wrong.

Had you done so you would have seen that this is what I was saying:
Quote:
Originally Posted by Splicer010 View Post

I'm not saying you can't get a +2.5dB gain using 2 antennas instead of a single antenna. I am saying that using a 2 way splitter as a combiner will net a loss of -3.5dB the same as when used as a splitter. You are saying there is only a loss of -.5dB when a splitter is used as a combiner and it just doesn't work that way.

Colm is stating that instead of a -3.5dB loss when used as a splitter, that when used as a combiner the loss is +3dB less and is only -.5dB. I corrected him and you are saying I am wrong, when it is the both of you that is wrong. That has been, and remains still as my point.

And since this has been so blown out of proportion and you guys seem so confused about all this, and post pointless links about combiners, then this will really blow your minds: The -3.5dB loss is PER LEG and not the total loss.
post #12167 of 16112
Are you saying that splitters and combiners are two different things?

Ron
post #12168 of 16112
Quote:
Originally Posted by dr1394 View Post

Are you saying that splitters and combiners are two different things?

Ron

Are you just being a troll or what? Because now it is my turn to ask, what is your point?

Did you bother to do what I told you about reading the whole conversation before jumping into it? Ehhhhh...no. I didn't believe you did. So go back and read the WHOLE conversation from the BEGINNING Ron.
post #12169 of 16112
Quote:
Originally Posted by Splicer010 View Post

Are you just being a troll or what? Because now it is my turn to ask, what is your point?

Did you bother to do what I told you about reading the whole conversation before jumping into it? Ehhhhh...no. I didn't believe you did. So go back and read the WHOLE conversation from the BEGINNING Ron.

I'm not trying to be a troll and I have read the whole conversation. I'm just trying to clearly understand where you're coming from.

On one hand, you agree that a combiner can add two 5 microwatt signals to produce a 10 microwatt signal (ignoring losses). On the other hand, you state that a splitter being used as a combiner will attenuate each leg by 3 dB, therefore applying two 5 microwatt signals will produce 2.5 + 2.5 = 5 microwatts.

So I asked you, "are splitters and combiners two different things?" because that is what you are implying.

Ron
post #12170 of 16112
A combiner is a splitter.

Quote:
On one hand, you agree that a combiner can add to two 5 microwatt signals to produce a 10 microwatt signal (ignoring losses). On the other hand, you state that a splitter being used as a combiner will attenuate each leg by 3 dB, therefore applying two 5 microwatt signals will produce 2.5 + 2.5 = 5 microwatts.

Ehhhhhhh...no. Ignoring losses then 5 in + 5 in = 10 out. Not ignoring losses then 5 in + 5 in = 3 out. This really isn't complicated as you are trolling, err, trying to make it.

And you ask me why I can't understand.
post #12171 of 16112
Quote:
Originally Posted by Splicer010 View Post

A combiner is a splitter.

Okay, that's a starting point. Then why is the loss entirely different in one direction versus the other? How can a passive network know about direction?

As a splitter, the loss is 3.5 dB per leg. We put in 10 microwatts on the input and we get 4.47 microwatts on each output. The total loss is 10 - 4.47 - 4.47 = 1.06 microwatts or 0.5 dB.

As a combiner, the total loss is the same. We put in 5 microwatts on each input and get 5 + 5 = 10 microwatts minus 0.5 dB or 8.91 microwatts on the output.

Ron
post #12172 of 16112
Quote:
Originally Posted by Splicer010 View Post

Incredible. I hope you aren't really a dr and just play one on the internet. I know exactly what a splitter is and what it does. I've only used them professionally for 27+ years. Nobody here that I am aware of, including myself, has ever denied the fact that combining 5+5=10 on the output. The whole point is that a PASSIVE combiner cannot add or raise the signal. The ONLY way to raise the signal is to raise the input level. I'll say it again, it is IMPOSSIBLE for a PASSIVE combiner to raise/add signal level on its own. The key word is PASSIVE. Now if you are talking about an ACTIVE combiner (and you are not) that would be a different story.

I think I'm with dr1394 on this one, FWIW (maybe not much; I'm no expert).

Have you ever heard of a transformer? They're used to step voltage up as well as down, and they're passive. They do have some inherent losses going either way, of course, but that may only be a few percent. They work fine for the power company, among others.
post #12173 of 16112
Quote:
Originally Posted by Splicer010 View Post

...then this will really blow your minds: The -3.5dB loss is PER LEG and not the total loss.

That is simply not true in theory (or in practice) when using a typical hybrid splitter/combiner in the fine art of ganging or stacking phased antennas.

Think about it... if you are only getting half of each whole antenna (plus some loss) then the stacked duo would have less gain than the single whole, and there would generally be little benefit to doing it phased beyond some nulls.

You and Colm are really both half correct. In your configuration you are losing up to -3.5 per leg not -.5 per Colm. But when both legs are in phase and equal then it instead approaches +2.5 after the -.5 loss and this is why the hybrid splitter/combiner can be so effective for such application.


Now they sure aren't all created equal and I'd still rather have a stripline to play around with, but with careful attention to phasing the simple 49 cent hybrid T works wonders with both improved gain and desired nulls used with a perfectly balanced gang of two.


Read this section about Superposition analysis to get better idea how the circuit behaves in these two different situations.

Quote:


...The doubling of the output power is equivalent to a 3 dB increase in the signal. If the combiner is 90% efficient then a 2.5 dB gain is seen. Note the dichotomy:

· If the antennas point in different directions, there is a 3.5 dB loss at the combiner.

· If the antennas point in the same direction, there is a 2.5 dB gain at the combiner.

This is a 6 dB swing. 3 dB of this is just the adding of the second antenna, but the other 3 dB is from the combiner becoming a much more effective device.

Obviously in such case the loss is not -3.5dB PER LEG and field experience backs up the good dr's theory here.

If you don't still don't believe it try both configurations (matched same direction, unmatched different directions) for yourself.
post #12174 of 16112
post #12175 of 16112
Can't we all just get along?
post #12176 of 16112
superorb,

HA ! , "Get Along", you GOT to be kidding !

Agreed, you can get along with a Modified Range (Ch7-69) Antenna.

Additionally, from what I see on your Chart, and knowing that at times one really likes to "look around", you'd be limiting your Channel selection a lot, by getting a relatively Directional Antenna.

If you want to pick up that WRPX Ion AND your Majors without Rotating, you might think about one of the Omni's.

Just to get you started in that direction, take a look at...
Winegard MS2002

Then, at the bottom of the above Page/Link, there are several other applicable Antennas listed. Check um out !

Have a good Day !
S.W.
post #12177 of 16112
Quote:
Originally Posted by SWHouston View Post

superorb,

HA ! , "Get Along", you GOT to be kidding !

Agreed, you can get along with a Modified Range (Ch7-69) Antenna.

Additionally, from what I see on your Chart, and knowing that at times one really likes to "look around", you'd be limiting your Channel selection a lot, by getting a relatively Directional Antenna.

If you want to pick up that WRPX Ion AND your Majors without Rotating, you might think about one of the Omni's.

Just to get you started in that direction, take a look at...
Winegard MS2002

Then, at the bottom of the above Page/Link, there are several other applicable Antennas listed. Check um out !

Have a good Day !
S.W.

I'm not against an Omni, but I am against the $50 price. I'd like to limit it to $25 shipped if possible.
post #12178 of 16112
superorb,

Ok then, this is close, look at the...
Winegard HD7000R

You can just aim it at your Magnetic 124°, and enjoy !

Have a good Day !
S.W.
post #12179 of 16112
Quote:
Originally Posted by SWHouston View Post

superorb,

Ok then, this is close, look at the...
Winegard HD7000R

You can just aim it at your Magnetic 124°, and enjoy !

Have a good Day !
S.W.

Anything that's $25 after shipping? I found this 2-Bay Bowtie Antenna for $24.xx shipped.
post #12180 of 16112
Superorb,

Follow Arxaw's suggestion. He knows his stuff. His recommendation should work well for you and is priced at half your $25 limit.
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: HDTV Technical
AVS › AVS Forum › HDTV › HDTV Technical › The Official AVS Antenna and Related Hardware Topic!