Signal Amplifiers (Amps, Preamps, Distro Amps) - See Chart in Post #1

[tballister]

It's for combining (or splitting) UHF and VHF signals. Check summitsource, It's made by Pico-Macom.

[holl_ands]

tballister:
It appears that those articles (actually the SAME article) mis-labeled "G" as "Conductivity",
when it should have been called "Conductance":
http://en.wikipedia.org/wiki/Electrical_conductance

Conductance (Siemens) = Conductivity (Siemens/meter) * Area (meter-sq) / Length (meter)
Conductance is also known as "Specific Conductivity" (no doubt the source of all this confusion)....

Note that "Siemens" is also called a "Mho" (more familiar to us old tube guys). See also:
http://en.wikipedia.org/wiki/Electrical_resistance

ERRATA: In my earlier post I left off "meters" in the units for Conductivity (now corrected).

[stampeder]

Paulo head over to the following thread:

Splitters, Attenuators, Filters, Diplexers, Other Signal Gear

If you use the Search This Thread tool to the upper right of a post beside Thread Tools and put in UVSJ you'll find out all about them since they're a very useful device in OTA.

[tballister]

Originally Posted by holl_ands

tballister:
It appears that those articles (actually the SAME article) mis-labeled "G" as "Conductivity",
when it should have been called "Conductance":
http://en.wikipedia.org/wiki/Electrical_conductance

Conductance (Siemens) = Conductivity (Siemens/meter) * Area (meter-sq) / Length (meter)
Conductance is also known as "Specific Conductivity" (no doubt the source of all this confusion)....

Musn't there be more to it than that? Can you plug any numbers into that formula the produce relationships that make any sense?

I mean, if their formula was:
C = G x (A/L) instead of C = G x (L/A)
then it would express a relationship that hangs together?

[goforit]

In my quest to get my edge channel (WNYO- RF 49), I just tried inserting a CM7777 into the equation. I heard many members talk of how important noise level is to the signal- lower the better, since it will replace/overcome/compensate (?) for the noise level of the TV's own tuner and should help with edge channels- "getting the signal off the floor".

Well, when I added the CM7777, it did not make a difference to WNYO- no signal, no lock. However, it did improve the signal of other stations, especially analogs, and there was no overload, thanks to the traps. So in a sense, the CM7777 did improve things, but did not get me WNYO- I tried just using the stack of 4221HDs (disconnected the 4228HD), additional UVSJs, and other types of attenuation.

Furthermore, If I just used the coax line from the 4221HD stack, without amplification I can get WNYO, but add in the CM7777 and WNYO is a no show.
As mentioned, I tried many types of attenuation with the CM7777, but WNYO still wouldn't show, while other stations were not affected.

For my situation, I don't think noise level (TV vs. amp) is the key in getting the edge channel...

[holl_ands]

tballister:
Bluddy head-cold....let me be a bit more specific re erroneous use of Conductivity vice Conductance....

In the article(s), the "Definition of Conductivity" should read "Definition of Conductance" and
first para, last sentence should read "....is measured, Conductance (G), the inverse of Resistance (R)...."
Formula G=1/R is correct, using label conventions found in wiki articles. G is in Siemens or mhos, R in ohms.
Clearly, if you measure the ratio of amps/volts, you get Conductance, the inverse of Resistance.

In "Units of Measurement", "G" should be "Conductance", not "Conductivity" (same mistake as above)
and "C" is mis-labeled as "Specific Conductivity" (a non-existent term....close but no banana).
"C" should be "Conductivity" or "Specific Conductance", and is the same as "sigma" in wiki.
Formula C=G x L/A is correct, same as Sigma=G x L/A or G=Sigma x A/L, as found in wiki Conductance article.

Resistivity (rho, in ohm-meters) is inverse of Conductivity (Sigma in Siemens/m or mhos/m)
Resistance (ohms) = Resistivity x L/A and is the inverse of Conductance
Conductance (Siemens or mhos) = Conductivity x A/L.

So it makes sense that there is more current flow as the surface area increases and
decreases (due to increased Resistance) as the separation between plates (L) increases.

[tballister]

Originally Posted by holl_ands

So it makes sense that there is more current flow as the surface area increases and
decreases (due to increased Resistance) as the separation between plates (L) increases.

That part of your last email makes perfect sense. To amplify on the first part of this, "... there is more current flow as the surface area increases ..." must mean resistance goes down. Therefore conductivity must have gone up as the area increases.

But:

Formula C=G x L/A is correct

still makes now sense to me at all.

It still says the opposite to me; that C "Specific Conductance" goes down as area increases ?!?!?! That says less current flows as the area increases!?!?!?

dazed and confused...

[otafool]

Hi folks, I have an issue with delivering a strong signal to 3 receivers. My setup is as follows:

CM4228 -> 50ft RG6 -> Kitz KT-100VG -> splitter A

    -> TV #1
    -> 30 ft RG6 -> splitter B

        -> TV #2
        -> TV #3

TV #1 gets good signal on all channels. TVs #2 and #3 are poor.

So I bought a CM3412 distribution amp to replace splitter A. The signal actually got worse. I also tried it in the place of splitter B, with one output of the CM3412 feeding the Kitz - same result, worse signal.

Is this a case of overloading amp inputs, or maybe a defective CM3412?

Any advice would be appreciated.

[tballister]

Originally Posted by otafool

Is this a case of overloading amp inputs, or maybe a defective CM3412?

Best way to help you is if you're willing to post your tvfool report. If you're worried about publicizing your location you can easily open those .png files with windows "Paint", cut out the area where the coordinates appear and save (make sure as a .png file and not .bmp).

That picture tells a big story. Without it we don't know what you're dealing with. We'd all just be guessing a little.

If one of your receivers is small & fairly portable, and best of all a Sony, you can you use it as a poor man's signal meter. The Sony's "Product Support" page includes both a S/N (Signal to Noise) as well as AGC indication. 100 on the AGC is "No Signal", numbers below 30 indicate very high signal levels, and numbers around 50 indicate marginal signal levels. Note this is only an indication of signal level, it says little to nothing about signal quality.

On the other hand, a S/N indication can be quite independent of signal level. It does provide an indication of signal "quality" in terms of interference, multipath and otherwise. The Sony's S/N indication, at least on my receiver, is pretty well calibrated to the theorical limit of 15 dB minimum necessary to recover a signal. Anything below that blanks, anything hovering between 16 and 18 dB will exhibit regular pixilation, 20 dB or so exhibits much less frequent pixellation, and above 25 dB things start to get reliable.

Moving that one receiver between nodes will give a view into the relative signal at all points, as seen by that one receiver. This removes one variable, the quality of receiver front ends themselves. E.g., you're using a common "test" instrument, it will let you observe relative performance at different points in the distribution system.

- What are the numbers before the Kitz amp?
- What are the numbers after the Kitz amp?
- What are the numbers at TV1?
- What are the numbers into Splitter B (After the additional 30 ft of coax)?
- Whar are the numbers at TV2 output?
- What are the numbers at TV3 output?

If you write those down as you go for each channel, you may find which intermediate component most adversely affects reception of the poorest channels.

[holl_ands]

tballister:
First lets consider Resistivity (rho), which is the inverse of Conductivity (sigma or "C"):
Resistance = R (ohm) = rho (ohm-meter) x L/A

Resistivity is a property of the material which does NOT depend on the size of the object.
Resistance, R=V/I, is what you actually measure with voltage & current meters and
varies as the the object's size varies.

Conductivity (sigma or "C") is a property of the material, irrespective of it's size.
Conductance (G = I/V = R^-1) is what you can measure and varies as the object size varies: G = C x A/L

"Specific Conductance" is for a specific value of A/L=1, which is preferably called "Conductivity"
to avoid confusing this subject any more than necessary.....

[tballister]

Originally Posted by holl_ands

tballister:
First lets consider Resistivity (rho), which is the inverse of Conductivity (sigma or "C"):
Resistance = R (ohm) = rho (ohm-meter) x L/A

Resistivity is a property of the material which does NOT depend on the size of the object.
Resistance, R=V/I, is what you actually measure with voltage & current meters and
varies as the the object's size varies.

Conductivity (sigma or "C") is a property of the material, irrespective of it's size.
Conductance (G = I/V = R^-1) is what you can measure and varies as the object size varies: G = C x A/L

"Specific Conductance" is for a specific value of A/L=1, which is preferably called "Conductivity"
to avoid confusing this subject any more than necessary.....

holl_ands:
This was exceptionally well stated, and I see now the flaw in my thinking. Mainly not differentiating carefully between Conductivity and Conductance. The above provides a concisely progressed introduction to the dependent definitions.

I now realize the relationship C = G x (L/A) can be interpreted as saying something like, "... for a fixed measured Conductance G, if the distance L is increased then the Conductivity of the material must increase... if G is to remain constant".

That finally makes sense, thanks.

I think if the form of the relationship had been written as G = C x A/L, or better yet as R = L / (C x A), I might have seen it earlier because, at lest for my test bench mind, R = 1/G is so much more tangible; its what we so often directly measure, calculate, shop for, burn up, etc...

Thanks again, good lesson.
t

[otafool]

Thanks for your reply, tballister. My TVfool is below.

I tried out a cheapo 20 db adjustable gain distro amp today, and had the same results as the channel master. So that rules out one thing.

The main problem I have is with TV #3 which actually is a cheopo USB ATSC capture device that I use for recording. With the configuration I originally posted (2 passive splitters), I get signal strength of ~12% at this tuner for 17.1 WNED. Note I have my antenna pointed as to get maximum signal from this station. The software I'm using also reports quality, which usually is 100%, but this can decrease according to weather conditions (and that messes up recording).

[tballister]

- You said CM4228. Do you mean the older CM4228, or the new CM4228HD?
- Where is the antenna mounted, indoors or out?
- If outdoors, how high?
- Are there any signficant obstructions? (Trees, other buildings, etc.)

60 Miles at 644-650MHz (Ch 43) is a lot of miles, and you've got a lot of energy hitting that antenna from all those stations closer to you. Even with a majority of them hitting the back side of the antenna, they all add up. I'm not surprised things get worse when you add 20 dB (more) gain. I does seem there's a good chance you wind up overloading (saturating) the amplifier.

If you had a VHF/UHF splitter handy, you might try inserting its UHF port into the path.
That is, connect the antenna to the Common port, and connect your first splitter to its UHF port. You can at least knock down the power of the VHF stuff. You may lose CHCH-TV on 11 by adding the VHF/UFH splitter, but you may be able to add the amplifier without overloading it with those few higher power VHF signals reduced.

While the result might not be optimal, in terms of stations you might lose, as an experiment it would tell whether, or not, removing some of the total energy would improve the amplified performance of Ch 43, or not.

As far as the amplifier goes, I'm not a big fan of "Distribution" or "Line" amplifiers because of they generally have poor noise factors. But if you are using the Kitz 100, you know you can also experiment with reducing its gain. Use a small phillips screw driver to get into that internal "gain" pot. But be careful to use very light force; you can break it if you put too much torgue on it.

But let me know about the antena location details, ok? They might suggest a few other things...

[goforit]

tballister:

Below is my TV Fool Link.

I have FM and Channel 11 traps- that work well. My edge channel is WNYO which can come in WITHOUT amplification, and no splitter. Adding a pre-amp or distro amp does not cause any overload (I do not lose channels), but it does weaken WNYO. I thought using a good quality pre-amp (CM 7777) would lower the noise level and allow WNYO to "come off the floor", but not in my case. (See also previous post.)

http://www.tvfool.com/?option=com_wr...3cf4246b85c40d

[otafool]

- You said CM4228. Do you mean the older CM4228, or the new CM4228HD?
The older one

- Where is the antenna mounted, indoors or out?
Outdoors

- If outdoors, how high?
On a 10 ft pole mounted just below the eaves

- Are there any signficant obstructions? (Trees, other buildings, etc.)
No, pretty much a clear line of sight with the CN tower. No houses behind, maybe a tree or two a few hundred feet away.