Question about signal amp

[PabloTincho]

I have 6 tuners connected to my sound system, I am using a 6 way coax splitter and
Channel Master 3043, which is connected to outside antenna.
the amp is around 10db, so around 1.6DB of gain in each tuner, is anything wrong with my set up ? any other recommendations

https://www.summitsource.com/Channe...Output-75-Ohm-120-VAC-Part-CM-3043-P7718.aspx

here is some pic of my system

but the way the Sausui Tu-99dx is the best when it comes to noise stations
and the Sony St-333ESG gives me the best sound, also best ergonomics

 

[RxDx]

Nice collection. I recommend an antenna switch. Next would be an amp at the antenna, picks
up less noise. Then your option. Or your option with a simple A/V switch. My experience of
indoor amps is that everything gets amplified in the same proportion. The signal is louder
and so is the noise floor.

 

[PabloTincho]

Nice collection. I recommend an antenna switch. Next would be an amp at the antenna, picks
up less noise. Then your option. Or your option with a simple A/V switch. My experience of
indoor amps is that everything gets amplified in the same proportion. The signal is louder
and so is the noise floor.

Do you have a link for a antenna switch ?

 

[RxDx]

Browse this. Most of these are 4 position a/v switches. I built my own, I needed
a lot more options. It routes FM and AM antenna input to the tuners or receivers,
and it also routes the output of the tuners to my receiver. I didn't see anything
close to this commercially available.

On the box itself:
Audio switches determine which input goes to the amp (audio only; video is handled
at the main receiver).
Antenna switch routes antenna input to individual tuners or receivers.
AM antenna rheostats reduce the input from the long wire outside. It has so
much signal it overloads everything but the Drake R8. Even the Sony XDR-F1HD
soft mutes when it gets full signal.






Right now I have only two tuners in the rack- T-9090 II, and T-4711. The Drake and
Sony are in other systems. I use an Integra receiver to drive two receivers that have
4 ohm output for the AR-3a systems. Also two EQs, DVD, HD TV converter box (for
dxing), one preamp, Channel Master controller for the FM antenna rotor, and FIOS box.
TV on top.

 

[audiotemp]

here is some pic of my system

These images seem not to be visible except to those logged in to teh google.

 

[PabloTincho]

These images seem not to be visible except to those logged in to teh google.

IMG_20180917_163502706

• PabloTincho
• Sep 17, 2018

IMG_20180917_163458769

• PabloTincho
• Sep 17, 2018

IMG_20180917_163437608

• PabloTincho
• Sep 17, 2018

 

[audiotemp]

Thanks for the pics. What do you have running off the other arm of the CM3043?

 

[PabloTincho]

Thanks for the pics. What do you have running off the other arm of the CM3043?

https://www.newark.com/stellar-labs...-element/dp/97W3565?ICID=mcm-redirect-product

 

[audiotemp]

I mean the other output arm.

You say you have 10dB gain, so that suggests you are doing a 6-way split of one output of the amp.

 

[PabloTincho]

I mean the other output arm.

You say you have 10dB gain, so that suggests you are doing a 6-way split of one output of the amp.

each output is 10db, I am just using one and connected to the 6-way, around 1.66db of gain in each tuner, that my guess

tuners from top to bottom
Sansui tu-99x. original
Mitsbushi DA-F30 modded
Sony ST-S333ESG,original
KENWOOD KT-770B, 1st Kenwood with Direct Linear Loop Detector
Yamaha T-80 modded
Sony ST-SA50ES, modded

 

[Bob@FM]

If you use a switch, get a proper coax switch, like this
https://www.amazon.com/Philmore-Del..._rd_t=40701&psc=1&refRID=VTQ3A2DXNMBAHGT686VR

 

[Bob@FM]

Usually, with splitters you have a 3.5 dB loss per split. So 2 way split = 3.5 dB loss, 4 way split = 7 dB loss, 8 way split = 10.5 dB loss.
A 6 way is either an 8 way with 2 outputs not used (internal) or a combination of 4 way with an additional 2 more 2 way.

I hate amps for FM, but they work fine for TV signals. I would use a 2 way splitter followed by two 3 way switches to feed 6 tuners. And no amp.

 

[I LIKE MUSIC]

It is difficult to recommend a particular antenna configuration for any one location, because the RF field strength (the amount of signal available to the antenna) is not know.

Putting a passive loss of about 3.5 dB inline (a 2 way splitter) will have a negative impact on the noise figure of a little over 2 dB. This may or may not be an issue depending on local conditions and the reduction in signal level may have a negative impact on the quieting slope of the tuner/receiver.

In terms of the impact of the signal loss in the coaxial cable between the amplifier and the antenna, if it is about 1 dB (a reasonable number as an example) the impact on the overall noise figure is about 0.5 dB, and that is not all that bad and fair amount less than the impact of a 2 way splitter.

The distribution amplifier that the OP is using is one of the better amplifiers. It has a reasonable amount of gain and fairly good noise figure of about 2 dB (the lower the number the better), some of the ones that a person might run into on the interwebs may have noise figures in the range of 6 dB to 10 dB, not good at all. Unfortunately it is not uncommon for the specifications to not include noise factor, but rather focus on gain, indicating that the higher the better and that is not always the case.

When it comes using RF signal amplification, it is important to use a quality RF amplifier/preamplifier with a low noise figure and and and high IP3 (3 intercept point) and a sufficient 1 dB compression point, although in the above context one would hope that the gain of the RF amplifier is chosen to keep the output signal below these points.


His antenna system as configured is okay. The question is, does it meet his needs? Are all of his stations of interest being received at a quality level that he is comfortable with?

 

[amptramp]

It sounds like the user could benefit from an array of coax switches rather than a splitter:

or the classic Barker & Williamson:

or for BNC:

The advantage of a switch is low loss because the connection is still one antenna to one receiver.

 

[Bob@FM]

Putting a passive loss of about 3.5 dB inline (a 2 way splitter) will have a negative impact on the noise figure of a little over 2 dB.

The distribution amplifier that the OP is using is one of the better amplifiers. It has a reasonable amount of gain and fairly good noise figure of about 2 dB (the lower the number the better), some of the ones that a person might run into on the interwebs may have noise figures in the range of 6 dB to 10 dB, not good at all.

His current config has both the amp and a 6 way splitter, not 2 way. What is the noise figure for a 6 way splitter? Combined with the amp he is using?

That above link says the CM 3043 has a noise figure of 3.5 dB. Do you have other data that says it is better?

 

[Bob@FM]

It sounds like the user could benefit from an array of coax switches rather than a splitter:
The advantage of a switch is low loss because the connection is still one antenna to one receiver.

Agreed. Many tuner guys like to listening tests to directly compare 2 tuners, both on the same antenna. So in that case, you end up using at least one 2 way splitter. In this instance, using the above CM3043 splitter / amp (1 input, 2 outputs) to drive two 3 way switches (see my link above - 1 input, 3 outputs) would allow comparison of any 3 tuners on one switch bank with any 3 on the other bank.

For someone dealing with strong signals, this is probably splitting hairs.

For very weak signals, it may be important though. I mostly deal with weak signals - i.e. from 100W college stations 20 miles away.

 

[I LIKE MUSIC]

That above link says the CM 3043 has a noise figure of 3.5 dB. Do you have other data that says it is better?

Remember this device a a very broad band device. Over the frequencies of the FM broadcast band the noise figure runs about 2 dB as measured.

His current config has both the amp and a 6 way splitter, not 2 way. What is the noise figure for a 6 way splitter? Combined with the amp he is using?

The advantage of a switch is low loss because the connection is still one antenna to one receiver.

Just for example lets use a receiver/tuner with an RF noise figure of about 4 dB, some may be better and some may be worse.

In round numbers with his amplifier and splitter configuration the noise figure will degrade by less than 1 dB, likely in the 0.5 db range over using just a switch and nothing else.

This is a result of the loss in the splitter and the gain and noise figure of the amplifier (which is likely to be less than the noise figure of the tuner/receiver alone, although that is known exactly).

When it comes to cascade noise figure calculations it is about the first active device, in this case the RF amplifier. If his amplifier had a little more gain, for example 15 dB with the same noise figure, it would actually improve the over all noise figure in this example to about 3dB from 4 dB. Remember the smaller the number the better.

Of course all of the factors of my first post come into play and more gain is not always the best thing, it depends on local conditions.

Of course if all of the receivers are in one location, making the use of a switch convenient then that would work well. If the receivers are in a different locations and one does not want to be able to listen to more than one at a time (more than one person listening) and it is not to inconvenient to go the switch, then again that will work well.

The OP asked about his configuration. It will be close in performance to using a switch only.

What is the noise figure for a 6 way splitter?

The actual noise added by a passive splitter alone is just its thermal noise, with will be quite low. The impact on noise figure of a passive splitter is related to its loss, and the RF amplifier in the system makes up for this loss.



Again, remember the loss is being counteracted by the amplifier's gain. This why the noise figure can decrease if the gain of the amplifier is greater than the splitter loss, if the RF noise factor of the amplifier is less than the RF noise factor of the tuner/receiver. And this is why it is likely a good idea to choose an RF preamplifier/ RF distribution amplifier with a low noise figure.

Channel Master devices, are in general quite good when compared to some to the cheap Chinese built devices.

One possible issue when using an RF amplifier is the amplification of signals outside of the FM broadcast band. That is one of the reasons why more gain is not always the best idea.

Again, it is all about local conditions.

This is why I asked the OP is he is satisfied with his reception as it stands now.

 

[rcs16]

I was looking around and noticed this one rather cheap LNA device from ADI, they even have the pcb gerber/fab files for the proto/eval pcb
http://www.analog.com/en/products/hmc599.html

The HMC599ST89(E) is a GaAs PHEMT High Linearity, Low Noise Gain Block MMIC SMT amplifier covering 50 to 1000 MHz. Packaged in an industry standard SOT89, the amplifier can be used as a cascadable 75 Ohm RF or IF gain stage as well as a PA or LO driver with up to +19 dBm output power. The HMC599ST89(E) offers 14 dB of gain with a +39 dBm output IP 3 at 250 MHz, Low Noise Figure: 2.2 dB, Cascadable 75 Ohm I/Os and can operate directly from a +3V or +5V supply.

The HMC599ST89(E) is ideal for:
• VHF / UHF Antennas
• HDTV Receivers
• CMTS Equipment
• CATV, Cable Modem & DBS

 

[Bob@FM]

Remember this device a a very broad band device. Over the frequencies of the FM broadcast band the noise figure runs about 2 dB as measured.
...
One possible issue when using an RF amplifier is the amplification of signals outside of the FM broadcast band. That is one of the reasons why more gain is not always the best idea.

Thank you for posting all that good information, especially the recommendation for Channel Master amplifiers, and actual NF of 2 dB when using them in the FM band. Great stuff.

One point that needs highlighting is the issue you mentioned the problem of signals outside the FM band. I would further mention it's not just signals outside the FM band, but also other strong FM signals that cause big problems.

All FM tuners have one, or two tuneable bandpass filters BEFORE their gain stages. We normally call these "gangs".
These pre-gain bandpass filters are fairly wide, maybe 2-3 MHz, so they don't help with other very strong close FM signals. But will attenuate say a strong signal at 102.5 MHz when tuned to 90.3. In addition, they will attenuate all out of FM band signals - WIFI, cell phones, TV, etc. All this is done with passive filters BEFORE any gain stages, inside the FM tuner.

This is why I prefer to use the internal tuner gain as the primary gain stage, instead of a broad band external gain stage that amplifies everything. As pointed, it really depends on your local situation. And wholly depends on the quality and gain of the external amplifier. In this example, a very good one, with reasonable gain was chosen.

But it would be very easy for others to use a 20+ dB gain, high NF amplifier, and make things worse. I think there must be 100 bad consumer grade 75 ohm amps for sale, for every good one like the Channel Master unit.

 

[I LIKE MUSIC]

It is all about what is called the RF budget. It starts with the amount and quality of the FM broadcast band RF field strength that is available to the antenna.

It can become somewhat complicated if one is trying to receive a very weak signals in the presence of one or more rather strong in band signals. This is why the selection of an RF amplifier is important. Even using a high gain antenna can be problematic if the weak station(s) are in the same direction of the rather strong station(s).

The internal RF gain of a receiver/tuner can't make up for losses that are up stream of the receiver/tuner such as feed line or splitter loss. In the OP's case it appears that he has just a slight amount of net gain, nothing that would likely lead to overload issues with a receiver/tuner. Again it is all about the the RF budget for each different case.


BTW, the OP might pick up a little bit of added performance if he used two 4-way splitters with each one connected to the separate outputs on the RF amplifier( from his post it appears that he is using a single 6-way splitter). Each amplifier output has 10 dB of gain and the loss for a 4-way splitter is about 7 dB. This could lead to a lowering of the overall noise figure by around 0.7 dB or so. Not a lot, but there is not much down side to doing this.

He could also try running one of his receivers (the best one maybe) directly from one of the outputs of the RF amplifier. This would supply more signal to the receiver.

That could result in an additional lowering of the overall noise figure. This could also give an indication of any possible RF overload issues.