Dropping TV channels

Bill.Satellite wrote:
It's always fun to watch 2 smarty pants arguing a point that no one understands and won't help answer the posters question.
Happy Thanksgiving. I hope the OP got to watch the parade!

Yeah, well your "smarty" answer does not help the OP in any way either..

My point is, SWR should have NEVER been mentioned, it has no business in this entire thread and it was brought up by someone who felt it would "contribute" but instead it MUDDIES the water with unneeded extra terminology..

I pitty the poor fool who thinks they will help there tiny little UNDERSIZED RV antenna by cutting the antenna length..

TV antennas are by design a WIDE BAND RECEIVING antenna and are not designed for low SWR, there is no way you could design any antenna which covers the entire TV band and have a 1:1.1 - 1:2 SWR match, just is not happening.

Yeah, I do have a Ham license, I also have a degree in electronic technologies, I have repaired thousands of TVs, stereos, Sat receivers, computers and much, much more electronic technologies over the years..

Built many of my own home brew Ham antennas, stacked and matched dual 13 element 440 Yagis was one of my favorites using 1/2" copper pipe and 10 gauge solid wire soldered to the pipe (even the driven element is soldered to the copper pipe, wrap that around your head on how that was done!).. Worked a fellow Ham simplex 30 miles away with 150 Milliwatts of power with that one on 440 mhz.

Edd505 wrote:
I sort of get what you are both saying, brother was avid HAM. I have 3 TV connections, bedroom, living, basement. That mean I have two splitters? I know where to find one. Then how do you know it's a good splitter vs cheap? Last is there a way to test them? That's my project in the next few days.

You can buy 2 way, 3 way, 4 way or more passive splitters.

You can "nest" splitters.. In other words take a two way then on one output put another 2 way.

The problem however is each time the signal is split you get massive losses (three DB is like cutting your signal in half so 3.5 DB is even a bit worse than half..

Two way splitters are 3.5 DB loss.

Nesting a pair of 2way gives you one port with 3.5 DB loss and two ports of 7 DB loss.

Three way splitters basically are the same as nesting two 2 way splitters with one port with 3.5 DB loss and two ports with 7 DB loss.

Simply put, in the digital age passive splitters will kill your signal enough that the RF noise surrounding your trailer can easily drown out the channels.

The base of ALL passive splitters is nothing more than 75 ohm 1/8 watt resistors.. Yep $.05 cent resistors, so whether you buy $1 splitter or a $100 splitter the heart of it is nothing more than $.05 resistors.

They are completely passive with no other electronic devices inside.

Sure, you could buy gold plated ones but in reality it won't fix the 3.5 DB loss of the resistors.

You don't NEED to buy expensive splitters, anything more than $2.00 is wasting money no matter what some of the supposed smart folks on this forum say (perhaps I can make them a deal on a certain bridge in New York?).

I sort of get what you are both saying, brother was avid HAM. I have 3 TV connections, bedroom, living, basement. That mean I have two splitters? I know where to find one. Then how do you know it's a good splitter vs cheap? Last is there a way to test them? That's my project in the next few days.

Gdetrailer wrote:

SWR affect on reception is so small of a problem it really does not affect reception.

You are a "Ham" and you should understand this.

As I said. I have seen the difference nearly Every day as I change from one band to another and re-tune the antenna.> When the SWR hits 1:1 (Matched) the received signal is much, much, much, stronger.

If The TRV signal is borderline, a 3:1 SWR or even a 2:1 can make the difference.. I also studied this stuff in college.

It's always fun to watch 2 smarty pants arguing a point that no one understands and won't help answer the posters question.
Happy Thanksgiving. I hope the OP got to watch the parade!

wa8yxm wrote:

Gdetrailer wrote:


No.

SWR and impedance DOES NOT COME INTO PLAY when it comes to RECEPTION.

TRANSMITTING, yes, RECEIVING, NO.en the OP would be LOOSING ALL

Again I have to disagree. in part. THe part I disagree with is above.
SWR affects both Transmission and reception.

IF there is SWR (and there should not be) then power is reflected back to the source, and it bounces back and forth,, WIth loss, till it's all lost. Kind of like dropping a ping pong ball. Each bounce is less high then the last bounce till there are no more bounces.

Does not matter if Transmitting or receiving.. When I hit the "TUNE" button on my TS-2000. the received signal gets STRONGER

THe part I agree with.

The televison presents the same (72-75 OHM) load on or off. Turning it on will not make a difference in SWR, and even if it did a proper SPLITTER will block it. (Even disconnecting it WHICH WILL cause an SWR issue, the splitter will take care of it).

But turning it on generates RF noise, (The local oscillators inside the beast among other things) And these can land on frequencies that will cause interference to the other television.

SWR affect on reception is so small of a problem it really does not affect reception.

You are a "Ham" and you should understand this.

If you don't believe me try hooking a random long wire directly to a HF rig and tune away.. then compare to a antenna tuner and try peaking the antenna in receive.. You will notice nearly zero affect on the receive strength.

Same thing with TV frequencies happens..

TV antennas are not designed for low SWR, SWR is Standing wave ratio and really only comes into affect when you are TRANSMITTING.. Standing waves are reflected back into the transmitter and can destroy the outputs at worst, at best it reduces the effective radiated power from your antenna.

Has nothing to do with the OPs problem..

I would hate to see someone go out and start CUTTING their expensive RV TV antenna from stupid "advice".. Not even sure how one would attempt to adjust a TV antenna SWR since it would be highly illegal to TRANSMIT ON TV FREQUENCIES.

Gdetrailer wrote:


No.

SWR and impedance DOES NOT COME INTO PLAY when it comes to RECEPTION.

TRANSMITTING, yes, RECEIVING, NO.en the OP would be LOOSING ALL

Again I have to disagree. in part. THe part I disagree with is above.
SWR affects both Transmission and reception.

IF there is SWR (and there should not be) then power is reflected back to the source, and it bounces back and forth,, WIth loss, till it's all lost. Kind of like dropping a ping pong ball. Each bounce is less high then the last bounce till there are no more bounces.

Does not matter if Transmitting or receiving.. When I hit the "TUNE" button on my TS-2000. the received signal gets STRONGER

THe part I agree with.

The televison presents the same (72-75 OHM) load on or off. Turning it on will not make a difference in SWR, and even if it did a proper SPLITTER will block it. (Even disconnecting it WHICH WILL cause an SWR issue, the splitter will take care of it).

But turning it on generates RF noise, (The local oscillators inside the beast among other things) And these can land on frequencies that will cause interference to the other television.

TVs are new this year. No, this is not a new problem. Similar problems with a 2006 vintage & a 2009. Some improvement when I changed out the original omni directional ant for the Jack.

Veebyes wrote:
Both TVs are Samsungs. Both were bought together so same age, different sizes. The ant is a newish Jack that has a little light on it, assume indicating an amp of some sort. No LEDs in the trailer.

That leaves me with the splitter which came with the trailer. Will check connections when next on trailer, next April, & maybe find a better splitter.

How old are the TVs?

Has this been an issue when you first put the TVs in?

If this has been an issue from day one then you may have got defective or CHEAPLY BUILT TVs to start with (and yes, Samsungs are often not any better quality than other brands).

Brand names don't mean much now days since they are simply a name stamped on a chassis for marketing purposes. Samsung often has a third party manufacturer build their products like pretty much all of the other brands, in fact a good chance it is the same plant that other brand names came from.

Good chance since you have two different size/models of Samsungs they came from two DIFFERENT third party manufacturers..

If this was not a problem when the TVs were first installed and has slowly started to become a problem then you may be having issues with the TVs power supplies with filter caps going bad..

Age is important, I have seen switching power supplies fail from bad caps as soon as one year old..

Roadpilot wrote:
While I think the RF interference is likely, another possible explanation is a changing VSWR. The impedance if the TV antenna is likely 75 or 300 ohms. The cable maybe 60 ohms or 50 ohms or 300 ohms if it's a flat cable. The splitter if used is unknown and then there is the input impedance or termination impedance. Unless all these impedances are equal you get interactions from a voltage standing wave ratio reflected back towards the source and then to a downstream device.

No.

SWR and impedance DOES NOT COME INTO PLAY when it comes to RECEPTION.

TRANSMITTING, yes, RECEIVING, NO.

The antenna input circuits of a tuner does not change impedance when powered or not powered. The tuner inputs are typically FET semiconductors which have an inherent HIGH IMPEDANCE to start with. The input of the TV is buffered via a resistive, capacitive and inductive network that presents a nominal 75 ohm impedance whether the TV is on or off.

If what you state is really true then the OP would be LOOSING ALL channels, not SPOT channels nor in the OPs case DIFFERENT channels are affected depending on what TV is turn on.

I have SEVEN, thats right SEVEN TVS in my sticks and bricks all running off the SAME outside antenna PLUS a FM tuner for the whole house audio system..

I have no problems or issues loosing channels when one or all are turned on.

What I did have was my system performed perfectly well for TV when it was ANALOG NTSC TV broadcasts and my system was setup using PASSIVE splitters.

Once the broadcasts switched to DIGITAL ATSC my splitters caused to much signal loss and all but a couple of stations were to weak.

My eight port passive splitter had too much signal loss in my case, had nothing to do with quantity of TVs or if they were on or off.

The fix I found in my case was replacing the passive splitter with a amplified coupler which gives a small amplified gain on each output of the coupler.

In a RV you have either a non amplified antenna or a amplified antenna PLUS one two way PASSIVE splitter.

Passive splitters are nothing more that a simple resistor inside the box, for two way splitters they are 75 ohm resistors which are in series with the output.. That makes each TV appear to be 150 ohms and with two TVs in parallel you now have 75 ohms (Ohms law).

Does not matter whether you spend $1 or $100 on a passive splitter, they ALL use RESISTORS which means signal loss.

The OP IS dealing with RFI which IS MOST LIKELY being generated within the TVs.

I suspect that the OPs TVs may have a power supply issue, specifically capacitors which ARE WEAK or going bad.

This is a typical problem that starts to surface after one or two years where the final filtering caps on the power supply board start to weaken and allow the high voltage/high FREQUENCY spikes generated by the switcher in the supply to not be filtered..

TV will work fine for several years then one day not power up, but in the mean time the TV radiates a lot of RFI, transmitting it throughout the TV and even into the wiring.

There are three main spots in a TV which use switching power supplies.

Main power, LCD driver and LED or fluorescent backlight driver.

Switching power supplies by their nature generate large amounts of RFI and the manufacturer must use care in the design of the switcher to minimize the RFI outside the TV.. But sometimes they skimp on the filtering and use components which are marginal to start with and when they age are no longer effective.