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post #18301 of 18529 Old 03-27-2020, 06:46 PM
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Quote:
Originally Posted by rabbit73 View Post
Tyler The Antenna Man has posted a video about testing the Channel Master CM-3201 LTE Filter. In the video, he shows an example of LTE interference which he calls LTE Pulse Pixelation; 1:43 to 1:49 and 2:17 to 2:23 in the video.

https://www.youtube.com/watch?v=B87GMPdKZ5E

Here are two frame captures of the LTE Pulse Pixelation:





The pixelation is very brief, not like the usual pixelation we are used to seeing that he shows 2:59 to 3:06.
I wonder what the signal quality and symbol quality looked like while that was happening.

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post #18302 of 18529 Old 03-27-2020, 06:47 PM
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I'm wary of this video. First, AntennaSearch is not a complete set of all towers used for cell phones. It's not exhaustive; no such dataset exists. Second, I think the interference shown is on the uplink side, which means it has more to do with the proximity and transmit power of the phone than the cell tower. Given the bursty nature of it, that seems likely. Further, with the move to the 600 MHz band, the downlink is going to be closer to the TV band than the uplink, and will look more like continuous interference in most cases I would think.

- Trip
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post #18303 of 18529 Old 03-27-2020, 06:55 PM
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Quote:
Originally Posted by shoman94 View Post
I wonder what the signal quality and symbol quality looked like while that was happening.
Tyler uses a converter box that gives only signal quality for testing antennas. I don't know what the TV shown in the video gives.

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post #18304 of 18529 Old 03-27-2020, 07:04 PM
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Quote:
Originally Posted by Trip in VA View Post
I'm wary of this video. First, AntennaSearch is not a complete set of all towers used for cell phones. It's not exhaustive; no such dataset exists. Second, I think the interference shown is on the uplink side, which means it has more to do with the proximity and transmit power of the phone than the cell tower. Given the bursty nature of it, that seems likely. Further, with the move to the 600 MHz band, the downlink is going to be closer to the TV band than the uplink, and will look more like continuous interference in most cases I would think.

- Trip
Hello, Trip; hope you are staying well.

I answered your 2nd PM on DHC; did you read it? I talked about my ham adventures when I was younger.

Yeah, it's difficult to say exactly what caused the interference, but I thought it was an interesting test of the filter.

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post #18305 of 18529 Old 03-27-2020, 07:05 PM
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Quote:
Originally Posted by Trip in VA View Post
I'm wary of this video. First, AntennaSearch is not a complete set of all towers used for cell phones. It's not exhaustive; no such dataset exists. Second, I think the interference shown is on the uplink side, which means it has more to do with the proximity and transmit power of the phone than the cell tower. Given the bursty nature of it, that seems likely. Further, with the move to the 600 MHz band, the downlink is going to be closer to the TV band than the uplink, and will look more like continuous interference in most cases I would think.

- Trip
It does seem odd that it fixed it anyways.

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post #18306 of 18529 Old 03-27-2020, 07:09 PM
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Yes, staying well; I hope you are too. I forgot to reply to your DHC message and will do so over the weekend.

I'm not saying it's not LTE interference, I'm saying that it's not necessarily representative of what everyone who has LTE interference will see, especially going forward when the last lingering stations above channel 37 clear out.

- Trip

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post #18307 of 18529 Old 03-27-2020, 07:17 PM
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Originally Posted by rabbit73 View Post

Yeah, it's difficult to say exactly what caused the interference, but I thought it was an interesting test of the filter.
Sure was.

Today I went on the roof and removed the reflector on my DB4e. I was able to get an adjustment that removed the glitch from RF-36 along with adding the CM3201 on my UHF input of my AD combiner.

Here is whats odd. I still get the weird Signal quality bounce but I'm not not losing my symbol quality. I decided to time my signal bounce and every 18 seconds on the money my Signal Quality drops 10-11% for a second the climbs back up. This repeats every 18 seconds! Even aiming at the tower did not remove this bounce.

The other odd thing I noticed was that I have two channels RF-15 and RF-17 that are on the same tower and have totally different signals. I can aim my antenna to the point I'm losing RF-17 and RF-15 is still 90+ signal. With the reflector removed I can spin the antenna 360 and never lose RF-15. Odd stuff.

Below are the specs from the two Antennas.

RF-17:
1572' 1000 kW DA (E) (Vertical ERP: 250 kW)
(58.95 kW + 12.3 dB gain = 1000 kW ERP)
70.9 mile contour / 15807 sq. mi. area / Est. Pop. 1,256,014
1527' AGL; 1952' AMSL; (1024383)
0.75° Elec Beam Tilt; Full Service Filter
[H-Pat] DIELECTRIC TFU-26DSC/VP-R C130

RF-15:
1640' 1000 kW ND (E) (Vertical ERP: 266.3 kW)
(55.78 kW + 12.54 dB gain = 1000 kW ERP)
74 mile contour / 17203.7 sq. mi. area / Est. Pop. 1,644,168
1596' AGL; 2021' AMSL; (1024383)
0.75° Elec Beam Tilt; Full Service Filter
DIELECTRIC TFU-33JTH/VP-R O6

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post #18308 of 18529 Old 03-28-2020, 08:31 AM
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Quote:
Originally Posted by shoman94 View Post
Today I went on the roof and removed the reflector on my DB4e. I was able to get an adjustment that removed the glitch from RF-36 along with adding the CM3201 on my UHF input of my AD combiner.
What do you mean by "adjustment?" Did you rotate the antenna?

Quote:
Originally Posted by shoman94 View Post
Here is whats odd. I still get the weird Signal quality bounce but I'm not not losing my symbol quality. I decided to time my signal bounce and every 18 seconds on the money my Signal Quality drops 10-11% for a second the climbs back up. This repeats every 18 seconds! Even aiming at the tower did not remove this bounce.
Symbol Quality, with a few exceptions, is either 0% or 100%. In the very narrow range of SNR just below 15.2 dB when there are uncorrected errors but the TV is still able to display a broken picture and sound, the Symbol Quality will be <100%. Symbol Quality really doesn't help you much.

Without a spectrum analyzer, troubleshooting a problem like this is very hard or impossible. Are you seeing this on every channel, a couple channels or just one? It could be some sort of local interference or a problem at the transmitter. A Signal Quality drop of 10% probably isn't enough to drop out the station.

Attached is a spectrum analyzer image showing a transmitter power cycling. Every time the transmitter reached full power it would turn off and restart the power up cycle. Without an analyzer I would never have known what was going on.

Quote:
Originally Posted by shoman94 View Post
The other odd thing I noticed was that I have two channels RF-15 and RF-17 that are on the same tower and have totally different signals. I can aim my antenna to the point I'm losing RF-17 and RF-15 is still 90+ signal. With the reflector removed I can spin the antenna 360 and never lose RF-15. Odd stuff.
At first glance it seems odd but it's more like the rule than the exception. Even stations sharing the same antenna can be different. It has a lot to do with it being a different frequency. Receive/transmit antenna patterns are different and mulitpath is different with frequency.
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post #18309 of 18529 Old 03-28-2020, 08:58 AM
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Quote:
Originally Posted by Calaveras View Post
What do you mean by "adjustment?" Did you rotate the antenna?







Symbol Quality, with a few exceptions, is either 0% or 100%. In the very narrow range of SNR just below 15.2 dB when there are uncorrected errors but the TV is still able to display a broken picture and sound, the Symbol Quality will be <100%. Symbol Quality really doesn't help you much.



Without a spectrum analyzer, troubleshooting a problem like this is very hard or impossible. Are you seeing this on every channel, a couple channels or just one? It could be some sort of local interference or a problem at the transmitter. A Signal Quality drop of 10% probably isn't enough to drop out the station.



Attached is a spectrum analyzer image showing a transmitter power cycling. Every time the transmitter reached full power it would turn off and restart the power up cycle. Without an analyzer I would never have known what was going on.







At first glance it seems odd but it's more like the rule than the exception. Even stations sharing the same antenna can be different. It has a lot to do with it being a different frequency. Receive/transmit antenna patterns are different and mulitpath is different with frequency.
By adjustment I mean I was able to rotate or adjust the height tons pint where I don't get any glitches with PBS while maintining the rest of my channels.


I understand that about Symbol Quality. The 10% drionis instant and when that happened previously, PBS, RF36, was losing Symbol Quality and glitching the picture. Now it's not but I have the same 10% drop.

I was and still am thinking it is a local interference but it only affects that one channel. One thing I found out yesterday is that I have a Acurite Weather station on the same pole and it's my understanding from my research is that it broadcasts information to the Acurite Hub every 18 seconds but is uses a signal in the 433mhz band. It would make no sense to only affect RF36 IMO, but I do plan to turn it off and see what happens. It is a simple check for me.

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post #18310 of 18529 Old 03-28-2020, 09:16 AM
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Originally Posted by shoman94 View Post
I was and still am thinking it is a local interference but it only affects that one channel. One thing I found out yesterday is that I have a Acurite Weather station on the same pole and it's my understanding from my research is that it broadcasts information to the Acurite Hub every 18 seconds but is uses a signal in the 433mhz band. It would make no sense to only affect RF36 IMO, but I do plan to turn it off and see what happens. It is a simple check for me.

Seems to me that the 18 seconds nails it down. There could be a spurious signal coming out of the weather station. I would say it's not a good idea to have any transmitter that close to your TV antennas unless you can control when it transmits.

One set of my TV antennas are on my ham radio tower. When I transmit it wreaks havoc on the TV signals but I have 100% control of the transmitters. I just don't transmit when I'm recording a TV program.
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post #18311 of 18529 Old 03-28-2020, 09:25 AM
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Originally Posted by Calaveras View Post
What do you mean by "adjustment?" Did you rotate the antenna?



Symbol Quality, with a few exceptions, is either 0% or 100%. In the very narrow range of SNR just below 15.2 dB when there are uncorrected errors but the TV is still able to display a broken picture and sound, the Symbol Quality will be <100%. Symbol Quality really doesn't help you much.

Without a spectrum analyzer, troubleshooting a problem like this is very hard or impossible. Are you seeing this on every channel, a couple channels or just one? It could be some sort of local interference or a problem at the transmitter. A Signal Quality drop of 10% probably isn't enough to drop out the station.

Attached is a spectrum analyzer image showing a transmitter power cycling. Every time the transmitter reached full power it would turn off and restart the power up cycle. Without an analyzer I would never have known what was going on.



At first glance it seems odd but it's more like the rule than the exception. Even stations sharing the same antenna can be different. It has a lot to do with it being a different frequency. Receive/transmit antenna patterns are different and mulitpath is different with frequency.

Can I use the RTLSDR USB dongle along with RTLSDR Scanner software to use as a spectrum anaylzer as @rabbit73 alluded to? I am having the same problem I believe with Fox 11 WLUK in Green Bay.


EDIT: I am talking about the transmitter issue you used as an example
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post #18312 of 18529 Old 03-28-2020, 10:31 AM
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Originally Posted by MBrown2020 View Post
Can I use the RTLSDR USB dongle along with RTLSDR Scanner software to use as a spectrum anaylzer as Rabbit alluded to? I am having the same problem I believe with Fox 11 WLUK in Green Bay.

I'm not familiar with this so maybe Rabbit73 or someone else can answer that for you.
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post #18313 of 18529 Old 03-28-2020, 11:07 AM
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Originally Posted by MBrown2020 View Post
Can I use the RTLSDR USB dongle along with RTLSDR Scanner software to use as a spectrum anaylzer as Rabbit alluded to? I am having the same problem I believe with Fox 11 WLUK in Green Bay.

MBrown2020, I use an AirSpy HF+ tuner with SDR Console to look at DTV signals, in addition to tuning 50-108 MHz frequencies. You can certainly try using yours for a spectrum analyzer. I've used it to troubleshoot some FM signals that were having problems and alerted engineers of situations they didn't know existed.

I have a couple hi VHF channels that have regular signals on them - channel's 9 and 10. Channel 10 is a very local signal and it seems to overwhelm the AirSpy HF+ tuner. I don't mean that it overloads it - the spectrum displayed in SDR Console when tuned to 192.31 MHz is just a total space of white. I've attached a screen capture of what it looks like.

When I zoom in I can see the signal activity, including the pilot signature at 192.31. You might be able to see what you're looking for in looking at the spectrum for 11.

Jim - Springfield, Missouri
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Antennas - Antennacraft MXU59 UHF antenna & home-brew version of Antennacraft VHF Y-10-7-13 antenna @ 25'. Both antennas fed through a Channel Master 7777 30dB pre-amp.
Tuners - Zenith DTT901 converter box; AirSpy HF+ sdr; Silicon Dust HDHomerun Dual ATSC tuner, using Rabbitears autologger support.
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post #18314 of 18529 Old 03-28-2020, 01:02 PM
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@rabbit73


I received the RTL USB dongle and installed RTLscanner and did a quick scan to get started.(See pic) I just don't know how to interpret the results. Am I close?


EDIT: Perhaps you can DL the scan and load it in your RTLScanner?
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post #18315 of 18529 Old 03-28-2020, 01:16 PM
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I changed Gain to 25dB as I saw in an example and got something a little more useful, i guess?
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post #18316 of 18529 Old 03-28-2020, 03:05 PM
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Originally Posted by MBrown2020 View Post
I changed Gain to 25dB as I saw in an example and got something a little more useful, i guess?
That was exactly the correct thing to do. The rule is to increase the gain until just before the noise floor starts to rise.



I suggest you change the color scale from jet to winter so that the top of the channel scan is darker.



This is what happens if you set the gain too high:



You have less electrical noise interference than I have on VHF-High. Here is a severe case of electrical noise interference:

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post #18317 of 18529 Old 03-28-2020, 03:18 PM
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Originally Posted by rabbit73 View Post
That was exactly the correct thing to do. The rule is to increase the gain until just before the noise floor starts to rise.



I suggest you change the color scale from jet to winter so that the top of the channel scan is darker.




You have less electrical noise interference than I have on VHF-High.

I guess I'm still a little lost? What on the graph tells you this (The smaller amount of vertical spikes along the bottom between the channel?)
What does this scan tell us about channel 11?

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post #18318 of 18529 Old 03-28-2020, 04:24 PM
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Originally Posted by MBrown2020 View Post
I guess I'm still a little lost? What on the graph tells you this (The smaller amount of vertical spikes along the bottom between the channel?)
That is correct

Quote:
What does this scan tell us about channel 11?
It tells me this:



What else do you want it to tell you?
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post #18319 of 18529 Old 03-28-2020, 05:04 PM
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Originally Posted by rabbit73 View Post
That is correct

What else do you want it to tell you?

I was hoping it would confirm my issue with it being transmitter ramp up on Fox 11 WLUK, like @Calaveras showed in his pic.


I don't know how he measured that output, though.


I know this most likely will be moot after 5/1/2020 repack to channel 12, but was still trying to verify it.
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post #18320 of 18529 Old 03-28-2020, 05:41 PM
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Quote:
Originally Posted by MBrown2020 View Post
I was hoping it would confirm my issue with it being transmitter ramp up on Fox 11 WLUK, like @Calaveras showed in his pic.


Quote:
I don't know how he measured that output, though.
He would be best able to answer that question, but it looks like he connected his antenna to the Rigol spectrum analyzer and did a scan across 8 MHz; 6 MHz for the channel plus 1 MHz on each side. The spectrum analyzer measures amplitude vs frequency, so the scan must be very slow across the channel to record a dropout during the scan.

You might be able to set the scan for 197 to 205 MHz in the continuous mode with the scan speed set slow (dwell).
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post #18321 of 18529 Old 03-29-2020, 08:06 AM
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Quote:
Originally Posted by rabbit73 View Post
He would be best able to answer that question, but it looks like he connected his antenna to the Rigol spectrum analyzer and did a scan across 8 MHz; 6 MHz for the channel plus 1 MHz on each side. The spectrum analyzer measures amplitude vs frequency, so the scan must be very slow across the channel to record a dropout during the scan.

You might be able to set the scan for 197 to 205 MHz in the continuous mode with the scan speed set slow (dwell).

You are correct. In the lower right of the display is "SWT." That is Sweep Time and it was set to 20 seconds, which means 20 seconds to scan the entire range. I just let it sweep over and over until the power cycling fell nicely in the range and I froze the trace and saved it.

KMMD is a LP station running 15KW. It looks like the "ON" power was 13 dB below full power which would put the ON power at 750 watts.

This is another example of a low power station monitored by no one. They had no idea that there was a problem until I e-mailed them.
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post #18322 of 18529 Old 03-29-2020, 02:29 PM
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Quote:
Originally Posted by Trip in VA View Post
I'm wary of this video. First, AntennaSearch is not a complete set of all towers used for cell phones. It's not exhaustive; no such dataset exists. Second, I think the interference shown is on the uplink side, which means it has more to do with the proximity and transmit power of the phone than the cell tower. Given the bursty nature of it, that seems likely. Further, with the move to the 600 MHz band, the downlink is going to be closer to the TV band than the uplink, and will look more like continuous interference in most cases I would think.

- Trip
The power output of an LTE base station does vary quite a bit. When it doesn't have any data to send, the resource block sub-carriers are not modulated. Here's an example. The fainter trace is the peak hold function. You can also see a resource block (a group of sub-carriers) being used in the current trace. This base station is right across the street from me.


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post #18323 of 18529 Old 03-29-2020, 06:53 PM
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Originally Posted by MBrown2020 View Post
I was hoping it would confirm my issue with it being transmitter ramp up on Fox 11 WLUK, like @Calaveras showed in his pic.
I did some tests with my VHF-High signals. A $22 dongle is certainly no match for the Rigol SA, but it might work for you.

In Dec, I was moved from a room on the 1st floor to a room on the 2nd floor with a window that faces the transmitters. I thought the signals would be better, but they are worse; might have something to do with the trees and a roof peak in the signal path.





In spite of the crappy signals, my Sony TV gives an SNR of 16 dB for ch7 and an SNR of 20 dB for ch 13.

I don't have a channel 11, but I do have a channel 13:



The above scan took about 50 seconds.



The antenna switch was turned off for about 10 seconds. I can't explain the double step down and up. It might have something to do with the fact that the dongle can't do a scan this wide; it stitches together shorter scans in the spectrum analyzer software. Some of the test scans didn't show the pilot, probably because of the poor signal quality; I forgot to save one.

I tried other SA software for the dongle:





I used a single scan instead of a continuous scan. If you use a continuous scan, you must stop it at the end of the first scan or the second scan will overwrite the first scan. You can see that the ambient noise is higher than the noise floor of the dongle, which reduces the SNR of the signals.

I'm wondering if the SDRplay RSP1A
https://www.hamradio.com/detail.cfm?pid=H0-015965ideo

with Steve Andrew's Spectrum Analyser Software
https://www.sdrplay.com/spectrum-analyser/

would do any better with this problem?
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post #18324 of 18529 Old 04-08-2020, 09:51 AM
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Im considering splitting my main antenna line in the attic (simplest approach) to run to a total of 3 tvs in my home instead of the 1 tv my main antenna is connected.

Im currently using a RCA TVPRAMP1Z mast mounted amp with its power supply near the tv.

I was considering something like the CM-3414 which looks to be powered by a standalone F cable.

If Im understanding correctly I just need to remove my current power supply (& adapter/inserter) at the tv since these splitter units have there own power supply & leave the mast part.

Im concerned about having the unit (like the CM-3414) in the attic due to the summer temperatures, im not sure if it has heat sensitive electronics.

Any incite?
Thanks


EDIT
Looks like the CM3414 is only +8db.
The CM-3412 lists at 11db.
The RCA Im using shows VHF +16db & UHF +22db on the package.
The RCA VH240R at my local lowes lists at 10db & about half the cost of the CM3414.
May have to rethink this plan.

I did order some F Type 75 Ohm Terminator caps but not sure how much they help.
.

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post #18325 of 18529 Old 04-08-2020, 12:34 PM
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Quote:
Originally Posted by DeweyNC View Post
Im considering splitting my main antenna line in the attic (simplest approach) to run to a total of 3 tvs in my home instead of the 1 tv my main antenna is connected.

Im currently using a RCA TVPRAMP1Z mast mounted amp with its power supply near the tv.

I was considering something like the CM-3414 which looks to be powered by a standalone F cable.

If Im understanding correctly I just need to remove my current power supply (& adapter/inserter) at the tv since these splitter units have there own power supply & leave the mast part.

Im concerned about having the unit (like the CM-3414) in the attic due to the summer temperatures, im not sure if it has heat sensitive electronics.

Any incite?
Thanks


EDIT
Looks like the CM3414 is only +8db.
The CM-3412 lists at 11db.
The RCA Im using shows VHF +16db & UHF +22db on the package.
The RCA VH240R at my local lowes lists at 10db & about half the cost of the CM3414.
May have to rethink this plan.

I did order some F Type 75 Ohm Terminator caps but not sure how much they help.
.
Why don't you try a 4-port power passing splitter 1st. You may have enough gain to accommodate the loss of the 4-port splitter for your existing system to work. The channel master amplified splitters don't have a power output port. Hooking the amplified splitter up as you describe will de-power the preamp so you will get nothing at the TV.
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post #18326 of 18529 Old 04-08-2020, 03:02 PM
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Quote:
Originally Posted by MBrown2020 View Post
I was hoping it would confirm my issue with it being transmitter ramp up on Fox 11 WLUK, like @Calaveras showed in his pic.
I wasn't completely satisfied with the performance of the RTL-SDR dongle with your VHF-High problem, so I tried the SDRplay RSP1A SDR with the SDRuno and RSP-SpectrumAnalyser softwares.

Today, my channel 7 was stronger than my channel 13, so I used 7 for some tests.

The RSP1A with SDRuno software can show a continuous spectrum display up to 10 MHz wide. If a channel drops out, you will certainly see it happen:



This is what the spectrum analyzer software looks like with a 20 MHz span:



and with a 10 MHz span:



I haven't found a way to slow down the sweep time like in the SDR dongle software to show dropout and recovery in one scan, but you will be able to see the dropout and recovery as you watch the trace.

I did a review of the RSP1A SDR here:
Testing the SDRplay RSP1A Software-Defined Radio
https://www.avsforum.com/forum/25-hd...ned-radio.html
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post #18327 of 18529 Old 04-08-2020, 08:57 PM
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So with power passing splitters, which way would be more efficient?

The splitter images are generic images I grabbed to make the illustrations.
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post #18328 of 18529 Old 04-09-2020, 07:40 AM
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Originally Posted by DeweyNC View Post
So with power passing splitters, which way would be more efficient?

The splitter images are generic images I grabbed to make the illustrations.

They'll be very close to equal. 2-way splitters typically have 3.5 dB loss per port so two cascaded 2-way splitters will have 7 dB loss. 4-way splitters typically have 7 db loss.

How long is the antenna to splitter coax?
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post #18329 of 18529 Old 04-09-2020, 08:03 AM
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Antenna to the 1st splitter would be about 20ft (once I cut the R6-cable).
Currently my R6-cable on the roof top antenna to the main tv is about 30ft.

So I figure about 70ft to the second splitter (Antenna to 2nd splitter)
& the short leads off it to the tvs maybe 10ft each.


Quote:
Originally Posted by Calaveras View Post
They'll be very close to equal. 2-way splitters typically have 3.5 dB loss per port so two cascaded 2-way splitters will have 7 dB loss. 4-way splitters typically have 7 db loss.

How long is the antenna to splitter coax?

Last edited by DeweyNC; 04-09-2020 at 08:10 AM.
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post #18330 of 18529 Old 04-09-2020, 09:52 AM
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Quote:
Originally Posted by DeweyNC View Post
Antenna to the 1st splitter would be about 20ft (once I cut the R6-cable).
Currently my R6-cable on the roof top antenna to the main tv is about 30ft.

So I figure about 70ft to the second splitter (Antenna to 2nd splitter)
& the short leads off it to the tvs maybe 10ft each.

Using the UHF gain and Noise Figure that I measured for your preamp and 70' of coax with a 4-way splitter, the system noise figure is degraded only 0.5 dB. You should not need a distribution amp. A distribution amp will only get you a couple tenths of a dB improvement in signal-to-noise ratio.
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