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Old 31-Aug-2015, 8:10 PM   #41
sl1982
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That makes sense. Almost like audio amplifiers producing harmonics when clipped. Thanks for all the help guys. This is very interesting stuff but not for the faint of heart.
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Old 31-Aug-2015, 8:30 PM   #42
rabbit73
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ADTech did some interesting tests that show how weak signals are damaged when a preamp is overloaded by strong signals:

Just the antenna, no preamp:



This is what the same signals look like when the preamp is moderately overloaded. Notice that the weakest signals are damaged first. The noise floor rises from the spurious signals created by the IMD. This reduces the SNR of the weak signals to less than the required 15 dB minimum:



This is what the same signals look like with a badly overloaded preamp:



This is what the same signals look like with a high quality preamp that isn't easily overloaded:

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File Type: png ADTech parkig lot1 (2).png (193.2 KB, 249 views)
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File Type: jpg AD Preamp Overload 1-7 TVF Report (2).jpg (250.9 KB, 252 views)
File Type: jpg AD TVFool report for Kirlwood MO tests (2).jpg (241.8 KB, 243 views)
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Last edited by rabbit73; 4-Sep-2015 at 1:44 PM.
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Old 31-Aug-2015, 8:42 PM   #43
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Quote:
Almost like audio amplifiers producing harmonics when clipped.
Yes, exactly. Clipping produces harmonic distortion products. Intermodulation distortion produces spurious signal products.

Quote:
This is very interesting stuff but not for the faint of heart.
I think you are ready for it because of your desire to improve your reception.
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Old 31-Aug-2015, 11:23 PM   #44
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Ok, removing the db8e from the equation gives me identical results. Any other ideas? Too much FM?

edit: ok it seems to be worse. Signal quality is around 45 now

Last edited by sl1982; 31-Aug-2015 at 11:49 PM.
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Old 1-Sep-2015, 1:03 PM   #45
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Just ran a test by hooking up the antenna output to my stereo. I am still able to bring in local fm channels crystal clear even with the fm trap on in the preamp. Could this be causing the problem?

edit: also interestingly enough while trying to tune in to a detroit fm station I am getting spillover from one of the locals even though they are about 5 MHz apart (turning the trap back on stops this)

Last edited by sl1982; 1-Sep-2015 at 1:09 PM.
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Old 1-Sep-2015, 4:22 PM   #46
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Sorry to keep adding stuff on here but I am unsure if this is pertinent information or not. It seems as the temperature outside gets warmer throughout the day the signal gets worse.
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Old 2-Sep-2015, 12:51 AM   #47
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Quote:
Originally Posted by sl1982 View Post
I just got my c5 and got it installed. I was having issues with picking up fox vhf channel 7). I found a local antenna shop and they suggested getting a preamp. Got it installed and all working. The problem is the signal quality on that channel is only around 50% and it cuts in and out. Any ideas? The preamp has a fm trap built in and it doesnt seem to make any difference having it on or off.


Well, at least your getting Fox even if it's not a high quality signal.
Quote:
Ok, removing the db8e from the equation gives me identical results.
That eliminates the strong UHF signals coming in from the DB8E. The C5 is still picking up UHF signals, but they will be attenuated by the low pass filter in the combiner by 25 to 40 dB before reaching the preamp.
Quote:
Just ran a test by hooking up the antenna output to my stereo. I am still able to bring in local fm channels crystal clear even with the fm trap on in the preamp. Could this be causing the problem?
That test is inconclusive. You are probably getting some attenuation from the FM filter in the preamp, but it's not going to completely eliminate FM signals. A good FM tuner doesn't need much signal to function.
Quote:
edit: also interestingly enough while trying to tune in to a detroit fm station I am getting spillover from one of the locals even though they are about 5 MHz apart (turning the trap back on stops this)
That proves the filter is doing some attenuation. Your strongest FM signal is 65 dB stronger than Fox. I suspect that the preamp doesn't like that, and it is creating distortion products that reduce the SNR of Fox which gives you a low Signal Quality reading. You would need test equipment to see exactly what the numbers are, but you can still try a preamp that is more resistant to overload and some different filters.

All FM filters aren't alike; they have different attenuation curves and a HLSJ can also be used as an FM filter. It attenuates all signals below CH7, including the FM band. See attachments 2-4.

I'm wondering if you could go back to your original setup where you were using the preamp for both antennas but insert several filters before the preamp input. That might also be inconclusive if the strong signals were getting into the plastic case of the preamp which would bypass the filters.

Then you could try a preamp with a metal case that is resistant to overload in place of the preamp with the plastic case. You missed the boat on the Juice, but another one might do.

You could also try a preamp in a metal case that is resistant to overload with an FM filter in front of it to amplify just VHF, but you would need a UVSJ that passes DC to the preamp.

Is your coax grounded with a grounding block? That reduces interference and makes filters much more effective.

Quote:
edit: ok it seems to be worse. Signal quality is around 45 now........It seems as the temperature outside gets warmer throughout the day the signal gets worse.
OTA signals constantly vary in strength, especially non-LOS signals, and are affected by temperature inversions.
Quote:
Sorry to keep adding stuff on here but I am unsure if this is pertinent information or not.
Keep the ideas coming, one of them might click. It's too soon to give up.

Was this TL;DR?
Attached Images
File Type: jpg sl1982TVFrf7WJBK.JPG (37.0 KB, 717 views)
File Type: jpg ADvsRSFMfilter.JPG (135.6 KB, 2576 views)
File Type: gif MCM%20FM%20Trap%20Attenuation.gif (15.5 KB, 471 views)
File Type: gif ADTechHLSJs3.GIF (22.5 KB, 279 views)
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Last edited by rabbit73; 2-Sep-2015 at 2:11 AM.
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Old 2-Sep-2015, 2:50 AM   #48
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Not TL;DR at all. I will order up some fm traps and see if that helps. Buying another amp right now is out of the question as i am running out of money lol. Are the Antennas Direct FM traps good for the job? Oh and i have a coax grounding block with a wire that runs to my plumbing, is that good?
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Old 2-Sep-2015, 11:57 AM   #49
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Quote:
Are the Antennas Direct FM traps good for the job?
They are good, but you have to look at the strongest FM signals to pick the best filter. The AD filter does a good job at the 88 MHz end of the FM band, but is a little lacking at the 108 MHz end. The Radio Shack filter does a good job at the 108 MHz end but doesn't attenuate well at the 88 MHz end to allow reception of TV channel 6. The MCM filter does well at both ends.
CJFIFM 99.9 MHz -14.4 dBm
CHKS-FM 106.3 MHz -22.1 dBm
CBEGFM 90.3 MHz -27.2 dBm
WSAQ 107.1 MHz -29.2 dBm

http://www.mcmelectronics.com/produc...800829%2Cd.eXY
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Old 2-Sep-2015, 2:44 PM   #50
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Alright, I ordered 4 of the MCM ones. I guess i may as well work on some of the other stuff while i wait. Mainly grounding since I already have the guy wires installed.

Right now the wires come in the front of my house and are grounded to the water pipe there. Looking at the ground in my electrical panel it seems to hook up to my water line there ( I am sure this is not to code anymore but it may have been when the house was built)

Another option is i could run my coax to the back of the house and ground at the same spot the panel is. I have bought one of these: http://www.amazon.com/TII-Broadband-...tning+arrestor

Also for mast grounding can I run a wire to the same spot?
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Old 2-Sep-2015, 3:00 PM   #51
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You have done the most important thing when you grounded the coax with a grounding block, to protect yourself from leakage current shock if any of the AC equipment that is connected to the coax becomes defective. The code also requires that the mast is grounded by a separate 10 gauge wire connected to the house electrical system ground.



Quote:
Right now the wires come in the front of my house and are grounded to the water pipe there. Looking at the ground in my electrical panel it seems to hook up to my water line there ( I am sure this is not to code anymore but it may have been when the house was built)
Probably OK
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File Type: gif NEC Grounding.gif (16.5 KB, 653 views)
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Last edited by rabbit73; 2-Sep-2015 at 3:03 PM.
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Old 2-Sep-2015, 3:03 PM   #52
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Right. But since my house ground system is connected to my water pipes I should theoretically be able to ground to any one of them? Or should it be close to my panel?
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Old 2-Sep-2015, 3:11 PM   #53
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I'm not an electrician and I can't see your setup. The local electrical inspector has the final say, but you might not want to get him involved; some are more friendly than others. A local electrician could advise you. Todd Humphrey doesn't speak for the NFPA that publishes the NEC code, but he has some ideas that are helpful.
Satellite System Grounding
Part 2 - NEC Overview
Presented by Todd Humphrey
http://www.dbsinstall.com/diy/Grounding-2.asp

Quote:
I have bought one of these: http://www.amazon.com/TII-Broadband-...tning+arrestor
That device will ground a spike from the center conductor of the coax to ground. It is not required by the code but some people feel better when they have one. There is a similar device built-in some surge suppressor power strips that ground the coax. It has been known to degrade OTA signals and pick up electrical interference from the AC line in the same housing.

For the price of that device you could have bought an RCA TVPRAMP1R preamp. The RCA TVPRAMP1R preamp does have a history of quality control problems, but you can buy three of them for the price of one Channel Master 7778. One of the problems is with the separate/combined switch. If you have the switch in the separate position to use two antennas, one for VHF and one for UHF as in your case, sometimes the switch doesn't make good contact with the VHF antenna. The workaround is to use a UVSJ to combine the two antennas and connect the UVSJ to the combined input of the preamp.

Quote:
Buying another amp right now is out of the question as i am running out of money lol.
I'll think about a way for you to use what you have now.
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Last edited by rabbit73; 2-Sep-2015 at 7:28 PM.
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Old 2-Sep-2015, 3:20 PM   #54
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Haha yeah i know. Trust me you do not want to know what I paid for the amp i bought. Sometimes it sucks when you want to get things done right away.

edit: Would this work for all my connections to keep them weatherproof? http://www.homedepot.ca/product/liqu...des-bru/411161

Last edited by sl1982; 2-Sep-2015 at 4:28 PM.
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Old 2-Sep-2015, 5:53 PM   #55
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Quote:
you do not want to know what I paid for the amp i bought. Sometimes it sucks when you want to get things done right away.
Been there; done that.

Quote:
edit: Would this work for all my connections to keep them weatherproof?
http://www.homedepot.ca/product/liqu...des-bru/411161
It looks like it would work, but I don't have any experience with it.

http://static.dxengineering.com/pdf/...ax-TechTip.pdf

https://www.youtube.com/watch?v=6eHgyxo3e9A

http://www.qsl.net/n9zia/con_seal.html

http://forums.radioreference.com/ama...t-weather.html
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Old 2-Sep-2015, 7:47 PM   #56
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Try this with your preamp if you want to amplify VHF and UHF, using the combiner that came with the C5:

Code:
DB8E >
      \
       combiner > FM trap > preamp > coax > power inserter > tuner
      /
  C5 >
If the preamp is still overloading even with the FM trap, insert an attenuator between the FM trap and the input of the preamp:

Code:
DB8E >
      \
       combiner > FM trap > attenuator > preamp > coax > power inserter > tuner
      /
  C5 >
The idea is to find the value of attenuation that will provide enough gain for the weak signals without overloading the preamp with the strong signals. For this test the control on the inside power unit should be set for max gain, because you want the attenuation to be before the preamp.

You can use a combination of an adjustable attenuator and fixed attenuators for the test, then replace with a fixed attenuator/attenuators.

variable attenuator:
https://www.antennasdirect.com/store...ttenuator.html

fixed attenuators:
http://www.3starinc.com/drop_in-line_attenuator.html
http://home-automation.smarthome.com...=&w=attenuator
http://mjsales.net/collections/atten...ant=1083705673
Attenuation values 1, 3, 6, 8, 10, 12, 16, 20dB (FAM)
click on 1 dB for other values; the up and down arrows are faint
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Last edited by rabbit73; 2-Sep-2015 at 8:08 PM.
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Old 2-Sep-2015, 10:39 PM   #57
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Alright thanks. I will let you know how it goes when i get the FM traps. I got a few just in case one wouldnt cut it.
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Old 3-Sep-2015, 9:15 PM   #58
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So right after a thunderstorm i get 85% quality. Wtf
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Old 3-Sep-2015, 10:49 PM   #59
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Quote:
So right after a thunderstorm i get 85% quality. Wtf
On WJBK? That's a clue for power line noise, which is common on VHF.
Quote:
Originally Posted by MikeBear View Post
For instance, WJRT-12 averages only 18-19db, which isn't much above the minimum.

The other day (Friday 8/7) was pretty bad, but then the rain started later in the evening, and the problem settled down and got better as the night went along and the signal level came up 5-8 points.

I thought about some sort of electrical issue, but if it's that, I don't know what could be doing it, and why it would be intermittent.
I answered:
Quote:
Originally Posted by rabbit73 View Post
My guess is electrical interference from power line noise, which is worse on VHF than UHF.
Quote:
Originally Posted by No static at all View Post
Powerline interference is usually worst during dry weather (low humidity) from my experience. As humidity rises the interference tends to lessen, especially when raining.
It was power line noise.
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Last edited by rabbit73; 3-Sep-2015 at 10:53 PM.
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Old 3-Sep-2015, 10:59 PM   #60
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Well it hasnt been very dry here lately. Over 90% humidity every day. If anything the humidity has dropped since it rained. If that is the culprit how would I go about fixing it?

edit: something like this perhaps? http://www.amazon.ca/CyberPower-CP85.../dp/B00429N18S

Last edited by sl1982; 3-Sep-2015 at 11:09 PM.
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