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That was for the DB4e, before he got the VHF dipole.

The UP2A PCB balun in the DB4e is very good at UHF, but doesn't pass much VHF according to ADTech.



 

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Discussion Starter #43
Hi all,

Sorry for the delay -- yes, my antenna is still pointed towards Toronto (maybe 50 deg due to how my antenna is set up). I've snapped the VHF kit on top of the reflector as recommended, so as far as I know, it is pointed the same direction as the antenna.

I ordered the Winegard preamplifier and installed it today, and now I'm getting even fewer channels. Of course, this is what happens when your cable run is installed by amateurs (yours truly and his father-in-law), combining various coaxial cables of dubious quality and varying ages, and connecting them with a variety of connectors (both screw-on and crimp), without the proper tools.

Actually, it's a miracle I get any channels at all. So I did some light research which suggested the preamplifier probably isn't getting power at all, so that's a dead end. To fix that, I'll have to re-do the run, which can wait until summer.

In the meantime it seems the last option is for me to remove the two splitters I have along the run. Yes, I know I said one before. Turns out I forgot there are actually two. One goes to the basement, which we don't use, and another goes to the master, which doesn't even have a TV. Hoping I can reclaim enough signal to finally put this issue to bed.

rabbit73, majortom, you are proving some very insightful commentary and demonstrating exceeding amounts of patience. Thank you both :)
 

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Oh, and when I tune to 183MHz, it's 86dBm
That would be -86 dBm, wouldn't it? Your tuner would be toast with an input of 86 dBm.

Unit Conversion

75 ohm 86 dBm

= 398107170.5535 mW
= 134.8 dBmV
= 194.8 dBuV
= 5464250.8902422 mV(rms)

https://www.soontai.com/cal_exunit.html

A signal of -86 dBm is very weak, just at the "Digital Cliff."

75 ohm -86 dBm

= 2.5118864315096E-9 mW
= -37.2 dBmV
= 22.8 dBuV
= 0.013725577669563 mV(rms)

For the Old Cable Guys:

 

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Discussion Starter #47
Ah, yes -86dBm. Typo from me. What's odd is I removed a splitter today but the reading hasn't changed. Would've expected at least a small jump...
 

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What's odd is I removed a splitter today but the reading hasn't changed. Would've expected at least a small jump...
I also would have expected an increase in the signal strength.
.....my antenna is still pointed towards Toronto (maybe 50 deg due to how my antenna is set up). I've snapped the VHF kit on top of the reflector as recommended, so as far as I know, it is pointed the same direction as the antenna.

I ordered the Winegard preamplifier and installed it today, and now I'm getting even fewer channels. Of course, this is what happens when your cable run is installed by amateurs (yours truly and his father-in-law), combining various coaxial cables of dubious quality and varying ages, and connecting them with a variety of connectors (both screw-on and crimp), without the proper tools.

Actually, it's a miracle I get any channels at all. So I did some light research which suggested the preamplifier probably isn't getting power at all, Iso that's a dead end. To fix that, I'll have to re-do the run, which can wait until summer.
ahh yes, connection problems, number one on the list of things to check.
I also now suspect a connection problem.

Yesterday I set up another antenna for my local channels. The UHF channels were OK, but the VHF-High channels were much weaker than usual. I changed the cables, and the VHF channels were back to normal strength.

I remembered seeing this many years ago with analog cable channels. The high frequency channels were OK, but the low frequency channels were very snowy.

The cause of the problem was a bad F-81 adapter that connected two lengths of coax. If the center conductor of the coax isn't quite touching the connector, there will be a gap. There can also be a gap in the threaded connector for the shield if it isn't tight. This gap has a small capacitance that is sufficient to pass UHF frequencies, but isn't sufficient to pass VHF frequencies without attenuation. The fix was a new F-81 adapter. You can test the adapter with a small length of 18 gauge bare solid copper wire (which is the same gauge as the center conductor of RG6 coax) to see if the F-81 adapter (or any other female F-type connector) grasps the center conductor securely.









A gap in the coax would also account for a preamp not working. It is often necessary to check the voltage to the preamp at the preamp when troubleshooting. This is a little tricky because you need access to the center conductor to measure the voltage when the preamp is connected to the upper end of the coax. I use a T-adapter for that measurement.





You need to run a known good length of coax without any splices up to the antenna as a test to see if that solves the problem.

I still think it would be a good idea to spend about $20 on an RTL-SDR dongle and add free open-source spectrum analyzer software to see what VHF-High looks like at your location. The spectrum analyzer will show you what the channels look like, even if the tuner doesn't pick them up. This is what mine looks like; my channel 9 is marginal:



RTL-SDR Dongle with SMA to F Antenna Adapter Cable

https://www.rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/
 

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Discussion Starter #49 (Edited)
I am happy to report that upon removal of both splitters (and replacing them with F-type connectors), I am now able to lock onto CFTO.

Code:
[email protected]:~$ dvb-fe-tool -mg -a0   # one splitter removed
FREQUENCY = 183000000
MODULATION = VSB/8
DELIVERY_SYSTEM = ATSC
Carrier(0x03) Signal= -86.00dBm
Carrier(0x03) Signal= -86.00dBm
Carrier(0x03) Signal= -87.00dBm
^C
[email protected]:~$ dvb-fe-tool -mg -a0  # removal of the second splitter
FREQUENCY = 183000000
MODULATION = VSB/8
DELIVERY_SYSTEM = ATSC
Lock   (0x1f) Signal= -83.00dBm C/N= 18.30dB
Lock   (0x1f) Signal= -83.00dBm C/N= 18.17dB
Lock   (0x1f) Signal= -83.00dBm C/N= 18.23dB
^CLock   (0x1f) Signal= -83.00dBm C/N= 18.23dB
When replacing the second splitter, I did note that one of the cable ends had a rather short center conductor. Whether it was too short or not, I don't have the expertise to say. When I threaded it onto the F connector, I didn't have to insert the connector like I usually have to. I think I might've answered my own question there, eh?

I will likely revisit this issue again in the spring, when I replace the entire cable run with a single length of cable, but as it stands now the signal comes in... well enough I suppose. I find it rather interesting that with my result of -83dBm, I am able to receive a full HD signal, while majortom's result suggests the signal is of poor quality. Apples and bananas, I suppose, but it seems usable to me, but I will have to do some first-hand data sampling to make sure, if you get my drift ;)
 

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I am happy to report that upon removal of both splitters (and replacing them with F-type connectors), I am now able to lock onto CFTO.
Thank you for the report with the encouraging news. The reading of -83 dBm is good enough to be usable, but I would expect it to be higher at your location for reliable reception; you are at the edge of the cliff just before dropout.

The center conductor of the coax should extend about 1/8" beyond the connector, so that could have been a factor.
 

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Discussion Starter #51
... you are at the edge of the cliff just before dropout.
Can you predict the future, because that's exactly what happened. Not long after I sorted out CFTO, the signal degraded again.

I did finally end up buying a 100' RG-6 cable and routed it the other way 'round the house (we initially routed it the long way 'round because we wanted to split the signal down to a second TV set).

Code:
$ dvb-fe-tool -mg -a0
FREQUENCY = 183000000
MODULATION = VSB/8
DELIVERY_SYSTEM = ATSC
Lock   (0x1f) Signal= -72.00dBm C/N= 18.56dB
Lock   (0x1f) Signal= -72.00dBm C/N= 18.23dB
Lock   (0x1f) Signal= -72.00dBm C/N= 18.30dB
Lock   (0x1f) Signal= -72.00dBm C/N= 18.36dB
Lock   (0x1f) Signal= -72.00dBm C/N= 18.43dB
Lock   (0x1f) Signal= -72.00dBm C/N= 18.63dB
Lock   (0x1f) Signal= -71.00dBm C/N= 18.23dB
^CLock   (0x1f) Signal= -71.00dBm C/N= 18.36dB
Got CFTO again, but still no luck with Think/Create/WNED/PBS, but I think that's because my antenna is still pointed towards Toronto, and not towards Buffalo.

I'm afraid if I point the antenna south, I might lose CFTO again, but worth trying...
 

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Discussion Starter #52 (Edited by Moderator)
I spoke too soon! I found WNED had a "rescan day" on the 13th of March, and upon rescanning I now have 32 channels, including all the QVC /SHOP channels that I'd never watch anyway, hah!

I have one other query, and let me know if I should start a new thread... I use SD to get my channel listings, but they don't work for the American channels. Is there a specific ZIP code I should use to get those listings in addition to the Toronto channels I already get?

I am using the XMLTV JSON API, I'll see if I can find my config file to share...

Edit: Found it:

Code:
cache=/home/media/.xmltv/tv_grab_zz_sdjson.cache
channel-id-format=default
previously-shown-format=date
username=XXXXX
password=XXXXX
mode=lineup
lineup=CAN-OTA-L7L4J6
Username/Passwords redacted
 
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