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Partial/No Lock to CFTO-DT?

9K views 51 replies 8 participants last post by  mailtodevnull 
#1 ·
Hi all,

tl;dr Starting a couple days ago, no longer able to get a lock onto CFTO-DT (9.1).

Have cut the cord a couple years back, but am new to consuming OTA broadcasts through MythTV. A couple days ago, my recordings for late night TV shows on CFTO-DT started failing. As far as I know there were no hardware or software changes made. Yesterday I adjusted the angle of the antenna to be closer to 45deg, so I'd get a stronger reflected signal to CHCJ-DT in Hamilton, but this made no difference in getting a lock onto CFTO-DT.

When I attempt to tune to 9.1, MythTV reports that I should've gotten a lock by now, but there was no lock. A rescan does not bring the channel back. What's odd is that I had no problem tuning to 9.1 prior to a couple days ago. Unfortunately I have no idea where to look to resolve this.

Thanks in advance for any help!
 
#2 ·
Comes in OK here south of Buffalo with a VHF-Hi Yagi.
So guessing the issue is on your end.
What are you using for an antenna?
 
#3 ·
AntennasDirect DB4e and a Hauppauge WinTV-QuadHD installed on a machine running MythTV.

Once my other recordings stop, I'll plug the cable back into my TV... something tells me 9.1 will work just fine using the TV tuner, but yes... it definitely seems like something's up on my end.
 
#4 ·
You are using a UHF only antenna.Make a folded dipole for VHF channel 8 and combine using a UVJ connector and CFTO will come in strong.Are you using the VHF dipole attachment from antennas direct ?
 
#5 ·
agree that might be all you need, simple dipole.

https://store.antennasdirect.com/VHF-Antenna-Kit.html
couple years ago back when cfto was still on RF9, I had stuck one of those up here,
just to demonstrate that the simple dipole could pull CFTO in most of the time from here. Left it up for about 3 months till I switched antennas around again.

If you install the v4l-utils package, included there is a tool name dvb-fe-tool, which will let you monitor some stats while one of your tuners are tuned to a signal.
Be interesting to see how close to a lock you are, C/N wise. below is the output from a WinTV HD Dual here, which I believe uses the same demod chip as your device, lgdt3306a. eg two demods, instead of your 4 demods. For the lgdt3306a, this is about the minumum required before the signal fails, so I think the 17.8 dB or so indicated is really about 15.5 dB on most of the other tuners that I have. And I have plenty others.

Code:
~]$ dvb-fe-tool -mg -a 2  
FREQUENCY = 183028000
MODULATION = VSB/8
DELIVERY_SYSTEM = ATSC
Timeout(0x3f) Signal= -63.00dBm C/N= 17.84dB
Timeout(0x3f) Signal= -63.00dBm C/N= 17.77dB
Timeout(0x3f) Signal= -63.00dBm C/N= 17.84dB
 
#6 ·
Thanks for the replies everyone, looks to be a pretty simple solution. The worst part is probably getting up on the ladder again to install it :)

Some follow ups...

1. I was reading on the other CFTO-DT thread from years ago that CFTO is actually broadcasting on a UHF frequency and then remapped (via PSIP?) to 9.1, so it should work regardless, no?

2. Any thoughts on why it used to work and suddenly does not?
 
#7 ·
Code:
~$ dvb-fe-tool -mg -a 2
FREQUENCY = 4294967295
MODULATION = VSB/8
DELIVERY_SYSTEM = ATSC
       (0x00) Signal= -111.00dBm C/N= 28.79dB
       (0x00) Signal= -111.00dBm C/N= 28.79dB
       (0x00) Signal= -111.00dBm C/N= 28.79dB
       (0x00) Signal= -111.00dBm C/N= 28.79dB
It was actually the dvb-tools package, by the way. Signal looks good, even though the coax cable is wrapping around the outside of my house.
 
#8 ·
CFTO in Toronto does not broadcast on UHF, it broadcasts on 183 MHz, which is in the VHF-Hi Band. It may have temporarily used a UHF channel more than 8 years ago, prior to the analog shutdown in 2011 though however not any more.


I agree the C/N looks fine, but the frequency and signal Strength reported by your device looks strange to me, -111 dBm is well below the noise floor. I am not certain the state of the kernel module for your device, as I use a custom kernel that you wouldn't find in the distributions. What distro and kernel are you using?

On another note, some time ago with the help of user 'knight' I posted a little hack to make mythtv report the SNR in dB. It seems the last time I checked, mythtv 0.30 still has the same old bug I saw 9 or 10 years ago, where it reports inaccurate SNR in dB in the OSD / User interface due to a bogus formula they are using in the code...
If interested you would need to apply patch and compile it from source.
Would have to modify this section of code in mythtv/libs/libmythtv/tv_play.cpp and compile.

https://www.digitalhome.ca/forum/31...3-evga-indtube-atsc-tuner-linux-solved-2.html

Again, below is mine this AM.
Code:
 ~]$ dvb-fe-tool -mg -a 2
FREQUENCY = [B]183028000[/B]
MODULATION = VSB/8
DELIVERY_SYSTEM = ATSC
Lock   (0x1f) Signal= [B]-64.00dBm[/B] C/N= 20.00dB
Lock   (0x1f) Signal= -64.00dBm C/N= 19.85dB
Lock   (0x1f) Signal= -64.00dBm C/N= 20.00dB
Lock   (0x1f) Signal= -64.00dBm C/N= 20.00dB
 
#9 ·
You mention that I should be running the dvb-fe-tool while tuning or watching a channel, but I am not sure how to do that, since the results are identical no matter whether the tuner(s) are idle or active.

Nevertheless...

Code:
Not entirely sure why mediatree and hauppauge are in my uname string... hum...
 
#11 ·
If you are using the OTA signal to populate the mythtv epg, then mythv will tune your tuners for you to periodically parse the EPG from the OTA signal of each channel.
I don't know if that is how you are configured, but that would be one explanation.
Simple, Just Play a channel in LiveTV.
Then use the dvb-fe-tool to monitor the signal stats for the adapter that you are watching in Live TV.
 
#13 ·
based on the strange frequency indicated in his dvb-fe-tool log, and lack of the frontend status bits being set... s/be (ox1f) if locked, while he has (0x00), I think his device isn't really tuning when he thinks it is.
Another path would be to install another application like kaffeine, and do some testing in there to ensure his device is locking all the frequencies it should be, independent of mythtv. If that looks solid, once that's done he can then chase down his mythtv problem.
 
#14 ·
majortom -- how would dvb-fe-tool know which tuner to look at, since the card is a quad tuner? I was only tuning to one channel at a time when testing earlier.

Last night was able to get CFTO-DT with heavy distortion (basically unwatchable), but it does mean the antenna can get it even if it's not meant to. However due to how it's mounted, it just isn't pointed directly to it (or 180 degrees from it), and that's probably the issue.

Nevertheless, the VHF retrofit kit is on its way... a whole bunch of the amazon comments specifically talk about this issue (and one even mentions CFTO-DT, heh)
 
#15 ·
Judging by the USB based WinTV DUAL HD that I have, the two demods show up as separate DVB Adapters. In the snippet below they are /dev/dvb/adapter2, and /dev/dvb/adapter3. adapter0 and adapter1 on my system below are satellite tuners.
I am guessing your system will have 4 adapters, one for each demod.


Code:
 ~]$ ls /dev/dvb
adapter0  adapter1  [B]adapter2  adapter3[/B]
So, if I wanted to monitor the stats from adapter 2 I would specify that on the command line. eg:
Meanwhile Adapter 3 shows as not tuned yet.
Code:
~]$ dvb-fe-tool -mg -a2
FREQUENCY = 183028000
MODULATION = VSB/8
DELIVERY_SYSTEM = ATSC
Lock   (0x1f) Signal= -58.00dBm C/N= 19.01dB
Lock   (0x1f) Signal= -59.00dBm C/N= 18.95dB
^C


 ~]$ dvb-fe-tool -mg -a3
FREQUENCY = 0
MODULATION = QPSK
DELIVERY_SYSTEM = ATSC
Timeout(0x20) Signal= -21.00dBm
Timeout(0x20) Signal= -21.00dBm
 
#16 ·
The direction an antenna is pointed is often irrelevant to the ability to receive out-of-band stations.
So the ability to receive physical channel 8 from the back or the side of an antenna designed for UHF has very little to do with the antenna's ability to receive UHF stations off-axis.
Sometimes it works, and sometimes it doesn't.
Thee is also the frequency dependent impact of the balun, as well.
 
#17 ·
Thanks for the additional insight, I have the VHF retrofit kit in hand, but of course, now that I've gone and ordered it, 9.1 is coming in without issue again.

However I'll probably go ahead and install it regardless. I did read a review saying their UHF signals were impacted negatively by the VHF pass-through kit, but that might've been a one-off.
 
#18 ·
I just recently redid my whole software installation and after channel scanning it did not pick up CFTO.....

I am using tvheadend which is different software though.. but the way it works is you choose your region and it scans for frequencies from that region.
After lots of head scratching it was discovered for whatever reason the frequency for CFTO is not listed in Toronto Ontario "channel bouquet" for tvheadend.
I redid a scan this time for "America - Central" and it picked it up no problem.
Also missing from the Toronto bouquet was WKBW (ABC) which was super frustrating as CFTO and WKBW carries the same shows the wife likes to watch.

Does MythTV do a scan based on location? If so this might be the issue. I know CFTO changed to channel 8 in April of this year but still shows as virtual channel 9-1......
 
#19 ·
Mythtv's Channel scanner doesn't use initial tuning data files like tvheadend does.

You set a range of channels to scan, say from Ch 2 thru 69 by default, or u can change it to CH 2 thru 51 for instance. It is possible for a mythtv user to have stale previously scanned channels in their database though. Upon which you'd just go in to mythtv-setup and delete the old, then rescan, etc. This is the reason I had previously mentioned for the OP to try another simple application like Kaffeine. To rule out mythtv
configuration issues. Not sure if he ever did or not though.
 
#20 ·
Does MythTV do a scan based on location? If so this might be the issue. I know CFTO changed to channel 8 in April of this year but still shows as virtual channel 9-1......

Its the norm that when TV stations move to a new rf channel that they do not change the virtual channel for the convenience of the viewers.
 
#21 ·
Mythtv channel scanner doesn't know or care where you are located.
If I remember right the exact UI is a little different if using an hdhomerun (an IP based tuner interface) vs say a more traditional USB or PCI based ATSC tuner.
Overall jist being the same though.

FULL scan, Scan based on a previous scan (import previous), what they call existing transports, couple other options..

I can take some screenshots and u'll get the jist, But I don't have a USB based ATSC tuner hooked up at the moment to compare and verify the differences still exist.

In his first post on Oct 5th, he said his issue had started "a couple days ago..."
 
#22 ·
Hello, back again. CFTO-DT has been hit and miss. Some days it comes in strong and my recordings work well. Other days I cannot achieve a lock at all.

I did end up installing the VHF retrofit kit, now that it's semi-warm outside again, but this has not resolved the issue. I still am unable to lock on to 9.1 CFTO-DT.

The S/N is 2.3dB, which is similar to neighbouring channel CBC 5.1, 2.5dB

----

majortom -- I did also try hooking the antenna up to my TV tuner, and it also cannot lock onto CFTO-DT.
 
#23 ·
When CFTO 9.1 moved to RF channel 8, I also encountered drop outs. I'm using a 4221Hd pointed at Grand Island NY. CFTO is received on the back side of the antenna. I made a folded dipole for RF channel 8. Fed both antennas into a UVSJ and all is well. LOS I'm 13 miles from the CN tower. You would think that being so close to the transmitter that CFTO would not be an issue.
 
#24 ·
The Snr indication in Mythtv is broke... I don't know why they don't fix that... but has been broke that way for over 10 years,
as long as I can remember...
They are taking the log base 10 of a number that is already in decibels...
You would have to download the source code, edit one file, 'tv_play.cpp' compile it and install in order to fix that....
 
#25 ·
majortom -- sorry, I keep forgetting the MythTV SNR is broke. I'll give dvb-fe-tool another try next time I am able to receive 9.1

Today I deleted all the channels and re-scanned, and CFTO didn't make the cut. Duh, should've seen that one coming. So now I am actually unable to do any further testing until the channel shows up again. Tried manually adding the channel but MythTV won't even try tuning to it for whatever reason.

Back to the original issue, though... some contextual clues that may be relevant:

* I am located ~50km as the crow flies from the CN tower
* The cable run from antenna to tuner is likely over 50 feet long, and contains a single splitter.
* Here's a report from rabbitears.info: https://www.rabbitears.info/searchmap.php?request=result&study_id=31321 -- CFTO is listed as "fair", maybe due to lower power VHF signal?

Choose your own adventure:

1. An email to CTV Engineering returned an auto-reply suggesting that FM interference could cause issues, and suggested an FM trap. Does the VHF Retrofit kit come with an FM trap already?
2. Likewise, the same email suggested a preamplifier may be recommended. (Is the db4e already amplified?)
3. Get up on the ladder and disconnect the splitter.

Re: option 3 -- is there still signal loss if I disconnect the coax going to the 2nd TV and keep the splitter in place, or do I have to remove it altogether and join the two cables...
 
#26 ·
CTV engineering is providing you sage advice...

But being that close to TO, what I would do in order...
1.) install the Antennas Direct VHF adapter kit that you bought on to the DB4e. I am betting that will work.
2.) buy a preamp, such as the RCA tvpreamp1z
https://www.google.com/search?q=RCA...WQct8KHVwRCnwQ_AUoAXoECA0QAw&biw=1366&bih=591
The preamp will make up for the losses in your 50' coax run + splitter, which I'd expect to be around 3 dB coax + 3.5 dB 2way splitter, and then some. Allowing for more TVs / tuners to be connected to the system without any further degradation. Here i have an 8 way splitter in my basement, and since my preamp is up top near the antenna, every TV in the house receives ~ the same SNR.
It comes with a switchable FM trap (you can switch it in or out). I'd do this 2nd cause it will likely improve your Buffalo reception as well.
You might have to re-orient your antenna for best reception when the preamp is introduced.
3.) If any of that is still unreliable, get a VHF Hi yagi and aim it for the CN Tower.
https://www.newark.com/stellar-labs...559827|&CMP=KNC-GUSA-GEN-SHOPPING-AllProducts

You might even be able to aim the yagi to Springville, NY and get WBBZ from Springville on RF 7, and CFTO on RF 9 from the rear.
That is what I do here, but in reverse.. For me since I'm south of Buffalo I aim the Yagi to the CN tower for CFTO (70 mi from me), and there is still
enough signal on RF 7 for WBBZ from Springville on the rear.
 
#27 · (Edited)
Prompt reply :) The VHF kit was installed and did not resolve the issue unfortunately. A rescan picked up no new channels, but that was expected since CFTO-DT is the only station broadcasting within VHF range. Still am unable to lock, but would definitely be interested in seeing what the SNR is, should I be able to pick up the station again.

Edit: I figured out how to tune to things using VLC.

Here is CBC:
Code:
$ dvb-fe-tool -mg -a0
FREQUENCY = 509000000
MODULATION = VSB/8
DELIVERY_SYSTEM = ATSC
Lock   (0x1f) Signal= -60.00dBm C/N= 30.41dB
Lock   (0x1f) Signal= -60.00dBm C/N= 30.41dB
Lock   (0x1f) Signal= -60.00dBm C/N= 31.14dB
Lock   (0x1f) Signal= -60.00dBm C/N= 31.14dB
Here is CFTO-DT:
Code:
$ dvb-fe-tool -mg -a0
FREQUENCY = 186000000
MODULATION = VSB/8
DELIVERY_SYSTEM = ATSC
       (0x00) Signal= -95.00dBm
       (0x00) Signal= -95.00dBm
       (0x00) Signal= -96.00dBm
 
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