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Old 12-Mar-2019, 2:56 AM   #1
johnnyboygomez
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Just a little bit more...

Hello forum. Last week I replaced my RCA ant751 with a modified 91xg on an outside tower. Good idea! The reception is obviously much better. But I'm greedy of course and want just a little bit more. I am in far eastern ontario about halfway between montreal and ottawa.

Here's my setup:
Antenna: modified 91xg. The center section was removed to make a shorter antenna (not by me!) I do not know if the directors were adjusted.
Winegard LNA-200 Boost XT Preamplifier
Cable: 75' RG-6
Philips Rotator

TVFool report: http://www.tvfool.com/?option=com_wr...9038800e341c92

I am only interested in uhf channels with the exception of wvny-dt (real channel 13) so I'll ignore those channels under 13 (actually I can get channel 12 no problem. )

I can get all the UHF channels all the way down to CFMT-DT (NM -23.3dB) with these exceptions:

WPTZ 14 Very rarely (transmitter 650kW)
CJNT 49 Very rarely (but not tropo incidents I don't think)
WVNY 13 Never (transmitter 10kW)
CITS 43 Don't need
CIVS 24 Don't need

Here's the interesting part. The three American channels (WPTZ and WVNY) are broadcast from Mount Mansfield, VT. Three other channels are also broadcast from there, I believe on the same tower:
WCAX 22 Always good (strength 54%, quality 100%, 423kW)
WETK 32 Always good (strength 54%, quality 100%, 90kW transmitter)
WFFF 43 Some pixels for a couple seconds then good (strength 33%, quality 3%, transmitter 47kW)
So it is interesting that I can get some of those but not the others. WVNY transmitter is 14 kW and on vhf 13 so that's understandable. But WPTZ is 650kW! Any ideas as to how I can push this channel over the edge? I think that it does not help that it is at the low end of the UHF range.

I've heard you can add 1/2" hardware cloth to the corner reflectors.

Thanks!

Last edited by johnnyboygomez; 12-Mar-2019 at 3:18 AM. Reason: typos
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Old 12-Mar-2019, 2:32 PM   #2
rabbit73
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Hello, johnnyboygomez; welcome to the forum.





Quote:
Originally Posted by johnnyboygomez View Post
I am only interested in uhf channels with the exception of wvny-dt (real channel 13) so I'll ignore those channels under 13 (actually I can get channel 12 no problem. )

I can get all the UHF channels all the way down to CFMT-DT (NM -23.3dB) with these exceptions:

WPTZ 14 Very rarely (transmitter 650kW)
CJNT 49 Very rarely (but not tropo incidents I don't think)
WVNY 13 Never (transmitter 10kW)
CITS 43 Don't need
CIVS 24 Don't need
If you look at your TVFool report, you will see a red "c" next to the WVNY callsign. This is because WVNY has co-channel interference from CJOH-DT also on 13, unless it has moved. WVNY will move to real CH 7 because of UHF Repack by the FCC. WVNY must be at least 15 dB stronger than CJOH-DT to be received.
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Last edited by rabbit73; 12-Mar-2019 at 3:28 PM.
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Old 12-Mar-2019, 2:36 PM   #3
Nascarken
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Hello there you should use the hole antenna the antenna Direct 91xg
is a good pick how hi is the antenna i suggest you look at the channel master
7777 amp I have used both the 91xg and the SOLiD single HDB91 it beem pattern of
60,making it easier to lock on too the broadcasting tower's and I have received
With both of these antennas at a 100Ft hi with the channel master amp 80miles away day or night in bad weather conditions single of 90% in mass and then I stack the antenna Direct 91xg side by side 3ft apart with the channel master amp receive was the same
SIGNAL100% and I have done this with the hi vhf as well with good results.With stagger stacking them the reason why you can put the antenna's closer together with good results
So then I went with a Winegrud 8200U with a channel master amp and with it's hi&low band vhf/uhf was the best ANTENNA for the money and I stacked them up out of this world.And with 2Johansson amp kits uhf45dbgx2 vhf35dbgx2 this set up is worth every penny spent it's been up for 3years and no problem with the ANTENNA's installe
and that vhv 1500miles away of RECEIVE,well good luck and be safe and look out for power lines when installing an outdoor tv antenna!!!!
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Old 12-Mar-2019, 3:24 PM   #4
Tower Guy
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It appears that WPTZ shares channel 14 with CIII. WPTZ will remain on channel 14 during the repack. In order to eliminate the interference would would need to create a null toward CIII. One way to do this would be to stack a pair of identical antennas such as the 43XG horizontally spaced precisely 26” apart. Feed them with identical lengths of coax to a two way splitter.

http://www.hdtvprimer.com/antennas/ganging.html
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Old 12-Mar-2019, 4:38 PM   #5
johnnyboygomez
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Thanks very much for the input.
The only two channels I really about adding are WPTZ and CJNT. So am I right to conclude that the reason I can get WCAX but not WPTZ is co-channel interference with CIII? Creating the null sounds interesting but beyond what I can tackle right now. Am I feeling any love for bolstering the reflectors with hardware cloth and maybe extending them a bit? It's not that hard a to do so I'll give it a try unless it for sure won't do anything.

And as for CJNT is it maybe just too damn weak?

Thanks again.
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Old 12-Mar-2019, 4:40 PM   #6
jrgagne99
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WPTZ and WVNY both have co-channel interference which is probably why reception is poor. That said, WCAX is actually on RF-22 presently (switching to RF-20 after the repack) and yet you claim to receive it well, even though it has co-channel with CHCH. But the directions to the transmitters come into play as well. I'd be surprised if it is co-channel interference since the offending channels are almost 180 degrees away. That's interesting.

More likely is that Mt Mansfield signals are 2-edge and over 100 miles away so hot-spots and cold-spots are probably abounding at your locale. I get the Mt Mansfield stations from 72 miles in the other direction and had to work very hard to find a hot spot that worked for all five of the American stations.
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Old 12-Mar-2019, 5:11 PM   #7
johnnyboygomez
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That is interesting. When you got all 5 channels did you get them all at once? I would have thought that WPTZ and WCAX would come first then WETK then WFFF then finally WVNY which has the weakest transmitter. But it's probably not that simple.

It's just an interesting experiment because they are all from the same tower which removes many variables
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Old 12-Mar-2019, 6:34 PM   #8
rabbit73
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Quote:
Originally Posted by johnnyboygomez View Post
The only two channels I really about adding are WPTZ and CJNT. So am I right to conclude that the reason I can get WCAX but not WPTZ is co-channel interference with CIII?
Yes. WCAX does have adjacent channel interference from CBFT and CBMT on 19 and 21, but they aren't quite strong enough to knock out WCAX. They would have to be more than 33 dB stronger than WCAX to interfere with WCAX.

CJMT-DT is also on channel 20 with WCAX, but it doesn't seem strong enough to cause co-channel interference with WCAX.

Quote:
And as for CJNT is it maybe just too damn weak?
I haven't figured out the Industry Canada repack list. They will have to vacate 49 and move to 17 maybe..
https://www.ic.gc.ca/eic/site/smt-gs...g/sf11281.html
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Last edited by rabbit73; 12-Mar-2019 at 7:14 PM.
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Old 12-Mar-2019, 6:44 PM   #9
Tower Guy
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To receive CJNT you will need an antenna with more gain or a higher mast. Another complication is that CJNT is scheduled to move to channel 17, the same channel as CITY. The direction difference between the two channels is 175 degrees. Horizontal stacking can’t null a station that close to 180 degrees ( off the back). A suggestion for CJNT is a pair of 91XG’s stagger stacked one above the other. Stagger stacking increases the front to back ratio by 10-20 dB and adds 2.5 dB forward gain. To stack, move one antenna 3” forward and the other 3” back. (you will need to redrill the booms). The feedline to the antenna moved forward would be 5” longer than the one moved back.
http://www.anarc.org/wtfda/stagger.pdf
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Old 12-Mar-2019, 6:48 PM   #10
Tower Guy
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Quote:
Originally Posted by rabbit73 View Post
Yes. WCAX does have adjacent channel interference from CBFT and CBMT on 19 and 21, but they aren't quite strong enough to knock out WCAX. They would have to be more than 33 dB stronger than WCAX to interfere with WCAX.

CJMT-DT is also on channel 20 with WCAX, but it doesn't seem strong enough to cause co-channel interference with WCAX.
WCAX is currently operating on channel 22. They are scheduled to move to 20 on August 2, 2019.
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Old 12-Mar-2019, 7:28 PM   #11
rabbit73
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Quote:
Originally Posted by jrgagne99 View Post
WPTZ and WVNY both have co-channel interference which is probably why reception is poor. That said, WCAX is actually on RF-22 presently (switching to RF-20 after the repack) and yet you claim to receive it well, even though it has co-channel with CHCH.
Quote:
Originally Posted by Tower Guy View Post
WCAX is currently operating on channel 22. They are scheduled to move to 20 on August 2, 2019.
Thank you; I missed that while focusing on co-channel and adjacent channel interference. My analysis above is not correct. I blew it that time.

https://www.rabbitears.info/market.p...&callsign=wcax

https://www.rabbitears.info/repackch...=&lss=&status=
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Last edited by rabbit73; 13-Mar-2019 at 12:57 AM.
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Old 13-Mar-2019, 6:31 PM   #12
jrgagne99
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Quote:
Originally Posted by johnnyboygomez View Post
That is interesting. When you got all 5 channels did you get them all at once? I would have thought that WPTZ and WCAX would come first then WETK then WFFF then finally WVNY which has the weakest transmitter. But it's probably not that simple.

It's just an interesting experiment because they are all from the same tower which removes many variables
In my case, it was really difficult to get all 5 at once. Even with good UHF-only antennas (HDB91X, HDB8X, dB8e, etc.) it was difficult to find a hot spot on my roof for even the two strongest ones (WCAX and WPTZ) simultaneously. Signals that are 2-edge UHF can be super-finicky like that in terms of hot spots. Even 6-inch movements of the antenna in X, Y, and Z can make a big difference. I ended up mounting the antenna 50' up in a pine tree where I consistently get all five >99% of the time.
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Old 13-Mar-2019, 6:51 PM   #13
johnnyboygomez
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Thanks for all the input. Think what I will do now is wait for a nice warm wind-free Saturday and climb up the tower, detach the antenna and do some free form experiments while a watcher down below gives me feedback. Changing height and tilt. I may also try holding foil covered foamcore near the back and side to block interference. Just to see what happens. I'll report back in a few weeks. Thanks again.

One final note. I never did get any feedback on the idea of adding 1/2" hardware cloth to the corner reflectors. Is that a myth?
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Old 13-Mar-2019, 7:28 PM   #14
ADTech
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Quote:
One final note. I never did get any feedback on the idea of adding 1/2" hardware cloth to the corner reflectors. Is that a myth?
I don't see any benefit to it, at least relative to the effort. The UHF wavelengths are such that the stock reflectors do an adequate job.


A couple of points regarding the suggestions that TG made:


The 43XG is discontinued and we liquidated remaining stock a few years ago. Unless you can find the ones that the liquidator purchased and is still trying to sell, they're NLA.


On the 91XG, no need to drill any holes to achieve a stagger-stack configuration. The large U-brace simply clamps onto the main boom and you have a little bit of fore and aft adjustment between directors. Also, the mast clamp is not fixed in any single location on the U-bace so it can be moved fore or aft as needed as long as you can get the mast (pole) through the directors on the lower antenna unit.



Cheers!
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