: Stacking, Ganging, Combining TV Antennas
2011-11-19, 01:33 PM
I once tried with 2 UHF antennas looking in different directions and even the residual signal of one antenna can cancel the good signal of the other, below the minimum level required by the TV. Your lucky since you have 1 UHF and 1 VHF.
As ProjectSHO89 implied, a VHF/UHF splitter can solve the problem.
Trying to phase both antenna (by adjusting the length of cables) will not go well, because different phasing will happen for various directions of the rotor.
If your signals are week, beware of insertion loss !
2011-11-19, 04:48 PM
I want to keep my VHF up high and be able to use my rotator.. so I have my vhf probably 10+ feet above my UHF 8 bay.
But that way youve got an unstable balance. Thats pretty hard on the rotor gears and makes it easier to topple the antenna over.
I would have the heavy vhf antenna closest to the rotor. Which uhf 8 bay ? By experimenting with the separation distances (and it wont be near 10 ft) the bottom of the uhf antenna could serve as either a director or reflector to the vhf channel youre most interested in, helping not hurting.
A UVSJ could help, but the channel master titan 7777 amp with the separate VHF and UHF inputs is a much better solution.
2011-11-20, 09:54 AM
the 8 bay I got is just a cheap $59 one off ebay, I ordered it before doing too much research and actually thought it was a CM 4228. none the less it seems to do a good job. it's picking up the only other UHF channel that I was unable to reach before.
also it's mounted on the side of the tower, not the pole or rotator so it's not creating any extra stress on the equipment.
I was going to post a pic but the servers must still be having issues.. uploads but won't save.
2011-11-20, 12:14 PM
i don't believe you can add attachments directly to a post,
think it will let ya go thru the motions, but it won't work.
but you can upload pictures to ur own personal photo album,
then ya can put an http link from the picture album in to the post.
you can read this post on how to proceed.
2011-11-20, 02:25 PM
I actually figured out the picture procedure already.. I have an album and have posted pics already but there actually is something up with the servers. the day before yesterday I got a message they moved to new servers and I could not see the forums and now I can't upload any new pics...
here is the message...
Failed to write file. Check disc quotas and permissions for the path: /home/digital/public_html/forum/pictures/4/d65ca7aa44261a5b46c6ce3b853421e6_4794.jpg
2011-11-20, 02:42 PM
use a UVSJ.
Very low loss on precious Db's.
That is what I use.
2011-11-20, 03:28 PM
PanaMark, got one on order from Solid Signal as we speak :) thx
and here is the tower.. We'll try photobucket since I can access my album here.
I'm sure those power lines help my signal alot lol.. I guess beggars can't be choosers ;)
2011-11-20, 06:55 PM
I'm sure those power lines help my signal alot lol.. I guess beggars can't be choosers ;)
If the powerlines do in fact affect the signal, the detrimental affects will diminish during rainy/humid conditions.
2011-11-21, 10:03 AM
wow I ordered a UVSJ for $1.47 plus shipping from solid signal... came to about $5...
Then I got an email a few minutes ago stating I have to pay $35 more to complete my order because I'm in Canada... sounds completely reasonable.. yeah right. hope they refund my $5.
2011-11-25, 07:20 PM
UVSJ is definitely recommended. Or a pre-amp with separate VHF and UHF inputs.
Note that placing UHF antenna at the very top of a mast (above VHF) is not a requirement. Obviously there are some situations--such as yours--where doing the opposite is more desirable.
Just as an FYI: Antennas Direct Canadian distributors sell a UVSJ with an excellent weather enclosure. Cost is obviously higher than $5 (~$25), but well worth it for the added weather protection. Though you could also make a decent weather enclosure yourself with parts from a hardware store.
2011-11-25, 07:34 PM
Hi everyone and happy Black Friday to whom it applies!!!
With the relatively mild weather we're enjoying in Montreal, I'm planning a dual CM4228 setup for the weekend amidst Christmas decorations!!! And I am looking for pointers. For this project, I have acquired a second brand new 4228a and will mount both antennas on J-poles aimed in the general direction of Mount Mansfield (to me that means VT-NH-MA).
For the time being I'm planning to leave both 4228 unmodified and so far, I have sort of tried them using your basic 0-2400 MHz splitter with identical RG6 cable lengths and am getting way more loss than gain. Is this obvious or do splitters act as joiners as well when things are properly alligned???
Beyond that, I have browsed the pages of SolidSignal and other online retailers for a dedicated joiner. I have the following in mind:
- the Winegard CC-7870 2-Way Joiner
- the Winegard SD 3700 300 Ohm Coupler
In a nutshell, what's the difference between a joiner and a coupler (impedance?). I understand the antenna balums already bring it down to 75 ohms... So that might mean the coupler is out!
The phone just rang and I don't want to loose my signing so I'll leave my question to this for now.
2011-11-25, 07:58 PM
OK, as a follow-up to my initial post, I did my homework and searched the Oracle. I now understand that a coupler will connect directly to 300 ohms (I suppose flat twin-lead cables) straight out from the antenna nuts, thus discarting the ballum. I kind of like that ideal, reminds me of the good old days| Furthermore, you may have understood by now that my purpose is not to receive stations from multiple paths but rather aim both in the same direction.
This being said, am I figuring things right? Is the theoretical (or practical gain attained by some of you) worth the endeavor?
If the answer were no, I'd dedicate one 4228 to an eastward horizon and use an A|B switch to toggle. But I hope there's something to gain (no pun) from this!!!
Thanks, Denis from Montreal.
2011-11-25, 08:29 PM
This being said, am I figuring things right?
Yep, use the the Winegard SD 3700 300 Ohm Coupler for the least loss in gain. Youll need some 300 ohm twin lead of course. Youll save the losses from the baluns and the internal coupler is more efficient than using a splitter in reverse. Its also weatherproofed.
When stacking the CM4228a, spacing is an issue and can produce some different effects. I dont think your J pole is long enough to do any good.
Heres some tips from an expert who has stacked the CM4228a
2011-11-25, 09:20 PM
Thank you very much for your input 300ohms and especially for the link which means the world at this point. I remember reading parts of this page back in 2008 but haven't been able to locate it since.
For your information, I ordered two J-pole for horizontal ganging, The way I see it, the J-pole will allow me to stretch the contraption well outside the reach of the balcony overhead (the 28th floor balcony that is). I cannot affoard vertical stacking due to space limitations so I'll have to resort to spacing the antennas just right along a balcony rail which I certainly can do. It may also be that sticking a standard 5-foot mast pipe inside the J-pole snug at the very base of the rail might provide enough room for vertical stacking which certainly sounds like the most efficient pattern where both 4228s are sure to be aimed right. Doing so I'll have to think about some restrainers to make sure the J-pole pivot (or the rail for that matter) doesn't give in to weight!!!
What stands out from a quick diagonal reading of your article is that I can realistically expect an overall 2.5 dB gain from a decent arrangement and with the use of a coupler (instead of a 75 ohms joiner) I can steer away from the potential mismatch from using two balums not exactly the same (one is the big fat original while the other is a 0.99cents generic thingie).
And I suppose 300-ohm cables are still easy enough to come across??? I mean, the last time I played with those was way back in the 70s when freezing my fingers on those big beams we had available back then!!!
Mind you, from youth I've always been an antenna freak, always trying to grab that weak signal, whatever it was. Nowdays, I live in a high rise condo building and cannot affoard the yagis that country living allowed so I find 4228s just fine, especially since pretty much everything is confined to the VHF-HI_UHF portion of the band which this thing handles just fine (especially ganged). Seasonal tropo indicates that I have a relative amount of PSIP decodes that are just waiting for a lock and hopefully, the 2.5-3 dB gain will win me some of them... We'll see about that.
So again, thank you very much for the reply. Cheers from Denis in Montreal. Got some work to do. I'll post my results when done.
2011-11-25, 10:10 PM
And I suppose 300-ohm cables are still easy enough to come across???
Well, if you cant, and since youll only need relatively short lengths, brew your own from stripped house wiring and vinyl siding spacers. Open wire twin lead is the lowest loss cable in dry conditions.
Youll want to have some slow twists in it, about 3 to a ft for uhf, to keep the cable from being a radiator itself.
2011-11-25, 10:47 PM
Looks like the local electronics shop (Mastervox) still sells flat 300 ohm cable in spools at 15 cents a foot! So I'm good to go. An outdoor antenna setup without balums is a very refreshing prospect indeed. Kind of like cutting the middleman!
2011-11-25, 11:03 PM
An outdoor antenna setup without balums is a very refreshing prospect indeed.
The Winegard SD 3700 300 Ohm Coupler has one internal balun for the 75 ohm output.
The balun section is on the right.
2011-11-26, 01:42 AM
ChannelMaster, this summer I installed the SD3700 coupler on my stacked CM4228s. I previously used the balun and reversed splitter method and found a very slight improvement with the coupler. I also found that flipping one of the 300 ohm leads at the coupler makes a real difference. ie, look at a signal and then flip one the leads and see what happens.
2011-11-26, 08:58 AM
@300ohms, thanks for the exploded view and I do understand there has to be a balum at some point down the feedline. This one is most likely better suited than the two el-cheapo mismatches at the root of the antennas.
@Jaygeetee, I'll be sure to pay attention to that little detail when I get to that point. And allow me to ask you these:
Was the effort generally worth your while?
Did you stack (vertically)?
Are both pointing in the same direction?
Now because channels 7-13 are all occupied here, can you see a slight improvement in the HI-VHF too?
Does the suggested 2.5-3 dB gain equal to your "slight" improvement???
2011-11-26, 10:50 AM
Some info about Winegard SD-3700 loss was posted in the thread:
Splitters, Attenuators, Filters, Diplexers, Other Signal Gear
Measure Winegard SD-3700 Loss vs. Frequency (http://www.digitalhome.ca/forum/showpost.php?p=1355409&postcount=1382)