Splitters, Attenuators, Filters, Diplexers, Other Signal Gear - Page 114 - Canadian TV, Computing and Home Theatre Forums

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post #1696 of 1748 (permalink) Old 2016-05-09, 02:31 PM
 
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That device is a UVSJ with 300 ohm UHF/VHF inputs and a 75 ohm output (or vice versa).

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post #1697 of 1748 (permalink) Old 2016-05-09, 02:35 PM
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Maury, check out the discussion beginning in Post #1382 in this present thread - terrific info on combining 300Ω inputs. Let us know what you come up with.
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post #1698 of 1748 (permalink) Old 2016-05-09, 02:47 PM
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I don't recall suggesting using unshielded 300-ohm TWINLEAD for ANYTHING....it has high LOSS and SWR when wet/moist or covered in snow/ice:
Ganging 2 M4s: Avoiding the Balun?

For some Stacked Antenna purposes, I HAVE suggested using 300-ohm, 450 or 600-ohm OPEN LADDER LINE which is NOT affected since it's all BARE WIRE with no Plastic Insulation except for some infrequent spacers....300-ohm type is VERY difficult to locate, but you COULD build your own:
Home-Brew Parallel Transmission Lines
http://www.zs6hvb.za.net/index.php/o...hy-ladder-line

old sparks suggested using Garner-Bender PS-75 Romex Staples with AWG14 Copper Wire....but my calculations indicate that 0.75-in spacing results in 347-ohm Impedance (SWR = 1.15) which is probably close enough for most purposes, but AWG12 or AWG10 would be closer to 300-ohms...although you MIGHT have to drill out each and every Staple....and fortunately, the stiffer wire spacers wouldn't need to be as close together:
Ganging 2 M4s: Avoiding the Balun?

HOWEVER, the BEST approach is to use individual Baluns with KNOWN LOW LOSS (e.g. OUTDOOR Philips or C-M....or Coax Half-wave Balun) with a VHF/UHF Combiner with KNOWN LOW LOSS (e.g. A-D, R-S and fol. that do NOT have DC PASS on UHF Port: Pico-Macom, Hollands)...all of which are unaffected by rain, snow or ice.

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands

Last edited by holl_ands; 2016-05-09 at 03:06 PM.
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post #1699 of 1748 (permalink) Old 2016-05-09, 05:02 PM
 
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Quote:
Originally Posted by ADTech View Post
That device is a UVSJ with 300 ohm UHF/VHF inputs and a 75 ohm output (or vice versa).
So, then, not useful in this case I guess.
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post #1700 of 1748 (permalink) Old 2016-05-09, 05:17 PM
 
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Thanks stamp. Yikes, I'll stick with the 75-ohm model and eat the dBs.

I saw some home-brew 300 ladder on eBay, but it looked terrible, like he had his kids punch it out.
Quote:
Originally Posted by holl_ands
HOWEVER, the BEST approach is to use individual Baluns with KNOWN LOW LOSS
Do you mean using 300-to-75 baluns and then a 75 combiner? If so, would that be likely to be better than the build in 300-to-75 network on the antenna?
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post #1701 of 1748 (permalink) Old 2016-05-10, 03:04 PM
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There are no "dBs to eat". Using individual 300-to-75 ohm Baluns [Insertion Loss 0.5 to 1.0 dB MAX] on each of two Antennas feeding a 75-to-75-ohm VHF/UHF Combiner (aka UVSJ) [Insertion Loss 0.5 to 1.0 dB MAX] results in a Total Insertion Loss of about 1.0 to 2.0 dB MAX. I dare you to compare that to whatever alternative you want (e.g. VANCO)....if you can FIND any Specs (and actual measurements) to compare.....either way there WILL be Loss in whatever 300-to-75 ohm Balun is used in the device PLUS whatever Filters are employed in an alternative Diplexer. you should go with what is KNOWN to be a superior approach....and avoid 300-ohm Twinlead like the plague it is....

????? "using 300-to-75 baluns" would be the SAME as "the built-in 300-to-75 network on the antenna"....IF a particular Antenna came with a PCB Balun Box.

And I would be remiss if I didn't mention that the BEST way to Stack two identical Antennas is to use either the HVH (Horizontal Vertical Harnesss) or the HHH (Holl_ands Horizontal Harness) which I ran Optimizations for several different types of Antennas. It OPTIMIZES the Impedance and Dimensions of the Interconnect, while eliminating the Loss in the RF Combiner. I can do more if requested and have a model of the target Antenna:
http://imageevent.com/holl_ands/stacked

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands

Last edited by holl_ands; 2016-05-10 at 03:22 PM.
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post #1702 of 1748 (permalink) Old 2016-05-24, 02:52 PM
 
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Channel Master LTE Filter

Greetinsg all!

CM came out with an LTE filter (700 Mhz to 2000 Mhz). I was wondering how would I know if I have LTE high noise pollution causing issues on OTA reception? Maybe the sun during the day?


I have one channel (UHF 43, 647 mhz) causing issues. During the day, the channel will totally disappear and during the night, it comes back. I'm in the Montreal area, 88 miles from the tower. Power transmitter is 47Kw (not very strong). I have 2 LTE/GSM/UMTS towers (Rogers/Bell) 311 yards from my house. This is my tvfool report:

TV Fool

Can LTE noise affect VHF-Hi channels as well? I would assume not because of the frequency gap (vhf 13 216 mhz).
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post #1703 of 1748 (permalink) Old 2016-05-25, 05:46 PM
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See fol. post, incl. two other posts before it and after it re Available LTE Filters:
The Official AVS Antenna and Related Hardware Topic! - Page 547 - AVS Forum | Home Theater Discussions And Reviews
NOTE that an LTE Tower transmitting at HIGH Power levels would need to be within about 2-miles to cause interference to HIGHER UHF Channels....and many Towers are at LOWER levels, which increases the range of possible interference....and 2G, 3G, GSM Towers et. al are on MUCH Higher Freqs and hence are NOT a problem...

BTW: We have NO IDEA how effective CM LTE Filter is compared to OTHER LTE Filters, whose mfrs have actually published MEANINGFUL specs:
The Official AVS Antenna and Related Hardware Topic! - Page 547 - AVS Forum | Home Theater Discussions And Reviews

Antenna Simulations, Overload Calculations, etc: http://imageevent.com/holl_ands
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post #1704 of 1748 (permalink) Old 2016-05-30, 08:41 AM
 
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Thanks for the reply!

I contacted CM (forgot to ask for insertion loss) to see if this filter can help. The reply was pretty vague and they mentioned if LTE towers are nearby, the filter should help. I did some research and, from what I read, I'm most likely loosing my UHF 43 because of troposphere ducting phenomenon. Reading the specs for this filter on CM's web site; they don't give much information on how to determine if someones issues are caused by LTE 700 Mhz interference. It's almost like a gimmick, you end up buying it but might night resolve your problems. Not to say that the filter wouldn't work for certain scenarios but simply stating that if you have OTA signal issues + LTE towers you automatically need this filter. I can imagine the insertion loose is a function of the frequency you want to tune in? In some cases, that insertion loose might "kill" some weaker channels. I will ask CM for insertion loose and post it. Happy Memorial day!
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post #1705 of 1748 (permalink) Old 2016-06-02, 11:16 AM
 
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I got the reply from the folks at CM about the LTE Filter. The typical loss is between 1- 1.5 dB
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post #1706 of 1748 (permalink) Old 2016-06-04, 11:30 AM
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CM3412 Distrubution Amp with power supply for CM7777

Hello All,

I'm not sure where the power inserter should be placed for my pole mounted CM7777. Right now it's behind my single TV and it works just fine. But I'm adding a distribution amp (CM-3412) where the antenna feed comes into the house and will then splitting it off for a second TV. Will the CM3412 send the power it receives from the CM7777 power supply behind my TV back up to the CM7777? Or should I move the CM7777 power supply in between the CM7777 and CM3412?

I tried: Antenna - - > CM7777 - - > CM3412 (not using AC plug) - - - > CM7777 power supply - - > TV

But I went from 39 channels to 5. And the 5 that I got were local channels. I suspected I might be getting to much gain with the CM3412, but then why would I only get the closest and strongest channels? Hence my question about the power supply... maybe I've got it in the incorrect location in the chain?

Thoughts?
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post #1707 of 1748 (permalink) Old 2016-06-04, 12:33 PM
 
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RE: CM7777 and CM3412

Most often, you will not not need a distribution amp like the CM3412 when you have such a strong pre-amp. The 30db gain of the CM7777 will most likely overcome the losses of your home wiring.
I suggest you try it alone without the distribution amp.

To answer your question:

"Will the CM3412 send the power it receives from the CM7777 power supply behind my TV back up to the CM7777? Or should I move the CM7777 power supply in between the CM7777 and CM3412?"


The correct scheme would be: CM7777 pre-amp as close to the antenna as possible>>power inserter>> splitter (it might work better than a distribution amp)/distribution amp.

Your current arrangement is not allowing the pre-amp to be powered and as a result your unpowered pre-amp is acting as a signal attenuator allowing only local stations enough power to your tuner(s)
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post #1708 of 1748 (permalink) Old 2016-06-04, 01:21 PM
 
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Chinadog has correctly diagnosed the problem. You cannot put the distribution amp between the CM7777 and it's power inserter.
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post #1709 of 1748 (permalink) Old 2016-06-04, 03:51 PM
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Thanks guys. I moved the power inserter and things are working again.

I'm relatively happy with the CM3412 but I did lose Fox29. A few other dropped in SNR but are still within acceptable levels.

TV Fool

Fox was the one I was worried about. Its usually 20ish dB on a single TV. I feared adding a regular splitter would leave me with 20dB-3.5dB = 16.5dB or a very margin signal. Was hoping the CM3412 would overcome that but I guess not.
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post #1710 of 1748 (permalink) Old 2016-06-04, 07:26 PM
 
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Re: WUTV FOX 29

Your TV fool indicates that CHCH 11 broadcasting on RF 15 is your biggest obstacle to reliable reception of WUTV 29 on RF 14. A strong local adjacent signal can cause problems for a weaker signal on an adjacent frequency. The powerful CM7777 amplifying the already strong CHCH 11 can cause interference and overload at your TV tuner(s). The lower -powered CM 3412 used alone could work better for Fox 29 than the CM 7777. Hopefully your CM 7777 improves reception on other channels.

Regarding your concern about 3.5 DB of signal loss at a splitter, the gain of the CM 7777 compensates for up to 30 DB of losses due to connectors, long runs of cable, splitters as well as losses at your TV tuner inputs. You would have to try really hard to lose 30 DB between your antenna pre-amp and your TV sets. You do not lose any signal until you create a loss greater than 30 DB.

Hope that this helps improve your signals.
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