Splitters, Attenuators, Filters, Diplexers, Other Signal Gear

[Mark_OB1]

threeflags commented:

> Currently the setup is in the attic so weather won't be much of a problem. <

These push-on baluns are meant to be used indoors. Since yours is in the attic, you may not consider it to be 'outdoors', and you'd be correct. However, located in the attic, it is probable that the temperature extremes are far wider than they are inside your home (also humidity). As a result, you may find that your connection has degraded after a while, due to thermal expansion and contraction. Or corroded, due to humidity and oxidation.

Bottom line: I'd only consider using that one as a short-term 'solution', in that environment.

[Jase88]

I don't recommend push-on f-connectors under any circumstances. Even indoors, I've found pets have walked on wires behind TV's and disconnected them accidentally. PITA.

[gculley]

Thanks for the advice guys. I did some noise tests and it looks like my VHF noise is much worse than my UHF noise and they don't seem to be correlated.

I agree that a separate high-vhf antenna would be best so that UHF doesn't get affected by the insertion loss of the filter, but adding another antenna simply "won't fly" with my wife.

This is a tough one, especially since the notch filters are expensive!

[majortom]

The diplexor could also be at the other end of the downlead plugged in the uhf port. The vhf antenna doesn't need to be anything elaborate, just has to work. Just use a pair a rabbit ears & a balun to plug in the the VHF port inside the house somewhere. It should pick up rf 13 CKCO easily given ur in it's immediate neighborhood. You can test if this will work with very little effort. Since CHCH 11 is moving back to UHF this summer, you won't be missing anything else on VHF hi. Effectively CKCO 13 = CFTO 9, since they're both CTV, CFTO would be redundant.

[nbound-au]

The inserion loss of the filter will be small compared to the added noise you already have. And yeah, notch filters arent the cheapest things out :P

[gculley]

Thanks again guys,

MajorTom, I didn't know about CHCH, so that's good news. I still need to get CFPL London (ch. 10) for CTV 2, other than that I agree, I don't need more than rabbit ears for VHF. CFPL has an NM of +10 according to my TVFool report, so I may get away with one of those non-amplified omni-directional saucers plugged into the VHF input of the CM7777 (through a notch filter) for VHF. As I already have a rotator, perhaps even a pair of rabbit ears at the top of the mast?

I've been trying to interpret the Holl_ands overload spreadsheet, but I'm not sure if it applies to VHF. It's very difficult to follow at a glance, it will require more study.

[roger1818]

Originally Posted by gculley

This is a tough one, especially since the notch filters are expensive!

Use a Join-Tenna as a notch filter (just terminate the single channel input with a 75ohm terminator). You may also want to connect it backwards to ensure no leakage from the single channel input. You would want the CM-0583 channel 13 Join-Tenna. They are available for about $4 (just Google CM-0583).

Edit: I see a store in Winnipeg has one for more $, but may be cheaper with shipping.

[roger1818]

Originally Posted by gculley

I may get away with one of those non-amplified omni-directional saucers plugged into the VHF input of the CM7777 (through a notch filter) for VHF.

A better option would be to get a C2 VHF Reflector Assembly (available from the forum sponsor), remove the reflector and use U-clamps to attach it to your mast. It will be both better and smaller than the saucer.

[gculley]

Thanks for the ideas Roger. The jointenna looks like a good inexpensive option, but its insertion loss of 3db will hurt, especially since it would be before the preamp. If I go with an additional VHF-only antenna, then the jointenna may be a good option for that antenna as my VHF signals should be strong enough to support that much loss.

The reason I was considering a saucer was that it supports VHF-low as well as VHF-high frequencies. I'd like to use the VHF input of my CM7777 so that I don't have any insertion loss from a filter on my UHF channels, so I'd really like an all-round VHF antenna. I'm finding that CIII-HD Toronto is a bit weak for 100% reliable reception, but it has a relatively local VHF station on channel 6 (VHF-low). Unfortunately the CM4228HD attenuates the +40db NM signal so heavily that the CIII UHF station in Toronto is actually stronger! I would do better with rabbit ears for channel 6.

I've formed a bit of a game plan. I believe that the CM4228HD is a bit weak at the higher UHF channels. Forum results seem to confirm this and my experience is that it's probably true. At my location, CBC Toronto (channel 20) is at about +0.2 NM, where CIII (channel 41) is supposed to be at +1.4 NM, yet CBC comes in at about 95% signal strength and 95% quality where CIII is at about 70% signal strength and 62% quality. Sounds like the higher frequencies are suffering to me (particularly when 70% represents something less than -15 dbmV for my tuner while 95% is somewhere around -3dbmV).

My understanding is that the CM4228HD can be improved for the higher UHF frequencies by taking off the harness and using two coaxial baluns and a combiner. I'm going to give the mod a try. If CIII Toronto suddenly comes in a lot stronger, then I don't need VHF-low and should have everything I need for VHF-high with the CM4228HD.

Regarding the notch filter, my father emailed me that he still has an old channel 13 filter that he doesn't use anymore since he moved out of our area. I'll give that a try to see if there is a reduction in noise floor that is greater than the insertion loss.

[roger1818]

Although the "saucer" antennas claim to receive VHF-LO, they aren't very good at it. To receive channel 6 well, the antenna needs to be about 6' wide (over 9' for channel 2). I would suspect the C2 VHF dipole will do as well for channel 6 as the saucer.

You could lengthen the elements on the C2 VHF dipole to improve its VHF-LO performance, but I wouldn't put too much effort into that as I am sure Global will move off of 6 in the not too distant future (they recently applied to move from 6 to 14 in Ottawa). I don't have any inside knowledge on this, it is just a gut feeling.

[gculley]

I agree, I wouldn't expect much from the saucer, but for a signal that is +40 NM I wouldn't need much. I'm just surprised at the amount of loss that the CM4228HD has at VHF-low. I honestly thought that a coat hanger would be all I need and the 4228 is doing worse than that!

If necessary, I think I'll experiment with a simple dipole or a high-VHF antenna and see if it works better than the 4228 for the one low-VHF channel I need. RCA makes a small high-VHF antenna, so I'd be curious if it will be ok for a strong station on channel 6.

[roger1818]

VHF-LO has been proven to be very problematic for DTV (which is why stations are moving away from it). The FCC estimates the broadcasters need more than 20dB more power then they first estimated (which is not practical). TVFool uses those old models so you can subtract 20 to 30 dB from the NM it predicts for VHF-LO stations.

Try using a cheap pair of rabbit ears (the Source has some on clearance for about $3 if you can find them in stock nearby).

[gculley]

Thanks Roger, that's interesting about VHF. VHF-hi doesn't seem so problematic, but you could have knocked me over with a feather after finding I couldn't pull in such a strong VHF-low signal. I may just try the rabbit ears on an antenna switch.

[roger1818]

Ya. VHF-HI still causes problems, but many of those are from people trying to use a UHF antenna. Even still, the FCC estimates that about 10dB more power is needed than initially expected.

[BCNU]

Hello everone,

I was scanning the forum looking for help in combining an ota antenna with my shaw satelite on one rg6 cable. I had hoped to use an ampifier on the antenna but the general consensus seems to be that this cannot be done. While looking at other sites I came across a site called Denny's TV antenna service and he stated the following on his site.

TV Antenna - Satellite Dish Diplexer


SKU: 135 Diplexer
Power pass satellite port only



SKU: 136
Power pass both ports


Denny,

>

Can you explain the use of a Diplexer? Example your Skywalker SKU#136. Could I use this with a DirectTV/DishNetwork Satelite signal and a antenna signal through one line(RG6QUAD) into the house and to my TV's?

>

Wes
>
>

A diplexer can be used to combine the signal of a satellite dish and a over the air TV antenna together onto the same coax cable feed. This method cannot be used with HDTV satellite receivers.


Two diplexer's are required. One outdoors that combines the satellite signal and the antenna signal together and one indoors that takes the two signals back apart.
>


To combine a non preamplified antenna and a dish use the power pass satellite port only diplexer SKU:135 outdoors and indoors. Outdoors connect the antenna and dish to the appropriate labeled diplexer input ports. Indoors connect the satellite receiver dish signal input to satellite port of the diplexer and the antenna input connection to the antenna port of the diplexer.
>


To combine a preamplified antenna system use the power pass both ports SKU: 136 diplexer outdoors. Connect the satellite dish and antenna to the appropriate ports of the diplexer. Indoors use the same diplexer as used above SKU: 135 for the non amplified system. When using this method the preamplifier power supply/injector is not used. The operating power for the mast mounted preamplifier is supplied by the satellite receiver.
>


For the best performance I do recommend a preamplifier for most diplexed systems.
>


Best Regards,

Denny

TV Antenna Source

1/ Does anyone think this will work on an amplified ota antenna without damaging anything and
2/ Where would you find one of these power pass both port diplexers?