Now that my 3 antenna combo to multiple TVs setup is finally integrated I am left with one problem. My analog TV (Sony Wega) is showing a strong interference from Ch4 when tuned to Ch11. Now, the frequency on channel 11 is 3 x the frequency of ch4 so that is certainly part of it. What I do not quite understand is that my hauppauge card does not have the same level of problems when fed from the same signal, (i.e it is way less visible) . I have attenuated the signal to the Sony but that did not have any effect. I have played with additional earthing of the diplexers/splitters etc but no effect. The only difference between the two tuners' setup is that the RG6 cable to the Sony is about 30 ft longer.

My next step is to order some ferrite tubes for in case the strong channel 4 is picked up on the RG6 coax screen and then picked up by the less noisy Sony tuner.

Any other ideas?

I would suspect you’re using an Amp and it’s creating a 3rd harmonic of channel 4 that is causing you the interference on channel 11. This is a dreaded problem that can be caused when using an Amp. Channel 4 must also be a very strong signal in your area... am I right?

You need a filter or trap on the input of the Amp for channel 4.

Correct, I am using an amp to overcome the losses of the cables and splitters following the amp (and the attic environment). I could not see any evidence of amp saturation though. The amp is a Winegard AP8700 which I picked because of its ability to handle higher strength signals and that it included a dual FM trap due to known problems with FM interference on channel 6. We have a relative weak channel 6 here from the same tower and what I did to somewhat attenuate channel 4 was to optimize a dipole / single reflector combo for channel 6 and that gave me about a 9 dB or so (IIRC) difference in gain between channels 6 and 4. I will see if I can construct a simple RLC filter to further attenuate channel 4 - thanks for the idea.

mlord gave me this idea which worked wonders. He suggested adding a stub to the antenna line tuned to channel 4 to attenuate it a bit. There are basically two options, 1/4 wavelength and 1/2 wavelength. In the case of the latter one has to short the end of the stub and in the case of the former one has to leave it open. I picked the former (less work:)) and with the added advantage of being able to trim it easily and using less coax (my dutch heritage ;)). A 35 inch of RG6 and a $-store splitter were all that was needed. I have not installed it in the attic yet but putting it in just before the TV made a noticable difference.

The fact that it made such a difference after the amplifier confirmed to some extend ? that the interference happens in the TV tuner and not in the pre-amp, however probably caused by the pre-amp overdriving the tv tuner on channel 4.

Still have to open the splitter to ensure that there are no non required passive components - however, from what I have seen I doubt it.

Here is the evidence - thank you mlord

Before ...................

http://img7.imageshack.us/img7/5969/p1040435a.jpg

and after

Well as you can see there is still a tiny bit left - but I will tweak it once I have the stub before the pre-amp

http://img341.imageshack.us/img341/6603/p1040437.jpg

PS When including this image in the post above I got the error message back that I am including 4 images :confused:

PS 2 I stopped at out local electronic component supplier this PM to get some goodies, including a trim cap for a filter should the stub idea not work. The sales person told me that they don't stock trim caps anymore - no requirement for it.:(

Could you show us a photo or diagram of the custom Channel 4 stub you built?

Finaly got rid of the remaining interference. I opened the $-store splitter to remove the guts

Here is what it looked like after opening it up

http://img198.imageshack.us/img198/6017/twoway.jpg

I then replaced the thin wire / ferrite bead combo with solid copper from the core of RG59 coax.

That pretty much almost killed channel 4 and 11. (Channel 11 being an odd multiple of channel 4). The good about it is that it comfirmed that the selected velocity factor for the RG6 coax was correct.

With the TV tuned to channel 11 and I started trimming the stub length cutting only an 1/8th of the an inch at a time until channel 11 returned to a satisfactory picture. Tuning to channel 4 I found that it was still a tad noisy so I repeated the procedure till I was happy with channel 4.

One have to check all channels after this procedure since the final stub length may end up an odd multiple of the 1/4 wavelength of another channel, which will affect it. One easy way to check if the channel is close to an odd multiple is to touch the centre core at the end of the stub with your bare finger. If there is a noticible difference in the picture then that channel is close to a 1/4 wavelength odd multiple. Remove the stub, if it improves that channel, then you have some more trimming to do.

Another way would be to start with the stub an inch or so longer longer than a 1/4 wavelength. If the interference is there then trim untill it is gone. This will move the odd multiple wavelenght problem to lower channels at the higher end of the scale.

The best is, as my final installation will be, to install this filter before the HLSJ or UVSJ diplexer. That way one doesn't have to be concerened about the higher channels feeding into the other end of the diplexer.

This is what the final solution looked like. I coiled the stub so that it would fit in the picture. (Notice how the centre core has pushed out in the coiling up process)

http://img195.imageshack.us/img195/4815/tconnection.jpg

Wow, that's a very handsome and tidy job, RamKat! I'm happy to hear that the theory held true in real-life for this. ;)

EDIT: The theory is thus: With a 1/4 wavelength stub tapped from the main coax run, the signal for Channel 4 runs up the stub, hits the end, and reflects back down again to the main cable.. where it arrives exactly two 1/4 wavelengths (1/2 wavelength) out of phase, thus cancelling out much of the channel 4 signal on the main cable. Other channels are not affected as much, because they reflect back down the cable in varying degrees of phase, never 1/2 wavelength out.

Note to others: I'm sure that RamKat reinstalled the cover plate (shielding) to the splitter housing after taking that last photo of it for us here.

Cheers

Just a tip: label that 1/4 wavelength stub's splitter so that you don't mistake it for a standard splitter in the future. ;)

I was wondering about an alternative adjustment method targeted at adjusting the depth of the notch. If one would put an adjustable carbon strip resistor in between the stub centre core and the wire connecting the main coax run. My guess is, given that we are using a 75 ohm setup, that something in the order of 680 to 1 kOhm value would allow a few dB's to work with. Would that work? Would the parasitic characteristics of the adjustable resistor have any noticable effect? I wanted to try it out but could not find an adjustable resistor with a close enough value in my scrap box.

PS Yes, the lid is back on and the thought of the label crossed my mind - will do that !:)

Is there a notch out filter that has a selectable range or individual station capability ?

kinda like ip address were you can select ranges or individual channels ?

that way I could group out a bunch of local stations ,

(would be cool under computer control on a web interface like a wireless router with a gain setable pre amp ):D

to access the far distant station

thanks guys for all the info !!

Is there a notch out filter that has a selectable range or individual station capability ?

kinda like ip address were you can select ranges or individual channels ?

that way I could group out a bunch of local stations ,

(would be cool under computer control on a web interface like a wireless router with a gain setable pre amp ):D

Nothing that sophisticated, but you can get tunable notch filters. They are a challenge to tune accurately without a spectrum analyzer, which is very expensive. You can also buy them pre-tuned, but they aren't cheap. Even then it may not be worth it as everything is going to change in a couple years after the analog shutdown. Besides, the digital broadcasts will likely be at a much lower power and you may not need the filters then.

I was wondering if anyone knows of good 2 way splitters that include DC power pass in both directions?

What I am trying to do is use a couple Kitztech pre-amps to amplify the signal from two antennas while passing the power to them via one co-ax cable. As a result, I am looking for a low insertion loss splitter/combiner which passes power from the in to the two outputs (the Winegard CC-7870 unfortunately only passes power to one output).

I picked up a GE branded (it was actually made by a different company in China) splitter from Canadian Tire last week and found that it only passes DC from the two outputs to the input but not in the reverse direction. After that experience, I have become more wary which is why I am performing additional research.

I also noticed the Channel Vision HS-2 which appears to pass in both directions and has a 3.5 dB insertion loss but I am having trouble confirming that and my emails to Channel Vision have so far gone unanswered.

I also saw that Save and Replay had sold the Channel Master 3212 which they list as all ports DC pass through but again, looking at the box, I could not confirm that (I also didn't hear back from Save and Replay).

Looking at Winegard's website, it seems they only sell splitters/combiners/couplers which pass power on one port. As a result, their products would not suffice for this job.

Finally, I contacted another manufacturer, ******** which seems to be a Canadian company. After an initial email, I am also still waiting to hear back on whether they offer a splitter with DC pass through on all ports.

So, I was wondering if anyone has tried the Channel Vision HS-2 splitter/combiner or knows of other alternatives which pass power in all directions or at least from the IN to both OUT ports?

Ott8915, just to clarify, you've confirmed with KitzTech that one power supply will properly power 2 preamps when split? Electronically it means that the power supply's voltage will be halved because the preamps will be in parallel.

I have confirmed with KitzTech that it will power it, provided the power supply is adequate for the job. It should be a 4-6 VDC, 160 mA supply, ideally regulated at 5 VDC (the normal supplies he ships are 80 mA). The primary concern was that the unregulated voltage would be too high and overload the amplifiers.

KitzTech is sending me a supply which should be sufficient to power both pre-amps, in addition to the normal supplies that are used on a 1-1 basis.

I will admit that the person I have been speaking to at KitzTech, who has been very responsive to my emails (I have been extremely impressed with that company), did not recommend using one supply for 2 preamps and instead two separate coax lines, one per pre-amp/antenna, in order to avoid any potential problems.

How do I remove all the interference from channel 6 and 11?

Channel 6 shows 79% signal strength and Channel 11 shows 85% signal strength.

(My antenna is attic mounted coat hanger, which works great as I am getting the OMNI 2 HD with it, and rest of the local channels, no US)

First picture is channel 6, second is channel 11. Any help would be appreciated.

http://img32.imageshack.us/i/dscf1548p.jpg/
http://img337.imageshack.us/i/dscf1550.jpg/

one per pre-amp/antenna, in order to avoid any potential problemsYou should probably plan to set that up as a fallback if needed.

You should probably plan to set that up as a fallback if needed.
My current fallback is to set one pre-amp before the splitter so it will amplify both antenna signals. The downside to this is I will have already lost a great deal of signal before it gets amplified. Using a borrowed amplifier (not a preamp), I was able to get all of the local digital channels but I still had trouble with some of the analog channels. I hope with the pre-amp closer to the source, it should greatly improve my reception of the analog channels.

KitzTech has sent me two normal power supplies in addition to the greater amperage one intended to power both pre-amps at the same time. Therefore, I have both options.

The other option I have is to use the line I have set up solely for satellite and instead use it for the antenna or find a way of diplexing the signal while still passing power to both the satellite and antenna (I have a feeling this will not work as the satellite power requirements are very different from the antenna requirements). I would prefer not to lose my NASA TV (full screen during a mission is like going to see an IMAX movie for free)!

I will set up a baseline, which is to remove the splitter and try amplifying each antenna separately so that I know what my ideal conditions are and then try to modify the existing conditions to best approximate ideal while still getting signals from both antennas.

I think almost all diplexers do DC Power Pass so you won't have problems finding any.

The two diplexers I have only pass DC on the satellite port.