Where to put modulators?

[stvcmty]

I get TV over the air from Baltimore and DC. There are some channels from FTA I would like to modulate to unused channels to send my house. Aside from spacing analog modulator channels every other channel (for double sideband modulators), what rules should be followed to keep my analog modulated channels from hurting OTA digital channels?
On the Baltimore/DC beam, I receive stations on the following real UHF RF channels:
15, 16, 24, 27, 29, 33, 34, 35, 36, 38, 39, 40, 41, 42, 46, 48, 50.

I have seen “taboo” channel relationships for everything from +/-1, +/-3. +/-5, +/-7, +/-9, +14, +15. If I try to avoid all those taboo relationships, all I am left with is putting analog modulators on 58, 66, 67, 68, and 69.

At one point I had a modulator on channel 63, and it killed my reception of WDCW 50 from DC.

I have a low pass filter for my UHF antenna. It has 50 dB of rejection for channel 59 and up.

 

[boba]

I get TV over the air from Baltimore and DC. There are some channels from FTA I would like to modulate to unused channels to send my house. Aside from spacing analog modulator channels every other channel (for double sideband modulators), what rules should be followed to keep my analog modulated channels from hurting OTA digital channels?
On the Baltimore/DC beam, I receive stations on the following real UHF RF channels:
15, 16, 24, 27, 29, 33, 34, 35, 36, 38, 39, 40, 41, 42, 46, 48, 50.

I have seen “taboo” channel relationships for everything from +/-1, +/-3. +/-5, +/-7, +/-9, +14, +15. If I try to avoid all those taboo relationships, all I am left with is putting analog modulators on 58, 66, 67, 68, and 69.

At one point I had a modulator on channel 63, and it killed my reception of WDCW 50 from DC.

I have a low pass filter for my UHF antenna. It has 50 dB of rejection for channel 59 and up.

Where to put the modulator? Behind the FTA receiver where the composite connectors are available. How many channels are you going to modulate? Between channels 16 & 24 there is room for at least one modulator and between 42 & 46 possibly 1 channel. Channels 52-69 may be used by other services now so your local experience will determine if there is interference.

 

[stvcmty]

I have seen “taboo” channel relationships for everything from +/-1, +/-3. +/-5, +/-7, +/-9, +14, +15. If I try to avoid all those taboo relationships, all I am left with is putting analog modulators on 58, 66, 67, 68, and 69.

At one point I had a modulator on channel 63, and it killed my reception of WDCW 50 from DC.

See http://www.tvtechnology.com/digital-tv/0148/does-dtv-interference-from-taboo-channels-exist/214566

A consumer modulator on UHF 63 puts junk on 62-64. Junk on 64 is probably what killed my reception of UHF 50, 50 + 14 = 64. I thought it was stupid, but with the modulator on, 50 either disappeared or lost most of its signal quality. With the modulator off, I could watch Friends on DCW50. I thought maybe the modulator was throwing off interference, so I got a band pass filter for 700 to 860 MHz, which did not help.

Has anyone else had issues where an analog modulated channel killed an OTA DTV channel from rather far away on the dial?

Between channels 16 & 24 there is room for at least one modulator and between 42 & 46 possibly 1 channel.

Channel 16 is a LP analog, so it puts junk in 17.
Channels 17 and 18 are used for Land Mobile in DC so there is enough noise coming in on them to make a modulated picture on 18 to have static.
Channel 20 has a LP on it, I do not get enough signal for a DTV lock, but there is enough noise to make a modulated picture on 20 to have static.
Channel 21 is in use on the Eastern Shore of MD. In the morning if the sun is right, enough signal comes in for my TVs to get a DTV lock on WBOC.
Channel 22 has a LP analog translator way off the main beam of my antenna, but a side lobe of my antenna picks up enough of it for a modulated picture on 22 to have static
Channel 23 is used by a close station to the north. My Baltimore/DC UHF antenna does not get enough signal on UHF 23 to get a DTV lock, but there is enough noise to make a modulated picture on 23 have static.

19 might work, but when I check the noise on it with my HDHR, it comes up around 25%.

Channels 52-69 may be used by other services now so your local experience will determine if there is interference.

I have a low pass that cleans up channels 59 to 69 for use in house.

From my experience with a modulator on 63 killing 50, I think sidebands from analog modulators and the +14 +15 taboo rules keep me from using anything less than 67.

Right now, it looks like if I can tolerate a little of static, I can modulate on CH19. For clear signals, I think all I get is 67 and 69.
I had wanted to modulate Create, The Pentagon Channel, and a few security cameras.

 

[FaT Air]

If all of your OTA is UHF, instead of trying to 'share the band', put the modulators on VHF. 2/4/6 and then 7/9/11/13. Mix them together with a 6 way splitter, then a low pass filter, and maybe a distribution amp. Add in to the OTA coax with another 2 way splitter.

 

[Trip]

DC and Baltimore have 7/8/9/11/13, so those are out.

But I agree, doing 2/4/5 (6 has WDCN-LP on it, but there's a gap between 4 and 5) seems like the best way to go.

- Trip

 

[Peter Parker]

What is on Channel 8 in that area?

 

[Trip]

WMDO-LD.

- Trip

 

[madmadworld]

Modulate 12 channels here and just gave up and ran 2 rg6 runs and simple a/b switch at sets......Magic works great
good luck