Satellite dish "interference"?

AuntEnvy · Aug 11, 2013

I guess this topic should be here... or in the "general" forum...?

I have a question to pose and any thoughts would be helpful.

Would a tv satellite dish, either working/being used or not, cause any interferrence with my scanner antenna?

I have one located somewhat nearby and wondered if I should remove it.

Does anyone have any experience with this?

Thanks

krokus · Aug 11, 2013

Is power still supplied to the amplifier(s) in the feed horn? If not, then it is not going to generate interference.

If there is exposed metal that has oxidized, and more than one nearby strong transmitter, you could get what is called IMI. Basically, those transmitters mix with each other in the oxidation, and the products of the mix can cause problems. This is not likely to be a major issue, in most cases.

The other possibility would be the dish making a "shadow" in the incoming signals. Most signals are coming from multiple directions, so this is not a problem for most cases.

Blackink · Aug 11, 2013

AuntEnvy said:
I guess this topic should be here... or in the "general" forum...?

I have a question to pose and any thoughts would be helpful.

Would a tv satellite dish, either working/being used or not, cause any interferrence with my scanner antenna?

I have one located somewhat nearby and wondered if I should remove it.

Does anyone have any experience with this?

Thanks

I have a working Dish satellite dish about 35' from my exterior ST-2 antenna, doesn't seem to bother it any.

KD4UXQ · Aug 11, 2013

I have a few antennas near my Direct TV dish and have had no problems. The IF tuning range of the receiver appears to be anywhere from 950-2150 MHz. This is the output of the LNB. Depending on the mixing scheme, the LO would likely be that amount higher than the satellite downlink which appears to be 12.2-12.7 GHZ and 18.3-18.8 GHZ. Unless the LNB is generating some sort of spurious product due to incorrect operation, I wouldn't think there would be any problem receiving anything below 950 Mhz and only a problem with things near or above 950 MHZ if there were a problem with the cable from the LNB to the switch or receivers.

rss3781 · Aug 11, 2013

The dish may be

for every radio/dish/lnb that TX even over coax there is a mirror on a freq lower that could be an issue and VFO in the LNB could cause RFI on close by RX devices and check your coax connections! have u ever put 2 radar detectors in the same car they set them selves off due to the VFO

prcguy · Aug 12, 2013

The IF range of newer Directv LNBs can include signals in the 250 to 2150MHz range and also lower frequency data between the receivers and LNB plus video sharing between DVRs.

Besides the 18.3 to 18.8GHz downlink range there is also 19.7 to 20.2GHz.
prcguy

KD4UXQ said:
I have a few antennas near my Direct TV dish and have had no problems. The IF tuning range of the receiver appears to be anywhere from 950-2150 MHz. This is the output of the LNB. Depending on the mixing scheme, the LO would likely be that amount higher than the satellite downlink which appears to be 12.2-12.7 GHZ and 18.3-18.8 GHZ. Unless the LNB is generating some sort of spurious product due to incorrect operation, I wouldn't think there would be any problem receiving anything below 950 Mhz and only a problem with things near or above 950 MHZ if there were a problem with the cable from the LNB to the switch or receivers.

KD4UXQ · Aug 12, 2013

prcguy said:
The IF range of newer Directv LNBs can include signals in the 250 to 2150MHz range and also lower frequency data between the receivers and LNB plus video sharing between DVRs.

Besides the 18.3 to 18.8GHz downlink range there is also 19.7 to 20.2GHz.
prcguy

Interesting that the new LNBs go down to 250MHz. I have one I believe since I have the latest DVR with the whole Genie setup. I still have no unexplained interference since upgrading a few months ago. I expect you wouldn't, provided you had no cable leaks or faulty equipment. Signal levels should be pretty low, although I don't know what that would be exactly. I get more interference from leaky cable TV out at the street on VHF air than anything inside or around my house. Much less so these days than in the past. Many years ago it got so bad it was reported by someone I think, because it wasn't long after that they replaced some cable and amps in our neighborhood. I almost reported it myself. Someone apparently beat me to it. I wondered if it interfered with aviation. Don't remember the frequency, but some of the CATV channels are in the VHF air band. Weird they allow that even on a closed circuit system.

prcguy · Aug 12, 2013

Aha, if you have the Genie you also have the newer SWM (single wire multiswitch) where the IF is confined to L band plus the lower frequency data between receivers and the SWM.

I have not heard of any interference from the SWM or Genie.
prcguy

KD4UXQ said:
Interesting that the new LNBs go down to 250MHz. I have one I believe since I have the latest DVR with the whole Genie setup. I still have no unexplained interference since upgrading a few months ago. I expect you wouldn't, provided you had no cable leaks or faulty equipment. Signal levels should be pretty low, although I don't know what that would be exactly. I get more interference from leaky cable TV out at the street on VHF air than anything inside or around my house. Much less so these days than in the past. Many years ago it got so bad it was reported by someone I think, because it wasn't long after that they replaced some cable and amps in our neighborhood. I almost reported it myself. Someone apparently beat me to it. I wondered if it interfered with aviation. Don't remember the frequency, but some of the CATV channels are in the VHF air band. Weird they allow that even on a closed circuit system.

AuntEnvy · Aug 12, 2013

Thanks for the input guys

That's a lot of information I never expected, but very interesting just the same.

I'm thinking I should probably remove it but this one isn't being powered/used.

I appreciate all the replies and thank you.

Darth_vader · Aug 12, 2013

"Don't remember the frequencies, but some of the CATV channels are in the VHF air band."

Code:

Numeric Alp Video    Audio
            Carrier  Carrier
98/67   A2  109.25   113.75
99/66   A1  115.25   119.75

14      A   121.25   125.75
15      B   127.25   131.75
16      C   133.25   137.75

http://mistman.pdp10.org/pub/radio/frqlists/cblchart

17 & 18 also overlap the 140 MHz HAM radio band (139.25-149.75 MHz).

Satellite dish "interference"?

AuntEnvy

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krokus

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Blackink

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KD4UXQ

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rss3781

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prcguy

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KD4UXQ

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prcguy

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AuntEnvy

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Darth_vader

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