HR20 susceptible to RF interference

[Chop69]

I have a new HR20 and have been noticing some pixelation on my HD locals. I thought it was a problem with the satellite line, because the twist on connector was a little loose. I replaced the cable with another I had, but it didn't seem to help. Well come to find out, the pixelation happens when I turn on my XBox 360, and to a lesser extent, a window AC unit. The only satellite affected if 103(a).

The 360 is on a separate shelf about 5 in below the HR20 and the AC unit is on the other side of the room. The 360 and the HR20 are both plugged in to a UPS, with the HR20 on the battery side, and the 360 on the surge only side. The AC is plugged into a different outlet in the same room.

I'm kind of stumped. This did not happen on the H20 the the HR replaced. I'm going to try to swap my 2 HR's to see if it still does it. If that doesn't work, maybe I will wrap it in tin foil :D

Anybody else have any RF interference problems?

[Chop69]

OK an update,

I swapped my two HR20's, left all the cabling as is, and it works fine.

I've already got an appointment set for Wednesday to run the second line for the new HR20, so now I just have to see if DirecTV can have the installed swap it out at the same time.

[Stuart Sweet]

Don't wrap the HR20 in foil, it will overheat. However, you might with some research construct a Faraday cage that will solve the problem and leave plenty of ventilation space.

[carl6]

I run a 50 watt VHF transmitter, and a 45 watt UHF transmitter, within two feet of my HR20 with no problems whatsoever. I have never had interference problems.

Carl

[paulman182]

I run a 50 watt VHF transmitter, and a 45 watt UHF transmitter, within two feet of my HR20 with no problems whatsoever. I have never had interference problems.

Try 500 watts of HF! it wipes one of mine out.

However, I've pretty much given up ham radio except in the car since I've got so much HD to watch!

[stevecon]

I run a 50 watt VHF transmitter, and a 45 watt UHF transmitter, within two feet of my HR20 with no problems whatsoever. I have never had interference problems.

Carl

Same here.. 50w on VHF is unnoticeable. 100w on HF (really bad on 10m) into a tuned G5RV run above the house however is a different story, but only to the audio portion. PC speakers and home entertainment speakers suffer.. TV picture however, is fine.

[sstv]

Hi all
I had a"RF" problem big time. I called Directv and after many CSR'S I got to someone that knew what amateur radio was.
A replacement H20 was sent and installed but 500 watts still wiped it out but 100 watts was ok. That was a improvement but still not right.
My installation has all the coax from the 5 lnb dish wired to a grounding block and the grounding block grounded back to the dish assembly.
There was no "earth" ground so I hooked the grounding block to the same ground system that my Ham Shack uses and my RF problem went away.
I have been with Directv since 1993 and NEVER had a RF problem and never had a grounded dish.
The H20 changed all that, but a simple ground wire corrected the problem.

[hasan]

I run a 50 watt VHF transmitter, and a 45 watt UHF transmitter, within two feet of my HR20 with no problems whatsoever. I have never had interference problems.

Carl

Assuming those radios are feeding coaxial antennas, there will be very little RF exposure of the HR20 from their proximity (unless their antennas are right there in the room with you (which from an RF exposure point of view is frowned upon by the FCC)). The key factor is how close your antennas for those radios are to the HR20.

I have three 65 watt VHF radios (144 Mhz) whose antennas are as close as 20 feet to my HR20. I also have a 50 watt UHF (436 Mhz) radio, whose antenna is about 60 feet away.

The king of the hill is a 1000 watt output amplifier whose antenna is 35' (at it's base, ground fed inverted L for 80m (3.5 Mhz), from the HR20.

I get no RF interference from any of them. The VHF and UHF radios are on 24/7 and transmit every few seconds, automatically controlled by a computer.

Now, back to the XBox as a potential source for interference and it's cure:

I would suspect a dirty switching power supply in the XBox (or whatever it was, I already forgot). You might consider a couple ferrite beads...or the square rf chokes from Radio Shack. Wind a few turns of your AC line cord for the 360 through the snap on choke (close to the 360 side of the cord, near the chassis, not out by the wall plug). Also, put one of these snap on RF chokes on each of your antenna lines going into the HR20, as well as one on the AC line of the HR20.

I have snap on RF chokes on all my HR20 leads (as mentioned above), as well as on my HT amp AC line cord, and my HDTV antenna lead in.

This prevents ( or chokes) common mode currents from flowing on the outside of the coax braid/foil. No amount of shielding of the coax itself will prevent this type of interference, as it isn't flowing on the inside (center) conductor of the coax....it's hitching a ride on the ground/braid side. If your Xbox is radiating RF noise (as opposed to conducting it out the power line), the chokes will reduce it dramatically.

If the Xbox is just so poorly shielded that it is radiating directly to the dish itself, then you have to do something more dramatic for the Xbox. It shouldn't do this, and the most likely culprit is power line conduction or common mode currents on the coax, both of which should be taken care of using the chokes I describe above.

My preference for chokes is not Radio Shack. A much higher quality choke is available from DXEngineering (google). They are a first rate outfit and I have bought dozens of these RF chokes from them over the internet. Buy the larger ones for half-inch diameter coax....then wind several turns through the choke (while you have it snapped open), then snap it closed.

The choking "action" of a ferrite choke goes up at the square of the number of turns ...for example:

If you put just one 1/4 inch rf choke bead on a piece of RG-6 it will produce "x" ohms of choking impedance. If, on the other hand, you use the larger half inch choke and wind two turns through it, you get 4 times the choking impedance, and if you run 3 turns through it, you get 9 times the choking impedance. So in the end you are better off with the larger diameter choke, simply because you can wind more turns on it.

[K4SMX]

Here's the url (http://www.dxengineering.com/Parts.asp?ID=290&PLID=182&SecID=89&DeptID=33&PartNo=DXE-CSB-750P) for the DX Enginnering RF chokes which Hasan mentioned. They're hard to find on the main website.

[Chop69]

This has me so baffled.

An update to my update. My second HR20 does exhibit the same behavior when connected in the trouble location, just not as bad.

I have spent all afternoon trying different combinations with some luck tracking down the problem. I'm not sure if it is a result of RF interference or the dip in power when the AC or Xbox comes on. Here are some things I've tried:

1. I got some snap on RF chokes. I got the biggest diameter (13mm) that they had at Fry's. I put one on the air conditioner where the cable goes into the unit. The diameter of the cable only allowed for one turn. I put one on the HR20's power cable, and got 3 turns on it. I put one on the satellite in line (only one line connected at the moment), also only one turn. I left the xbox unplugged. AC off, HR20 works fine. Turn on the AC, and the HR20 works fine until the compressor on the AC kicks in, and then the signal strength starts bouncing.

All the rest of the tests were done with the chokes on.

2. Plug in the HR to an extension cord to another room, AC and Xbox still plugged in like they were. Same result, signal bounces when compressor kicks in.

3. Plug in the AC and Xbox to extension cords, and the HR into the ups in the room, and it works fine.

According to the display on the ups, the output voltage drops from 121v to 118v when the compressor on the AC kicks in. It the HR that sensitive to to a voltage dip that it could be causing my problems? Also why am I only having problems on 103(a)?

I'm so stumped.

[houskamp]

I bet the drop is worse than that, you just can't see it that fast.. you would need a scope to see how bad it realy is...

[Chop69]

So if we go on the assumption that it is a voltage drop, what would help? The ups is a cheap APC that doesn't do boost and trim, would a better one that does help? Power conditioner? Something else?