Pulse Killer query

Tim.ivn

New Member
I have read somewhere that the HDR Fox T2 and other similar devices have "Pulse Killer" chips in them which can, to some degree, filter out impulse interference. Is this correct?

As well as an HDR Fox T2, I also have a Samsung BD-E8300 Bluray player with inbuilt PVR. The aerial is plugged into the "Antenna In" of the HDR Fox T2 and the "Antenna Out" of the HDR Fox T2 is plugged into the "Ant In" of the BD-E8300. I have sometimes recorded the same program in HD on both machines and whenever impulse interference has corrupted part of the recording on the HDR Fox T2, the recording on the BD-E8300 has been completely free of interference. This suggests to me that the Pulse Killer chip in the BD-E8300 is much better than the chip in the HDR Fox T2. Is this possible?

I would very much like to solve the interference problem on the HDR Fox T2 because the disadvantage of the BD-E8300 is that its recordings can't be backed up.

I expect not but does anyone on this forum think that there is any chance that the Pulse Killer technology in the HDR Fox T2 could be enhanced using some sort of software (perhaps a new package for the custom firmware)?

What about a piece of hardware? My aerial is already plugged in via a Group A bandpass filter which seems to be able to filter out a bit of interference but not much.

Thank you very much.
 

Ezra Pound

Well-Known Member
Your Blu-ray player will probably be benefiting from both the filtering in the Humax and it's own filtering so it is in a better position to reject it. Any filtering done in the Humax won't be software controllable, so a custom mod. is out of the question. The only suggestions I can come up with is a anti-interference band A aerial (possibly already fitted), not fitting a bigger aerial than is required for stable TV reception, using good quality UHF cable, as interference can be induced into bad quality cable and finding the source of the interference e.g. suppress noise from central heating thermostats, fridges etc.
 
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Tim.ivn

New Member
Hi Ezra

Thank you very much for your reply.

I have actually tried swapping the two machines in the aerial chain but the HDR Fox T2 is still the poorer of the two in terms of interference. I have done my best to minimise interference from appliances in my flat so I think that the sources of interference are beyond my control.
 

Black Hole

May contain traces of nut
I have read somewhere that the HDR Fox T2 and other similar devices have "Pulse Killer" chips in them which can, to some degree, filter out impulse interference. Is this correct?
I have never heard of anything like it, nor can I imagine what such a chip would be. If you are referring to short random data corruptions in the received broadcast stream, the transmission system includes error correcting codes which all DVB decoder chips would implement in the same way (in accordance with specification).
 

Wallace

Traveler 34122
@BH

IIRC, Philips mentioned such a chip in some of their AV equipment, but it was several years ago now. I remember thinking it was a marketing ploy, but I could well be wrong as my memory could be letting me down, again!
 
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Tim.ivn

New Member
Hi Black Hole

Thank you very much for your reply. I would be very interested to know your opinion on why my BD-E8300 seems almost immune to interference while my HDR Fox T2 is not.
 

Black Hole

May contain traces of nut
Nobody can draw any conclusions without an analysis of where the interference is coming from. If it is on the mains, one can point at a poor power supply. If it's RF noise in the immediate vicinity, one could look for a faulty thermostat or the fridge, and/or blame poor EM susceptibility performance. If it is coming in on the TV aerial, then maybe a poor tuner module.

In any case, this could be a faulty unit rather than a poor design.
 

ChrisDaniels

Well-Known Member
It could be that you have too many mods on the HDR and that is maxing out the CPU which breaks up the picture on the recording in the same way that interference does. I experienced this about a year ago when I had quite a bit installed including red ring, auto shrink & decrypt on lots of folders and the HDD temp logger that I forget the name of.

You don't say whether you run custom firmware or not..
 

Black Hole

May contain traces of nut
Indeed. Tho OP has only referred to "impulse interference" and not given any description of how this supposed interference manifests itself. If he describes the symptoms we might be able to pin down what it is.

I should also point out that all consumer electronics has to be approved for use by the CE mark regulations, and that approval requires a certain level of immunity to electromagnetic interference and a limit on the emission of EM interference. The immunity is not an issue, the regulations only require that if interference affects the unit it fails in a safe manner, but of course the manufacturers have their own design goals that the unit should operate normally within a typical domestic environment, and units will be tested for this during the design process (bombarding them with all manner of emitted and conducted interference).

I am more concerned with what is causing the interference (if that is what it is). The CE regulations specifically limit the production of interference which may cause potentially unsafe misoperation in other equipment.
 

EEPhil

Number 28
@BH

IIRC, Philips mentioned such a chip in some of their AV equipment, but it was several years ago now. I remember thinking it was a marketing ploy, but I could well be wrong as my memory could be letting me down, again!
Certainly Philips claimed to have such a chip in the DTR 1500 set top box. I have one that occasionally still gets some use. It probably was a marketing ploy - but, comparing the Philips with the first STB I had (the Pace DTVA) it did seem to do something. However, all it really did was stop the picture and cut the sound when the interference occurred. i.e. no picture break-up into squares and no ear-shattering noises. It was an improvement, but was probably over-sold.
 

gomezz

Well-Known Member
Don't good old-fashioned metal cases help by acting as a Faraday cage compared to modern flimsy plastic cases?
 

EEPhil

Number 28
Don't good old-fashioned metal cases help by acting as a Faraday cage compared to modern flimsy plastic cases?
That is indeed the theory. But then you can still have the problem of getting the signals in and out of the box. (Aerial, power, SCART etc.). Any one of those that isn't properly shielded could let a rogue signal in.
 

Black Hole

May contain traces of nut
However, all it really did was stop the picture and cut the sound when the interference occurred. i.e. no picture break-up into squares and no ear-shattering noises. It was an improvement, but was probably over-sold.

This is just a strategy for handling the output when the error correction codes fail - try to make it degrade gracefully. Audio CD players do something similar: there are all manner of error correction mechanisms built into a CD to cope with the types of read error that are likely in those circumstances, but when the checksum is still wrong after correction it is necessary to mute the output rather than send the speaker cones to the limits of their travel.
 
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Tim.ivn

New Member
Hi Everyone. I have not checked this thread for a while because I have been very busy. Thank you very much for all the new replies.

Black Hole, you are wanting to know about the source of the interference and how it manifests itself. Well, the interference happens in short bursts of about a second or two on very random occasions. There can be several hours without any interference and then one program might have as many as three bursts of interference. I have done some experiments involving all of the appliances etc in my flat and the only device that I can deliberately create interference with is my shredding machine which I don't normally use very often so I am pretty sure that if RF interference is responsible for the symptoms then it is coming from outside my flat and is therefore very difficult to pinpoint and stop at source. While my shredding machine produces quite severe interference on the HDR Fox T2, it produces hardly any on the BD-E8300.

With reference to Gomezz's post, does anyone think that wrapping the HDR Fox T2 in aluminium foil will help?

Chris Daniels, yes I do have the custom firmware installed. The following is a list of all the packages that I have installed. Does anyone know which of the packages listed are non-essential and make frequent or continuous demands on the CPU without being triggered by user interaction via the web interface? In other words, which do you recommend I uninstall?

anacron
auto-unprotect
busybox
bzip2
cifs
cron-daemon
epg
ffmpeg
file
fix-disk
hmt
humaxrw
id3v2
inotify-tools
ir
jim
jim-binary
jim-cgi
jim-oo
jim-sqlite3
lamemp3
lsof
mongoose
multienv
nicesplice
nicesplice-magic-folders
openssl-command
recmon
rs
rsvsync
samba
Alternate screensavers
service-control
smartmontools
sqlite3
ssmtp
stripts
tmenu
trm
webif
webif-channelicons
webif-charts
 

MontysEvilTwin

Well-Known Member
Tim.ivn said:
With reference to Gomezz's post, does anyone think that wrapping the HDR Fox T2 in aluminium foil will help?
It is easy enough to try, but apart from the front panel the case is metal: the shiny black appearance of the case is a coating.

Edit: I have taken several apart, old ones (with loader 7.30a) to a relatively new one (bought second hand but came with loader 7.33a so must be quite new) and all have the same metal shell. I don't know if this was different in the last iteration (loader 7.34a, with 1.03.06 firmware and the new tuner with vertical rf terminals).
 

EEPhil

Number 28
With reference to Gomezz's post, does anyone think that wrapping the HDR Fox T2 in aluminium foil will help?

I would have thought this was a very bad idea. To be of any use you would need to cover every ventilation slit and fan vent. I can smell the fried chips from here!
 

Black Hole

May contain traces of nut
The HDR has a metal case, the aerial lead has a screen, and the screen is electrically connected to the case. The only thing left to do is to check there is a good electrical connection between the various parts of the case and the aerial screen, and to make a connection from the case to mains earth (the power connection is currently double-insulated two-pin).
 
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Tim.ivn

New Member
I would have thought this was a very bad idea. To be of any use you would need to cover every ventilation slit and fan vent. I can smell the fried chips from here!

Hi EEPhil

Thank you for your post.

I fully agree with you that covering the vent slits etc would be a bad idea. However seeing as the back of the unit where the vents etc are situated is clearly made of metal, I don't plan on covering the back.
 
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