RF dummy loads

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pm

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#18934 30-Jan-2008 11:18

Does anyone know if these things are useful?
I know they maintain a good VSWR, but would it improve signal quality if I attached it onto unused ports of an RF splitter or coax wall connections?

If so, does anyone know where I can get "nice" flush mount '75ohm coaxial dummy loads'? I've only seen F-connector type dummy's.

cyril7

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#107531 30-Jan-2008 11:58

The only ones I know of are the ones that you get from teh likes of MasterTrade or Corys, and whilst they are quite small and unobtrusive they are not flush.

Normally folk dont reroute there coax feeds that often, so I normally leave any un used feeds disconnected from any splitters, also only use as many splits as required to both reduce loss and eliminate any unterminated splitter ports. If you want to add a service to a particular room/faceplate then a quick visit to the coax distribution point to attach the suitabley labeled cable is not a biggie.

A splitter with an untermintated port that has no coax attached will normally not cause any issues, in either V/UHF or Lband. Once you attach a unterminated cable to a splitter you expose the system to the potential of reflections that can cause issues.

Cyril

pm

78 posts

Master Geek

#107540 30-Jan-2008 13:41

The problem is my splitter is sandwhiched between the two stories of my house so it's in-accessible. I was thinking of terminating the unused wall ports since someone told me they make a difference to signal quality.
MasterTrade don't have retail outlets do they? I assume I would have to call a technician to come over with the parts? What about cory's - are they a retail store?

manhinli

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#107541 30-Jan-2008 13:52

pm: MasterTrade don't have retail outlets do they? I assume I would have to call a technician to come over with the parts? What about cory's - are they a retail store?

Not sure about MasterTrade, but we go to Cory's once and a while (my closest one is down in East Tamaki). They do retail.

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cyril7

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#107543 30-Jan-2008 13:56

Both mastertrade and Corys will flog their wares to anyone who walks in the door. Obviuosly you will pay retail as opposed to trade, but these things are only a buck or so a piece.

Is this network of cabling feeding Lband Satellite or analog TV aswell. With satellite feeds if the quality reading or BER of your Skybox is ok then any reflections that are in the system are probably below the threshold of upsetting the decoder, which in my experince is nearly always the case. If its analog TV you are feeding about then you may notice a reduction in ghosting.

Cyril

pm

78 posts

Master Geek

#107575 30-Jan-2008 16:25

I wasn't looking at trading with MasterTrade/Cory's...I just wanted to know if they do sell retail to the general consumer. It seems they do from what you guys have said.

As for my network its carrying all analogue because the satellites digital signal is coming from the RF out of the decoder. My BER is fairly good, but as I said the digital signal isn't an issue.
At least I know where to get those plugs from. I'll give it a go. Thanks.

richms

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#107577 30-Jan-2008 16:27

terminating the unused feeds solved heaps of the intermodulation issues I was having on the distribution amp here - no idea why since I assumed that the amp would be an ideal 75 ohm source and not really be effected by its loading, but sure enough, terminating the unused feeds cleaned up the signal heaps of the herringbones that were on all the upper uhf channels.

Richard rich.ms

pm

78 posts

Master Geek

#108668 5-Feb-2008 13:16

I've been and spoke to people at Cory's and Mastertrade - they both say they havn't heard of a "75 ohm dummy load" and each one referred me to the other company. Does anyone on this forum work there and know what I'm talking about?
RS Components use to sell "75ohm PAL/Belling Lee Dummy Loads" but not anymore. I can't find them on the net too.

I bought an F-connector dummy load from Jaycar with the corresponding converters and they work well (reception slightly improves) but with these adapters it makes one ugly looking extrusion from the wall plates...

Can anyone help me find what I'm looking for? Thanks.

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sbiddle

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#108681 5-Feb-2008 13:39

pm: I've been and spoke to people at Cory's and Mastertrade - they both say they havn't heard of a "75 ohm dummy load" and each one referred me to the other company. Does anyone on this forum work there and know what I'm talking about?
RS Components use to sell "75ohm PAL/Belling Lee Dummy Loads" but not anymore. I can't find them on the net too.

Mastertrade sell F style ones, I actually saw them yesterday in a store when I went to grab some F connectors.

cyril7

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#108698 5-Feb-2008 14:34

They call them terminations (which is correct) only just picked up a handfull from mastertrade 20mins ago for job.

Cyril

pm

78 posts

Master Geek

#108764 5-Feb-2008 18:46

Yeah I mentioned the word "terminator" as well.

cyril: are they "pal" or "belling lee" terminators at mastertrade?

hashbrown

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Ultimate Geek

#108767 5-Feb-2008 19:23

A dummy load is usually used for calibration and testing as a "dummy" for an antenna. The ones I remember using had heatsink fins to dissapate a continuous 25W without radiating RF.

As above terminators or terminations more accurately describe what you are after.

kevthesparky

79 posts

Master Geek

#108836 6-Feb-2008 08:40

If I think I know what you are talking about I call these 75ohm terminators when I go in to my wholesaler.

pm

78 posts

Master Geek

#108876 6-Feb-2008 12:43

yes they are terminators. Its just jaycar call the "terminators" "dummys".
Anyway, anyone know for sure who has a male PAL or Beling Lee Terminator? I don't mind second hand ones too.

kiwisat

147 posts

Master Geek

#109189 7-Feb-2008 22:17

I am sure a 75 ohm resistor from hot pin to ground is all you will find inside a terminator.
It worked fine for me to ground unused ports with a resistor on hard wired vhf splitters in days gone by.

cyril7

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#109220 8-Feb-2008 07:55

Thats all they are I have made terminators by soldiering a resistor into a crimp body on occasions when I have not been able to get them at suppliers.

Cyril