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Karride
Slower Traffic Keep Right
Premium
join:2000-04-17
Germantown, TN

Cheaper source for this or something similar

I really want this so I can use an old dish cable to run one of my cameras. Problem is, this companies shipping charges are outrageous (cheapest would be ~$17)

I've googled without success, anyone got a source for something like this that charges a *reasonable* shipping rate?


IllIlIlllIll
EliteData
Premium
join:2003-07-06
Hampton Bays, NY
kudos:7
thanks for that.
didnt know those existed.
sorry i cant answer your question though.
--
Suffolk County NY Police Feed - »www.scpdny.com
PS3 Gaming Feed - »www.livestream.com/elitedata

TheMG
Premium
join:2007-09-04
Canada
kudos:3
Reviews:
·NorthWest Tel

1 edit
reply to Karride
Cheapest would probably be to make them.

For a basic DC over coax, a couple of capacitors and an inductor is really all that is needed. One of the capacitors will block DC from reaching the RF port of the devices, while the inductor and another capacitor form a filter to prevent RF from reaching the DC source.

Here's some good old ASCII art:

DEVICE RF-----||-----*------COAX
                     |
              C1     (
                     ( L1
                     (
                     |
                     *----
                     |    |
                     |    - C2
                     |    -
                     |    |
                     |   ___
                     |
                DC IN/OUT
 

Commercial units may have additional components for protection, voltage regulation, etc. But you can get away without those, especially for a shorter run.


tschmidt
Premium,MVM
join:2000-11-12
Milford, NH
kudos:9
reply to Karride
I assume you are aware the adapters in your link use BNC connectors not F. I assume the camera uses 50 ohm rather then TV 75 ohm coax.

Not sure how critical correct impedance will be for base-band video.

/tom

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
reply to Karride
Google for "Bias T" or search any microwave surplus stores to find similar DC injectors used to power RF amplifiers.


54067323

join:2012-09-25
Tuscaloosa, AL

1 recommendation

reply to tschmidt
said by tschmidt:

I assume the camera uses 50 ohm rather then TV 75 ohm coax.
/tom

Most cameras are 75 ohm, RG59, 6 etc.


54067323

join:2012-09-25
Tuscaloosa, AL

2 edits
reply to lutful
said by lutful:

Google for "Bias T" or search any microwave surplus stores to find similar DC injectors used to power RF amplifiers.

In 75 ohm and at what cost?


54067323

join:2012-09-25
Tuscaloosa, AL
reply to Karride
said by Karride:

I really want this so I can use an old dish cable to run one of my cameras. Problem is, this companies shipping charges are outrageous (cheapest would be ~$17)

The link you posted is for both units at $40 and free shipping that is about as low in retail as you are going to go.


SparkChaser
Premium
join:2000-06-06
Downingtown, PA
kudos:4
Free shipping is for orders over $500


54067323

join:2012-09-25
Tuscaloosa, AL
said by SparkChaser:

Free shipping is for orders over $500

Then just buy a few more.

None the less it's not a bad retail price for both units, that is unless the OP already has the injection side built into the DVR in which case all that is needed is to break it out at the camera.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
reply to TheMG
said by TheMG:

Cheapest would probably be to make them.

Bias Tees with F connectors are widely available from local satellite installers. Maybe $15 new but surplus ones are even cheaper.

Minicircuits also sell just the guts (your ascii schematic) as a tiny module which can be soldered to any type RF and DC connectors. Less than $10 but involves shipping.

TheMG
Premium
join:2007-09-04
Canada
kudos:3
Reviews:
·NorthWest Tel
reply to tschmidt
said by tschmidt:

I assume you are aware the adapters in your link use BNC connectors not F. I assume the camera uses 50 ohm rather then TV 75 ohm coax.

BNC connectors exist in both 50 ohm and 75 ohm flavors.

However, since the mismatch loss of using a 50 ohm BNC on a 75 ohm system is often negligible (especially when dealing with baseband video), most manufacturers don't even bother and simply use the much more common 50 ohm BNC connectors.

I've even seen multi-thousand dollar professional video broadcast gear that has 50 ohm BNC connectors on all 75 ohm inputs/outputs.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
said by TheMG:

said by tschmidt:

I assume you are aware the adapters in your link use BNC connectors not F. I assume the camera uses 50 ohm rather then TV 75 ohm coax.

BNC connectors exist in both 50 ohm and 75 ohm flavors

Built-in BNC on CCTV products are always 75 Ohm. There are also really cheap BNC-F couplers because many people use off-the-shelf TV coax assemblies for cameras.

*** Another option for OP would be to use BNC to RJ45 adapter with power inserter like the one shown above. They are cheap and widely available in security shops and online.


54067323

join:2012-09-25
Tuscaloosa, AL
said by lutful:

Another option for OP would be to use BNC to RJ45 adapter with power inserter like the one shown above. They are cheap and widely available in security shops and online.

said by Karride:

I really want this so I can use an old dish cable to run one of my cameras.

How would the OP connect that to the coax he intends to use?

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
You are concerned because OP really wanted to use "dish cable" ... right?

I had already suggested the common power adders/inserters used for satellite LNBs which are designed for 75 ohm "dish cable" and later mentioned that 75 ohm BNC-F adapters are quite common and very cheap.

I also mentioned that the DIY ascii schematic posted by TheMG See Profile is available as a tiny module from minicircuits, ready to be soldered to any type of coax and DC connector.

I mentioned the BNC-RJ45 power inserters just as another alternative to power security cameras. OP may not use it, but others could.

public

join:2002-01-19
Santa Clara, CA
reply to lutful
said by lutful:

said by TheMG:

Cheapest would probably be to make them.

Bias Tees with F connectors are widely available from local satellite installers. Maybe $15 new but surplus ones are even cheaper.

The camera is likely baseband video, not rf.

TheMG
Premium
join:2007-09-04
Canada
kudos:3
Reviews:
·NorthWest Tel
said by public:

The camera is likely baseband video, not rf.

Same difference. NTSC composite baseband video has content up to about 4.2MHz.

The same principles of transmission lines, impedance, filters, etc apply.

public

join:2002-01-19
Santa Clara, CA
said by TheMG:

said by public:

The camera is likely baseband video, not rf.

Same difference. NTSC composite baseband video has content up to about 4.2MHz.

The same principles of transmission lines, impedance, filters, etc apply.

Yes but at the low end your inductors will not be feasible.


54067323

join:2012-09-25
Tuscaloosa, AL
reply to public
said by public:

The camera is likely baseband video, not rf.

Which is why satellite coax should not be used to carry such a signal.

Baseband video requires a coax with a solid copper core, not copper plated steel which is what is found in satellite and CATV coax.


54067323

join:2012-09-25
Tuscaloosa, AL

1 edit
reply to lutful
said by lutful:

I had already suggested the common power adders/inserters used for satellite LNBs which are designed for 75 ohm "dish cable" and later mentioned that 75 ohm BNC-F adapters are quite common and very cheap.

Which of course, will not work in this application.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1

1 edit
reply to public
said by public:

The camera is likely baseband video, not rf.

I am curious how that commercial power injector device (linked in original post) is working.

The fluctuating "dc" power waveform will be superimposed on the lower end of the baseband video waveform.


54067323

join:2012-09-25
Tuscaloosa, AL
?


54067323

join:2012-09-25
Tuscaloosa, AL
reply to lutful
said by lutful:

since fluctuating "dc" power waveform will be superimposed quite far into the baseband video waveform?

Thats an incorrect assumption.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
said by 54067323:

said by lutful:

since fluctuating "dc" power waveform will be superimposed quite far into the baseband video waveform?

Thats an incorrect assumption.

OK genius, what do YOU think will the DC waveform look like as the camera is operating? Please draw a sketch showing 0 Hz to ??? Hz spectrum content.

Of course, you also have to draw what you think the baseband video spectrum will look like from 0 Hz to ??? MHz.


54067323

join:2012-09-25
Tuscaloosa, AL
said by lutful:

OK genius, what do YOU think will the DC waveform look like as the camera is operating?

First you can knock off the condensending comments, then you need to realize without knowing the cable length, gauge and makeup and the power drawn by the camera, coming up with anything would be a pure assumption.

But assume on if you wish.

BTW what do you think happens if you cut off 2 meg of the videos bandwidth?


lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1
said by 54067323:

... you need to realize without knowing the cable length, gauge and makeup and the power drawn by the camera, coming up with anything would be a pure assumption.

If you search my old posts in DSLR, you will probably find hundred entries on every technical aspect of supplying power over ethernet and coax cable to WISP nodes. FYI some nodes require 100W.

said by 54067323:

BTW what do you think happens if you cut off 2 meg of the videos bandwidth?

There will be no video at all if you cut off DC-2Mhz of NTSC spectrum.

However ... the devices used for satellite/antennas cut off just the DC-20Khz portion of the "baseband" spectrum to supply power and pass at least upto 650Mhz.


54067323

join:2012-09-25
Tuscaloosa, AL
said by lutful:

However ... the devices used for satellite/antennas cut off just the DC-20Khz portion of the "baseband" spectrum to supply power and pass at least upto 650Mhz.

Really now...

»www.solidsignal.com/pview.asp?mc···atellite Splitters&sku=874409002404

Last time I checked 2MHz was slightly different than 20KHz.


54067323

join:2012-09-25
Tuscaloosa, AL
reply to lutful
said by lutful:

However ... the devices used for satellite/antennas cut off just the DC-20Khz portion of the "baseband" spectrum to supply power and pass at least upto 650Mhz.

Um, BTW satellite LNB's output on "L band" which is 950-1450, as such "up to 650Mhz" ain't gonna make it.

Just thought you would want to know.

lutful
... of ideas
Premium
join:2005-06-16
Ottawa, ON
kudos:1

3 edits
Click for full size
said by 54067323:

said by lutful:

However ... the devices used for satellite/antennas cut off just the DC-20Khz portion of the "baseband" spectrum to supply power and pass at least upto 650Mhz.

Um, BTW satellite LNB's output on "L band" which is 950-1450, as such "up to 650Mhz" ain't gonna make it.

a) The phrase "pass at least upto 650Mhz" implies that there are other devices which pass even higher frequency.

I personally use a custom bias tee design which passes upto 6Ghz and we do need that for TV whitespace, 900Mhz, 2.4Ghz, 3.6Ghz and finally 5.8Ghz radios.

b) However ... there are many satellite down converters which convert C/Ku band RF directly to (70Mhz or 140Mhz) intermediate frequency. These devices need a lot more power than a LNB. There are also bias tees for HF antenna amplifiers which need not go that high in frequency.

P.S. I helped to bring satellite-based internet to my country way back in 1996 ( »Re: low on budget middle of nowhere ) and founded a WISP equipment company back in 2002. I hope you will not continue the argument just to educate me.

*** Perhaps you, public See Profile, and TheMG See Profile will together come up with L and C specs for the generic bias tee schematic. A design which passes 10Hz-10Mhz should be perfect for the baseband cameras. Keep the power supply spectrum below 10Hz and don't forget to match 75 ohm coax.


54067323

join:2012-09-25
Tuscaloosa, AL

3 edits
said by lutful:

a) The phrase "pass at least upto 650Mhz" implies that there are other devices which pass even higher frequency.

Funny way to imply that and it leads me to believe you didn’t even know the specs of what you where recommending until you read the link I posted and then realized it would not work as recommended.

However ... there are many satellite down converters which convert C/Ku band RF directly to (70Mhz or 140Mhz) intermediate frequency.

Which has nothing to do with what you recomended.

said by lutful:

I had already suggested the common power adders/inserters used for satellite LNBs which are designed for 75 ohm "dish cable" and later mentioned that 75 ohm BNC-F adapters are quite common and very cheap.

Which by your own admission, will not work.

said by lutful:

There will be no video at all if you cut off DC-2Mhz of NTSC spectrum.

But nice try at covering that error up by changing the subject, which you do so often it's predictable...