MMDS Analogue

HarryD

Can someone confirm how this system works ?

From the pick-up on the antenna, there is a down-converter box
that converts the signal from ~3Ghz to 600Mhz ..?
From there it's then fed into the STB, ?
Do they use Jerrold STBs ?

How is the downconverter powered ?

Thanks in advance,
HarryD

watty

There is a 2.5GHz dipole that feeds a unit identical to a Satellite LNB, except the input is an "N" connector and not a horn and about 1/5th the frequency.

Output is about 190 MHz to 390MHz (part of band III and hyperband). Allegedly "some" do output in UHF band (Satellite LNB actually overlaps top of satellite band).

In theory same Dish with Downconvertor/LNB can feed the Sagem Digital receiver used by Chorus, but what a Chorus installer tells me may not be 100% accurate. (This also is true of Satellite, same LNB *CAN* feed a digital or analog box)

12V up the cable via an RF choke (inductor) powers it.

The Jerrold box is a USA Cable TV box made for NTSC. IT is horrid.

The Scrambling method is horrid and is not encryption. More than that about it I won't say.


Some channels (vary per transmitter) are "Clear" and thus can be legally received with YOUR OWN GEAR.

Using ANYTHING to defeat the scrambling is offically criminal in Ireland (Piracy/Theft of service). Even an official Jerrold box is illegal unless you pay for the channels it descrambles.


Many TV/VHS will tune Hyperband/ Band III. Some old BandIII only TVs get only the first 4 or so channels.

Each transmitter uses 1/2 the possible channels in the band so that nearby transmitters use alternate channels. Polarisation tends to be opposite on nearby to each other transmitteres too.


The system is pathetic using AM video and FM sound just like UHF TV. Analog at that band should have been FM video.

The quality is inherently rubbish.

A 100 Euro "video sender" transmitter/receiver pair is MUCH higher quality. They will do over 6km on MMDS style dishes if an N connector is fitted instead of the build in aerial/plates. In this case the "Downconvertor"/LNB is disconected.

The dishes can be purchased in Kerry at about 40 Euro upwards (different sizes etc) and work for "video senders" and "WiFi 802.11" Wireless LAN (up to 10km).

The ones installed by Chorus /NTL belong to the cable company, NOT the user (a Sky dish even on a €15 subsidized install belongs to user from day 1).

If you move into a house with no evidence of Chorus / NTL (If is has they will knock at door looking to sell you a sub) but a Dish on the roof I suppose you don't KNOW it is Chorus's and can do what you like. If they come looking for it, don't argue, give them benefit of doubt as someone messing with "WiFi" or "Video Senders" (Legal CB TV?) is unlikely to left dish behind....


If you see someone with an "MMDS" style dish on a telescopic pole it is more likely a Wireless LAN site survey as Chorus will tend to assume that if other houses have it it will work (Their definition of "work", not an Ex-BBC broadcast Engineers' definition).

Hope you arn't sorry you asked!

HarryD

Originally posted by watty
Hope you arn't sorry you asked!

Not at all.. I find it very interesting

Some channels (vary per transmitter) are "Clear" and thus can be legally received with YOUR OWN GEAR.

The dishes can be purchased in Kerry at about 40 Euro upwards (different sizes etc) and work for "video senders" and "WiFi 802.11" Wireless LAN (up to 10km).

So you can legally tap into the clear channels in some places?
Will chorus not come knocking wondering about the antenna on
the roof ?

If you see someone with an "MMDS" style dish on a telescopic pole it is more likely a Wireless LAN site survey as Chorus will tend to assume that if other houses have it it will work (Their definition of "work", not an Ex-BBC broadcast Engineers' definition).

What u mean by this ?

THanks,
HD

watty

Anyone can buy a dish (a downconvertor / LNB) is a bit harder to buy.

You don't "tap in". It is radio waves. if it is "clear", i.e. not scrambled or encrypted it is legal to watch with your own gear it you have TV licence.

"Tapping in" to a CABLE is illegal, even if the channel is "clear". Even plugging into an active cable point in your house without paying is now "Theft of service" and illegal even if no decoder box is used.

WiFi or Wireless lan are boxes in offices and cards in lap tops or PCs to "network" computers like Ethernet, but without wires.

If you fit external aerials you can "beam" the signals between buildings quite legally *AS LONG AS YOU DO NOT CHARGE FOR THE SERVICE*

Charging for access to Wireless LAN is illegal. It is only legal if free! (you have to buy your own gear though).

Many sites in Ireland broadcast beams or in all directions allowing people to connect.

Contact someone in http://www.irishwan.org/ to find out if it is in your area. Some enthousist may then come and check if your house can get a signal by using an MMDS type aerial on a telescopic pole.

If you can get a signal, then you can go off and buy an MMDS dish, WiFi card or box, cable, connectors etc and get connected.

The Limerick area has I think a network Doom on tuesday nights (20 times faster than broadband!) and some big FTP file stores. I'm not connected at present due to equipment incompatibility.

I have two dishs on my chimney that are identical to MMDS. Big plastic box on pole instead of Chorus "Downconvertor/LNB". One is for WiFi Networking (8Km .. 18Km range) and one for a "Video Sender Transmitter" (Maybe 8km range).

Range depends on what size / type of dish BOTH ends have.

maxheadroom

Originally posted by watty
If you fit external aerials you can "beam" the signals between buildings quite legally *AS LONG AS YOU DO NOT CHARGE FOR THE SERVICE*

Charging for access to Wireless LAN is illegal. It is only legal if free! (you have to buy your own gear though).

Emm - what about Wireless ISPs - this is pretty much exactly what they do, and they charge for the privledge...

watty

Originally posted by maxheadroom
Emm - what about Wireless ISPs - this is pretty much exactly what they do, and they charge for the privledge...

They have a licence..

In theory a baby intercom wire between two houses breaks the law (unlicenced telecoms cable) but a free Wifi does not (It is actually "pre-licenced" by CE/CEPT).

Mostly wireless "licence free", i.e. pre-licenced such as:
* Headphones
* Videosenders (2.4GHz FM)
* Domestic wireless TV security (2.4GHz FM)
* Wireless Speakers
* Wireless baby monitor
* PMR 3km radios (Personal Mobile Radio)
* Dect Cordless phone
* WiFi / Wireless lan
* 27MHz 40 Ch FM CB with CE mark (SSB probabily illegal)
* Some domestic wireless microphones
* some 49 MHz very low power toy Walky/talkies
* some R/C gear (toy cars etc)

are actually "pre-licenced" with conditions (such as not selling a service based on it, exceeding a certain power or on the PMR you must not add external aerial).

A 2m dish on a WiFi card might be breaking the licence as the "beamed" power (ERP compared with isotropic radiator) would be very very high.

The items below need a licence obtained by the named user:
Amatuer Radio
Marine Radio
Amatuer TV
Public Mobile Radio (taxies, Building sites etc)
Professional Wireless Microphones
Private Microwave links (Video, Data or Voice)
Some higher power R/C gear ???

The items below need a Licence for location and organisation:
TV "Deflector"
Student or Hospital Radio
Local Radio
Local TV (may get this someplace eventually)
National Radio
National TV
Satellite Uplink
Microwave link for carrying other users material for charge
Wireless ISP (i.e. Chorus PowerNet)
Wireless Phone (Chorus)
Analog Cell Phone (old mobiles)
Digitial Cell Phone (GSM, 3G etc)
Analog MMDS TV
Digital MMDS TV
Professional Wireless Security Video
Telemetry links (i.e. Water, Gas pumping stations)

Items NEVER legal AFAIK:
UHF AM TV "video Sender"
FM Radio band "home" transmitter (any type)
Radio bugs
SSB / AM 27MHz CB
High power amp for 27MHz CB

Items that might now be illegal to sell or shortly illegal
27MHz toy walkietalkies
non-crystal controlled R/C or walkytalkie toys
1.8MHz/49MHz Analog cordless phones or baby alarms

Infra Red low power "wireless systems" till now did not even need approval. They may now need to meet safety requirements in terms of limit to output power to get a CE mark. Some "Wireless" headphones and toy R/C (i.e. Lego Robot) use InfraRed, not radio.

Many items from Abacus to Zylophone need a CE mark to be legally sold in Ireland now.

Capt'n Midnight

I've been told that 27MHz wireless computer keyboards are illegal here (they are OK in other EU countries)

TVDX

Originally posted by watty
Local TV (may get this someplace eventually)

Remember RLOTV watty.