[UK-CONTEST] Fw: re ADSL Modem RFI

[ALEX LISTER]

----- Forwarded Message ----
From: ALEX LISTER <alexcom22 at btopenworld.com>
To: "David, G3YYD" <g3yyd at btinternet.com>
Sent: Tuesday, 17 November, 2009 12:36:22
Subject: Re: [UK-CONTEST] re ADSL Modem RFI


FIT THAT Filter !
 
All this chatter about RFI from HF into Modems etc reminds me I thought about sending in an article to Radcom on some of the basics.
Must admit despite 40 years of working for BT.  (Not the customer end thank goodness !)
Its only since the advent of broadband that I decided to tidy up my own instalation.
More from a view of increasing my broadband rate which now runs at a usfull 5-6mB.
Think all the obvious things have been covered in all the recent emails.
1. Faceplate filter option is best if u have a modern NTE box..
2. If you have an older NTE then suggest a new back box with an integral filter fitted in parallel.
 Splitting the ADSL and phones is really worthwhile. 
3. If possible split at point of entry into property.
 If thats not a suitable point for your ADSL Router then wire from this point using RG45 connectors from  filter   point to Router.
After tidying up instalation then think about the additional filters as recomended. If you still have problems.
 
Do not recomend ever hacking into any of the BT line instaltion itself.. U might get a nasty charge by the openreach chap.
If you have the older style terminal block then a remedy may  be awkward.
Perhaps if BT are your broadband supplier they will be happy to change the terminal block for a NTE 
You can purchace similair NTE boxes without the BT Logo but it could be expensive if a visiting Openreach man found fault was down to you !
 
I have  had no problems EMC wise 160 - 70 cms here using either a BT (Older style Wireless Hub)  or currently using a Talk Talk device, In both cases with both wireless and LAN connections.
However only run 100-300 watts !!
Run mainly balanced antennas on HF.
 
 
Alex Lister G8FCQ
alexcom22 at btopenworld.com
 0753 120 1640




________________________________
From: "David, G3YYD" <g3yyd at btinternet.com>
To: uk-contest at contesting.com
Sent: Tuesday, 17 November, 2009 11:34:08
Subject: Re: [UK-CONTEST] re ADSL Modem RFI

Ian

Did you try a ferrite ring (one of those the RSGB sells works well) on 
the drop wire pair running into the BT master socket. In my case it fits 
inside the master socket. You need a minimum of 14 turns. This will then 
force the RF on the line at HF to be equal on both legs of the drop 
wire. When the RF reaches the balanced input of the router it will 
maximise the cancellation of the RX signal. By the way do not wind the 
toroid with enamelled copper wire it does not have a high enough voltage 
rating. I used internal phone cable with the outer sheath stripped off.

I do not have any added  filtering on the power lead supplying the router.

In theory you should not alter anything between the master socket and 
BTs line but they are not going to throw away your custom (£notes) so in 
practice that regulation is not enforceable in this context.

I use a DG834G  with the drop wire ferrite in place plus a ADSL 
faceplate in the master socket to isolate the extension wiring from the 
router. I run full power on all bands 160-10 plus 2m without any 
degradation in the broadband signal to noise. One leg of my 80m dipole 
and my 160m vertical top loading wire run above and to once side of the 
BT drop wire. The BT supplied modem router was very poor on RF immunity 
compared to the Netgear.

David G3YYD

Ian Maude wrote:
> This has been an interesting thread for me for several reasons.  Firstly,
> *both* my routers (main and spare) expired with different faults at the same
> time and it had to be a Sunday!  I nipped out and bought a Netgear router.
>  I should have known better due to past difficulties but I needed to keep
> the cluster running :)
> The Netgear hates 80m.  This newer model was better and could stand 50W
> without dropping the connection.  Anything toward 100W and a reasonable over
> and the connection would drop due to queue length.
> I bought a DLink G624T online and connected that up.  This is the same as
> the router that died and has no such problems.  I can run 400W without
> losing a single ping!
> I was a BT engineer for most of my working life and the dropwire crosses the
> trap dipole but at right angles and well away from the current maximum.  The
> line then comes straight into the shack and on to a filtered NTE.  I have
> done many tests, moving the router and reconnecting wiring etc.  The DLink
> works every time without issues.
> Now I know of other people who have the opposite experience and I have yet
> to discover why.  I cannot imagine why one router would be so much better
> than another in this regard.  I used the same line cord with both routers
> using 2 ferrite cores at each end of the cord with about 8 turns on each
> one.
>
> 73 Ian
>
>  
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