Distribution Amplifier problem!

LostInLM

Hi. This is my first time to use this board so here goes.

First a quick description of my system

Geographically I am located in south Leitrim close to the Longford border (~ 15 miles from Cairn Hill, Mast is clearly visible).

I have a Hirschmann FESA 817N37 Antenna pointed towards Brougher Mtn. and another antenna pointed at Cairn Hill. These are combined using a Triax group A/E combiner. All down leads are sat grade cable. I do not have a masthead amp on the Group A Hirschmann antenna. It's located ~30feet above ground on an elevated site with a relatively clear view north.

Reception on the the BBC's, ITV and C4 is good (not 100%, a little gainy when compared to the sky digital BBC, but acceptable, can fluctuate slightly depending on weather conditions!) Teletext is perfect but I can get breakup on C4 depending on weather conditions.

RTE, TV3 and TG4 are all perfect.

My problem is that when I introduce a distribution amp into the system in order to provide another TV point in a second room I get severe interference patterns on the BBC's, ITV and C4. This is most noticible on C4 where an RTE1 picture can be clearly seen breaking through on the C4 picture.

If I try a passive splitter the interference disappears but I get the expected drop in signal strength. Everything is still watchable but there is some slight lines on BBC1.

I suppose my question is what is causing the interference when I plug in the amp. I was wondering if it was because of the close proximity to Cairn Hill and that this was causing overloading with the amp. I've also ruled out the vcr as a possible source.

Has anybody any idea's how I could overcome this? I was wondering if I put a masthead amp on the BBC antenna before the combiner and used the passive splitter would I get a better picture? Or would it just overload it considering that I have a relatively decent signal already?

Any explanations or solutions greatly accepted?

Antenna

best thing to do is get a hi-gain (i.e. 30dB or so) masthead amplifier for your 'BBC' aerial (only), there is no risk of overload in your situation - try and get a Group A mast-head amplifier rather than a wideband UHF mast-head amplifer if possible. The Triax combiner you already have should have an option to allow DC pass on each 'group' (needed for an amplifier between the aerial and combiner) - this is done by screwing in a screw (supplied) on the circuit board for the group that has a mast-head amplifier, and leaving the unamplified aerial group disconnected.

you then have no need for a distribution amp (you have plenty of signal for the Irish channels by the sound of things) but try get the 'metal' type splitters (the plastic ones are usually lossy)

LostInLM

Hi Antenna,

Picked up a 25db Group A amp over the weekend. Installed it today and everything is working to perfection. Many thanks for the tip.

Picked up a freeview box up north today for the second TV and am able to get all channels Happy Days

legend99

Hey Lost, where did you manage to buy your grouped Amp?

LostInLM

Sourced it in Longford. Crossan Electrical.

Macy

LostInLM wrote:

Sourced it in Longford. Crossan Electrical.

Do they have much stock in there i.e. High Low Combiners etc? And whats the prices like?

LostInLM

Not too sure to be honest. Why not contact them yourself and they may be able to help you out.
http://www.crossan.ie/