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cleigh Profile
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Registered: 07-2011
Posts: 7
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TVI


I would be grateful for any pointers. I intend to use an albrecht into a 1/2 wave antenna with a Kenwood Low Pass Filter. The situation is 400 feet above sea level with clear horizonal view.

I have a small number of houses behind me that are taller than the antenna - nearest is 30 feet away What TVI problems might I face ? Do you use filters ? I have access to 200 watts - will using this likley give me any issues ?

Any pointers would be appreciated. Thank you
15/Jul/2011, 9:04 pm Link to this post Send Email to cleigh   Send PM to cleigh Blog
 
mikefox whiskey Profile
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Accomplished DX-er

Registered: 02-2009
Location: Northern Ireland
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Re: TVI


It is possible you may have problems with 200 watts, some people have had problems with a quarter of that power, each station and QTH is different so it's hard to tell if you will indeed have TVI problems though. Adding ground planes to your half wave will decouple the RF from your coax and will help reduce TVI probably, in theory a coax choke on the cable will prevent the coax from radiating also and with your filter in place that's really all I can think of. Other than that if there is TVI problems, you may have to use a lower power output.

Good Luck!

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(Forum user name is now SuperNasty)
15/Jul/2011, 9:14 pm Link to this post Send Email to mikefox whiskey   Send PM to mikefox whiskey
 
Hot Fusion Profile
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Registered: 03-2008
Location: South West England
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Re: TVI


In the interests of good neighbourly relations, is there anything stopping you from conducting experiments and asking them if there are any issues?

This is probably the best way if you feel the people involved are approachable.

I'd get someone on the TX end who can operate the equipment and who knowns how to vary the power.
Once you've got a potential 'victim' at the door and have explained that you operate a transmitter (licenced of course!) and would like to be sure you're not causing problems, get the TX guy to key up and modulate (SSB would be best here as this is most likely to be troublesome) and see if there are any issues.

If there are, turn down the power until you get the all-clear.

Wrinse and repeat with all neighbours in the immediate locality.

You may be surprised and very pleased to discover that you don't cause any problems, but if you do, you will be aware of it and the neighbour concerned will know where to go rather than just reporting it to Ofcom, which is never good.

As for ensuring your TX is clean, previous posts have covered this - with your Kenwood filter (which is darned good) you won't be radiating significant harmonics so you should be OK there; The big issue is simply too strong a signal.

If a particular friendly neighbour is suffering at your hands, sometimes a ferrite ring on their TV antenna downlead or hi-fi speaker leads, depending on the problem, may well fix it.

Good luck, and let us know how you get on.


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Andy - FB107
16/Jul/2011, 3:08 pm Link to this post Send Email to Hot Fusion   Send PM to Hot Fusion
 
cleigh Profile
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Registered: 07-2011
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Re: TVI


Many Thanks for the feedback. WIll report back. I shall be at the QTH (in the Adriatic) from 29th onwards. If any of you wish to attempt a QSO let me know what frequencies you may be on eves and morning. Regards
17/Jul/2011, 7:20 pm Link to this post Send Email to cleigh   Send PM to cleigh Blog
 
cleigh Profile
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Registered: 07-2011
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Re: TVI


All,

I said I would revert with feedback.

No problems caused to TVS or phones or my bose amplifier (when I turned it up next to the set up). Was using a Kenwood low pass 30 A filter which is well reviewed after the linear.

My next steps are that I will place another Low pass between radio and amplifier as well as earth both the radio and transformer with a short earth wire to be as sure as I can. Kenwood's rejection of harmonics is 90 db and they appear to be very good.

Regards
15/Aug/2011, 7:09 am Link to this post Send Email to cleigh   Send PM to cleigh Blog
 


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