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Date: Fri, 12 Sep 2008 10:24:21 +0200
From: "John RABSON" <john.rabson@wanadoo.fr>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: Re: AC Noise on RX...
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On 12/09/2008 at 08:55 Ken wrote:

>Hi Scot.
>Does the noise sound like 50Hz?, if so you probably have an 'earth loop'=20
>somewhere, always worth checking for earth loops.
>
>73.
>Ken M0KHW
Or 60Hz?

John F5VLF

>----- Original Message -----=20
>From: "Scott Tilley" <sthed475@telus.net>
>To: <rsgb_lf_group@blacksheep.org>
>Sent: Friday, September 12, 2008 3:16 AM
>Subject: Re: LF: Re: AC Noise on RX...
>
>
>> Hi Guys
>>
>> Thanks for the responses.
>>
>> This one has me still scratching my head.
>>
>> All of the LF bands are affected.  I have tried my RF isolation=20
>> transformer that worked rather well back in the city.  I have not tried=20
>> the AC mains iso xfmr yet.  Yes my iso is wound like yours.  No computer=20
>> yet.
>>
>> To answer others questions about a local noise source.  Can't be as I
>can=20
>> shut off all the breakers in the house save the one feeding the radio
>and=20
>> nothing else and the noise is still there.  Doesn't matter which PSU of=20
>> the many I have I use and the noise is still there.  Switch to the
>battery=20
>> and turn on everything and bang the noise is gone.
>>
>> The noise is only there AFTER I connect the antenna. So it has something=20
>> to do with the mains AC, coax run and the antenna...
>>
>> 73 Scott
>> VE7TIL
>>
>> PS - The day we get the band back on 2200m is the day I'm back on the=20
>> air...  This time with a 70' high big honking flat top about 500m from
>the=20
>> ocean...
>>
>>
>> jrusgrove@comcast.net wrote:
>>>
>>> Scott
>>>
>>> Welcome back! Agree with previous comments on checking the power supply=20
>>> first. What frequency range is affected?
>>>
>>> Is  the isolation transformer an ac mains isolation transformer or an
>rf=20
>>> isolation transformer? Even if you're using an ac mains isolation=20
>>> transformer an rf isolation transformer on the lead will probably be=20
>>> required. For this transformer I've found that a conventional wound=20
>>> ferrite transformer with the primary and secondary separated on the
>core=20
>>> work best. Bifilar wound transformers are not the way to go here. If
>you=20
>>> have a computer connected to your receiver a 600 - 600 ohm isolation=20
>>> transformer in that connection can also improve noise pickup.
>>>
>>> Any hope of transmitting again?
>>>
>>> Jay  W1VD  WD2XNS  WE2XGR
>>>
>>> ----- Original Message ----- From: "Scott Tilley" <sthed475@telus.net>
>>> To: <rsgb_lf_group@blacksheep.org>
>>> Sent: Thursday, September 11, 2008 12:10 AM
>>> Subject: LF: AC Noise on RX...
>>>
>>>
>>>> Hi All
>>>>
>>>> Been awhile since I've posted to the reflector.  I'm pleased to
>announce=20
>>>> I have escaped the noisy clutches of the City and bought myself a nice=20
>>>> piece of land up the coast in a very quiet spot.
>>>>
>>>> Presently I'm only using my passive RX loop which has a single turn=20
>>>> 'sense' loop for coupling into the main multi turn loop...  When the
>RX=20
>>>> is connected to an AC power power supply I get terrible AC growlers;=20
>>>> however, put the RX on a battery and bang not a peep of nasty AC noise.
>>>>
>>>> I presume this is due to some coupling between the AC mains and the RX=20
>>>> system and my isolation transformer doesn't seem to help so I wonder
>if=20
>>>> someone could set me straight on what is going on here so I can solve=20
>>>> the problem.
>>>>
>>>> Thanks for any support!
>>>>
>>>> 73 Scott
>>>> VE7TIL
>>>>
>>>
>>>
>>>
>>