[time-nuts] Active LORAN antenna
Chuck Forsberg WA7KGX N2469R
caf at omen.com
Fri Aug 26 22:17:21 UTC 2011
Try to get a DA-100 with a socket for the FET along with some spare FETs.
The FETs are very hard to get but a sub will work if strong local
signals are absent.
On 08/26/2011 02:46 PM, Brooke Clarke wrote:
> Hi Poul:
>
> You're correct.
> The noise floor for the AMRAD unit is caused by line conducted noise,
> not the background noise coming from the whip.
> The DA-100 seems to have filtered out the line noise so you do see the
> background.
> I live in a jungle (forrest?) so there's not as much noise as in a city.
>
> Have Fun,
>
> Brooke Clarke
> http://www.PRC68.com
> http://www.End2PartyGovernment.com/
>
>
> Poul-Henning Kamp wrote:
>> In message<4E580972.6080103 at pacific.net>, Brooke Clarke writes:
>>
>>> It looks like the noise floor is maybe 10 dB higher than the AMRAD
>>> http://www.prc68.com/I/Images/AMRAD_BT.GIF
>>>
>>> or 30 dB higher than the McKay Dymec active antenna.
>>> http://www.prc68.com/I/Images/Da100nf.GIF
>> If you are basing that claim on the SA plot in my blog-post, you
>> instantly win the "inappropriate apple-oranges comparison price of
>> the year"
>>
>> First there is nothing even remotely close to a natural noise-floor
>> in the LW broadcast band in the middle of a city here in Denmark,
>> there is far too much EMI from switchmodes etc etc.
>>
>> Second, there is a significant impedance mismatch between the antenna
>> and my SA in that plot. I backhaul the signal over a balanced
>> twinax cable (78Z I belive) and crank it up for the LORAN-C receiver
>> in the matching balun, so the feed impedance is way higher than 50Z
>>
>> Mind you, I don't dispute that you may be right, I just don't think
>> you have data to back up your claim...
>>
>>
>
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--
Chuck Forsberg WA7KGX N2469R caf at omen.com www.omen.com
Developer of Industrial ZMODEM(Tm) for Embedded Applications
Omen Technology Inc "The High Reliability Software"
10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430
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