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From: "Graham" <g8fzk@g8fzk.fsnet.co.uk>
To: <rsgb_lf_group@blacksheep.org>
References: <4FE0ED02.4080903@iup.uni-heidelberg.de>,<4FE0EF87.8060905@kpnmail.nl> <7E7DFBB4D102A04DB5ADC88D66628A4A0FAB195C@ICTS-S-MBX5.luna.kuleuven.be> <4FE100DB.60809@iup.uni-heidelberg.de> <4FE10B61.7060202@iup.uni-heidelberg.de> <4FE116B4.4080401@kpnmail.nl> <4FE25A8B.6000403@iup.uni-heidelberg.de>
In-Reply-To: <4FE25A8B.6000403@iup.uni-heidelberg.de>
Date: Thu, 21 Jun 2012 00:28:17 +0100
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Subject: Re: LF: Test signal needed, observations...
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Yes  just  a wall  of  noise  , now  can see  why  Digital  comms are 
popular  on 500  !

G. .

--------------------------------------------------
From: "Stefan Schäfer" <Stefan.Schaefer@iup.uni-heidelberg.de>
Sent: Thursday, June 21, 2012 12:19 AM
To: <rsgb_lf_group@blacksheep.org>
Subject: Re: LF: Test signal needed, observations...

> Jan, Rik, MF,
>
> I have made some measurements and observations:
>
> When using the active E field antenna while having the transmit antenna in 
> resonance, the signal levels are 10 dB higher then with a de-resonated 
> antenna. So there is definitely a coupling between then. HOWEVER the S/N 
> is much better when the transmit antenna is out of resonance. This can 
> clearly be heared because i'm using a medium fast AGC now (USR file of my 
> last mail), so the lower audio levels become compensated. But the QRN is 
> very clearly louder than the background noise. So there is a receive 
> improvement (in this location) when the transmit antenna is out of 
> resonance! Now, the higher local QRM could be produced in the first amp 
> stage of the active antenna or is could come from the transmit antenna 
> itselfe. So i have connected the receiver to the transmit antenna and used 
> a switchable attenuator in series and set about to the same signal level. 
> The RX and netbook was running on batteries during the test. When 
> comparing these results (small active E field antenna versus large 
> transmit antenna) the S/N (e.g. of IQ2MI) of the small antenna is clearly 
> higher! In other words, the MF earth seems to be contaminated by QRM!
>
> That means my receive sensitivity is another important step better than a 
> few days ago...
>
> 73, Stefan/DK7FC
>
> Am 20.06.2012 02:17, schrieb pa3abk:
>> Stefan,
>>
>> Just be sure that the TX antenna is not coupled to the E-probe. ( De-tune 
>> the system when you check it)
>> I'm mostly listening on my TX antenna, the E-probe is only a few meters 
>> away. These two interact in such that the E-probe is just a bufferamp of 
>> the main aerial.
>>
>> To give you an idea how  heavy this is: With a portable (AWP20 AKAI) I 
>> can enjoy MF in the toilet and bathroom providing the radio is near the 
>> waterworks and  TX aerial is tuned.
>>
>> IQ2MI is "good" beacon, just before sunset it manifest itself here and 
>> build up to S-6 during midnight. During the winter you can enjoy it the 
>> whole day.
>> I
>> FYI sometimes during clubevenings  (Tuesdays?) it comes "live" with CQ. 
>> But assume they will not listen on 477 :-(
>>
>> Checked Meteox, during our QSO a heavy thunderstorm was over your QTH, it 
>> moved away and lost a lot of it's activity.
>> Just to advise you that  you shouldn't misinterpret your observations.
>>
>> Jan/pa3abk
>>
>>
>> NNNN
>>
>>
>> On 20-6-2012 1:29, Stefan Schäfer wrote:
>>> MF,
>>>
>>> I took the QRSS/CW beacon signal from IQ2MI as the test signal. It was 
>>> very well audible here, R5. It was interesting to see the deep QSB. 
>>> Both, my small active antenna and the transmit antenna show the same S/N 
>>> but maybe it would be useful to use a antenna switch to compare the S/N 
>>> without having a time delay (changing the antenna cables), due to the 
>>> QSB...
>>>
>>> 73s..
>>>
>>> Am 20.06.2012 00:44, schrieb Stefan Schäfer:
>>>> Rik, MF,
>>>>
>>>> Right now i'm testing the TX antenna as a RX antenna. This works much 
>>>> better than expected. A 10 dB attenuator is needed but no problem. 
>>>> Maybe you can give me a test signal again on 502 kHz, or someone else?
>>>>
>>>> It looks like the QRN is much lower on that antenna. That means that 
>>>> many of the crashes during my CQ calls have been charged rain drops 
>>>> that were falling on the E field probe, just my guess.
>>>>
>>>> I will listen another 20 min. on 502 kHz and apprechiate any test 
>>>> signals from amateurs.
>>>>
>>>> 73, Stefan
>>>>
>>>>
>>>
>>>
>>
>>
>