Return-Path: X-Spam-DCC: paranoid 1102; Body=2 Fuz1=2 Fuz2=2 X-Spam-Checker-Version: SpamAssassin 3.1.3 (2006-06-01) on lipkowski.org X-Spam-Level: X-Spam-Status: No, score=-0.2 required=5.0 tests=BAYES_00,DNS_FROM_AHBL_RHSBL, HTML_40_50,HTML_MESSAGE,RATWARE_GECKO_BUILD,SPF_PASS autolearn=no version=3.1.3 Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by paranoid.lipkowski.org (8.13.7/8.13.7) with ESMTP id u3HGRd4I000602 for ; Sun, 17 Apr 2016 18:27:51 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1aroUp-0007ka-6I for rs_out_1@blacksheep.org; Sun, 17 Apr 2016 16:20:23 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1aroUo-0007kR-L5 for rsgb_lf_group@blacksheep.org; Sun, 17 Apr 2016 16:20:22 +0100 Received: from mout01.posteo.de ([185.67.36.65]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.87) (envelope-from ) id 1aroUm-0006En-MS for rsgb_lf_group@blacksheep.org; Sun, 17 Apr 2016 16:20:21 +0100 Received: from dovecot03.posteo.de (dovecot03.posteo.de [172.16.0.13]) by mout01.posteo.de (Postfix) with ESMTPS id A4350209D8 for ; Sun, 17 Apr 2016 17:20:17 +0200 (CEST) Received: from mail.posteo.de (localhost [127.0.0.1]) by dovecot03.posteo.de (Postfix) with ESMTPSA id 3qnw292DMnz5vMp for ; Sun, 17 Apr 2016 17:20:17 +0200 (CEST) Message-ID: <5713A9B1.30803@posteo.de> Date: Sun, 17 Apr 2016 17:20:17 +0200 From: DK7FC User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.1; de; rv:1.9.1.8) Gecko/20100227 Thunderbird/3.0.3 MIME-Version: 1.0 To: rsgb_lf_group@blacksheep.org References: <8D366B751B0C760-1FCC-66CCB4@webmail-vm012.sysops.aol.com> <579355A36AEE9D4FA555C45D556003AB53B6D0A7@servigilant.vigilant.local> In-Reply-To: <579355A36AEE9D4FA555C45D556003AB53B6D0A7@servigilant.vigilant.local> X-Scan-Signature: c1dcf088149efa0360827745859da381 Subject: Re: LF: TXing on VLF again, Iron powder cores... broomstick coil? Content-Type: multipart/alternative; boundary="------------020100080600040807020800" X-SA-Exim-Scanned: Yes Sender: owner-rsgb_lf_group@blacksheep.org Precedence: bulk Reply-To: rsgb_lf_group@blacksheep.org X-Listname: rsgb_lf_group X-SA-Exim-Rcpt-To: rs_out_1@blacksheep.org X-SA-Exim-Scanned: No; SAEximRunCond expanded to false X-Scanned-By: MIMEDefang 2.56 on 10.1.3.11 Status: O X-Status: X-Keywords: X-UID: 7763 This is a multi-part message in MIME format. --------------020100080600040807020800 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 8bit Hi Luis, Am 17.04.2016 17:02, schrieb VIGILANT Luis Fernández: > That gives me 204pF when calculated That sounds real. > > Have been playing adding small ferrite inductances to see if that > matches the calculations > I ended adding 5x100mH + 5x68mH + 5x47mH. A total of 1075mH plus 6,9mH > of the other coils > Then found the resonance at 10800Hz. Very bad SWR, high Z and minimum > bandwith but the angle > of Zs can be seen chaging at this frequency. That matches the 205pF > value, so it must be about that Oh, i see on which band you want to end :-) > > As Stefan said, I would need to increase capacity. So far I'm using > two 11m sloppers from top of the antenna > Can extend them to about 15m leaving 5m of rope to the supporting pvc > pipe. Not easy to add sloppers in other > directions. They would be short and in high angle. What I can do is > connecting the ends of the two sloppers > forming an horizontal arc following the building perimeter. Something > like half the horizontal loop I had last > year. Don't know if that will be a good idea or not, looking to > increase capacity That is the best idea if you want to get a high radiation resistance. Installing 4 towers in the corners of the building, hanging up a horizontal loop with the perimeter of the building and then using this loop as a capacitive top load for the vertical feed wire! If you can do that, it is the best solution you can get on the roof, if a kite or a wire to the other building is not possible. > > Getting down a couple of KHz there is HARD ! ........ just as Stefan > explained ! :( > But I'm sure it really worth the effort Yes. First you need a RX in your remote location, then you can start with veeeeery low power to see a faint trace on your own receiver :-) > > BTW: I'm using Shark110 for my measures and this reach down lo 10KHz. > I asked in the Google forum if > there is any possibility to get it usable at 8KHz. Overnight, Melchor > EA4FRB answered with an experimental > firmware version which works down to 7KHz ! :-) You can use an amperemeter for 100uA and a bridge rectifier in series to the antenna to measure the current. Resonance is at the highest current. Or, you could use a notebook with a short wire connected to the mic input, run SpecLab and slowly turn the frequency from 0...24 kHz, so you can see where the voltage across the antenna is maximum. This is resonance too... 73, Stefan --------------020100080600040807020800 Content-Type: text/html; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Hi Luis,

Am 17.04.2016 17:02, schrieb VIGILANT Luis Fernández:
That gives me 204pF when calculated
That sounds real.

Have been playing adding small ferrite inductances to see if that matches the calculations
I ended adding 5x100mH + 5x68mH + 5x47mH. A total of 1075mH plus 6,9mH of the other coils
Then found the resonance at 10800Hz. Very bad SWR, high Z and minimum bandwith but the angle
of Zs can be seen chaging at this frequency. That matches the 205pF value, so it must be about that
Oh, i see on which band you want to end :-)

As Stefan said, I would need to increase capacity. So far I'm using two 11m sloppers from top of the antenna
Can extend them to about 15m leaving 5m of rope to the supporting pvc pipe. Not easy to add sloppers in other
directions. They would be short and in high angle. What I can do is connecting the ends of the two sloppers 
forming an horizontal arc following the building perimeter. Something like half the horizontal loop I had last
year. Don't know if that will be a good idea or not, looking to increase capacity
That is the best idea if you want to get a high radiation resistance. Installing 4 towers in the corners of the building, hanging up a horizontal loop with the perimeter of the building and then using this loop as a capacitive top load for the vertical feed wire!
If you can do that, it is the best solution you can get on the roof, if a kite or a wire to the other building is not possible.

Getting down a couple of KHz there is HARD ! ........  just as Stefan explained ! :(
But I'm sure it really worth the effort
Yes. First you need a RX in your remote location, then you can start with veeeeery low power to see a faint trace on your own receiver :-)


BTW: I'm using Shark110 for my measures and this reach down lo 10KHz. I asked in the Google forum if
there is any possibility to get it usable at 8KHz. Overnight, Melchor EA4FRB answered with an experimental
firmware version which works down to 7KHz ! :-)
You can use an amperemeter for 100uA and a bridge rectifier in series to the antenna to measure the current. Resonance is at the highest current.
Or, you could use a notebook with a short wire connected to the mic input, run SpecLab and slowly turn the frequency from 0...24 kHz, so you can see where the voltage across the antenna is maximum. This is resonance too...

73, Stefan
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