Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-mp01.r1000.mx.aol.com (Internet Inbound) with ESMTP id C6EE2380000CD; Wed, 10 Aug 2011 13:29:40 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QrCaE-0003gr-3B for rs_out_1@blacksheep.org; Wed, 10 Aug 2011 18:28:46 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QrCaD-0003gi-1W for rsgb_lf_group@blacksheep.org; Wed, 10 Aug 2011 18:28:45 +0100 Received: from mail-iy0-f173.google.com ([209.85.210.173]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QrCaB-000516-67 for rsgb_lf_group@blacksheep.org; Wed, 10 Aug 2011 18:28:45 +0100 Received: by iyk2 with SMTP id 2so2595678iyk.4 for ; Wed, 10 Aug 2011 10:28:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type; bh=vJCwykrSmf7E2He8wQLIJVcsmWnBuJe9cjjeXAHFYsQ=; b=ig8IU+cgnofqqR0Mc2CSBhOR6AmljY1jQHgV1+5fpJ4OyEYqFO5nkIGUeVGsfdbsbc Z2YLIC+vXpVw1lxz4CrK0W2Sqplbnl5Ef54TcdCWhRbo+0fIfr8dPy3wQg1koTQk5t0D GPwZlNyyg6BpRAL4Ojwa6ZgJR/fPTMvLPGOUE= MIME-Version: 1.0 Received: by 10.231.117.132 with SMTP id r4mr6162574ibq.71.1312997316835; Wed, 10 Aug 2011 10:28:36 -0700 (PDT) Received: by 10.231.206.139 with HTTP; Wed, 10 Aug 2011 10:28:36 -0700 (PDT) In-Reply-To: <004e01cc5780$a98a3820$0401a8c0@xphd97xgq27nyf> References: <4E418609.6020500@iup.uni-heidelberg.de> <67A6F7BF45BF4A0193A3DCB53000A283@PcMinto> <008401cc56ce$2f1fb2c0$0401a8c0@xphd97xgq27nyf> <12C475F3F4C84B818461753F2E8A60A6@PcMinto> <4E41AECB.90808@iup.uni-heidelberg.de> <8D68749D37B94275855FDBA46A3F6C97@PcMinto> <4E427DFB.50801@iup.uni-heidelberg.de> <0FA38FC9F88F41738D007D00C0B66503@PcMinto> <002e01cc5772$40601a30$0401a8c0@xphd97xgq27nyf> <09706552FC574901BA413DC5295F48F5@AGB> <004e01cc5780$a98a3820$0401a8c0@xphd97xgq27nyf> Date: Wed, 10 Aug 2011 18:28:36 +0100 Message-ID: From: Andy Talbot To: rsgb_lf_group@blacksheep.org X-Spam-Score: 0.0 (/) X-Spam-Report: autolearn=disabled,HTML_MESSAGE=0.001 Subject: Re: LF: Re: Re: HB9ASB... Content-Type: multipart/alternative; boundary=001636eeed27a93a2d04aa2a023d X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.0 required=5.0 tests=HTML_MESSAGE autolearn=no version=2.63 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-aol-global-disposition: G X-AOL-SCOLL-SCORE: 0:2:498033952:93952408 X-AOL-SCOLL-URL_COUNT: 0 X-AOL-SCOLL-AUTHENTICATION: mail_rly_antispam_dkim-d013.1 ; domain : gmail.com DKIM : pass x-aol-sid: 3039ac1dc1454e42c0047e29 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none --001636eeed27a93a2d04aa2a023d Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable Not if the link-Tx is built into the same housing as the head amplifier and a battery is used for power. Then the antenan can only work against its own mast / mounting-point. THAT is the counterpoise; or as I prefer to think about it, the other element of the dipole antenna. (See my previous posting) RF linking is a near-perfect solution as far as local QRM is concerned. Linearity, a different matter perhaps. Andy www.g4jnt.com On 10 August 2011 18:12, mal hamilton wrote: > ** > Graham > Of course there is a FEEDER to the RX at the remote site before it is > relayed via a radio link. > As explained the feeder is the main element for signal es noise pickup. I= f > there was no feeder to act as the other main element there would be no > signal pick up at all because the 10 mm probe element would pick nothing > up. > G3KEV > > > ----- Original Message ----- > *From:* Graham > *To:* rsgb_lf_group@blacksheep.org > *Sent:* Wednesday, August 10, 2011 5:23 PM > *Subject:* Re: LF: Re: Re: HB9ASB... > > Im sure one station uses a battery and radio link from the > probe Ae so no feeder ? > > G. > > *From:* mal hamilton > *Sent:* Wednesday, August 10, 2011 4:29 PM > *To:* rsgb_lf_group@blacksheep.org > *Subject:* LF: Re: Re: HB9ASB... > > This miniwhip/probe seems to be a very complicated antenna and difficult = to > explain its properties. > I suggest someone takes this antenna out into the middle of a field away > from any noise source and work out how it actualljy performs. > because using it in a noisy environment at various heights in different > locations introduces too many variables for accurate evaluation. > A random simple piece of wire with a suitable preamp and a counterpoise > would probably work better. > Decca used a metal barrell probe and preamp at their RX stations maybe > someone knows how they performed, although their sites were in a rural qu= iet > environment. > The argument at present about this type of antenna needs to be concentrat= ed > on actual performance and not about environmental LOCATION, move it up or > down a bit, use longer feed line, get it above the roof etc, Earth the ou= ter > braid before it enters the shack, use an isolation transformer. > Let us have your observations. > de mal/g3kev > > > ----- Original Message ----- > *From:* Minto Witteveen > *To:* rsgb_lf_group@blacksheep.org > *Sent:* Wednesday, August 10, 2011 4:01 PM > *Subject:* LF: Re: HB9ASB... > > Hi Stefan,**** > > Some comments:**** > > *I think the mechanism is that the unwanted signal on the screen causes a > potential difference between gate and source of the first (J)FET. So > this causes a current flow in the output stage and so a signal at the RX > input.* > > I fail to see how that could be the main cause=85 because cutting the pow= er > to the miniwhip should then eliminate the QRM, but it does not! It probab= ly > attributes somewhat - only some 10-15 dB, but that leaves 9+20 dB for > another explanation. (i.e. my balanced-unbalanced hypothesis) **** > > *It would almost have the same effect (when ignoring the C between cable > and ground along to the choke near the antenna ground) as placing the > choke near the antenna ground, both are in series and increase the > current reducing impedance, yes...* > > But I have to disagree. A choke (only) at the TX would accomplish nothing > (in fact it may even make it worse). With a choke at the RX end the coax > will =96 acting as an antenna - still pick up all kinds of noise in the h= ouse, > and this get transported via the outside of the coax to the miniwhip. > Placing the chocke+ground near the miniwhip will on the other hand attenu= ate > all the noise that is picked up along the coax. > An (additional) choke at the RX end _might_ make things worse at LF becau= se > in that case the noise will not be bled to earth there, with the result t= hat > the overall noise voltage on the outside might be still higher.**** > > *Hm, i rather expect a galvanic coupling i.e. stray currenty on the > supply cable of the RX. What happens if you run the RX on batteries? The > same dependency?* > > Running the 817 on batteries makes no difference. And galvanic coupling i= s > unlikely because the QRM completely disappears when I disconnect the coax= in > the shack=85. And the coax is not connected to anything else up to the > miniwhip. > As for the necessity of a current balun or common mode choke when going > form unbalanced to balanced: picture a classic dipole fed by coax. (TX) > current runs through the center conductor. Kirchofs law states that the s= ame > current must flow in the other direction (on the inside of the braid). No= w > at the dipole the current from the center conductor only has one way to g= o: > into 1 half of the dipole. But the current on the inside of the braid has > two paths: into the second half of the dipole AND into the outer side of = the > braid. The actual distribution is determined by the relative impedances > these two other halves of the dipole have at the specific frequency. Ente= r > the choke, which effectively blocks the path to the outer side of the bra= id. > The same mechanism is true for reception.**** > > *Today it's nice WX here! And in NL?* > > What can I say=85 at least it isn=92t raining today. But unfortunately I = have > other duties (QRL)**** > > Overall an interesting discussion!! I am curious if there are any other > (competing) theories J**** > > **** > > Regards, > Minto pa3bca**** > > Hi Minto, > > Am 10.08.2011 13:10, schrieb Minto Witteveen: > > Hi Stefan, (et al) > > > > Well I beg to differ.. :-) > > What I think happens is this: The outside of the coax picks up > > electromagnetic radiation like any antenna (including QRM generated by > > fluorescent lamps and Alinco switching power supplies). This signal > > travels along the coax to the Miniwhip. (also in the direction of the > > receiver but that is not important here as the signal is on the > > outside of the coax). > > Upon arrival at the miniwhip this signal on the outside of the coax > > has nowhere to go =ADbut to the _inside_ of the outer mantle of the coa= x > > =96 it =91rounds the corner=92 at the end of the coax so to speak. > I think the mechanism is that the unwanted signal on the screen causes a > potential difference between gate and source of the first (J)FET. So > this causes a current flow in the output stage and so a signal at the RX > input. > A common mode choke between RX and the antenna ground should form a low > pass filter for unwanted signals coming from the shack. Using a common > mode choke without a local ground should have little effect, except the > coax is some 100m long (between choke and probe) ;-) > > Ah BTW regarding the discussion "the cable to the E field probe is the > actual antenna": One could just try what happens if one disconnects the > power supply. If the signal is still present then the cable is the > antenna, if the signal is gone: The probe must be the antenna. Isn't > it?! :-) > > > > So how to avoid the QRM that is picked up by the coax to =91travel back= =92 > > via the inside: for the miniwhip it is indeed best (as Roelof > > mentioned) to short these signals to earth _outside_ the house, > > preferably as close to the miniwhip as possible. Grounding there would > > to the trick, aided by a (large enough) common mode choke between the > > ground point and the house. The QRM that is picked up in the house > > would be =96 after attenuation by the choke - directed into the ground > > and not up into the pole and the miniwhip. > > Yes yes, totally agreed. > > Whatever happens in the house would then be largely irrelevant. Adding > > a common mode choke close to the rig will do little extra. (it would > > only attenuate QRM getting from the shack=92s earth system to the > > outside of the coax). > It would almost have the same effect (when ignoring the C between cable > and ground along to the choke near the antenna ground) as placing the > choke near the antenna ground, both are in series and increase the > current reducing impedance, yes... > > > Any signals picked up by the vertical coax between the earthing point > > and the whip will add to the received signal, but at low frequencies > > it will not be much. > > So far for theory. Now the proof of the pudding: DCF39 is now > S9+40 > > dB. My old trusty QRM generator (Alinco SMPS) generates S9+25 at > > 135.500. When I switch off the miniwhip (cut the power) DCF39 drops > > down to just above the noise floor. As expected. > Ah yes, that's what i meant above (should have read your mail completely > before answering ;-) ). This is the proof that Mal cannot be right when > saying "the coax is the actual antenna". > > But the Alinco signal only drops down some 15 dB and remains the only > > signal that is audible. This is exactly what I would expect: the QRM > > travels along the outside of the coax to the miniwhip, =91rounds the > > corner=92 and comes back via the inside of the coax shield. Further > > proof that it indeed takes this route: if I disconnect the coax in the > > shack the Alinco smps signal disappears also (so it is not received > > via any other path). > Hm, i rather expect a galvanic coupling i.e. stray currenty on the > supply cable of the RX. What happens if you run the RX on batteries? The > same dependency? > There could be several reasons apply here... > > > Last year I already bought 3 meters of copper pipe to drive into the > > ground in the backyard. Bet never got around to finish the job=85 > Today it's nice WX here! And in NL? > > > > The main reason the signal strength is much higher with the elevated > > miniwhip is (I think) caused by the fact that I am surrounded by other > > houses, gardens, trees etc. Not comparable with an open field=85 > Yes. > > 73, Stefan /DK7FC > > > **** > > > > --001636eeed27a93a2d04aa2a023d Content-Type: text/html; charset=windows-1252 Content-Transfer-Encoding: quoted-printable
Not if the link-Tx is built into the same housing as the head amplifie= r and a battery is used for power.=A0=A0 Then the antenan can only work aga= inst its own mast /=A0mounting-point. THAT is the counterpoise;=A0 or as I = prefer to think about it, the other element of the dipole antenna.=A0=A0(Se= e my previous posting)
=A0
RF linking is a near-perfect solution as far as local QRM is concerned= .=A0=A0 Linearity, a different matter perhaps.
=A0
Andy


=A0
On 10 August 2011 18:12, mal hamilton <g3kevmal@talktalk.net= > wrote:
Graham
Of course there is a FEEDER to the RX at the remo= te site before it is relayed via a radio link.
As explained the feeder is the main element for s= ignal es noise pickup. If there was no feeder to act as the other main=A0el= ement there would be no signal pick up at all because the 10 mm probe eleme= nt =A0would pick nothing up.
G3KEV
=A0
----- Original Message -----
From: Graham
Sent: Wednesday, August 10, 2011 5:2= 3 PM
Subject: Re: LF: Re: Re: HB9ASB...

Im sure=A0 one=A0 station=A0=A0 uses a= =A0=A0 battery=A0 and=A0 radio=A0 link=A0 from the=A0=A0 probe=A0 Ae=A0=A0 = so=A0 no=A0 feeder=A0 ?
=A0
G.

Sent: Wednesday, August 10, 2011 4:29 PM
Subject: LF: Re: Re: HB9ASB...

This miniwhip/probe seems to be a very complicate= d antenna and difficult to explain its properties.
I suggest someone takes this antenna out into the= middle of a field away from any noise source and work out how it actualljy= performs.
because using it in a noisy environment at variou= s heights in different locations introduces too many variables for accurate= evaluation.
A random simple=A0piece of wire with a suitable p= reamp and a counterpoise would probably work better.
Decca used a metal=A0barrell probe and preamp at = their RX stations maybe someone knows how they performed, although their si= tes were in a rural quiet environment.
The argument at present about this type of antenn= a=A0needs=A0to be concentrated on actual performance and not about environm= ental LOCATION, move it up or down a bit, use longer feed line, get it abov= e the roof etc, Earth the outer braid before it enters the shack,=A0use an = isolation transformer.=A0
Let us have your observations.
de mal/g3kev
=A0
----- Original Message -----
Sent: Wednesday, August 10, 2011 4:0= 1 PM
Subject: LF: Re: HB9ASB...

Hi Stefan,<= /u>

Some comments:=

I think the = mechanism is that the unwanted signal on the screen causes a
potential = difference between gate and source of the first (J)FET. So
this causes = a current flow in the output stage and so a signal at the RX
input.

I fail to see how tha= t could be the main cause=85 because cutting the power to the miniwhip shou= ld then eliminate the QRM, but it does not! It probably attributes somewhat= - =A0only some 10-15 dB, but that leaves =A09+20= dB for another explanation. (i.e. my balanced-unbalanced hypothesis)

It would alm= ost have the same effect (when ignoring the C between cable
and ground = along to the choke near the antenna ground) as placing the
choke near t= he antenna ground, both are in series and increase the
current reducing impedance, yes...

But I have to disagre= e. A choke (only) at the TX would accomplish nothing (in fact it may even m= ake it worse). With a choke at the RX end the coax will =96 acting as an an= tenna - still pick up all kinds of noise in the house, and this get transpo= rted via the outside of the coax to the miniwhip. Placing the chocke+ground= near the miniwhip will on the other hand attenuate all the noise that is p= icked up along the coax.
An (additional) choke at the RX end _might_ make things worse at LF because= in that case the noise will not be bled to earth there, with the result th= at the overall noise voltage on the outside might be still higher.

Hm, i rather= expect a galvanic coupling i.e. stray currenty on the
supply cable of = the RX. What happens if you run the RX on batteries? The
same dependenc= y?

Running the 817 on ba= tteries makes no difference. And galvanic coupling is unlikely because the = QRM completely disappears when I disconnect the coax in the shack=85. And t= he coax is not connected to anything else up to the miniwhip.
As for the necessity of a current balun or common mode choke when going for= m unbalanced to balanced:=A0 picture a classic dipole fed by c= oax. (TX) current runs through the center conductor. Kirchofs law states th= at the same current must flow in the other direction (on the inside of the = braid). Now at the dipole the current from the center conductor only has on= e way to go: into 1 half of the dipole. But the current on the inside of th= e braid has two paths: into the second half of the dipole AND into the oute= r side of the braid. The actual distribution is determined by the relative = impedances these two other halves of the dipole have at the specific freque= ncy. Enter the choke, which effectively blocks the path to the outer side o= f the braid. The same mechanism is true for reception.

Today it'= ;s nice WX here! And in NL?

What can I say=85 at = least it isn=92t raining today. But unfortunately I have other duties (QRL)=

Overall an interestin= g discussion!! I am curious if there are any other (competing) theories J

=A0

Regards,
Minto pa3= bca

Hi Minto,

Am 1= 0.08.2011 13:10, schrieb Minto Witteveen:
> Hi Stefan, (et al)
>= ;
> Well I beg to differ.. :-)
> What I think happens is this: = The outside of the coax picks up
> electromagnetic radiation like any antenna (including QRM generated by=
> fluorescent lamps and Alinco switching power supplies). This sign= al
> travels along the coax to the Miniwhip. (also in the direction = of the
> receiver but that is not important here as the signal is on the
&g= t; outside of the coax).
> Upon arrival at the miniwhip this signal o= n the outside of the coax
> has nowhere to go =ADbut to the _inside_= of the outer mantle of the coax
> =96 it =91rounds the corner=92 at the end of the coax so to speak.
= I think the mechanism is that the unwanted signal on the screen causes a potential difference between gate and source of the first (J)FET. So
= this causes a current flow in the output stage and so a signal at the RX input.
A common mode choke between RX and the antenna ground should form= a low
pass filter for unwanted signals coming from the shack. Using a = common
mode choke without a local ground should have little effect, exc= ept the
coax is some 100m long (between choke and probe) ;-)

Ah BTW regardin= g the discussion "the cable to the E field probe is the
actual ant= enna": One could just try what happens if one disconnects the
power supply. If the signal is still present then the cable is the
ante= nna, if the signal is gone: The probe must be the antenna. Isn't
it= ?! :-)


> So how to avoid the QRM that is picked up by the coa= x to =91travel back=92
> via the inside: for the miniwhip it is indeed best (as Roelof
>= mentioned) to short these signals to earth _outside_ the house,
> p= referably as close to the miniwhip as possible. Grounding there would
> to the trick, aided by a (large enough) common mode choke between the =
> ground point and the house. The QRM that is picked up in the house=
> would be =96 after attenuation by the choke - directed into the g= round
> and not up into the pole and the miniwhip.

Yes yes, totally agr= eed.
> Whatever happens in the house would then be largely irrelevant= . Adding
> a common mode choke close to the rig will do little extra= . (it would
> only attenuate QRM getting from the shack=92s earth system to the
= > outside of the coax).
It would almost have the same effect (when ig= noring the C between cable
and ground along to the choke near the anten= na ground) as placing the
choke near the antenna ground, both are in series and increase the
curr= ent reducing impedance, yes...

> Any signals picked up by the ver= tical coax between the earthing point
> and the whip will add to the= received signal, but at low frequencies
> it will not be much.
> So far for theory. Now the proof of the p= udding: DCF39 is now > S9+40
> dB. My old trusty QRM generator (A= linco SMPS) generates S9+25 at
> 135.500. When I switch off the mini= whip (cut the power) DCF39 drops
> down to just above the noise floor. As expected.
Ah yes, that's= what i meant above (should have read your mail completely
before answe= ring ;-) ). This is the proof that Mal cannot be right when
saying &quo= t;the coax is the actual antenna".
> But the Alinco signal only drops down some 15 dB and remains the only =
> signal that is audible. This is exactly what I would expect: the Q= RM
> travels along the outside of the coax to the miniwhip, =91round= s the
> corner=92 and comes back via the inside of the coax shield. Further > proof that it indeed takes this route: if I disconnect the coax in t= he
> shack the Alinco smps signal disappears also (so it is not rece= ived
> via any other path).
Hm, i rather expect a galvanic coupling i.e. s= tray currenty on the
supply cable of the RX. What happens if you run th= e RX on batteries? The
same dependency?
There could be several reaso= ns apply here...

> Last year I already bought 3 meters of copper pipe to drive into t= he
> ground in the backyard. Bet never got around to finish the job= =85
Today it's nice WX here! And in NL?
>
> The main rea= son the signal strength is much higher with the elevated
> miniwhip is (I think) caused by the fact that I am surrounded by other=
> houses, gardens, trees etc. Not comparable with an open field=85<= br>Yes.

73, Stefan /DK7FC





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