Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dh04.r1000.mx.aol.com (Internet Inbound) with ESMTP id ED9863800011D; Wed, 10 Aug 2011 13:45:20 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QrCoQ-0003nx-Cy for rs_out_1@blacksheep.org; Wed, 10 Aug 2011 18:43:26 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QrCoP-0003no-6T for rsgb_lf_group@blacksheep.org; Wed, 10 Aug 2011 18:43:25 +0100 Received: from out1.ip09ir2.opaltelecom.net ([62.24.128.245]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QrCoN-0005IE-9v for rsgb_lf_group@blacksheep.org; Wed, 10 Aug 2011 18:43:25 +0100 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: Au0AAInCQk5Ok8U0/2dsb2JhbABCgk2RIAOEAI9FeIE7BQEBBAEIAQEDPA0CDQ8KBgEBAwUCAQMRBAEBChcOFAEEGgYWCAYTCgECAgEBCodTAr5zhkYEglCaKoZ9 X-IronPort-AV: E=Sophos;i="4.67,351,1309734000"; d="scan'208,217";a="487046794" Received: from host-78-147-197-52.as13285.net (HELO xphd97xgq27nyf) ([78.147.197.52]) by out1.ip09ir2.opaltelecom.net with SMTP; 10 Aug 2011 18:43:17 +0100 Message-ID: <006601cc5784$f636d530$0401a8c0@xphd97xgq27nyf> From: "mal hamilton" To: 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 18:42:56 +0100 MIME-Version: 1.0 X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 6.00.2600.0000 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2600.0000 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="----=_NextPart_000_0063_01CC578D.523768B0" 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: 0:2:499723264:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d41184e42c3b015b7 X-AOL-IP: 195.171.43.25 X-AOL-SPF: domain : blacksheep.org SPF : none This is a multi-part message in MIME format. ------=_NextPart_000_0063_01CC578D.523768B0 Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Andy Highly unlikely that the link-tx is in the same box, even so the other = element as u say would be the the mast/mounting and that could be say 20 = plus feet, just as bad as the feeder senario!! g3kev ----- Original Message -----=20 From: Andy Talbot=20 To: rsgb_lf_group@blacksheep.org=20 Sent: Wednesday, August 10, 2011 6:28 PM Subject: Re: LF: Re: Re: HB9ASB... 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 =20 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. If 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 -----=20 From: Graham=20 To: rsgb_lf_group@blacksheep.org=20 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=20 Sent: Wednesday, August 10, 2011 4:29 PM To: rsgb_lf_group@blacksheep.org=20 Subject: LF: Re: Re: HB9ASB... This miniwhip/probe seems to be a very complicated antenna and = difficult to explain its properties.=20 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 quiet environment.=20 The argument at present about this type of antenna needs to be = concentrated 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 outer braid before it enters the shack, use an isolation = transformer.=20 Let us have your observations. de mal/g3kev ----- Original Message -----=20 From: Minto Witteveen=20 To: rsgb_lf_group@blacksheep.org=20 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=20 potential difference between gate and source of the first = (J)FET. So=20 this causes a current flow in the output stage and so a signal = at the RX=20 input. I fail to see how that could be the main cause=85 because = cutting the power to the miniwhip should then eliminate the QRM, but it = does not! It probably attributes somewhat - only some 10-15 dB, but = that leaves 9+20 dB for another explanation. (i.e. my = balanced-unbalanced hypothesis)=20 It would almost have the same effect (when ignoring the C = between cable=20 and ground along to the choke near the antenna ground) as = placing the=20 choke near the antenna ground, both are in series and increase = the=20 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 house, 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 attenuate all the noise that is picked 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 that the overall noise voltage on the outside might be still = higher. Hm, i rather expect a galvanic coupling i.e. stray currenty on = the=20 supply cable of the RX. What happens if you run the RX on = batteries? The=20 same dependency? Running the 817 on batteries makes no difference. And galvanic = coupling is 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.=20 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 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 one way to go: 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. Enter the choke, = which effectively blocks the path to the outer side of 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 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=20 > fluorescent lamps and Alinco switching power supplies). This = signal=20 > travels along the coax to the Miniwhip. (also in the direction = of the=20 > receiver but that is not important here as the signal is on = the=20 > outside of the coax). > Upon arrival at the miniwhip this signal on the outside of the = coax=20 > has nowhere to go =ADbut to the _inside_ of the outer mantle = of the coax=20 > =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=20 potential difference between gate and source of the first = (J)FET. So=20 this causes a current flow in the output stage and so a signal = at the RX=20 input. A common mode choke between RX and the antenna ground should = form a low=20 pass filter for unwanted signals coming from the shack. Using a = common=20 mode choke without a local ground should have little effect, = except the=20 coax is some 100m long (between choke and probe) ;-) Ah BTW regarding the discussion "the cable to the E field probe = is the=20 actual antenna": One could just try what happens if one = disconnects the=20 power supply. If the signal is still present then the cable is = the=20 antenna, if the signal is gone: The probe must be the antenna. = Isn't=20 it?! :-) > So how to avoid the QRM that is picked up by the coax to = =91travel back=92=20 > via the inside: for the miniwhip it is indeed best (as Roelof=20 > mentioned) to short these signals to earth _outside_ the = house,=20 > preferably as close to the miniwhip as possible. Grounding = there would=20 > to the trick, aided by a (large enough) common mode choke = between the=20 > ground point and the house. The QRM that is picked up in the = house=20 > would be =96 after attenuation by the choke - directed into = the ground=20 > and not up into the pole and the miniwhip. Yes yes, totally agreed. > Whatever happens in the house would then be largely = irrelevant. Adding=20 > a common mode choke close to the rig will do little extra. (it = would=20 > only attenuate QRM getting from the shack=92s earth system to = the=20 > outside of the coax). It would almost have the same effect (when ignoring the C = between cable=20 and ground along to the choke near the antenna ground) as = placing the=20 choke near the antenna ground, both are in series and increase = the=20 current reducing impedance, yes... > Any signals picked up by the vertical coax between the = earthing point=20 > and the whip will add to the received signal, but at low = frequencies=20 > it will not be much. > So far for theory. Now the proof of the pudding: DCF39 is now = > S9+40=20 > dB. My old trusty QRM generator (Alinco SMPS) generates S9+25 = at=20 > 135.500. When I switch off the miniwhip (cut the power) DCF39 = drops=20 > down to just above the noise floor. As expected. Ah yes, that's what i meant above (should have read your mail = completely=20 before answering ;-) ). This is the proof that Mal cannot be = right when=20 saying "the coax is the actual antenna". > But the Alinco signal only drops down some 15 dB and remains = the only=20 > signal that is audible. This is exactly what I would expect: = the QRM=20 > travels along the outside of the coax to the miniwhip, = =91rounds the=20 > corner=92 and comes back via the inside of the coax shield. = Further=20 > proof that it indeed takes this route: if I disconnect the = coax in the=20 > shack the Alinco smps signal disappears also (so it is not = received=20 > via any other path). Hm, i rather expect a galvanic coupling i.e. stray currenty on = the=20 supply cable of the RX. What happens if you run the RX on = batteries? The=20 same dependency? There could be several reasons apply here... > Last year I already bought 3 meters of copper pipe to drive = into the=20 > 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=20 > miniwhip is (I think) caused by the fact that I am surrounded = by other=20 > houses, gardens, trees etc. Not comparable with an open = field=85 Yes. 73, Stefan /DK7FC ------=_NextPart_000_0063_01CC578D.523768B0 Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable
Andy
Highly unlikely that the link-tx is in the same = box, even=20 so the other element as u say would be the the mast/mounting and that = could be=20 say 20 plus feet,  just as bad as the feeder senario!!
g3kev
 
----- Original Message -----
From:=20 Andy=20 Talbot
Sent: Wednesday, August 10, = 2011 6:28=20 PM
Subject: Re: LF: Re: Re: = HB9ASB...

Not if the link-Tx is built into the same housing as the head = amplifier=20 and a battery is used for power.   Then the antenan can only = work=20 against its own mast / mounting-point. THAT is the = counterpoise;  or=20 as I prefer to think about it, the other element of the dipole=20 antenna.  (See my previous posting)
 
RF linking is a near-perfect solution as far as local QRM is=20 concerned.   Linearity, a different matter perhaps.
 
Andy


 
On 10 August 2011 18:12, mal hamilton <g3kevmal@talktalk.net>=20 wrote:
Graham
Of course there is a FEEDER to the RX at the = remote=20 site before it is relayed via a radio link.
As explained the feeder is the main element = for signal=20 es noise pickup. If there was no feeder to act as the other=20 main element there would be no signal pick up at all because = the 10 mm=20 probe element  would pick nothing up.
G3KEV
 
----- Original Message ----- =
From: = Graham
To: rsgb_lf_group@blacksheep.org
Sent: Wednesday, August 10, = 2011 5:23=20 PM
Subject: Re: LF: Re: Re:=20 HB9ASB...

Im sure  one  = station  =20 uses a   battery  and  radio  link  = from=20 the   probe  Ae   so  no  = feeder =20 ?
 
G.

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

This miniwhip/probe seems to be a very = complicated=20 antenna and difficult to explain its properties.
I suggest someone takes this antenna out = into the=20 middle of a field away from any noise source and work out how it = actualljy=20 performs.
because using it in a noisy environment at = various=20 heights in different locations introduces too many variables for = accurate=20 evaluation.
A random simple piece of wire with a = suitable=20 preamp and a counterpoise would probably work better.
Decca used a metal barrell probe and = preamp at=20 their RX stations maybe someone knows how they performed, although = their=20 sites were in a rural quiet environment.
The argument at present about this type of = antenna needs to be concentrated on actual performance = and not=20 about environmental LOCATION, move it up or down a bit, use longer = feed=20 line, get it above the roof etc, Earth the outer braid before it = enters=20 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=20 4:01 PM
Subject: LF: Re: = HB9ASB...

Hi=20 Stefan,

Some=20 comments:

I = think the=20 mechanism is that the unwanted signal on the screen causes a=20
potential difference between gate and source of the first = (J)FET. So=20
this causes a current flow in the output stage and so a = signal at=20 the RX
input.

I fail to = see how that=20 could be the main cause=85 because cutting the power to the = miniwhip=20 should then eliminate the QRM, but it does not! It probably = attributes=20 somewhat -  only some 10-15 dB, but that = leaves=20  9+20 dB for another explanation. (i.e. my=20 balanced-unbalanced hypothesis)

It = would almost=20 have the same effect (when ignoring the C between cable
and = ground=20 along to the choke near the antenna ground) as placing the =
choke=20 near the antenna ground, both are in series and increase the =
current=20 reducing impedance, yes...

But I have = to disagree.=20 A choke (only) at the TX would accomplish nothing (in fact it = may even=20 make it worse). With a choke at the RX end the coax will =96 = acting as an=20 antenna - still pick up all kinds of noise in the house, and = this get=20 transported via the outside of the coax to the miniwhip. Placing = the=20 chocke+ground near the miniwhip will on the other hand attenuate = all the=20 noise that is picked up along the coax.
An (additional) choke = at the=20 RX end _might_ make things worse at LF because in that case the = noise=20 will not be bled to earth there, with the result that the = overall noise=20 voltage on the outside might be still higher.

Hm, = i rather=20 expect a galvanic coupling i.e. stray currenty on the
supply = cable=20 of the RX. What happens if you run the RX on batteries? The =
same=20 dependency?

Running the = 817 on=20 batteries makes no difference. And galvanic coupling is unlikely = because=20 the QRM completely disappears when I disconnect the coax in the = shack=85.=20 And the coax is not connected to anything else up to the = miniwhip.=20
As for the necessity of a current balun or common mode choke = when=20 going form unbalanced to balanced:  picture a = classic=20 dipole fed by coax. (TX) current runs through the center = conductor.=20 Kirchofs law states that the same current must flow in the other = direction (on the inside of the braid). Now at the dipole the = current=20 from the center conductor only has one way to go: into 1 half of = the=20 dipole. But the current on the inside of the braid has two = paths: into=20 the second half of the dipole AND into the outer side of the = braid. The=20 actual distribution is determined by the relative impedances = these two=20 other halves of the dipole have at the specific frequency. Enter = the=20 choke, which effectively blocks the path to the outer side of = the braid.=20 The same mechanism is true for reception.

Today it's nice=20 WX here! And in NL?

What can I = say=85 at least=20 it isn=92t raining today. But unfortunately I have other duties=20 (QRL)

Overall an = interesting=20 discussion!! I am curious if there are any other (competing) = theories=20 J

 

Regards,
Minto=20 pa3bca

Hi = Minto,

Am=20 10.08.2011 13:10, schrieb Minto Witteveen:
> Hi Stefan, = (et=20 al)
>
> Well I beg to differ.. :-)
> What I = think=20 happens is this: The outside of the coax picks up
>=20 electromagnetic radiation like any antenna (including QRM = generated by=20
> fluorescent lamps and Alinco switching power supplies). = This=20 signal
> travels along the coax to the Miniwhip. (also in = the=20 direction of the
> receiver but that is not important = here as the=20 signal is on the
> outside of the coax).
> Upon = arrival at=20 the miniwhip this signal on the outside of the coax
> has = nowhere=20 to go ­but to the _inside_ of the outer mantle of the coax =
>=20 =96 it =91rounds the corner=92 at the end of the coax so to = speak.
I think=20 the mechanism is that the unwanted signal on the screen causes a =
potential difference between gate and source of the first = (J)FET. So=20
this causes a current flow in the output stage and so a = signal at=20 the RX
input.
A common mode choke between RX and the = antenna=20 ground should form a low
pass filter for unwanted signals = coming=20 from the shack. Using a common
mode choke without a local = ground=20 should have little effect, except the
coax is some 100m long = (between choke and probe) ;-)

Ah BTW regarding the = discussion=20 "the cable to the E field probe is the
actual antenna": One = could=20 just try what happens if one disconnects the
power supply. = If the=20 signal is still present then the cable is the
antenna, if = the signal=20 is gone: The probe must be the antenna. Isn't
it?!=20 :-)


> So how to avoid the QRM that is picked up by = the=20 coax to =91travel back=92
> via the inside: for the = miniwhip it is=20 indeed best (as Roelof
> mentioned) to short these = signals to=20 earth _outside_ the house,
> preferably as close to the = miniwhip=20 as possible. Grounding there would
> to the trick, aided = by a=20 (large enough) common mode choke between the
> ground = point and=20 the house. The QRM that is picked up in the house
> would = be =96=20 after attenuation by the choke - directed into the ground =
> and=20 not up into the pole and the miniwhip.

Yes yes, totally=20 agreed.
> Whatever happens in the house would then be = largely=20 irrelevant. Adding
> a common mode choke close to the rig = will do=20 little extra. (it would
> only attenuate QRM getting from = the=20 shack=92s earth system to the
> outside of the = coax).
It would=20 almost have the same effect (when ignoring the C between cable =
and=20 ground along to the choke near the antenna ground) as placing = the=20
choke near the antenna ground, both are in series and = increase the=20
current reducing impedance, yes...

> Any signals = picked up=20 by the vertical coax between the earthing point
> and the = whip=20 will add to the received signal, but at low frequencies
> = it will=20 not be much.
> So far for theory. Now the proof of the = pudding:=20 DCF39 is now > S9+40
> dB. My old trusty QRM generator = (Alinco=20 SMPS) generates S9+25 at
> 135.500. When I switch off the = miniwhip (cut the power) DCF39 drops
> down to just above = the=20 noise floor. As expected.
Ah yes, that's what i meant above = (should=20 have read your mail completely
before answering ;-) ). This = is the=20 proof that Mal cannot be right when
saying "the coax is the = actual=20 antenna".
> But the Alinco signal only drops down some 15 = dB and=20 remains the only
> signal that is audible. This is = exactly what I=20 would expect: the QRM
> travels along the outside of the = coax to=20 the miniwhip, =91rounds the
> corner=92 and comes back = via the inside=20 of the coax shield. Further
> proof that it indeed takes = this=20 route: if I disconnect the coax in the
> shack the Alinco = smps=20 signal disappears also (so it is not received
> via any = other=20 path).
Hm, i rather expect a galvanic coupling i.e. stray = currenty on=20 the
supply cable of the RX. What happens if you run the RX = on=20 batteries? The
same dependency?
There could be several = reasons=20 apply here...

> Last year I already bought 3 meters of = copper=20 pipe to drive into the
> ground in the backyard. Bet = never got=20 around to finish the job=85
Today it's nice WX here! And in=20 NL?
>
> The main reason the signal strength is much = higher=20 with the elevated
> miniwhip is (I think) caused by the = fact that=20 I am surrounded by other
> houses, gardens, trees etc. = Not=20 comparable with an open field=85
Yes.

73, Stefan=20 = /DK7FC




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