Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-me02.r1000.mx.aol.com (Internet Inbound) with ESMTP id C0EBC380001B1; Wed, 10 Aug 2011 11:30:42 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QrAit-0002qb-U1 for rs_out_1@blacksheep.org; Wed, 10 Aug 2011 16:29:35 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QrAis-0002qS-Uh for rsgb_lf_group@blacksheep.org; Wed, 10 Aug 2011 16:29:34 +0100 Received: from out1.ip03ir2.opaltelecom.net ([62.24.128.239]) by relay1.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QrAiq-0002jb-1p for rsgb_lf_group@blacksheep.org; Wed, 10 Aug 2011 16:29:34 +0100 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: AtYAAPyiQk5cHYAl/2dsb2JhbABCgk2Be48khACPX3iBOwUBAQQBCAEBAxYzAg0PCgYBAQMFAgEDEQQBAQohAgIUAQQaBhYIBhMKAQICAQGHXQKtEpEmhTaBEASCUJoqhn0 X-IronPort-AV: E=Sophos;i="4.67,351,1309734000"; d="scan'208,217";a="356538784" Received: from host-92-29-128-37.as13285.net (HELO xphd97xgq27nyf) ([92.29.128.37]) by out1.ip03ir2.opaltelecom.net with SMTP; 10 Aug 2011 16:29:20 +0100 Message-ID: <002e01cc5772$40601a30$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> Date: Wed, 10 Aug 2011 16:29:10 +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: LF: Re: Re: HB9ASB... Content-Type: multipart/alternative; boundary="----=_NextPart_000_002B_01CC577A.A1F004B0" 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: 0:2:491132032:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d608a4e42a42226b5 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_002B_01CC577A.A1F004B0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable 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 =20 ----- 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=E2=80=A6 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 =E2=80=93 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=E2=80=A6. 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=E2=80=A6 at least it isn=E2=80=99t raining today. But = unfortunately I have other duties (QRL) Overall an interesting discussion!! I am curious if there are any = other (competing) theories J =20 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=20 > 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 =C2=ADbut to the _inside_ of the outer mantle of = the coax=20 > =E2=80=93 it =E2=80=98rounds the corner=E2=80=99 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 = 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 = 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 = =E2=80=98travel back=E2=80=99=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 =E2=80=93 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 = > only attenuate QRM getting from the shack=E2=80=99s 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 = > 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 = > travels along the outside of the coax to the miniwhip, = =E2=80=98rounds the=20 > corner=E2=80=99 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 = > ground in the backyard. Bet never got around to finish the = job=E2=80=A6 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=20 > houses, gardens, trees etc. Not comparable with an open = field=E2=80=A6 Yes. 73, Stefan /DK7FC ------=_NextPart_000_002B_01CC577A.A1F004B0 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable =EF=BB=BF
This miniwhip/probe seems to be a very = complicated antenna=20 and difficult to explain its properties.
I suggest someone takes this antenna out into = the middle=20 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 heights=20 in different locations introduces too many variables for accurate=20 evaluation.
A random simple piece of wire with a = suitable preamp=20 and a counterpoise would probably work better.
Decca used a metal barrell probe and preamp = at their=20 RX stations maybe someone knows how they performed, although their sites = were in=20 a rural quiet environment.
The argument at present about this type of=20 antenna needs to be concentrated on actual performance and not = about=20 environmental LOCATION, move it up or down a bit, use longer feed line, = get it=20 above the roof etc, Earth the outer braid before it enters the = shack, use=20 an isolation transformer. 
Let us have your observations.
de mal/g3kev
 
----- Original Message -----
From:=20 Minto Witteveen
Sent: Wednesday, August 10, = 2011 4:01=20 PM
Subject: LF: Re: = HB9ASB...

Hi = Stefan,

Some = comments:

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

I fail to see how = that could=20 be the main cause=E2=80=A6 because cutting the power to the miniwhip = should then=20 eliminate the QRM, but it does not! It probably attributes somewhat - =  only some 10-15 dB, but that = leaves=20  9+20 dB for another = explanation.=20 (i.e. my balanced-unbalanced hypothesis)

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

But I have to = disagree. A=20 choke (only) at the TX would accomplish nothing (in fact it may even = make it=20 worse). With a choke at the RX end the coax will =E2=80=93 acting as = an antenna -=20 still pick up all kinds of noise in the house, and this get = transported via=20 the outside of the coax to the miniwhip. Placing the chocke+ground = near the=20 miniwhip will on the other hand attenuate all the noise that is picked = up=20 along the coax.
An (additional) choke at the RX end _might_ make = things=20 worse at LF because in that case the noise will not be bled to earth = there,=20 with the result that the overall noise voltage on the outside might be = still=20 higher.

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

Running the 817 on = batteries=20 makes no difference. And galvanic coupling is unlikely because the QRM = completely disappears when I disconnect the coax in the = shack=E2=80=A6. And the coax=20 is not connected to anything else up to the miniwhip.
As for the = necessity=20 of a current balun or common mode choke when going form unbalanced to=20 balanced:  picture a = classic=20 dipole fed by coax. (TX) current runs through the center conductor. = Kirchofs=20 law states that the same current must flow in the other direction (on = the=20 inside of the braid). Now at the dipole the current from the center = conductor=20 only has one way to go: into 1 half of the dipole. But the current on = the=20 inside of the braid has two paths: into the second half of the dipole = AND into=20 the outer side of the braid. The actual distribution is determined by = the=20 relative impedances these two other halves of the dipole have at the = specific=20 frequency. Enter the choke, which effectively blocks the path to the = outer=20 side of the braid. The same mechanism is true for = reception.

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

What can I = say=E2=80=A6 at least it=20 isn=E2=80=99t 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 = J

 

Regards,
Minto=20 pa3bca

Hi = Minto,

Am 10.08.2011=20 13:10, schrieb Minto Witteveen:
> Hi Stefan, (et = al)
>
>=20 Well I beg to differ.. :-)
> What I think happens is this: The = outside=20 of the coax picks up
> electromagnetic radiation like any = antenna=20 (including QRM generated by
> fluorescent lamps and Alinco = switching=20 power supplies). This signal
> travels along the coax to the = Miniwhip.=20 (also in the direction of the
> receiver but that is not = important here=20 as the signal is on the
> outside of the coax).
> Upon = arrival at=20 the miniwhip this signal on the outside of the coax
> has = nowhere to go=20 ­but to the _inside_ of the outer mantle of the coax
> = =E2=80=93 it =E2=80=98rounds=20 the corner=E2=80=99 at the end of the coax so to speak.
I think the = mechanism is=20 that the unwanted signal on the screen causes a
potential = difference=20 between gate and source of the first (J)FET. So
this causes a = current flow=20 in the output stage and so a signal at the RX
input.
A common = mode=20 choke between RX and the antenna ground should form a low
pass = filter for=20 unwanted signals coming from the shack. Using a common
mode choke = without=20 a local ground should have little effect, except the
coax is some = 100m=20 long (between choke and probe) ;-)

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


> So how to = avoid the=20 QRM that is picked up by the coax to =E2=80=98travel back=E2=80=99 =
> via the inside:=20 for the miniwhip it is indeed best (as Roelof
> mentioned) to = short=20 these signals to earth _outside_ the house,
> preferably as = close to=20 the miniwhip as possible. Grounding there would
> to the trick, = aided=20 by a (large enough) common mode choke between the
> ground = point and=20 the house. The QRM that is picked up in the house
> would be = =E2=80=93 after=20 attenuation by the choke - directed into the ground
> and not = up into=20 the pole and the miniwhip.

Yes yes, totally agreed.
> = Whatever=20 happens in the house would then be largely irrelevant. Adding
> = a=20 common mode choke close to the rig will do little extra. (it would =
>=20 only attenuate QRM getting from the shack=E2=80=99s earth system to = the
>=20 outside of the coax).
It would almost have the same effect (when = ignoring=20 the C between cable
and ground along to the choke near the antenna = ground)=20 as placing the
choke near the antenna ground, both are in series = and=20 increase the
current reducing impedance, yes...

> Any = signals=20 picked up by the vertical coax between the earthing point
> and = the=20 whip 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: = DCF39 is=20 now > S9+40
> dB. My old trusty QRM generator (Alinco SMPS)=20 generates S9+25 at
> 135.500. When I switch off the miniwhip = (cut the=20 power) DCF39 drops
> down to just above the noise floor. As=20 expected.
Ah yes, that's what i meant above (should have read your = mail=20 completely
before answering ;-) ). This is the proof that Mal = cannot be=20 right when
saying "the coax is the actual antenna".
> But = the Alinco=20 signal only drops down some 15 dB and remains the only
> signal = that is=20 audible. This is exactly what I would expect: the QRM
> travels = along=20 the outside of the coax to the miniwhip, =E2=80=98rounds the
> = corner=E2=80=99 and=20 comes back via the inside of the coax shield. Further
> proof = that it=20 indeed takes this route: if I disconnect the coax in the
> = shack the=20 Alinco smps signal disappears also (so it is not received
> via = any=20 other 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 = batteries?=20 The
same dependency?
There could be several reasons apply=20 here...

> Last year I already bought 3 meters of copper pipe = to=20 drive into the
> ground in the backyard. Bet never got around = to finish=20 the job=E2=80=A6
Today it's nice WX here! And in = NL?
>
> The main=20 reason the signal strength is much higher with the elevated
> = miniwhip=20 is (I think) caused by the fact that I am surrounded by other
> = houses,=20 gardens, trees etc. Not comparable with an open = field=E2=80=A6
Yes.

73,=20 Stefan /DK7FC

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