Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by mtain-dh01.r1000.mx.aol.com (Internet Inbound) with ESMTP id A6573380003BE; Wed, 10 Aug 2011 13:18:36 -0400 (EDT) Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1QrCPT-0003Wc-1f for rs_out_1@blacksheep.org; Wed, 10 Aug 2011 18:17:39 +0100 Received: from [83.244.159.144] (helo=relay3.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1QrCPR-0003WR-W0 for rsgb_lf_group@blacksheep.org; Wed, 10 Aug 2011 18:17:38 +0100 Received: from out1.ip09ir2.opaltelecom.net ([62.24.128.245]) by relay3.thorcom.net with esmtp (Exim 4.63) (envelope-from ) id 1QrCPR-0000To-1n for rsgb_lf_group@blacksheep.org; Wed, 10 Aug 2011 18:17:37 +0100 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: Au0AAIG7Qk5cHYAl/2dsb2JhbABCgk2Be48ohACPRXiBOwUBAQQBCAEBAxYzAg0PCgYBAQMFAgEDEQQBAQohAgIUAQQaBhYIBhMKAQICAQGHXQKtLpElhTaBEASCUJoqhn0 X-IronPort-AV: E=Sophos;i="4.67,351,1309734000"; d="scan'208,217";a="487041790" Received: from host-92-29-128-37.as13285.net (HELO xphd97xgq27nyf) ([92.29.128.37]) by out1.ip09ir2.opaltelecom.net with SMTP; 10 Aug 2011 18:12:30 +0100 Message-ID: <004e01cc5780$a98a3820$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> Date: Wed, 10 Aug 2011 18:12:19 +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_004B_01CC5789.0B12F6B0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: X-Spam-Status: No, hits=0.5 required=5.0 tests=HTML_20_30,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: 0:2:491430048:93952408 X-AOL-SCOLL-URL_COUNT: 0 x-aol-sid: 3039ac1d41154e42bd6c0c18 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_004B_01CC5789.0B12F6B0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable 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 = 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 = 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 = 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 = > 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=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 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, = =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=20 > 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=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=E2=80=A6 Yes. 73, Stefan /DK7FC ------=_NextPart_000_004B_01CC5789.0B12F6B0 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable =EF=BB=BF
Graham
Of course there is a FEEDER to the RX at the = remote site=20 before it is relayed via a radio link.
As explained the feeder is the main element for = signal es=20 noise pickup. If there was no feeder to act as the other = main element there=20 would be no signal pick up at all because the 10 mm probe element =  would=20 pick nothing up.
G3KEV
 
----- Original Message -----
From:=20 Graham
Sent: Wednesday, August 10, = 2011 5:23=20 PM
Subject: Re: LF: Re: Re: = HB9ASB...

Im sure  one  = station   uses=20 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 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=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 sites=20 were in 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
To: rsgb_lf_group@blacksheep.org= =20
Sent: Wednesday, August 10, = 2011 4:01=20 PM
Subject: LF: Re: = HB9ASB...

Hi = Stefan,

Some=20 comments:

I think the mechanism is that = the=20 unwanted signal on the screen causes a
potential difference = between gate=20 and source of the first (J)FET. So
this causes a current flow in = the=20 output stage and 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=20 explanation. (i.e. my balanced-unbalanced hypothesis) =

It would almost have the same = effect=20 (when ignoring the C between cable
and ground along to the choke = near=20 the antenna ground) as placing the
choke near the antenna = ground, both=20 are in 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=20 run the RX on batteries? The
same dependency?

Running the 817 = on batteries=20 makes no difference. And galvanic coupling is unlikely because the = QRM=20 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 of a current balun or common mode choke when going form = unbalanced=20 to 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=20 conductor only has one way to go: into 1 half of the dipole. But the = current=20 on the inside of the braid has two paths: into the second half of = the dipole=20 AND into the outer side of the braid. The actual distribution is = determined=20 by the relative impedances these two other halves of the dipole have = at the=20 specific frequency. Enter the choke, which effectively blocks the = path to=20 the outer side of the braid. The same mechanism is true for=20 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=20 10.08.2011 13:10, schrieb Minto Witteveen:
> Hi Stefan, (et=20 al)
>
> Well I beg to differ.. :-)
> What I think = happens=20 is this: The outside of the coax picks up
> electromagnetic = radiation=20 like any antenna (including QRM generated by
> fluorescent = lamps and=20 Alinco switching power supplies). This signal
> travels along = the=20 coax to the Miniwhip. (also in the direction of the
> = receiver but=20 that is not important here as the signal is on the
> outside = of the=20 coax).
> Upon arrival at the miniwhip this signal on the = outside of=20 the coax
> has nowhere to go ­but to the _inside_ of the = outer=20 mantle of the coax
> =E2=80=93 it =E2=80=98rounds the = corner=E2=80=99 at the end of the coax=20 so to speak.
I think the mechanism is that the unwanted signal on = the=20 screen causes a
potential difference between gate and source of = the=20 first (J)FET. So
this causes a current flow in the output stage = and so a=20 signal at the RX
input.
A common mode choke between RX and = the=20 antenna ground should form a low
pass filter for unwanted = signals coming=20 from the shack. Using a common
mode choke without a local ground = should=20 have little effect, except the
coax is some 100m long (between = choke and=20 probe) ;-)

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


> So how to avoid the QRM = that is=20 picked up by the coax to =E2=80=98travel back=E2=80=99
> via = the inside: for the=20 miniwhip it is indeed best (as Roelof
> mentioned) to short = these=20 signals to earth _outside_ the house,
> preferably as close = to the=20 miniwhip as possible. Grounding there would
> to the trick, = aided by=20 a (large enough) common mode choke between the
> ground point = and the=20 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=20 ground) as placing the
choke near the antenna ground, both are = in series=20 and increase the
current reducing impedance, yes...

> = Any=20 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=20 the pudding: DCF39 is now > S9+40
> dB. My old trusty QRM=20 generator (Alinco SMPS) generates S9+25 at
> 135.500. When I = switch=20 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 have=20 read your mail completely
before answering ;-) ). This is the = proof that=20 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 the=20 miniwhip, =E2=80=98rounds the
> corner=E2=80=99 and comes = back via the inside of the=20 coax shield. Further
> proof that it indeed takes this route: = if I=20 disconnect the coax in the
> shack the Alinco smps signal = disappears=20 also (so it is not received
> via any other path).
Hm, i = rather=20 expect a galvanic coupling i.e. stray currenty on the
supply = cable of=20 the RX. What happens if you run the RX on batteries? The
same=20 dependency?
There could be several reasons apply = here...

> Last=20 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=E2=80=A6
Today=20 it's nice WX here! And in NL?
>
> The main reason the = signal=20 strength is much higher with the elevated
> miniwhip is (I = think)=20 caused by the fact that I am surrounded by other
> houses, = gardens,=20 trees etc. Not comparable with an open = field=E2=80=A6
Yes.

73, Stefan=20 /DK7FC



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