Return-Path: Received: from post.thorcom.com (post.thorcom.com [195.171.43.25]) by klubnl.pl (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id w6F6uNMv025703 for ; Sun, 15 Jul 2018 08:56:26 +0200 Received: from majordom by post.thorcom.com with local (Exim 4.14) id 1fearC-0000mO-W3 for rs_out_1@blacksheep.org; Sun, 15 Jul 2018 07:50:10 +0100 Received: from [195.171.43.32] (helo=relay1.thorcom.net) by post.thorcom.com with esmtp (Exim 4.14) id 1fearC-0000mF-1e for rsgb_lf_group@blacksheep.org; Sun, 15 Jul 2018 07:50:10 +0100 Received: from mail-ed1-x52c.google.com ([2a00:1450:4864:20::52c]) by relay1.thorcom.net with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91_59-0488984) (envelope-from ) id 1fear8-00042a-GP for rsgb_lf_group@blacksheep.org; Sun, 15 Jul 2018 07:50:08 +0100 Received: by mail-ed1-x52c.google.com with SMTP id w14-v6so27596150eds.6 for ; Sat, 14 Jul 2018 23:50:06 -0700 (PDT) X-DKIM-Result: Domain=gmail.com Result=Good and Known Domain DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:in-reply-to:references:from:date:message-id:subject:to; bh=fow9oRzMT4rlRF8l0jXHt7sWmVc5rB/eXJAP5iU136s=; b=PemYrF+mDUrfmi4Vl761gv2zZAiRfkvYhAQJVqaB6vzRVyt3YQEFt8AlL7796satPq TMa0b/jVrlrv18EerN6GVKvYDYaRn5zR0+EtS2tPgy3DBAbgc83lR6ZHRKKWuyLzffbo 8+APCrsDe/0HR5PGOtTb7t0S+z/vEvZNs8xUz194kmY2Ih3r7jdTvNoYWKHEiow9H8Z+ Pncn6/0CxW1yULSliiwgthUNdVmcPw2NSxW0YC+IYAEIt5lNJaH93hEz5zGILN1cALVT HfoCpy+2Kw9cI46iglO/3PL2kWnQwdDUJKXkc3eYQ/ozRK7dZ8f8CotbBJ9crPc5Evs1 d95g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to; bh=fow9oRzMT4rlRF8l0jXHt7sWmVc5rB/eXJAP5iU136s=; b=qmX2jMI9ZX7Bjxy7AD6zccymEvzS3EI5s8yn5X3eu4AQ3vwsjOSbw4ruu46Wx2u7J7 KzEI3XqsHY8WebsKhNy6Qatw4ZK5AbRO9zcqYfMVziNena7LbJH1Yi+NOS6Quxbqe+jb ZoIBdUw6dBog2BXVTe56aQdyh7Unt1JBdENWm6I/u9IUG4h0q9RmbPFHBipmoLBRpT44 VflaaczZ6+8ZQ0140HqP4aIuCq3XfxCQ1MkLNPjJ3w5L254IlMZ6K1iNwRs+CJYyrV3H UUUNBagc0DlFXaq6M7o36KbI0YOu95W53b9lt8im6EmrD3RU45Y1/lwYRrQmckI1QKqP 8/pw== X-Gm-Message-State: AOUpUlFN2ThqwVdYVhEwzKJllpwMnxtPXc7gXxsGPLWOVcoeEaNxDjrz rs8CWIoTUv2WVo1UxRso69Km07xFDZjTaaOqQdo= X-Google-Smtp-Source: AAOMgpei/vR/mgCBxC6PJPO+nIxySK9QXeqKO9apuFyJP/5O042h/mQS6HUija54nYuySbWW6zOSd6URkgBnnqRUYh8= X-Received: by 2002:aa7:d1cb:: with SMTP id g11-v6mr12806894edp.163.1531637405584; Sat, 14 Jul 2018 23:50:05 -0700 (PDT) MIME-Version: 1.0 Received: by 2002:a50:9626:0:0:0:0:0 with HTTP; Sat, 14 Jul 2018 23:50:05 -0700 (PDT) In-Reply-To: <1UQWn0FzVr.1HxCa9v5tM0@optiplex980-pc> References: <50f24ef2-2d1d-b537-7d66-e6d12ecf8cc3@n1bug.com> <8e720108-88eb-11a7-4f41-ef67c7ae74c9@n1bug.com> <1UQWeI91kE.7cbTRbTeCVJ@optiplex980-pc> <1UQWn0FzVr.1HxCa9v5tM0@optiplex980-pc> From: Andy Talbot Date: Sun, 15 Jul 2018 07:50:05 +0100 Message-ID: To: LineOne X-Spam-Score: 0.0 (/) X-Spam-Report: Spam detection software, running on the system "relay1.thorcom.net", has NOT identified this incoming email as spam. The original message has been attached to this so you can view it or label similar future email. If you have any questions, see @@CONTACT_ADDRESS@@ for details. Content preview: Yes, I agree with your figures and they are terrible. -125dBm MDS means -128dBm of noise in a CW (call it 300Hz) bandwidth, that means a noise figure of around 21dB so there is no front end gain, and almost certainly some loss before mixer. [...] Content analysis details: (0.0 points, 5.0 required) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at http://www.dnswl.org/, no trust [2a00:1450:4864:20:0:0:0:52c listed in] [list.dnswl.org] 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (andy.g4jnt[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 0.0 HTML_MESSAGE BODY: HTML included in message 0.0 T_DKIM_INVALID DKIM-Signature header exists but is not valid X-Scan-Signature: b64e297c4577ad617411a4f8f6174ca7 Subject: Re: LF: RE: Simple transverter for 472kHz Content-Type: multipart/alternative; boundary="0000000000007c11d30571041fa0" X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on post.thorcom.com X-Spam-Level: ** X-Spam-Status: No, hits=2.5 required=5.0 tests=DRASTIC_REDUCED,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 --0000000000007c11d30571041fa0 Content-Type: text/plain; charset="UTF-8" Yes, I agree with your figures and they are terrible. -125dBm MDS means -128dBm of noise in a CW (call it 300Hz) bandwidth, that means a noise figure of around 21dB so there is no front end gain, and almost certainly some loss before mixer. So a -36dBm IP3 is appalling. The increases to -14dBm at 75kHz just means there is some filtering in place. That low an IP3 is the sort of figure you'd expect, perhaps, from a single bipolar mixer; the sort of thing used in the 1960s and 1970s (as I did in my first homebrew HF receiver !) Could there have been something wrong with the test unit perhaps? LO power drastically reduced into a mixer? It would be difficult to make a mixer with that low an IP3 othewise Andy www.g4jnt.com On 15 July 2018 at 00:54, jrusgrove@comcast.net wrote: > Andy > > Maybe I can shed further light on my comments ... > > The ARRL receiver measurement system was developed by Wes Hayward of > Tektronics back in the mid 70's and has been used with minor changes > since. Instead of calculating 3IP the system quotes third order IMD dynamic > range relative to the noise floor (MDS - minimum descernable signal). The > MDS is deemed as the signal level at which a 3 dB increase over > 'background' noise is noted - as measured by an audio voltmeter. The > measurement is normally made with the receiver in a cw bandwidth and is > quoted in dBm. QST quotes the MDS for the this transverter as -125 dBm. For > the two-tone IMD dynamic range measurement, two tones (at selected > spacings) are injected into the receiver and the level is increased until > the third order products are 3 dB above the background noise - at the MDS > level. The two-tone dynamic range is the difference between MDS and the > signal generator level. > > For this transverter with a -125 dBm MDS and 60 dB dynamic range at 2 kHz > tone spacing, the indicated signal level to cause third order IMD > products would be -65 dBm. At 75 kHz spacing the signal level would be -51 > dBm. Calculating IP3 for 2 kHz spacing using -125 dBm and -65 dBm produces > an IP3 of -35 dBm. Calculating IP3 for 75 kHz spacing using -125 dBm and > -51 dBm produces an IP3 of -14 dBm. > > I normally think in dynamic range numbers, not IP3, since I've been using > the 'Hayward system' since the beginning. Since you think in IP3 numbers > how do those IP3's look to you? > > Jay W1VD WD2XNS WE2XGR/2 > > > > *----- Original Message -----* > *From:* Andy Talbot > *Reply-To:* > *To:* LineOne > *Sent:* 7/14/2018 7:38:16 AM > *Subject:* Re: LF: RE: Simple transverter for 472kHz > ------------------------------ > Those IMD figures don't in themselves say enough to say whether it is good > or bad. > > Firstly, that quoted paragraph doesn't give the input levels at which IMPs > were 60 [75dB] down. It is more usual to give a third order intercept > point (TOIP)when specifiying linearity; a figure quoted in dBm > > Secondly, specifying IMPs at different bandwidths is meaningless too, as > there is no indication of the receiver filtering. > > So all in all, rejecting that receive converter based on that quoted > paragraph is going too far. > > If a level-7 (+7dBm Local Oscillator) diode ring mixer were to be used at > the front end, with no preceding preamp and minimal loss filtering, you > might reasonably expect a TOIP in the +15 to +20dBm region. That means > IM Products will be, (in dB below theinput) twice the amount the RF input > is below the TOIP. An example : > > TOIP = +20dBm > Two tone input at a level of -20dBm > IMPS = +20dBm - 2 * (+20dBm - -20dBm = -60dBc on the input signals. > Or equivalent to -80dBm > > So two -20dBm signal into a typical 7dBm LO diode ring mixer give -60dBc > third order products. > A diode ring is what any self respecting designer might use on a basic LF > receiver converter > > A level 13 mixer (+13dBm) wpouild give a proprtionately higher TOIP, > perhaps +25 to +30dBm > For higher linearity / better strong signal handling still, a bus-switch > mixer offers a TOIP perhaps +35 to +45dBm. Like the Softrock receivers > > > Andy > www.g4jnt.com > > > On 14 July 2018 at 12:13, N1BUG wrote: > >> Ouch! Having operated on 160m and the HF bands for several years >> using a receiver that comes in at about -63 dB on 2 kHz spacing >> third-order IMD I would never again buy something with that kind of >> receiver "performance". >> >> Paul N1BUG >> >> >> On 07/06/2018 09:45 PM, jrusgrove@comcast.net wrote: >> > Saw the writeup in QST and immediately noticed the receive >> > two-tone, third-order IMD at 2 kHz spacing is 60 dB and at 75 kHz >> > spacing is only 74 dB! Good luck with that if you've got strong >> > signals at your location. >> > >> > Jay W1VD WD2XNS WE2XGR/2 >> >> > --0000000000007c11d30571041fa0 Content-Type: text/html; charset="UTF-8" Content-Transfer-Encoding: quoted-printable
Yes, I agree with your figures and they are terrible.=C2= =A0 -125dBm MDS means -128dBm of noise in a CW (call it 300Hz) bandwidth,= =C2=A0 that means a noise figure of around 21dB so there is no front end ga= in, and almost certainly some loss before mixer.=C2=A0

S= o a -36dBm IP3 is appalling.=C2=A0 =C2=A0The increases to -14dBm at 75kHz j= ust means there is some filtering in place.

That l= ow an IP3 is the sort of figure you'd expect, perhaps, from a single bi= polar mixer;=C2=A0 the sort of thing used in the 1960s and 1970s (as I did = in my first homebrew HF receiver !)

Could there ha= ve been something wrong with the test unit perhaps?=C2=A0 =C2=A0LO power dr= astically reduced into a mixer?=C2=A0 It would be difficult to make a mixer= with that low an IP3=C2=A0 othewise


On 15 July 2018 at 00:54, jrusgrove@comcast.net <jrusgrove@comcast.ne= t> wrote:
Andy
=C2=A0
Maybe I can shed further light on my comments ...=C2=A0
=C2=A0
The ARRL receiver measurement system was developed=C2=A0by Wes Hayward= of Tektronics back in the=C2=A0mid 70's and has been used=C2=A0with mi= nor changes since.=C2=A0Instead of=C2=A0calculating 3IP the system quotes t= hird order IMD dynamic range relative to the noise floor (MDS - minimum des= cernable signal).=C2=A0The MDS=C2=A0is deemed as the signal=C2=A0level at w= hich a 3 dB increase over 'background' noise=C2=A0is noted -=C2=A0a= s measured by an audio voltmeter.=C2=A0 The measurement is normally made wi= th the receiver in a cw bandwidth and is quoted in dBm. QST quotes the MDS= =C2=A0for the this transverter as -125 dBm. For the two-tone IMD dynamic ra= nge measurement, two tones=C2=A0(at selected spacings) are injected into th= e receiver and the=C2=A0level is increased until the third order products a= re 3 dB above the=C2=A0background noise - at the MDS level.=C2=A0The=C2=A0t= wo-tone dynamic range is the difference between=C2=A0MDS and the signal gen= erator level.
=C2=A0
For this transverter with a -125 dBm MDS and 60 dB dynamic range at 2 = kHz tone spacing, the indicated signal level to cause third order IMD produ= cts=C2=A0would be -65 dBm. At 75 kHz spacing the signal level would be -51 = dBm. Calculating=C2=A0IP3 for 2 kHz spacing using -125 dBm and -65 dBm prod= uces an IP3 of -35 dBm.=C2=A0Calculating IP3 for 75 kHz spacing=C2=A0using= =C2=A0-125 dBm and -51 dBm produces an IP3 of -14 dBm.
=C2=A0
I normally think in dynamic range numbers,=C2=A0not=C2=A0IP3, since I&= #39;ve been using the=C2=A0'Hayward system' since the beginning. Si= nce you think in IP3 numbers how do those IP3's=C2=A0look to you?
=C2=A0
Jay W1VD=C2=A0 WD2XNS=C2=A0 WE2XGR/2=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2= =A0
=C2=A0
=C2=A0
----- Original Message -----
From: Andy Talbot <andy.g4jnt@gmail.com>
Sent: 7/14/2018 7:38:16 AM
Subject: Re: LF: RE: Simple transverter for 472kHz
Those IMD figures don't in themselves say enough to sa= y whether it is good or bad.

Firstly, that quoted paragraph doesn't give the input levels at wh= ich IMPs were 60 [75dB] down.=C2=A0 =C2=A0It is more usual to give a third = order intercept point=C2=A0 (TOIP)when specifiying linearity; a figure quot= ed in dBm

Secondly, specifying IMPs at different bandwidths is meaningless too, = as there is no indication of the receiver filtering.

So all in all, rejecting that receive converter based on that quoted p= aragraph is going too far.

If a level-7 (+7dBm Local Oscillator) diode ring mixer were to be used= at the front end, with no preceding preamp and minimal loss filtering, you= might reasonably expect a TOIP in the +15 to=C2=A0 +20dBm region.=C2=A0 = =C2=A0That means IM Products will be, (in dB below theinput) twice the amou= nt the RF input is below the TOIP.=C2=A0 An example :

TOIP =3D +20dBm
Two tone input at a level of -20dBm
IMPS=C2=A0 =C2=A0=3D=C2=A0 =C2=A0 +20dBm - 2 * (+20dBm - -20dBm =3D -6= 0dBc on the input signals.=C2=A0 Or equivalent to -80dBm

So two -20dBm signal into a typical 7dBm LO diode ring mixer give -60d= Bc third order products.
A diode ring is what any self respecting designer might use on a basic= LF receiver converter

A level 13 mixer (+13dBm) wpouild give a proprtionately higher TOIP, p= erhaps +25 to +30dBm
For higher linearity / better strong signal handling still,=C2=A0 a bu= s-switch mixer offers a TOIP perhaps +35 to +45dBm.=C2=A0 =C2=A0Like the So= ftrock receivers


=

On 14 July 2018 at 12:13, N1BUG <paul@n1bug.com> wrote:
Ouch! Having operated on 160m and the= HF bands for several years
using a receiver that comes in at about -63 = dB on 2 kHz spacing
third-order IMD I would never again buy something wi= th that kind of
receiver "performance".

Paul N1BUG
<= br>
On 07/06/2018 09:45 PM, jrusgrove@comcast.net wrote:
> Saw the writeup in = QST and immediately noticed the receive
> two-tone, third-order IMD a= t 2 kHz spacing is 60 dB and at 75 kHz
> spacing is only 74 dB! Good = luck with that if you've got strong
> signals at your location.>
> Jay W1VD=C2=A0 WD2XNS=C2=A0 WE2XGR/2



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