[Premium-Rx] MULTICOUPLER IP2

[Karl-Arne Markström]

"On the other hand,
if you're building a multi-receive site which is a 1/2 mile from 100KW
transmitters, you have a different scenario."

I design and maintain professional HF receiving sites for a living, hence I comment from experience.

The mean RF power density in the HF region is much lower
in the Western hemisphere than on the Eurasian continent, with at least 20 - 30 dB,
depending on the season and time-of-day.

The effects of this are very much marked if a receiver without RF preselection is connected to a wideband
gain antenna in Europe. Even "top-end" HF receivers without input filtering fail miserably during night-time
conditions, and this is one of the reasons why European specifications for professional HF 
receivers almost invariably specify half-octave input filtering and input attenuators.

A very readable treatment of these questions can be found in B. Sosin's contribution to 
the IEE "Radio Receivers" textbook edited by W. Gosling.

On the other hand, even systems with a moderate IP2 work well connected to 
narrow-band or low-efficiency antennas.

73/

Karl-Arne
SM0AOM


----- Original Message ----- 
From: "k0dan" <k0dan at comcast.net>
To: "Karl-Arne Markström" <sm0aom at telia.com>; "Tracey Gardner" <tracey.gardner at talktalk.net>; <premium-rx at ml.skirrow.org>
Sent: Saturday, April 01, 2006 7:08 PM
Subject: Re: [Premium-Rx] MULTICOUPLER IP2


> "When people connect such a multicoupler to a large wideband antenna, they
> are in for an unpleasant surprise" depending on their environment.
> 
> I'm not gonna argue with the and/or comparisons of a $200-$300 multicoupler
> to a 4- or 5-thousand unit, but the facts are that the multicoupler which
> started this thread (sold, by the way, thanks for the inquiries!) worked
> FINE. Granted, it was not installed in Europe, at a Voice Of America site,
> etc., etc.
> 
> It WAS installed using broadband antennas, in a relatively quiet RF
> environment (Missouri, USA), and worked FINE. Never encountered intermod,
> distortion, crosstalk, etc. Sometimes the multicoupler was directly on an
> antenna, other times it was behind an amateur transceiver's bandpass filter,
> it worked FINE.
> 
> The key is to ask the question of what application and environment is a
> given piece of equipment being used in.
> 
> To suggest a blanket condemnation of low-end multicouplers (or anything else
> for that matter) is just stereotyping and generalization. On the other hand,
> if you're building a multi-receive site which is a 1/2 mile from 100KW
> transmitters, you have a different scenario.
> 
> Apples and oranges.
> 
> Have fun folks...
> 
> Dan
> 
> ----- Original Message -----
> From: "Karl-Arne Markström" <sm0aom at telia.com>
> To: "Tracey Gardner" <tracey.gardner at talktalk.net>;
> <premium-rx at ml.skirrow.org>
> Sent: Saturday, April 01, 2006 10:48 AM
> Subject: Re: [Premium-Rx] MULTICOUPLER IP2
> 
> 
> The low IP2 value (if it is not a misprint) implies that this multicoupler
> does not have balanced amplifier stages internally.
> 
> When people connect such a multicoupler to a large wideband antenna,
> they are in for an unpleasant surprise.
> 
> In order to work in the European RF environment, using wideband gain
> antennas,
> a reasonable IP2 requirement  is + 80 to +85 dBm. This level is
> representative for
> i.a. the Raven Research and R&S NV-14 multicouplers, and leaves the HF
> receiver IP2 as the
> dimensioning factor in the system.
> 
> 73/
> 
> Karl-Arne
> SM0AOM
> 
> 
> 
> ----- Original Message -----
> From: "Tracey Gardner" <tracey.gardner at talktalk.net>
> To: <premium-rx at ml.skirrow.org>
> Sent: Saturday, April 01, 2006 6:33 PM
> Subject: [Premium-Rx] MULTICOUPLER IP2
> 
> 
> > Hi Warren
> >
> > Take a look at this ARRL article
> >
> > http://www.arrl.org/tis/info/pdf/020708qex046.pdf
> >
> > To quote " In modern receivers, IPs may by quite high.
> > It is not unusual to see receivers with third-order intercept
> > points (IP3s) of +30 dBm (1 W) and second-order intercept
> > points (IP2s) of +80 dBm (100 kW).
> > IPs form an excellent basis for comparison of receiver
> > distortion performance"
> >
> > Looking at that +42dbm in a multicoupler ain't so hot
> >
> > Tracey
> >
> > >
> > >> In Europe you would not get very happy with an IP2
> > >> of +42dBm
> > >
> > >  Isn't +42dBMm 15 watts? Do you have more than 15
> > > watts of off channel signal into your antenna?
> > >
> > > Warren
> > >
> > > --- Clemens Paul <cpaul at gmx.net> wrote:
> > >
> > >> " 2nd & 3rd Order Intercepts 45 dB & 42 dB " (specs
> > >> from
> > >> http://www.testequipmentcanada.com/M-50-8.html.)
> > >>
> > >> In Europe you would not get very happy with an IP2
> > >> of +42dBm except you are using
> > >> very selective narrow banded antennas or additional
> > >> preselection before the coupler.
> > >>
> > >> Clemens
> > >> DL4RAJ
> 
> 
> 
> 
> 
> 
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> 


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