Hi, Leif,
I thought you would like to see this.
I don't think Bill understands your measurements.
I enclosed his email address for you, as well ;)
73,
Roger
W3SZ
----- Original Message -----
From: <btippett@alum.mit.edu>
To: <tentec@contesting.com>; <elecraft@mailman.qth.net>
Sent: Friday, April 30, 2004 10:32 AM
Subject: [TenTec] Re : [Elecraft] Trying to improve the K2's IIP3; mission
(almost...) impossible!
> Hi Dick,
>
> PA2DW wrote:
> >By the way, talking about IIP3 values. The New Icom radio IC7800 claims
+40
> dBm IIP3, but I can not find the spacing with which they measured that. 5,
> 20 maybe 100 kHz!?!?! Does anyone know that?
>
>
> Trying to improve the K2's IP3 may be nearly as impossible
> as finding Icom specifications! There is no qualification anywhere in
> their brochure or specifications as to signal spacing. The closest
> I have been able to find is the following which is a copy of the Test
> Report included with each 7800. It implies IP3 is measured at 100 kHz
> (which is stated for the dynamic range measurement).
>
> http://www.qsl.net/ab4oj/icom/ic7800/7800test.html
>
> The first couple of SM5BSZ's measurements in Table 6 below imply IP3
> of +40 dBm at 20 kHz, although the measurement technique is flawed
> for measurements at normal levels for interfering signals. However,
> if IP3 is met for interfering signals of -1 dBm (equivalent to an S9+72
dB),
> it should certainly be at least as good at normal levels (e.g. ARRL uses
> -17 dBm which is equivalent to S9+56 dB).
>
> http://antennspecialisten.se/~sm5bsz/dynrange/ssa2004/ssa2004.htm
>
> I believe a more worthwhile mod to the K2 would be a better
> filter. I've heard rumors that someone may be looking into this. My
> reason for saying so is the serious -24 dB degradation of the K2's
> IMD for spacings under 5 kHz. Here's the data:
>
> IMD @ 5 kHz 91 dB (ARRL)
> IMD @ 2 kHz 70 dB (Sherwood)
> IMD @ 1 kHz 67 dB (ARRL)
>
> Sources:
> http://www2.arrl.org/members-only/prodrev/pdf/lab/k2.pdf (graph page 20)
> http://www.sherweng.com/table.html
>
> By comparison, Orion's performance at close spacings using the 1000 Hz
> roofing filter degrades only about -8 dB from 5 kHz to 1 kHz:
>
> IMD @ 5 kHz 92 dB (ARRL)
> IMD @ 5 kHz 94 dB (Sherwood...measured 95 dB using 1800 Hz filter)
> IMD @ 2 kHz 93 dB (Sherwood)
> IMD @ 1 kHz 84 dB (ARRL)
> IMD @ 1 kHz 85 dB (Sherwood)
>
> BTW, these measurements give me confidence in both ARRL and
> Sherwood since they only differ slightly at 1 kHz and 5 kHz.
>
> Sources:
> http://www2.arrl.org/members-only/prodrev/pdf/lab/orion_etrr.pdf (bottom
> left graph p. 20)
> http://dayton.akorn.net/pipermail/orion/2004-March/000309.html
> http://dayton.akorn.net/pipermail/orion/2004-March/000310.html
>
> Please don't shoot the messenger...I own both a K2 and
> Orion and am very happy with both. And I also predict both will
> probably beat the IC-7800's IMD at 5 kHz spacings whenever ARRL
> or others publish test reports. A hint of this can be found in Table
> 5 of SM5BSZ's data which I belive is a convoluted measurement
> of BDR. Although it is impossible to make direct comparisons, it
> appears BDR performance degrades seriously at close spacings:
>
> Relative signal strength to cause 3 dB blocking (referenced to the
> + 1.2 dBm signal needed to cause the same blocking at 100 kHz):
>
> 50 kHz -6.2 dB
> 20 kHz -14.1 dB
> 5 kHz -36.7 dB
> 2 kHz -38.7 dB
> 1 kHz -51.8 dB
>
> These results are SO BAD it makes me wonder if either the 7800 or
> measurement technique was defective. If I've misinterpreted the data,
> please do comment! For comparison, both the K2 and Orion BDR
> degrade in the order of -10 dB over the same range of interfering signal
> frequencies, which is why I have trouble believing the above.
>
> Sources: BDR graph on page 19 of K2 ETR cited previously.
> BDR graph on page 19 of Orion ETR cited previously.
> SM5BSZ webpage cited previously.
>
> Please do not share this data with any Icom 7800 zealots...
> they simply do NOT want to see any performance comparisons
> with the $599 K2. ;-)
>
> 73, Bill W4ZV
>
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|