I suppose I am the "Bob" you refer to. The section in Rob's article on
Odd-Order Intermodulation he clearly explains "worse".
Our receivers have gotten much better over the years but unfortunately
our transmitters and amplifiers have gotten worse. To quantify, the ARRL
published a compendium of distortion products of linear amplifiers in
1997. The third order distortion was in the 40 and 50 dB PEP range.
In 2019 an ARRL review of solid state legal limit amplifiers reported
the third order distortion was only down 30 dB. This is a 10 to 20 dB
degradation from 1997 to 2019. I'd call this "worse".
73
Bob, K4TAX
On 11/3/2019 6:56 PM, Bill K9YEQ wrote:
“worse” seems a bit much when looking at the actual levels. Bob, did
you mean something else? I know this is semantics….
73,
Bill
K9YEQ
https://wrj-tech.com/
*From:*[email protected] <[email protected]> *On Behalf Of
*Rob Sherwood
*Sent:* Sunday, November 3, 2019 5:16 PM
*To:* [email protected]
*Subject:* Re: [Elecraft-K3] K3S to be discontinued
The K3S is excellent in respect to transmit composite noise. Transmit
IMD, on the other hand, is quite different at various power levels.
The sweet spot is around 35 watts, but much worse at 12 watts and 100
watts. Here is composite noise data. Hopefully the formatting will
hold up.
Rob, NC0B
Transmit Composite Noise Rig Comparisons 20 meters values in dBc/Hz
Rig @ 100 watts 2 kHz offset 10 kHz offset
20 kHz offset 100 kHz offset
K3S -141 n/a -143
FTdx-101D -133 -137 -138 -141
IC-7851 -129 n/a -138
IC-7610 -128 -130 -142
Flex 6400 -122 -127 -139
IC-7300 -121 -121 -124
FTdx-3000 -120 n/a -121
TS-890S -116 -119
-127 -139
Rig @ 30 watts 2 kHz offset 10 kHz
offset 20 kHz offset 100 kHz offset
FTdx-101D -129 -134 -135 -137
K3S -132 n/a -140
IC-7851 -123 n/a -133
IC-7610 -122 -124 -127
Flex 6400 -120 -125 -137
FTdx-3000 -117 n/a -117
TS-890S -112 -115
-124 -135
IC-7300 -110 -109 -116
*From:*[email protected] <mailto:[email protected]>
[mailto:[email protected]] *On Behalf Of *Wes
*Sent:* Sunday, November 03, 2019 10:32 AM
*To:* [email protected] <mailto:[email protected]>
*Subject:* Re: [Elecraft-K3] K3S to be discontinued
If TX IMD is the issue, K3 and K3S transmitters are a real mixed bag.
My old K3 at 30 watts is fantastic, with IMD at all frequencies better
than -40 dBc (ARRL method). The same radio at 10W is the worst of my
two radios, except at 24 MHz where the K3 and K3S tie at -22 dBc.
It's been hard to keep up with these measurements since the KLPA3A in
the K3S has been replaced twice and the KPA3A is IIRC, on the fourth
version.
Wes N7WS
On 11/3/2019 8:16 AM, Martin Sole wrote:
I suspect the quality of the transmitter particularly with regard
to its composite noise spectrum to be a large player. Some radios
with high end receiver performance have rudimentary (I'm being
kind) transmitter composite noise performance.
See what NK7Z, NC0B and K9YC have written about this.
Martin, HS0ZED
On 03/11/2019 21:30, Mark Morin wrote:
My experience is that the type of rig does make a difference
for close coexistence. We’ve found on DxPeditions that an
upgraded K3 with KPA500 and a Kenwood TS-590s also with
KPA500, can coexist quite well with antennas about 300 ft
apart. On most bands, we can operate SSB and CW simultaneously
with tolerable QRM. Other times we have tried different
high-end rigs in similar setup and found that opposite end of
same-band operation was nearly impossible due to QRM. I
suspect it’s mostly the receivers that makes the difference.
Mark VA2MM
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