Dirty Transmitters

Bob McGraw - K4TAX

The nice thing,  the K3S which contains the new synthesizers and a K3 updated with new synthesizers will be cleaner due to lower phase noise and amplitude noise.   Otherwise, lower composite noise which does and will affect any receiver.   Receiver filtering will not reduce the type of  noise which exists in the passband of the receiver.    If the transmitter is dirty, everybody suffers.   It it is fed through an amplifier, everybody suffers more.

Please read Rob Sherwood's article in QST, November 2019, pp 38 - 41.  "It's Time to Clean Up our Transmitters".   You may discover that the wonderful radio you just purchased may not be so wonderful after all. 


Bob, K4TAX

On 11/3/2019 11:32 AM, Wes wrote:
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

Join Elecraft-K3@groups.io to automatically receive all group messages.