[Elecraft] FW: Testing IMD3 (dB) K3S (#10490)

[Joe Subich, W4TV]

On 2020-02-08 7:22 PM, hb9cvq at hispeed.ch wrote:
 >
 > My K3S / K3 voltage under load (72W) was 13.1V DC.

13.1 V is too low for reasonable IMD with *any* 12V "100W" PA.
Get the power supply up to 14.0-14.5V. If you can't get at
least 14.0 V at full output, do not try to run more than 60W.

Note: this is into a *non reactive* 50 Ohm load.  If the load
differs from 50 +/- j0 Ohms, IMD is likely to be worse due to
the mismatched load.

73,

    ... Joe, W4TV


On 2020-02-08 7:22 PM, hb9cvq at hispeed.ch wrote:
> Hi from HB9CVQ Andy
> 
> My K3S / K3 voltage under load (72W) was 13.1V DC.
> 
> 
> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net <elecraft-bounces at mailman.qth.net> On
> Behalf Of K9MA
> Sent: Sonntag, 9. Februar 2020 00:01
> To: elecraft at mailman.qth.net
> Subject: Re: [Elecraft] FW: Testing IMD3 (dB) K3S (#10490)
> 
> Supply voltage, under load, at the radio?
> 
> 73,
> Scott K9MA
> 
> 
> On 2/8/2020 16:14, Conrad PA5Y wrote:
>> I have some comments.
>>
>> My TX IMD is even worse and I was not very happy with the advice I got
> from Elecraft.  I was advised to use the radio in test mode and use an
> external amplifier.
>>
>> Periodically I have a complain about it. My 10W PA is also poor even after
> the FW upgrade that allows additional attenuation to the drive. There are a
> few of us who discuss this off reflector and it is by no means uncommon.
>>
>> On a more positive note I must say that the transverter port output is
> exceptionally good. Its really impressive.
>>
>> As for the PA IMD, good luck, you will need it.
>>
>> Regards
>>
>> Conrad PA5Y
>>
>>
>>
>> -----Original Message-----
>> From: elecraft-bounces at mailman.qth.net
>> <elecraft-bounces at mailman.qth.net> On Behalf Of hb9cvq at hispeed.ch
>> Sent: 08 February 2020 01:00
>> To: elecraft at mailman.qth.net
>> Subject: [Elecraft] FW: Testing IMD3 (dB) K3S (#10490)
>>
>>    
>>
>>    
>>
>>
>> Subject: Testing IMD3 (dB) K3S (#10490)
>>
>>    
>>
>> Hi
>>
>>    
>>
>> Can anyone roughly confirm IMD3 K3S ?
>>
>>    
>>
>> 10W/100W module recently exchanged under Elecraft swap program Rev A
> (2019).
>>
>> Testing: Using K3S internal 2 Tone and -60dB power attenuator (50Ohms)
>> , HP 8591E Spectrum Analyzer (Span 10kHz)
>>
>>    
>>
>> 72W (Tune, LP100A)out into 50Ohm:
>>
>> IMD3 (#10490) -->about on 160m 34 dB, 80m 32dB, 40m 34 dB, 20m  26dB,
>> 17m 30 dB, 10m 30dB, 6m 26dB
>>
>> Yes, all was aligned (TX Gain test) and showing 100 to 90W full power on
> all bands.
>>
>> The driving signal to 10W PA (one tone) looked better than 50dBc.
>>
>>    
>>
>> I think these IMD3 values are not very impressive. A power amp. would
> typically further degrade the overall results.
>>
>> So K3S is rather good for CW but not really good as SSB preference? (I
>> have now also a FTDX101MP)
>>
>>    
>>
>> Comparing with K3 (#7848) upgraded myself to "S", but still maintaining
> the old 10/100W modules.
>>
>> 80m and 20m were better by about 6dB!?
>>
>>    
>>
>> The two tones (IMD3 Test Tones) however were in both cases never
> absolutely identical in amplitude (ca. +/-1dB) on the analyzer.
>>
>>    
>>
>> Any comments?
>>
>>    
>>
>> Tnx, Cu, vy 73 de Andy
>>
>> HB9CVQ, DK2VQ, AK4IG
>>
>>    
>>
>>    <https://www.qrz.com/db/HB9CVQ> https://www.qrz.com/db/HB9CVQ
>>
>>    
>>
> 
> --
> Scott  K9MA
> 
> k9ma at sdellington.us
>