[Elecraft] K2/100: PSK31 at 50 watts Screen Shot

[Jay Bromley]

HI Bill and Julian,
You can not go with the IMD readings in DM780.  I use the program all the 
time, Simon says this is one of things he is going to work on in the coming 
year.  In fact if you switch to MixW with the same signal you will see a 
huge jump/improvement in IMD readings.

I have also found by "centering" and Narrowing up the signal you can up the 
IMD readings as well.  I know the transmit IMD is not changing when I do 
this, so I think you just have to take most software IMD readings with the 
grain of salt.  They are useful if you understand the program's limitations.

The bottom line is KK7UQ meter and MixW reads pretty close, DM780 does not. 
However DM780 is the program of choice here except for RTTY.  Still using 
MMTTY because of FSK keying.

73 de jay/w5jay..


>
>
> Julian, G4ILO wrote:
>>
>>
>>
>> Bill Strong wrote:
>>>
>>> http://picasaweb.google.com/billstrong50/DigitalMaster780#
>>>
>>> This is a screen shot by KG3BOZ of my K2/100 running 50 watts on 40M
>>> PSK31. It shows IMD -23. This is a distance of about 1400 miles from
>>> Mississippi to Maryland at about 0100 UTC. My antenna is a Cobra
>>> Ultralite Senior up 20 feet. I tune it with the KAT100 and a big DXE
>>> balun.
>>>
>>> I usually run 20 or 30 watts but I wanted to see if I could run 50 watts
>>> mainly for use on 80M. If I blow a small fan on the heat sink the
>>> internal fan rarely comes on at 50 watts during converstaional PSK31.
>>>
>>> I use the Data Mode with the ALC set to light one bar. I transmit in the
>>> middle of the bandpass of the 2.2K SSB filter at 1000Hz.
>>>
>> I would think an IMD of -23dB is barely acceptable. (My KK7UQ IMD meter
>> defines "good" as better than -23dB.) However IMD measurements received
>> off-air by software are not reliable and often show poorer readings than
>> actual because the SNR is not good enough. Looking at the trace on your
>> screenshot I would have said your IMD was better than -23dB.
>>
>
> Thanks Julian for the observation. I did not know about the inaccuracy
> although I did suspect over the air measurement might be different than in
> the shack. The best IMD I have seen on DM780 is about -27 with a super
> strong signal. I posted this because I thought it might be of interest to 
> a
> newby like myself. It took me a while reading on the internet to begin to
> get a grasp of PSK31. Much of the best information has been on this forum.
> 73's
> Bill
>
> -- 
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> Sent from the Elecraft mailing list archive at Nabble.com.
>
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