Re: [Elecraft_K3] Compare the K3 with the IC-7300 [2 Attachments]


Richard Fjeld <rpfjeld@...>
 

You are a gentleman, Rob.  I was thinking it involved harmonics. 

Your pictures came through fine.  I didn't know the problem was this bad.
I'm glad you included a K3.

Thank you,
Dick, n0ce

On 4/10/2016 10:30 PM, Rob Sherwood. rob@... [Elecraft_K3] wrote:
 

Hi Dick,

 

Odd-order transmit distortion products are within a few 10s of kHz of your transmit frequency.

We are not talking about harmonics.

I have attached two small 100K pictures, if they make it through the reflector.

The span of the spectrum analyzer is 40 kHz, + 20 kHz and – 20 kHz of the transmit frequency.

If they don’t come through, e-mail me direct, rob@....

One is of a Collins 32S-3 and the other a K3.

This is what Knut is talking about.

The comparison is typical of a solid-state PA vs. a pair of 6146A tubes with negative feedback.

Most any solid-state rig today would look about the same.

 

Rob

NC0B

 

 

From: Elecraft_K3@... [mailto:Elecraft_K3@...]
Sent: Sunday, April 10, 2016 7:41 PM
To: Elecraft_K3@...
Subject: Re: [Elecraft_K3] Compare the K3 with the IC-7300

 

 

I hate to reveal my ignorance, but isn't that one of the reasons I have a low pass filter in-line to my antenna system?
I would welcome a brief explanation if the low pass filter is not effective. 

Also, forgive me for posting a reply before I have read the entire list.  I jumped the gun awhile ago.

Dick, n0ce

 

On 4/10/2016 4:43 PM, ab2tc@... [Elecraft_K3] wrote:

 

Hi Rob again,

 

Yes, the higher order products are the worst problem with most solid state transmitters. In tube transmitters there is the 3rd order and very little after that. In most solid state transmitters the spectrum goes on and on and on... This requires attention by mainstream companies, including Elecraft. I'd really like to see Elecraft take the lead with respect to SSB transmitter distortion. If there is ever a K4 it ought to have a clean transmitter. I don't really care about the receiver. If a direct sampling receiver saves them money and retains or improves the performance, kudos to them.

 

AB2TC - Knut

 

 

 


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