[TenTec] RF Speech Processor "TX IMD"

Tue Jun 18 12:26:32 EDT 2013

Yes, indeed: the introduction the PLL lead to wonderful flexibility in frequency coverage and generation along with mounds of phase noise. The phase noise has been largely corralled, but not IMD. I wonder: what IMD level is good enough? Something around -40 dB seems considered insufficient. Would -50 dB do it? -60 dB? What things affect the linearity and transfer function of a PA? Can IMD be "designed out" of a PA, or is it fundamentally caused by the transfer function inherent in the active, amplifying device (transistor or tube) itself? I honestly don't know. 

Oh, and when I heard K0RF's phase noise, I was about 10 mi from him :)

I will take issue with one aspect, though: band pass filters on the output of a transmitter can most certainly attenuate phase noise, or any other emitted RF, that falls outside the filter's pass band. Phase noise is Gaussian (white) in nature and we can turn white noise into anything we want with proper filtering. There's nothing special about phase noise or nth-order IMD products in this regard: band pass filters pass only what's in the pass band (the ultimately tautology!). The pass band may be, say, the entire 20 m band plus a bit for safety, but a good filter will stop anything outside of the pass band. So, a transmitter with a good band pass filter on it won;t much affect any other band but 20 m. 

I'll take my '930S out again this year and double check its noise generation as I know darn good and well that it makes some. I'll even try it on 'phone to see how much trash it makes because I really don't have any idea right now. No, I don't don't own the proper equipment, such as a spectrum analyzer, to allow me to measure it. I suppose that makes me an inadequate ham in some eyes (hangs head in shame). 

Kim N5OP

________________________________
 From: Rick - DJ0IP / NJ0IP <Rick at DJ0IP.de>
To: 'Discussion of Ten-Tec Equipment' <tentec at contesting.com> 
Sent: Tuesday, June 18, 2013 10:03 AM
Subject: Re: [TenTec] RF Speech Processor "TX IMD"

Guys, this is EXACTLY what I have been talking about.

BROADBAND PHASE NOISE - not just the 3rd order IMD.
This noise is not just wide, it's across the entire spectrum.

Now hang a 1.5KW linear amp on one of those!
You don't just bother others on your block, you bother those within a couple
of miles.

But of course some of the rigs are also pathetic on the higher order IMD.
NONE are as good as a 1960s Collins 30S-3.

(OK, sure the FT-5000 is if you run it at 75w in class A, but as soon as you
turn on the speech processor, it's hosed too!)

Nearly 50 years, not only have we seen no progress, the IMD has gotten
worse.

73
Rick, DJ0IP

-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Duane
Calvin
Sent: Tuesday, June 18, 2013 4:49 PM
To: 'Discussion of Ten-Tec Equipment'
Subject: Re: [TenTec] RF Speech Processor "TX IMD"

Same with the TS-430.  I have a neighbor less than 500' away running CW all
the time.  When he had his TS-430 he covered a major portion of the band he
was on with transmitted phase noise.  It was a pure delight when he up
graded to a TS-570 a few years ago and then I couldn't hear him until I was
within 5-10 KHz of him or so.

     73, Duane

Duane Calvin, AC5AA
Austin, Texas
www.ac5aa.com  

-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Barry N1EU
Sent: Tuesday, June 18, 2013 9:41 AM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] RF Speech Processor "TX IMD"

On Tue, Jun 18, 2013 at 1:16 AM, Kim Elmore <cw_de_n5op at sbcglobal.net>wrote:

>
> All that said, I never tried phone with it at FD but I'll give it a 
> shot this year as a quick test to see if the IMD wipes out everyone else.
>
>
We use a TS930S on ssb every year at Field Day and it just wipes out the rig
that's down in the cw portion of the same band due to phase noise.

Barry N1EU
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