If you don't mind, I want to jump on the soapbox here and mention something.
In discussions with hams on transmitted spectral purity, I keep hearing "I
don't have a SA" and "SA is an expensive box." This excuse is just not
For the purposes of understanding your transmitted signal, the cost to "gear
up" for that can be as little as $25. How do you do that?
1. Buy a single-band Softrock SDR from Tony Parks. $15 unassembled in kit
or about $35 assembled.
2. Download the free copy of Scott W2UX PowerSdr-IF-Stage.
3. Connect the ouput of the SDR into your PC sound card. Adjust based on
the instructions seen on Scott's site.
This combination gives you single band coverage with a spectrum width of
48-196 khz, depending on the capabilites of the sound card. Dynamic range
will be a minimum of 70db; and if you have a really nice sound card, maybe
as much as 110db.
Push the transmitter into a dummy load. Decouple the SDR antenna away from
the transmitter coax to ensure you are not clipping the SDR or the sound
card. And what you will see is a representation of the transmitted signal
every bit as accurate and valid as a $40K HP SA. Zoom in to your hearts
content. The SDR is very linear over at least a 60db range and that means
that even without any absolute calibration to a standard for levels, you can
measure the relative levels of the transmitted signal and their IMD
Of course, a real IMD test requires a 2 -tone source and you can download
those applications on the web free of charge. A good quick and dirty
solution is to switch your digi mode application over to PSK. In fact, if
it were up to me, it would be a legal requirement for all PSK ops to have
station monitors of this type when running PSK. Lot of misinformation and
nonsense in that community among the rookie ops.
My point here is that in 2010, hams don't need to consult data sheets and
handbooks and the wise ones like Carl as to what their beasts should be
producing. They, with minimal effort, can MEASURE IT DIRECTLY and then
End of rant!
From: "Carl" <firstname.lastname@example.org>
Sent: Sunday, May 23, 2010 11:34 AM
To: <Gudguyham@aol.com>; <email@example.com>; <firstname.lastname@example.org>
Subject: Re: [Amps] How to read the 3-500Z spec sheet?
> Try sticking to the 3-500Z and the service in the discussion Lou.
> You might also want to look at the 3-500Z Eimac specs at the Absolute
> Maximum Ip rating for Class B linear service.
> And at some point put an AL-80 on an SA and look at the IMD when operated
> full bore. It aint pretty.
> In a message dated 5/23/2010 11:16:53 A.M. Eastern Daylight Time,
> email@example.com writes:
> At 2700V @ 400 ma it doesnt matter if its CCS or not
> Carl, how do you account for a pulse rating on a tube? For a 3cpx1500a7
> the plate current is 50AMPS and the Anode V is 10KV and the output power
> 306KW!! Is it not a Po vs time?
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