[Amps] SPE 2K RTTY Duty Cycle

[Jim Thomson]

Date: Mon, 18 May 2015 12:57:38 -0400
From: "qrv at kd4e.com" <qrv at kd4e.com>
To: Dennis W0JX <w0jx at yahoo.com>
Cc: Dennis W0JX via Amps <amps at contesting.com>
Subject: Re: [Amps] SPE 2K RTTY Duty Cycle

PEP is not the same thing as key-down RTTY by a long shot.

How many switches, feedlines, and antennas, external to the
amp can survive 1500w carrier for long?

Especially heating at imperfect and/or marginal contacts
and connections?

I'm seeing estimates of 5 seconds, 10 seconds, and 15 seconds
of 1500w output in RTTY continuous-duty mode - but unlimited
at 1KW.

Most vendors will be cautious about running-at-the-edge as
they know that some Hams will push that margin then blame
them when something breaks.

Question:
Is RTTY so inefficient that one really needs 1500w output?

There are many other keyboard-keyboard digi modes that can
hold a qso under poor conditions at 30-50w.

Just wondering ...

David KD4E


###  My problem with these silly  SS amps is they need way too many heavy duty sub sections to make em work
correctly.  None of em will run 1.5 kw RTTY CCS.    You need a real RF section..plus the cooling.  They all lack in 
cooling. They have yet another problem.  None of em run more than 50% eff at best.  If you try and run them at reduced 
power,the eff drops off even more, like down to 35%.   The only way to get the eff back up to 50%  is to reduce the voltage.
At that point, if SSB was used, imd goes straight to hell. 

##  You require a 3 kw CCS  power supply to obtain just 1.5 kw into the ant.   Ok, now you require a 1.5 kw CCS rated  LPF
for each band to meet harmonic requirements.   That’s a helluve lot of LPFs.  You also require a myriad of relay switching that will 
handle  1.5 kw CCS, to switch the myriad of LPFs.   Ok,  now the SS devices wont handle SWR.  The SS devices will run hot,
the IMD will further degrade from the poor spec they come with.  Now you require a full automatic 1.5 kw CCS  rated  ant tuner.

##  The IMD is sub standard, on par with a 1970 vintage sweep tube amp, but worse. 

##  You don’t need any of this crap in a tube amp.   If tube amp makers  used something like the   superb jackson bros 6:1
ball drives and mating 0-100 scale on large diam skirts, it would make bringing up pre-sets a snap on any tube amp, resulting 
in extremely fast bandswitching.    The only thing a SS amp has going for it is fast band changing..and that’s it. 

##  switches, feedlines, antennas external to the  amp.....not being able to handle 1.5 kw CCS rtty ???    You are joking right ? 
1.5 kw is   a paltry 5.5 amps  into a 50 ohm load.  Its also  275 V rms across 50 ohms...=  388 volts peak.   Any switch,
feedline, balun, antenna will handle that and more.   You can easily stuff 15-20 kw into any M2 or F12 product. By paralleling
relay contacts, you will quadruple the power rating of the relay. 

##  yes, RTTY is inefficient.  There is NO handshaking going on...like between two modems. 

Jim   VE7RF