Date: Mon, 18 May 2015 12:57:38 -0400
From: "qrv@kd4e.com" <qrv@kd4e.com>
To: Dennis W0JX <w0jx@yahoo.com>
Cc: Dennis W0JX via Amps <amps@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
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