[Amps] SPE 2K RTTY Duty Cycle

[Joe Subich, W4TV]

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

Most of the modes that claim the ability to hold a QSO under poor
conditions at 30 - 50W fall apart very quickly with multipath or
QRM.  The claims are based on "flat noise" which is very rarely
the issue for typical amateur activity.

RTTY (FSK with 170 Hz shift, 45.45 baud) is still the winner with
multipath, polar flutter, QRM, etc.  It is only when you get to
the MS-110 type waveforms with heavy levels of redundant coding
(4800 BPS PSK to generate net 75 baud throughput) that the real
performance exceeds traditional RTTY - but then the bandwidth has
increased 10 fold.

73,

   ... Joe, W4TV


On 2015-05-18 12:57 PM, qrv at kd4e.com wrote:
> 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
>
>> I asked this very question from one of the two SPE vendors at Dayton.
>> I got very evasive responses until I insisted on a plain and simple
>> answer. Finally, the vendor stated that if you start at 1500 w out on
>> RTTY, the power will cut back to 1200 watts after ten seconds. I was
>> disappointed in his rather defensive posture on the question of
>> headroom. Yet there was a sign up that said the power out was 2000
>> PEP CW/SSB.
>>
>> 73, Dennis W0JX
>
>