Yes indeed Jim; I concur with all you say here.
Folk should well be disappointed with this mediocre SS amp.
See my earlier post today on my design philosophy for clean SS MOSFET amps.
Leigh
VK5KLT
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Jim Thomson
Sent: Monday, 16 November 2015 9:19 PM
To: amps@contesting.com
Subject: [Amps] SPE 1.3K-FA and FTDX-5KMP
Date: Sat, 14 Nov 2015 08:28:13 +1030
From: "Leigh Turner" <invertech@frontierisp.net.au>
To: <amps@contesting.com>
Subject: Re: [Amps] SPE 1.3K-FA and FTDX-5KMP
Charly, sadly there's an over-hyped obsession out there about Tx purity and
associated IMD specs for ham rigs....
Having said that many current SS amp offerings are poor performers in this
regard when driven to their rated PEP output :-(
Leigh
VK5KLT
### Leigh, the Yaesu FTDX-5000MP uses a PAIR of VRF-1511Gs. They are the
170 vdc rated version of the MRF-151G..... (50-60 vdc rated).
## Now comes along SPE..with its 2.0K...running a whopping 2 kW pep output
from just SIX MRF-151Gs. Now if SPE can achieve 2000w pep from 6 x
devices, then Yaesu should be able to get 666 watts pep from 2 x devices.
Can you imagine the FTDX-5K running 666 w pep out? Well it would fare a
little better than the SPE junk.
## at least yaesu, and also the SS in the ARRL handbook, both used
VRF-151Gs. SPE didn't even use the correct version of the 151G. The SS
devices usually fare a lot better with higher voltages, with reduced imd
being the result. If folks want to run high power on ssb, then at least
take advantage in the latest and greatest in technology...and use the 170
vdc rated VRF-151G. Doesn't cost anymore than the MRF-151G. The VRF-151G
has been out for several years now...its old news really. Perhaps SPE
didn't get the memo ?
## Like I mentioned b4, that SPE 6 x MRF-151G amp is a 600-750 watt pep
output max amp on ssb, that's it. 2000w pep out from it would be 4 steps
below an imd garage truck. And no, the FCC etc, don't regulate crap IMD
on the ham bands. No specs, no regulations pertaining to IMD, be as wide
as you want, as long as its within the ham bands etc.
## yaesu in class A..... driving any of the 3 x spe amps... to rated
output = IMD garbage. But folks like charly say they only look at one
spec... rated pep out on ssb.
## BTW, if you look through the online SPE manuals, they say not to use
speech processing, since this increases the duty cycle on the ss amp..and it
will cook. (it will also increase the average power in the imd products,
so the imd will then sound even louder).
## No folks, SPE didn't get it right. They are selling you a bill of
goods. End of story.
Jim VE7RF
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