Yes indeed Joe. The VRF-2933 FETS are good / arguably best of breed in
today's generation and offerings of modern RF Power semiconductors.
The key to success here is de-rating the combined module's PEP to steer well
clear of their 1 dB power compression and subsequent saturation points. Then
you will attain those desirously clean IMD numbers with good TLT output
xfmrs, diplexer style terminated harmonic output filter, etc, and FET bias
optimisation.
This has been shown to be so in practice.
The only other way around this intractable dilemma is the use of linearity
correction pre-distortion techniques in either analog or digital form, the
latter being implemented with an SDR Tx exciter running the requisite
correction algorithm.
Leigh
VK5KLT
-----Original Message-----
From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Joe Subich,
W4TV
Sent: Monday, 16 November 2015 1:55 PM
To: amps@contesting.com
Subject: Re: [Amps] SPE 1.3K-FA and FTDX-5KMP / IMD at rated PEP
On 11/13/2015 4:50 PM, Leigh Turner wrote:
>
> That sensible criteria Joe just about excludes all solid-sate
> commercial amps that are currently in the ham-market...rather sadly
> :-(
Which is a shame because the Quadra and PW-1 with 8 x MRF-150 *should*
*be* capable of -40 dB(PEP) at 800W output and -35 dB(PEP) at their
rated 1 KW output. Given the age of those designs, it is amazing that
the new designs are so sloppy.
A pair of BLF-188A based amplifiers with splitter/combiner each running
800W PEP for 1600W PEP total should be able to make the -40 dB(PEP) as
long as the designer takes care to keep the bias stable and avoid any
saturation of the output transformers.
I suspect, but have not seen the IMD curves, that the two of the old
EB-104 boards updated with VRF-2933 VFETs and new output transformers
could also make the grade (again 800 W (PEP) per board with transistors
capable of 2400W total saturated power).
73,
... Joe, W4TV
On 11/13/2015 4:50 PM, Leigh Turner wrote:
>
> That sensible criteria Joe just about excludes all solid-sate commercial
> amps that are currently in the ham-market...rather sadly :-(
>
> Leigh
> VK5KLT
>
> -----Original Message-----
> From: Amps [mailto:amps-bounces@contesting.com] On Behalf Of Joe Subich,
> W4TV
> Sent: Friday, 13 November 2015 8:06 AM
> To: amps@contesting.com
> Subject: Re: [Amps] SPE 1.3K-FA and FTDX-5KMP
>
> Given SPE's own IMD test results at 1 KW PEP - not even the rated
> 1300 W PEP Output - I would not drive an SPE 1.3K-FA with *any*
> transceiver. If an amplifier can't make at least -30 dB relative
> to PEP at rated power it belongs in the garbage rather than making
> garbage on the air.
>
> 73,
>
> ... Joe, W4TV
>
>
> On 11/12/2015 2:23 PM, Richard Solomon wrote:
>
>> What would folks think about running the FTDX-5KMP
>> in Class A to drive the SPE Amp ?
>>
>> 73, Dick, W1KSZ
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