Jim
Instead of internet, don't you mean Ethernet?
Just wondering.
73
Jim W7RY
On 10/30/2018 9:48 AM, Jim Garland wrote:
There has been considerable discussion on this group and elsewhere
about the forthcoming FlexRadio Power Genius XL high-end solid state
amplifier. Some of us, myself included, have wondered about the new
amp's CW performance, especially after learning that it uses plastic
enclosed open frame relays, rather than vacuum relay or PIN diode T/R
switching. I wrote Flex CEO Gerald K5SDR questions about the new amp's
CW performance, and received the response below. Two interesting
tidbits are that when using a Flex transceiver with the amp, there is
no control cable between it and the transceiver. Both plug into the
internet and all communication is via the internet. (Also, Flex
transceivers time shift CW as it's sent to allow any other brand of
amp to come on-line gracefully and to eliminate any potential latency.
I don't believe other transceivers have this capability.) In addition,
on CW the amplifier achieves about 70 percent efficiency, which allows
it to run cooler than most solid state amps, thus allowing less fan
noise.
73,
Jim W8ZR
Hi Jim,
Thanks so much for your questions and your interest in Power Genius
XL. I asked the engineering team and their answers are provided in
the text below.
73,
Gerald
Gerald Youngblood, K5SDR
President and CEO
FlexRadio Systems(TM)
Email: gerald@flexradio.com <mailto:gerald@flexradio.com>
Web: www.flexradio.com <http://www.flex-radio.com/>
---------- Forwarded message ---------
**
Dear Gerald,
I and my friends have been reading with great interest the updates on
your new amp, and very much appreciate them. However, we do have a few
questions about the amp's CW performance. It seems like a great deal
of effort has gone into making the Power Genius XL an excellent SO2R
amplifier, but I and my CW buddies are particularly interested in how
the amplifier works on CW. As I'm sure you know, CW operators are
vastly more numerous than SO2R operators, and many of them are curious
about the new amplifier's CW performance. Looking at general contest
participation (e.g., the CQ WW DX contests). there are many more CW
participants than SSB/Digital participants, and nearly all of these
participants are using amplifiers.
*Let me first state that Power Genius was designed by a CW op for XW
ops. 4O3A is a top CW operator and has been running the amp in CW
contests in Montenegro. In CW mode, the amplifier operates near 70%
efficiency based on the Maximum Efficiency Algorithm (Meffa).*
Here are the questions:
1. The PG-XL evidently doesn't run QSK, which isn't a problem for the
majority of CW operators who don't use QSK. However most of us (myself
included) use a very short drop-out time when running semi-break-in
(for me typically 150 msec), which can cause a lot of relay clicking
of an amplifier's T/R relays. That raises the issue of reliability,
which in turn leads to questions about relay sequencing and
hot-switching. Does the PG-XL sequence its T/R relays to prevent
hot-switching? For some transceivers, it is possible to set the TX
Delay time long enough to let the amp's relays close before it
receives RF, but many transceivers do not have this feature. For those
operators, how is hot-switching prevented, and more generally, how
does the amplifier handle relay sequencing? The proper sequence is to
close the output relay first, then turn on the operating bias, and
lastly close the input relay.
*While PG-XL is not designed for full QSK, it is designed for fast
switching times as low as 10 ms. **We do NOT hot switch the relays.
The amplifier also provides an inhibit output that can be used with
some radios that provide for that capability. This is not needed with
FlexRadio since all control and inhibit commands are sent over Ethernet.*
**2. The operating manual stipulates a 20 msec TX Delay time, which
isn't a problem for, e.g., the FLEX 6000 series, which "remembers"
whatever is sent during the first 20 msec and time-shifts the CW so
that no dits are shortened. Most transceivers don't do this, however,
so that whatever is sent during the first 20 msec is lost. With a 20
msec TX Delay and a short dropout time, this could lead to shortened
or lost dits on almost every word or sentence. Is your engineering
team aware of this potential problem, and if so how does the amplifier
deal with it? I'm sure you know that 20 msec is a very long TX Delay
time for CW operation.
*The current recommended transmit delay is 20 ms but we will drop that
to 10-12 ms soon subject to further testing. **For FlexRadio only,
this added delay is about to go away and will be incorporated into the
handshake interchange, so any transmit delay is transparent to the
customer. For Flex radios only, the radio delays the start of the CW
transmission, so no leading CW elements are lost. **For other brands
of radios, we will soon see a shortening to less than 15 ms. Other
brands of radios are not as sophisticated as to delay the transmit
stream.*
3. Much PG-XL discussion on the air centers around the fact that the
PG-XL uses open-frame, plastic-encased DPDT relays for T/R switching
instead of PIN diodes or vacuum relays. This is a curious choice for a
$7000 amplifier and an important issue for potential buyers, who
believe that general purpose relays have significant contact bounce,
slow closing and opening times, experience arcing at the contacts if
hot switched, and are noisier than vacuum relays or (completely
silent) PIN diodes. How does FlexRadio address these concerns?
*The relays are rated for a maximum contact bounce of 7 ms. That plus
some time to control the relay we allow for 10 ms. This is on the
order of the fastest transceiver key down to RF out. As stated above,
the relays are not hot switched. The relays are rated for 10 million
mechanical cycles. You can see the Finder 40.52 specification sheet
attached. Contacts are AgNi.*
3. Who is advising your design team about the amplifier's CW
operation? The CW deficiencies of the Flex 1500 series are well known,
and these were entirely eliminated in the Flex Signature 6000 series,
which are fabulous CW transceivers. It's important to the CW community
that this same design care be carried over to the PowerGenius, so it
would be helpful to know how your design team involved the CW
community in designing the amplifier.
*Primarily 4O3A and K9CT. There are many others on the alpha team as
well who are CW contesters.*
4. Fan noise is a big problem with solid state amplifiers, especially
with muffin-type fans which tend to have an irritating higher-pitched
sound than, e.g., squirrel cage blowers. The Elecraft KPA-1500 is
often criticized because of its whiny fan noise when running full
output. Can you explain how the PG-XL deals with this issue? A
related issue is relay clicking noise, which many CW operators find
bothersome, especially those who don't habitually wear headphones.
*We have significantly improved fan noise beginning with firmware
2.8.7 or later. CW mode operates at 70% efficiency and a fairly low
duty cycle compared to RTTY and FT8 so fans typically will remain on
the lowest speed in most CW operation.*
Thanks very much Gerald, for considering my questions. I and my
buddies are eagerly looking forward to leaerning more about your new
amplifier.
73,
Jim W8ZR
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|