Tom has great experience and knows what he is talking. He is using an
amplifier that he built himself. We focused on designing a modern amplifier
that has all the necessary specs to satisfy everyone from casual DXers to
serious contesters without making technical compromises.
I completely agree with Tom’s comments but would like to add a few
important points:
- Fast protection is certainly something that doesn’t need a lot of
discussion. It needs to be a feature of every amplifier. PG XL antenna
connector can be short circuited or the antenna disconnected at full power
and nothing will happen. Not even sparking. That’s because the protection
is fast enough. If you see sparking – protection is slow and transistor is
struggling to survive under remaining RF energy and in danger of burning.
Anyone who decides to go for a solid state amplifier should ask for such a
test from the manufacturer as a precondition.
- Filters are, of course, the next component that needs to be technically
great. Big SWR increases filter insertion loss and increases heating.
Somewhere between 1:2,5 and 1:3 SWR it becomes critical.
Filters should be designed for the maximum allowed SWR and the worst
impedance case with som*e *additional reserve as well.
Harmonic suppression is extremely important, especially for Multi stations.
For that reason, PG XL has duplex filters and suppress all harmonics
typically <75dB. This is much better then tube amplifiers. FCC regulations
require Harmonic suppression of <43dB which is insufficient for a multi
environment. This is why not even the FCC certificate guarantees that the
amplifier will be satisfying for a Multi station. With 70dB harmonics
suppression, and some additional filtering, you can easily realize very
comfortable operating on a Multi/Multi station.
- Efficiency. For all single tone modes, the efficiency can be controlled
in the same way PG XL does – with dynamic VDD modulation. MEffA controls
Vdd and makes sure highest efficiency for the given power.
-SO2R amplifier will become the standard. Today, with Flex Radio and PG XL
you have an SO2R setup. In a Multi Op setup SO2R is used for In Band
stations that operate on the same band. Also for all the categories where
one signal per band is allowed, regardless of whether it’s on the same or a
different band. How much cheaper, simpler and more efficient this setup is
doesn’t even need clarification.
- Finally, the last feature every device today needs, even an amplifier, is
flexibility. The technological trend takes us to new stations and
accessories connected to the local LAN or WAN networks so the time ahead
brings us new possibilities. We already have this and it will become a new
standard. Loads of data from various devices in LAN. PTT, inhibit,
frequency, modes, relay statuses, SWR, antenna direction, audio. Basically
everything.
This is why an amplifier must be a part of the system as well. In a future
concept it can become a server, client, send data, change parameters
remotely etc. This is why an amplifier must be upgradeable and have the
option to be completely controlled by software.
For this reason, PG XL has bias, protection unit and the power supply
completely controllable by software, as well as a touch screen display so
it could be updated WITH new functions in the future.
We are heading towards exciting times where station layouts will be
completely different and more powerful.
73 and HNY
Ranko, 4O3A
On Thu, Dec 28, 2017 at 7:54 PM, Tom Georgens <tomgeorgens15@gmail.com>
wrote:
> As I said, I am a believer, but the tradeoffs are more real than you allow
>
>
>
> While the LDMOS are more rugged than the MRF150 style parts, and a I have
> a jar full of 150s to show for it, they are still not as tolerant of faults
> as tubes. The 65:1 SWR metric is not under CW conditions. Likewise the
> open/short You Tube videos are not CW either. 3:1 is likely too high for
> most fully available SS AMPs, not just for the transistors but the filters
> and matching networks as well. Beyond survivability, you will see big
> variations in output when you switch between antennas with 1:1 and 3:1
> SWRs. You are correct on the issues of the filters. I have had more
> filter failures than RF module failures, with the most common component
> failure being the caps. If you are going to build single band amps, use
> heavy duty power caps. With today’s available SS amps with switched
> filters, and smaller parts, 3:1 SWR would be pushing it.
>
>
>
> Protection circuitry is important, but exhaustingly testing the many fault
> scenarios is a time consuming and expensive process where pure economics
> preclude completeness. A vendor with significant volume outside of the ham
> market will be more likely to fund this activity. However, nothing will be
> foolproof given the inherent small geometries of the LDMOS parts. Also,
> there are surely failure modes that need to be protected with analog
> hardware since microprocessor response times will be too slow.
>
>
>
> Using multiple parts improves IMD, but lowers efficiency. The dynamic VDD
> modulation from 4O3A sounds like an interesting way to keep the efficiency
> up. I am curious to see how effective this is.
>
>
>
> Overall, my approach to this may be conservative, but this is what it took
> to stabilize the amps in my environment. All antennas have SWR’s below
> 1:5:1. This helps with reliability and minimizes differing power levels
> when switching antennas on the same band. Lots of airflow and temperature
> monitoring with automated shutoff. All antennas selection is automated and
> interlocked with PTT to keep from changing while transmitting. Manual
> antennas selection will surely result in occasional errors. With all of
> that in place, antenna, coax, and switch failures can still occur. I
> protect the amp the best I can hope for the best. This is the risk I take
> for the operating efficiency they create.
>
>
>
> I am excited by some of the value add being brought to market on top of
> the traditional designs. 4O3A’s team is doing some interesting work and I
> expect some good work from Elecraft. K3LR will team with top engineers and
> produce top notch work that we can all benefit from. SS Amps are clearly
> the future, but there is a lot of overpromising going on now and people
> with marginal installations will experience failures and be disappointed.
>
>
>
> Tom
>
>
>
>
>
>
>
> From: Ria Jairam [mailto:rjairam@gmail.com]
> Sent: Tuesday, December 26, 2017 7:08 PM
> To: Tom Georgens <tomgeorgens15@gmail.com>
> Cc: Jeffrey Maass <jmaass@k8nd.com>; cq-contest@contesting.com
> Subject: Re: [CQ-Contest] Solid State Amps in Multi-Multi Stations?
>
>
>
> I’ve used three models of SS amps here.
>
>
>
> The dirtiest of them all is the Tokyo HyPower 2.5. Next up is the SPE
> 1.3K, which uses a single LDMOS. Cleanest is the Power Genius XL (2 LDMOS)
> which is under beta test here.
>
>
>
> I think the concern about SWR and ruggedness is based on outdated info.
> The latest LDMOS devices by design can tolerate high SWR, up to 66:1. With
> de-rating the devices can handle around 3:1 SWR continuous at reduced
> power. The limitation is in the output filter which are limited by
> saturation of toroidal inductors. The newest amps are also microprocessor
> controlled and protected to the hilt. I am more concerned I will blow up a
> tube amp than I will a modern solid state.
>
>
>
> IMD is less of a concern with two devices as there is plenty of headroom
> and again - microprocessor control of biasing and other parameters such as
> is done with MEffA in the PGXL produces a very clean signal, even without
> adaptive predistortion.
>
>
>
> I do agree that in a K3LR type of environment there is little benefit to
> change out all of those existing, working tube amps for SS ones. That is,
> other than as a trial run, or experiment to see how well they can do.
> However if designing from scratch or expanding, amps can be shared between
> run and mult stations in M/S or M/2. Even in M/M it provides some
> redundancy.
>
>
>
> Ria
>
> N2RJ
>
>
>
> On Mon, Dec 25, 2017 at 9:07 PM Tom Georgens <tomgeorgens15@gmail.com
> <mailto:tomgeorgens15@gmail.com> > wrote:
>
> I have been using home brew SS amps at my 8P5A station exclusively for the
> last two years. The flexibility and increased operator efficiency are a
> big advantage. As such, I am a true believer for this use case.
>
> However, I am not sure that they are a better solution than single band
> amps
> for the pure Multi Multi. With the operating efficiency of instant band
> change largely moot, there is less to offset the down sides. With
> potentially 6 full power signals at once, and in band receivers, signal
> cleanliness is a key factor. The LDMOS parts simply do not have the IMD
> specs of tubes. K3LR has supreme engineering skill and may be able to
> design around some of these limitations on a per band basis. Plus, the
> predistortion techniques are very exciting, but not limited to SS amps.
> Overall, if it can be done, K3LR will find a way, but I would not be sure
> that current off the shelf solutions would be the cleanest for M-M.
>
> Overall, I think creative engineering can help with IMD, but it is not
> standard today. Also, the parts have come a long way, but the LDMOS
> transistors are not as rugged as tubes in most fault situations. If kept
> cool, reliability will be fine with well matched antennas, but will not be
> as tolerant of antenna system faults. Without the need of the flexibility
> of instant band switching, I am not certain that SS amps are a better
> option than single band tube amps for the dedicated M-M station.
> Situations other than M-M can be good matches for SS Amps, but the need for
> a well controlled environment and well matched antennas is still there.
>
> Just to be clear, I am not claiming to have solved any of these problems,
> just that I feel the advantages outweigh the risks in my case. YMMV
>
>
> 73, Tom W2SC 8P5A
>
>
>
> -----Original Message-----
> From: CQ-Contest [mailto:cq-contest-bounces@contesting.com <mailto:
> cq-contest-bounces@contesting.com> ] On Behalf Of
> Jeffrey Maass
> Sent: Friday, December 22, 2017 10:13 AM
> To: cq-contest@contesting.com <mailto:cq-contest@contesting.com>
> Subject: [CQ-Contest] Solid State Amps in Multi-Multi Stations?
>
> Is anyone using solid-state amps at a competitive multi-multi station?
>
>
>
> Which? Any problems?
>
>
>
> 73, Jeff K8ND
>
>
>
> _______________________________________________
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