This year, I spent most of Friday in forums, most of
which were disappointing. I read a lot of the ham
pubs and online websites, and the forums I chose ended
up being just a rehash of stuff that's already
appeared in print. I was going to use Saturday to
cruise the flea market, but it rained the whole time,
and I ended up using the day to schmooze with some key
contacts for a project I'm cooking up, and doing a bit
of booth duty for a friend. If the AMPS recipients
were spending time in the flea market, that's why I
didn't meet many...
So I didn't get a particularly complete view of the
indoor exhibits, but here's my snapshot of what I saw,
amplifier related.
Alpha Power (aka Crosslink, Inc), had more personnel
in their booth than other manufacturers. On display
were the three amps on the website - the 87A
auto-tune, the 99 manual tune, and the 6 meter amp.
The 6 meter amp was open for inspection, as was one of
the HF amps. Also, they had one or two of the RF
Concepts amps on display, called "Max Amp". They
bought this line of amplifiers from Kantronics a
number of years ago, but I guess these days VHF FM ops
are pretty much an HT-only crowd and solid state
VHF/UHF amps don't sell much. I ended up yakking with
one of the part-time employees they brought along,
because it turns out his "day job" is with an
ex-employer of mine, so it was good to get caught up.
I did not see QRO, Commander or CTI Comtec. I don't
know if this means they're out of business, just don't
do Dayton, or were actually there and I missed them.
Ameritron was there, adjacent to the MFJ booth. All
of their HF amps were open for inspection.
Ten-Tec had the new Titan III amp on display, open for
inspection. This is the amp with two 4CX800 tubes. I
think it has the longest anode-to-tune-capacitor lead
length I have ever seen. That might explain why their
parasisitic suppressors included six carbon comp
resistors each, and had a very long strap. They also
had their twin 3-500Z amp on display. Their big deal
was the new Orion xcvr, which had no shortage of
attention paid to it by booth visitors.
Emtron was there with several amps. The DX-2 is
apparently available either with a single 2.5kW
dissipation Russian tube, or two 4CX800 tubes. The
rep claimed that you get far better lifetime if you
use only one tube, with the equivalent rating of two
tubes. Don't know that I agree with that coment.
They also have the DX-3, an over-power amplifier with
a 3.5kW dissipation tube. I told the rep, "I run no
more than the legal max of 1.5kW. What benefit would
I get by buying this oversize amp?" The rep said,
"It's more rugged." I then asked if ruggedness was a
concern about the smaller amplifiers - should I avoid
them? He said no, the DX-2 was plenty rugged. After
some exchange, he finally acknowledged that if you
plan to run at the legal limit and no more, there is
no reason to purchase the DX-3.
The Array Solutions booth also had a largish
amplifier, but it was not available for sale. After
some discussion, it would seem that the purveyor's
purpose was to look for potential non-ham markets for
RF Power.
Dishtronix had their new solid state amplifier on
display. He's cleverly solved the DC voltage
regulation issue for solid state amplifiers. Instead
of using a switchmode power supply, he's used a
torroid power transformer with oversized wiring, and a
choke input filter. He therefore needs relativly
small filter caps, and gets "good enough" regulation
that he doesn't have to use an electronic regulator.
And, such a power supply is far more efficient than a
passive electronic regulator. He's using 16
MRF150-class FETS (but not sourced by M/A-COM, who
bought out the Motorola RF Power FET line), so the
theoretical max power is 2.4kW. Having worked with
similar devices in the past, I can assure you that
power level would require gale-force winds. Solid
state devices must operate at about half the
temperature of tubes. Therefore, at the same total
power dissipation, you need to move about twice as
much air - or more. But it did look well-designed
enough to confidently run the 1.5kW limit all day
long. Another advantage of running it this far backed
off from saturation is that the IMD could be notably
lower. The IMD contribution of a power FET is
substantially caused by the radical increase in
feedback capacitance that happens when the
drain-source potential drops below about 5 volts. At
saturation, this happens in one FET, then the other,
as the push-pull stage delivers voltages close to the
supply voltage. Running below max helps avoid this
sudden change in capacitance. The individual
amplifier stages appeared to be similar in topology to
the amps in many of the Helge Granberg app notes, but
clearly the magnetics have been engineered, not
copied. Same for his power combining networks -
topology we've seen before, but clearly designed
specifically for this product. I agree with him -
it's the first legal limit solid state offering on the
market. Some info is on his webpage -
www.dishtronix.com.
Icom had the same PW-1 on display. I did not see the
Quadra in the Yaesu booth, but then again, I couldn't
get into the Yaesu booth the few times I tried.
Kenwood continues to not have an amplifier in their
lineup.
At least that's what I saw...others may have seen
things I didn't.
73 DE W8NF
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