[Amps] Amps at Dayton

Wed May 21 20:54:20 EDT 2003

Hi Dave,

Thank you for sharing with us your impressions. While Dishtronix amp seems
to be still in the very early engineering stages, it's good that they are
new players on already troubled amplifier market. As no R&D efforts on
hi-power devices are made, it looks that we have to accept for more years
IMD of not much than thirty dB on solid state. It is still interesting how
Dishtronix solved various thermal design problems, output filtering and
reliable solid state QSK-ing. The rest (protections, auto-tuning, digital
metering and all the uP related stuff) are less challenging today -
excluding of course the cost issues.
Commander and QRO are still on the market, it's possible they didn't find
anymore interest in Dayton.
The new Kenwood solid state TL-933 looks like they took the last JRC SS amp
and changed the logo only. It should be in the Quadra and IC-PW1 class of
price and performance.
I guess that the connoiseurs will still go for next years for conservative
designs around Eimac/Svetlana tubes.
By the way, it's a pity you didn't take the time visit the ACOM to see
inside the not-so-new 2000 model. It's very well built and designed
(surprisingly for AMP purists) and anyway it has a much better engineering
than Emtron. Their customer service is also very good.

73
Morel
4X1AD

----- Original Message ----- 
From: "Dave Haupt" <emailw8nf at yahoo.com>
To: <amps at contesting.com>
Sent: Tuesday, May 20, 2003 5:24 PM
Subject: [Amps] Amps at Dayton

> 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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