Thingking about the 813

Circumstances prevent me from running an amplifier with
my portable installation @W7AYT's QTH in the SF East Bay.
However, I am NoT prevented from designing and building
an amplifier of my own design.

Over the years, I have been warehousing the necessary components to build a 2 x 813 x 2 push-pull linear amplifier.  In the last 60+ years there have been dozens of unique construction articles on building single-813 500-watt amplifiers.  Because 813's can comfortably produce 375-watts, a pair should comfortably run 750-watts and adding another pair (in push-pull) should produce an amplifier that LOAFS @1375-watts, my eventual goal.

In a way, amplifier circuits are amplifier circuits, whether the tubes are small 2E26/6146's, 811's/572-B's, 813's, or the BiG 3-500/4-400 "Bottles".  Class-A is still Class-A; Class-C is still Class-C, Ab-1 is still Ab-1, Grounded-grid is still Grounded-grid.

With the basic configuration in mind, the place to begin is building a smaller version of the 813-amp using 2x6146's x 2 in a push-pull arrangement.  For aesthetic purposes, the goal is to surround each of the 4 tubes with a ventilated "Faraday" Cage.  Because amplifiers don't discriminate, any junk that comes in thru the input networked will be amplified many-fold at the other end.  Shielding the amp tubes all but eliminate the junk that those tubes can amplify.

Shielding the P.A. tubes also reduces RFI to the surrounding electronics in my portable setup.  Previously, power-levels as low as 99-watts down the 8JK ladder line was enough to reboot
an ancient Windoze-7 laptop.  Distance and shielding make all the difference.

While push-pull circuits are by design more complex, a major advantage of this approach is that distortion byproducts can be phase-cancelled out, resulting in cleaner-reception on the receiving-end.  In general, tube amplifiers produce more rich/warm audio, than their solid-state counterparts.  813 tubes are noteworthy for this, which is why audiophiles are so enamored by this 1938-design graphite plate medium-size "bottle".

However, I am a newbie when it comes to amplifiers. Before entering the KW "major-leagues",
I've decided to start with a smaller configuration using 6146's, scaling it up to the full 4x813 design later.  Beginning with a push-pull 6146 design allows testing the concept at lower voltage levels
(800v instead of 2500v).  The 6146-design should yield a ~350 amplifier; ideal for amping a QRP-style transceiver.  Properly designed, it will also look COOL, which a sexy power amp (6146 or 813) should be.

Rather than ramble on and on about a subject I have only a cursory knowledge of, here are
the rest of my scribbled notes which were scribbled, while scribbling notes for another scribble.

WQ6X Dual-OPs another NAQP Ssb contest

With being a part of NX6T's Multi-2 1st-place in the NAQP Cw contest (10+ days ago) and a reasonably successful run in the WAE Cw contest last weekend, the August NAQP Ssb GiG was destined to be an exact repeat of 2 weekends ago. Fortunately, that is what more-or-less happened. 

 Then again, there was a noticeable Space-WX difference between the two weekends.

This contest event was marked (or should I say marred) by the after-effects of solar events
on Thursday, streaming noise and fast-fading (S9 to S1 in 2-secs) into and throughout the
12 contest hours.  At no time during the NAQP was it ever QRN or QSB free.
The QRN and fast-fading was confirmed by numerous stations across the country.

The real issue for WQ6X was microphone audio.  The shack Electro Voice EV-664 mic worked fine with the FT-2000 to open the contest. 

However, after 2-hours remoting into NX6T (using a Heil PRO-Set), the 664 stopped functioning.  

Unfolding an EV-664 transforms it into a mic stand for the PRO-Set, which is more of a contest mic; unlike the Electro Voice, which is more broadcast quality.

The grating-action of the solar-QRN created a fatigue-effect after several hours.  The array of audio filters in use at the W7AYT QTH allows "shaping of the sound' differently in the hopes of remedying the noise-tedium.  However, in Ssb contests, over-use of audio filtering can render voices relatively unintelligible, whereas Cw copy is usually improved using those settings.  Once again, "Stereo-Cw" audio processing saves the operation.

Success in this NAQP event was all about persistence (not giving up) for WQ6X. 
Running as NX6T, it was all about running frequencies, with an occasional S&P search,
done for completeness.  I've written much about persistence in particular. 
([CLICK HERE] to read about that.)

When it was all over, it would seem that NX6T took 2nd-Place place overall
and 1st-place for left coast and the Southwest.

DiD YOU run the NAQP Ssb contest?

Is NX6T or WQ6X in YOUR Log?

WQ6X Works another Wonky WAE Contest

 

 

 

 

 

 

 

 

 

 

The opening page of the DARC website shares the following observation about what makes the Worked All Europe (WAE) radiosport events (Cw, SSb & RTTY) so unique among DX contests:

 

 

 

 

 

 

Over the years, next to the domestic November Sweepstakes contest, the WAE GiG has become my favorite Cw radiosport contest.  NoT surprisingly, BOTH contests simulate some aspect of message-traffic handling; whether it's sending a message header (for Sweepstakes) or a QTC traffic-summary (in WAE), these events keep our emergency preparedness skills prepared for real-life emergencies, should they ever be needed.

The rules for the WAE contest are very clever.  Instead of 2-points for each logged-QSO, we receive only 1-point.  The 2nd point is EARNED by sending a QTC message (to a different station) summarily detailing this QSO.  While sending QTC messages can be a bit tricky, programs like N1MM+ sport an easily invokable pop-up screen (Ctrl-Z), requiring only a single-click to send each QTC message.

Similar to the JIDX contest (back in April) and the All Asian GiGs, non-European stations work ONLY a specific area; in this GiG, Eu stations.  However just in case, I have defined N1MM's F-12 key to send "EU Only" (needed when I call "CQ EU Test").

Friday evening and the 1st-half of Saturday brought us reasonable AWEsome (and quiet) openings
to EU.  Altho the space-WX numbers didn't necessarily reflect it, atmospheric noise slowly moved
in, leaving 40-meters waning Saturday evening and 15/20 meters all but impotent on Sunday.  80/10 meters were miserable no-shows all weekend and 15-meters never came back in time on Sunday.

In WAE, the BiG "fear" is that we will be stuck with a bunch of undelivered QTC messages
(as happened to me a few years back).  During the last hour of the WAE contest, it would seem
that more QTC traffic  is sent than QSOs actually being made.  For WQ6X, QTC-traffic was delivered for all but the last QSO in the log - a 99.95% delivery rate.

Running only 100-watts all weekend, the secret to sustainability was the expansive antenna
farm at the WA6TQT QTH.  Being a single area (Europe) contest, pointing the stacked yagi's
to 30-degrees and a KT-36 yagi at 45-degrees allowed WQ6X to blanket Europe by running
both yagi systems in parallel; switching to either offered a barely perceptible 3db increase
in signal.  Numerous stations noted how strong the WQ6X signal was.

 

 

 

 

 

 

 

 

When it was over, WQ6X had put nearly 19 hours in the operator chair.

DiD YOU work the WAE Cw contest?

Is WQ6X in YOUR log?

WQ6X Dual-OP's another NAQP Cw Contest

 

The week prior to the NAQP Cw contest was full of fascinating intensity.  Needing respite
from it all, a 12-hour Cw contest essentially provided the playing field to make it all happen. 
Having an abundance of more-or-less equally-qualified operators reduced the need for my
operating-presence down to 3 out of the 12-hours, leaving the rest for operating as WQ6X
from the SF East bay.  Because single-OP operations permit only 10-hours on the air,
running from NX6T resolved what to do with WQ6X's off-time.

The goal for WQ6X was to run frequencies on 10m, 15m, 20m and then back to 10m. 
As 10m & 15m  eventually failed to produces, the move was eventually made down to
20-meters, parking there running frequencies until 40m made an early opening (early
for W7AYT's QTH at any rate).

Considering the horrible space-WX we've been up against, it is amazing
WQ6X made over 100 QSOs in the more-or-less 10 operating hours.

 

For NX6T, running as Multi-2 made all the difference in our probable 1st-place finish.

DiD YOU work the summer NAQP Cw contest?

Is WQ6X or NX6T in YOUR Log?

WQ6X gives an IOTA in the RSGB Island Contest

Operating the RSGB IOTA Islands on the Air) contest is always a confusedly-weird operation,
bringing up mixed feelings for me.    The IOTA GiG is loaded w/possibilities, yet often leaves
me disappointingly frustrated.  I have written about this GiG many times before:

• [X] - RSGB IOTA - Blast from the past
  
• [X] - 2021 RSGB IOTA Contest
  
• [X] - 2020 RSGB IOTA Contest
• [X] - 2017 RSGB IOTA Contest

Overall, I like the premise behind the IOTA event, which is to radio-activate islands around the world, 
which are differentiated by a unique numbering system.  All of this is explained on the RSGB Website ([CLICK HERE] to see the rules.)

The 2022 GiG was simply a repeat of the spirit of former IOTA GiGs.  Evidently, this weekend tied
in with some equipment cabling updates at the So. California (Anza) station, requiring us to keep
an eye on low-band SWR signatures.

With no notice that a remote operation was imminent, I began things in Concord as WQ6X. With barely 2 QSOs in the log, a text from N6KI informed me that NX6T could run a Multi-2 operation, beginning at 20:00z, giving us 16 hours to work the NX6T "magic".  During my dinner break, WQ6X managed a few more QSOs in the log - just to say that I was there.

Because the IOTA GiG runs well with WINTEST, I set up both stations at the WA6TQT site (in Anza) to run as a Multi-2 operation, with WQ6X running STN-1 and N6KI running on STN-2.  For the IOTA GiG, 160 meters is not allowed and 10-meters was a virtual no-show, leaving 80 thru 15 meters to make it all happen.  15-meters signals were rather sparse making 20-meters (and later 40-meters)
for most of the operation.

We experienced quite reasonable Southern California openings to Europe in this event.  With the Solar Flux Index  (SFI) down to 91+ for the weekend, I am left wondering what conditions to EU would have been like with an SFI of 170+ (as we had 10 days earlier).  Being mid-summer time, the usual high summer-time noise-levels made signal-copy quite difficult.  Attempting ssb communication amidst all that noise would've been a DISASTER - running Cw was the only way.

When I came on shift at 09:00z Sunday morning, the goal was to work everyone while focusing
on 40/80 meter Asian stations.  Because there are no NCDXF beacons on 40-meters, I rely on the Russian military beacons for signal-level checks.  The Vladivostok ("F") beacon has been off-air for several months.  The fickle "K" beacon has again changed its transmission to "K K" from last week's "K K K" identification.  Kamchatka was LOUD in BOTH Anza and Concord.  The "M" beacon (Magadan) was also present, altho comparatively, not nearly as loud.

JA stations are often plentiful in most DX-style contests.  Because they represent 3 "islands" (AS-007, AS-077, AS-078), 15-point QSOs just "across the pond" was an exciting prospect.  Unfortunately, the JA participation was poor this year, despite solid propagation paths to East Asia.  A couple of lengthy "CQ IOTA" calls on 3522.22 added a WHOPPING 2 QSOs to the log; at least both were island multipliers.

For me, this contest was mainly an exercise in testing antenna SWR in Anza.  It also afforded the opportunity for testing the recently-added AP-411 audio-delay unit along with remote radio operation.  Overall,the external JPS NIR filters on the receiving end seem more effective than the filters built-in to the remote K3 radios.  Stereo Cw with remote operations work just as well as with the local Yaesu FT-2000.

When it was all over, we learned that while the contest rules don't specifically state it, multi-OP operations are for Island Stations Only.  Attempting to submit a log, there was no multi-OP option
for "WORLD" stations.  In the end, all of our work will result in a CHECKLOG.

DiD YOU work the RSGB Islands on the Air contest?

How many islands did YOU Snag?

Is NX6T or WQ6X in YOUR LoG?