Tuesday, 12 September 2017

Drake 2NT And The Novice Rig Roundup (NRR)

One of this summer's radio workbench projects was to refurbish my Drake 2NT transmitter for this winter's NRR event. The 2NT was introduced in 1966 with the 'novice' ticket-holder in mind, selling for $129. It was the first and only CW-only transmitter produced by R.L. Drake.

As novice transmitters go, the 2NT was a cut above some of the others out there, boasting interesting features such as a built-in antenna changeover relay, sidetone oscillator, grid-block keying and built-in low pass filter.

The tune-up procedure was simplified as well and with Drake's reputation for quality construction, the 2NT became a popular choice for Novices and Generals alike.

My own 2NT was purchased, along with the matching 2C receiver and speaker/Q-multiplier combo over 25 years ago at a Washington state ham fleamarket. Ever since then they have been patiently sitting on the shelf, trying to catch my attention.

The motivation and much-deserved attention finally arrived this year after enjoying last winter's NRR and hearing several great-sounding 2NT's on 80, 40 and 15m CW. I operated the week-long Roundup with my homebrew 'Longfeller' at 5W output, in order to qualify for the QRP category.

6AG7 - 6V6 'Longfeller'
I have to admit, the Novice Rig Roundup, was one of the most enjoyable contests I have entered in many years! Hearing many rigs from the 50's and 60's sounding so good was just a bonus. It was particularly gratifying to be able to work the midweek daytime activity on 15m ... a luxury that we may not enjoy now for several years if most of the long term solar forecasts are correct.

I eventually ended up with 68 contacts, but at 5W, it was a challenge ... most of my many 'CQ NRR' offerings were unanswered, so it was mostly a 'search and pounce' operation. With this in mind, I soon decided that next time, I'll get the 2NT ready to go and hopefully, with a little more oomph, can attract some callers.

Each entrant received an NRR certificate - a nice touch

Rather than hunt down and purchase the individual replacement electrolytics, especially the multi-unit can capacitor which was impossible to source, I ordered the '2NT re-cap kit' from Hayseed Electronics. They supply replacement kits for several boatanchors and are able to make and stuff multi-section can capacitors to match the original size and specs ... and all at affordable prices.

After cleaning the chassis and all of the switches, re-tubing with new tubes and removing / replacing all of the electrolytics, the 2NT was ready to go. Using a crystal for excitation, the following results were obtained:

         80m 103W input 75W output efficiency = 73%
          40m  92W input 65W output efficiency = 71%
          20m  92W input 65W output efficiency = 71%
          15m  92W input 55W output efficiency = 58%
          10m  92W input 50W output efficiency = 54%

Keydown voltages averaged ~520V while plate current ranged from 170-200ma. All-in-all, right on target and not bad for a 51 year old transmitter!

The 6EA8 modified Pierce oscillator in the 2NT seems particularly 'crystal-friendly', as every old style FT-243 style crystal that I tried sounded great. Even the newer ones from AF4K using a modern HC-49 crystal slab mounted inside a vintage FT-243 holder sounded great and worked perfectly.

My newly refurbished 2NT - ready to go

A couple of days later, I returned to the bench to take some blog photos of the rig delivering power into the wattmeter. When I turned the 'stby' switch to 'transmit', the plate current suddenly shot up (with no keying) and the meter on my Variac supply indicated over an amp being drawn by the power transformer ... all with zero output and no crystal plugged-in!

A look at the schematic diagram revealed that with the grid-block keying system, the final amplifier's cathode is always grounded and a low voltage negative bias applied to the grid keeps the plate current cut-off until being keyed ... with cut-off bias missing, plate current will soar, along with transformer primary current. I suspected that something had gone haywire with the bias supply.

A quick check of the 2NT's printed circuit board containing the bias system components among others, indicated a discolored silicon rectifier (D5) in the bias supply. An in-circuit measurement revealed that it was indeed shorted, basically supplying raw AC across the filter capacitor and shorting out the transformer winding, quickly elevating the transformer's temperature in the bargain ... not good.

Although the diode only has to handle a small amount of current, it was mounted with a heat-producing 2W resistor straddling its top surface. As well, the phenolic circuit board was noticeably discoloured from the heat. I suspect this was the main reason that D5 eventually failed.

My 2NT was an early one, serial #670, so perhaps this parts-arrangement was re-engineered in later models. Once the diode was replaced with a much smaller modern one, of twice the rating, everything returned to normal. The last thing I would want to do at this stage is to burn out the transmitter's unique power transformer, undoubtedly impossible to replace nowadays.

The next bench project will be to refurbish and improve the stability of my Heathkit VF-1 VFO and to mate it with the 2NT.

'55 QST VF-1 ad
There are several things that can be done to a stock VF-1 to improve its performance. Its wonderful backlit green dial will bring back a lot of memories from my teenage operating days with the VF-1 ... most, but not all of them, warm and fuzzy.

Another small quirk noticed on my 2NT is the meter mount. My early model has the meter mounted so low that the silk-screened 'PLATE CURRENT MA.' label is not clearly visible when looking straight-on.

My #670
Later models show that this was changed by moving the meter a little higher so that the label can be easily seen without having to look down inside. Nothing major, but something apparently missed during the initial panel design.

Later models
I'll have more to say about the 2018 NRR later, but if it's something that you may be interested in trying and you don't yet have a suitable novice-style rig, it's not too late to start looking, building or refurbishing.

You can read many interesting soapbox comments and see some nice NRR station photos from the previous two events here and here, but read with caution as you could easily get hooked. I find pages like this very inspiring and they remind me of the days when QST would publish photos, soapbox comments and exacting equipment descriptions used by each section winner in the annual November Sweepstakes contest.

Winner's gear in '55 CW SS - remember these?
NRR activity really skyrocketed last winter and I expect that it will be an even busier event next time. There are several CW contests that I'm looking forward to this winter and the NRR is right near the top of the list. I hope to see many of you in the 2018 NRR!

Thursday, 7 September 2017

Cycle 24 - Still Kicking

This week's Sun

Well, just when the sun was showing some nice signs of growing quiet for the upcoming winter, Cycle 24 has once again demonstrated that it's not going down without a fight.

For the past few weeks of quiet solar conditions, low band propagation, in spite of the time of year, had been performing well, with both 40 and 80m having a nice level of evening CW activity stretching out to the central states and to the east coast.

That all changed this week when the Sun let loose with a series of powerful flares, one of which was the strongest in a decade ... all very surprising for a Sun that has already shown us many days of spotless conditions as it winds its way to the bottom of the cycle.

With Solar Cycle 24 being one of the weakest on record, it has shown levels of activity on the way down that could rival the past few much stronger cycles in their waning years. Another oddity for this cycle was its 'double-peak', not unusual per se except that 24's second peak was the stronger of the two.

courtesy: http://www.solen.info/solar/

With the recent flaring and accompanying radio blackouts, HF propagation has been poor and with auroral conditions forecast for the arriving CMEs, it may take some time to recover, especially on LF and MF. But it may not be all bad.

Disturbances like this will normally affect E-W, polar and Trans-Atlantic paths more than N-S paths. Oftentimes, paths to South America on MF and HF will be enhanced as will the Trans-Pacific path, so all is not lost.

There are many websites devoted to providing a 'heads-up' to what might be coming geomagnetically-speaking. Two of my favorites are here and here.

The more northerly you are, the more disruption you will notice and for some reason, VE7 land seems particularly in-tune with solar perturbations as the slightest hiccup on the Sun seems to immediately wreak havoc here. Even amateurs a hundred miles to the south or southeast, enjoy markedly less disruption than us out here on Canada's western edge ... for some reason, we seem more tied-in to the auroral zone activity than we should, given our westerly location. Perhaps the zone dips lower in this region than it does further east but it is something I have observed on LF and MF for decades now.

It seems as though the first hit has just arrived so hold on to your hats:

Space Weather News for Sept. 7, 2017

GEOMAGNETIC STORM WARNING: A CME has just hit Earth's magnetic field
(Sept. 7th at ~2300 UT). This is the debris from Wednesday's
decade-class X9 solar flare. It arrived earlier than expected,
confirming that the solar storm cloud is both fast and potent. The
CME appears to contain strong south-pointing magnetic fields that
typically do a good job of igniting geomagnetic storms. High-latitude
sky watchers should be alert for auroras in bright moonlight. Visit
Spaceweather.com for updates and more information about this developing event.

Hopefully the sun will outgrow its latest temper tantrum and get back to normal quickly so that this fall and winter will be one of the best for low band and MF work in the past decade ... with a quiet Sun, these frequencies can perform amazing magic at times.

Monday, 4 September 2017

VE7CNF / 630m Mobile ... almost.

If you think 160m mobile is a challenge...

Hot on the heels of his recent 630m maritime adventure, Toby (VE7CNF), continued to demonstrate the flexibility of his small 20W 630m portable system with an afternoon of fixed 'mobile' activity from his vehicle.

Local 630m op's in-boxes received a surprise alert on Tuesday:

"Are any of you available on Tuedsay for a 630m land mobile test with VE7CNF/7?"

Toby set things up at Sea Island's Iona Regional Park, situated on the ocean's edge just north of Vancouver International Airport. This gave him a good shot to several of the local 630m ops around the local region.

When Canadian amateurs first approached RAC and Industry Canada for a slice of spectrum near 500KHz, the main goal was to secure a frequency range that would support excellent groundwave propagation for a possible future emergency data network. Whether this will ever happen or not remains to be seen, but Toby's afternoon outing, along with the recent 630 marine mobile activity certainly helps to demonstrate the potential for the band to provide reliable signals with relatively small antennas and low erp.

Toby's basic transverter is rather unique in that the transmitter's FET power mixer also passes signals backwards to function in the receive mode:

"I’ve developed a 630m band linear transverter that produces 30W of transmitter power. It has no power amplifier and draws only 175 mA from a 12V power supply. It works for both transmit and receive with no T/R antenna relays or switching circuits.

I’ve used a bidirectional high-power mixer circuit to directly take 100W of power from a 160m band transceiver and produce useful output power on 630m. For receive, 630m signals can pass backwards through the circuit and are up-converted to 160m. 

My transverter is actually the small box on the dash above the steering wheel. The gear in the back near the variometer is used only during setup to resonate the antenna. It's a signal generator and oscilloscope. The AC transformers are just an isolation transformer that I need to make the test equipment work with my 12V-to-AC inverter."

Toby VE7CNF/7 at Iona
Toby's own report on the outing:

"VE7CNF/7 Operation was from the Iona Beach area near Vancouver, grid CN89jf. The location is right beside salt water. There are no nearby power lines so rx noise was S0. Operation was in daylight, around 4 pm local time. Signals were excellent and all CW was easy copy. 

On 475.0 kHz CW I managed to work Roger VE7VV (CN88il, him 529, me 579) and Jack VA7JX (CN79kv, him 569, me 579). I heard Steve VE7SL (CN88iu) at 599 briefly, then he had a problem and we didn't complete a QSO. He gave me 599 later by email.

The antenna is about 24 ft high and the fishing-rod-and-wire top load is pulled forward about 8 ft. The matching circuit is a loading coil, variometer, and autotransformer. My Tx power was 20W TPO and estimated EIRP 75 mW. The rig was my home brew transverter with an IC-7410."

"After CW I ran WSPR for a while, 23:42 to 00:08 UTC (4:42 to 5:08 pm local). WSPRnet lists my spots as my home QTH CN89ng, but I did have CN89jf entered in WSJT-X. I got spots from WI2XJQ -17, VE7BDQ +14, VE7AB +6, VE7VV +1, W7IUV -26, WH2XGP -30 dB. I also decoded WSPR from VE7VV +7 and VA7JX +9 dB."

"This was great fun. I'll have to try more locations, and see if I can improve the equipment for easier setup. I had great copy on Roger 529 and Jack 569. Working Jack was a surprise, and his signal was excellent. Being beside salt water is magic. Rx noise was so low at that location, near Iona Beach CN89jf."

Our 'new' band continues to demonstrate its ability to offer exciting opportunities to experimenters, home-brewers and DXers alike and for those with the creative imagination to push new boundaries, who knows where one of the first frequency ranges to be used by amateurs back in the 20's might eventually take us.

I can visualize, at some point in the future, the usefulness of a province-wide 630m emergency comms network utilizing a basic 'grab and go' system based on much of Toby's demonstrated work.

If you are a Canadian amateur why not join the fun on 630m now? U.S. amateurs will be arriving shortly and when they do, things should be getting even more exciting on the new band!