Workbench Documentation ...Keeping Track

It seems the older I get, the more 'Post-it' notes I find myself writing. But, for the past decade at least, I have paid close attention to keeping written records of what gets done at the radio workbench. The logbook takes care of 'on-the-air' data, along with QSL information but I ashamedly admit to not having switched, and likely never will, to computer based log keeping.

Time and time again, I find myself referring back to previous work... measurements, part values or wave patterns noted during the construction or testing of various circuits. In fact, I have found that gathering and recording as much data as I can about a particular circuit being built or fleshed-out is an immensely enjoyable part of the homebrewing experience. My notes may not be beautiful but they certainly have saved the day on many occasions when looking back at earlier builds or even just to see where I left off the day before!

When homebrewing, I usually build a test-bed version, allowing me to change components easily and observe or measure the results. For older style tube-based transmitters that I have come to enjoy building, this is usually done on a wooden base while more modern circuits are scratch-built 'ugly' style or 'ugly Manhattan' style on PC board. Once everything has been optimised, the final and better-looking version is built.

Along the lines of keeping track, the same can be said for documenting inspirational project ideas. I maintain several large spiral notebooks in which I cut-and-paste interesting circuit ideas or procedures that I have either seen on the Web or photocopied from books or magazines.

Doug Demaw Article

I have found, from past experience, that not everything on the Web stays on the Web and often times, grabbing a copy before it disappears is often a good idea.




Ideas & Reference Notebooks

The final documentation task is putting together a dedicated 'Operating Manual' for all finished projects, complete with schematics, parts list and operational procedures. I'm not going to keep this stuff forever and hopefully whoever gets it next will at least know where to start before sparking up!




Project Manuals

Keeping track surely adds a little more work to the hobby of homebrewing but the time is well spent and for me, most enjoyable.

W4DEX Crosses the Atlantic on 8.9KHz

W4DEX, Dexter McIntyre, has succeeded in getting his 8.9KHz signal from North Carolina to Europe. It was detected by Paul Nicholson in Todmorden, England. Paul's announcement on the RSGB's LF reflector heralded the breakthrough achievement.


At 2014-06-01 10:00 UT W4DEX began a long transmission of GPS
locked carrier at 8971.000 Hz from 35.273N,80.371W.

Between 2014-06-02 00:00 and 06:00 a carrier was measured
at that frequency here in Todmorden 53.703N,2.072W with flux
density around 0.05fT. It was not very significant so I
combined the H-field and E-field receiver outputs (correcting
for their known phase and amplitude response) to produce a
uni-directional antenna response. This brought the signal up to
a significant level.

The signal bearing was roughly west. W4DEX is bearing 285 deg
from here. The S/N is max on a bearing of 315 degrees which
puts the prevailing south-westerly background nearer to the
side of the antenna response.

This gave the signal a respectable 12.5dB S/N in 46uHz bandwidth.

 


W4DEX Carrier Received in England
 

This was the strongest peak in a span of over 6500 Fourier
bins so is quite significant.

The carrier was also visible during the daylight path in 23uHz
bandwidth with average strength of around 0.02fT and with
similar S/N thanks to the lower day time noise and reduced
bandwidth.

At 2014-06-02 12:00 Dex altered the TX frequency for a blind
confirmation test. Six hours later the carrier (in 46uHz)
had vanished and a new signal appeared at 8971.100 Hz with
the same strength.

An email response from Dex confirms 8971.1 as the new frequency.

Range W4DEX to Todmorden UK is 6194 km.

Ratio of day/night flux density agrees well with LWPC
predictions for this path. LWPC predicts strongest night
signal between 00:30 and 04:30 and a sliding spectrum window
agrees with this.

LWPC requires ERP of 150uW to reproduce the observed flux
density. This is in the center of the ERP range estimated
from W4DEX antenna dimensions and measured antenna current.

I was able to copy Dex's 74KHz QRSS signals in January but going ten times lower is difficult to imagine.

It seems the region below 9KHz is licence-free open-territory for experimenters in the U.S.
This achievement is even more impressive when one considers the low erp and the 'backyard' antenna system used by W4DEX.

Update: Dex has now posted a  LINK to a description of his transmitting setup.

Playing With Perseus

I have long been intrigued with the Perseus SDR and earlier this spring I decided to purchase one for myself. After several years of software updating improvements, Perseus seems to have reached its final state of evolution and has been a favorite amongst the BCB and NDB DXers for several years. The ability to record a 1600KHz swath of the spectrum all night long is one of its key features. Using a freeware add-on called Mestor will also allow several variations of pre-scheduled 'top-of-hour' recordings for those that like to DX the medium wave BCB.

Perseus GUI Screen
 

One of my main winter activities is hunting the low frequency NDB band, especially for some of the elusive pre-dawn Alaskans. Perseus now allows me to stay in my warm midwinter bed while doing all of the early morning listening for me.

The downside of being able to sleep and DX at the same time is the time that one needs to spend later, going over the recorded files and listening carefully to all frequencies of interest....which still beats crawling out of a warm bed at 0600 and heading outside to the shack!

The performance of Perseus below the BCB is nothing short of superb and is the best LF receiver I have used, slightly surpassing the excellent LF performance of my IC - 756PROIII.
Bandwidths as low as 2 - 3 Hz are possible, ideal for separating closely-spaced NDBs that are often stacked one on top of another. The adjustable notch filter can be slipped to the edge of an offending carrier and notch depth tweaked from there, making otherwise covered signals pop out of the pile.

I've also had a chance to use Perseus as a BCB DX - machine as well, where its performance and strong signal handling capability continued to impress me.

I bought my Perseus from Gerry at SSB Electronics where I found customer service to be superb.

Watching Six....Waiting For the Magic

It's that time of the year again. Those truly addicted to 6m know what I mean. Since the late 60's I have been held hostage by the 6m gods from mid May until late July. The 6m gods know when each of us leave the house, for it is usually then, that the band opens. Unsurprisingly, it closes just before we get home again. It's the time of the year when all activities must be carefully weighed against the risk of missing "the big one".

I first became intrigued by the magic of six meters even before getting my licence. As a highly impressionable early teen,  CQ's VHF column tantalised me with pictures of Japanese stations that had been working into North America during the peak of  Cycle 19, the monster of them all. Most of the stations were  homebrew AM and using amazingly simple transmitters, with single 6AQ5's or single 807's...tubes never designed to achieve such VHF greatness. As if that weren't enough, all had that beautiful M-131 microphone as well!



JA7JU's Homebrew 6m Cycle 19 Station

Today seems the first good opening to Europe for our east coast friends. More often than not, the rest of the country is left only to watch or to drool at what they are missing.

courtesy: ON4KST.org

But....every once in a while the gods shine favourably on the west coast and heaven help you and those you live with should it happen on one of those days that you left the house!

 

courtesy: ON4KST.org

It's still quiet today, here on the west coast, but soon the magic will happen once again.

Canadian Amateurs Get A New Band - 630m !

As of May 1 st, 2014, hams in Canada now have access to a new part of the spectrum...just slightly below the standard AM Broadcast Band, on 630m. The actual band is very close to the old Maritime International distress and calling frequency of 500KHz and runs from 472-479KHz. Hopefully we will soon see many Canadian stations using this very interesting MF band as it presents a wonderful opportunity for homebrewing and experimenting on several fronts.

I'm presently using my old 2200m transmitter, converted now for two-band operation, on 630m but will be building some lower powered transmitters which I will describe once underway. At the moment I have had just one contact on 630m, that being with John - VE7BDQ, near Vancouver and about 15 miles away.

630m Antenna Loading Wound on PVC

Over the next few months I hope to present as much information as I can about 'getting started on 630m' and would like to encourage anyone interested in the new band to warm up your soldering irons and join in on the fun.

For more information on LF and MF activity in Canada, see my website page 'Canadians On 630m / 2200m'.

http://www.qsl.net/ve7sl/136.html