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I've just added a new page to my website, The VE7SL Radio Notebook, that describes my NEOPHYTE 1 regenerative receiver spring construction project. The new page can be found here.







Like most simple regens, its performance far exceeds its simple circuit expectations. My listening adventures with it continue during The Radio Board's annual Homebrew DX Contest which runs from July 11 - 24th. You may want to give it a try, after of course, you've checked-out my new web page!

This weekend's upcoming CLE event will be the "Barn Door" listening event.




Participants are required to use receivers without the usual narrow filters. Some of the older tube radios can do this easily as can most homebrew receivers ... especially the regens!

If you've never listened to the NDB band with a wide bandwidth, it is a fascinating experience! If conditions are normal, you can typically hear a half dozen or more signals, all at various pitches, vying for your attention. It's almost as if you have plunked yourself down in the middle of the NDB forest of signals, and they are coming at you from all directions.

Many choose to use one of their homebrew receivers for this event, often as simple as a '1AD' or a '1 Active Device' circuit.

From organizer Brian Keyte:


    Days:      Friday 21 to Monday 24 February 2020

    Times:    Start at Midday on Friday 21st, your LOCAL time
                   End at  Midday on Monday 24th, your LOCAL time

    Frequencies:   Centred on 360 kHz (see below)

    NDBs:     NOT MORE than 100 'normal' NDBs including any UNIDs
                    (That is not intended to be a target to reach)

 

The next CLE, coming up at the end of the month, will be another ‘barn-door’ event where listeners are encouraged to use wider bandwidths than normal ... typically something that will allow you to hear beacons at least 2kHz each side of the frequency that you are tuned to.

Your ears will be the only filter that you need!

This will be the first winter event of this type and results could be very interesting! In the past, many participants have used their homebrew regens including the popular ‘1AD’ (1 Active Device) MOSFET regen, built for the NDB part of the spectrum.

The last time this event occurred, I whipped together a 1AD regen in a day which proved amazingly effective in spite of the mid-summer propagation.




There is still plenty of time for you to put something simple together and you can find some helpful suggestions in my previous '1AD' blog here.

I will have more details later, before the event, so please stay tuned and consider getting something ready ... maybe all you need to do is wind a new coil for your favorite regenerative receiver!

This past weekend's 'Barn Door' CLE' saw a lot of participation, in spite of the mid-summer doldrums and the universal nasty lightning noise.


After reading CLE-organizer Brian Keyte's interesting posting to the ndblist, describing his homebrew single transistor regenerative receiver, I was inspired enough to dig out the soldering iron and build one for myself.

The circuit widely described as a '1AD regen' was originally designed several years ago by crystal-radio guru Mike Tuggle out in Hawaii. Mike is widely known for his exquisitely designed "Lyonodyne" DX crystal radio, which inspired an entire decade of intense DX crystal radio building activity back in the late 90's.

Mike Tuggle's 'Lyonodyne' DX Crystal Radio

His  '1 Active Device' medium-wave regen consists of a handful of simple components and a MOSFET that is up to the task. His design was, and still is, being duplicated by many throughout the NDB DX listening community.

Mike's original 1AD regen

Mike recently sent me the circuit diagram that he eventually settled with, showing two possible ways of extracting audio with the widely popular Bogen T725 output transformer.



My own version used Mike's output scheme on the right and the RF circuitry in Roelof Bakker and Steve Ratzlaff's modified version, shown below. I had to increase the tickler (feedback) winding from 4 turns to 11 turns in order to get any regeneration. With 11 turns, my regeneration kicked-in at about three-quarters from the end of the regen control. At some point in time, while testing, some of the leads from my Bogen T725 output transformer momentarily brushed against each other, smoking my FET. Upon replacing it with another BF966, the receiver was much hotter, with regeneration kicking-in very close to the start of the pot. I'm not sure if the first FET was already damaged or that there is enough variation from FET to FET (of the same type) to make some have more gain than others. Accidentally blowing up the FET proved beneficial in the end!



Although most users employ sensitive sound powered headphones with their regens, including myself, some use modern phones with an extra stage of audio, such as an LM386.

Although not nearly as pretty as Mike's regen, my own 1AD was built in an afternoon, just for the recent Barn Door CLE.

My own MW 1AD regen

I later added a calibrated dial plate, breaking the segment from 200kHz to 550kHz into two separate bands, with calibration ~ +/- 1kHz so that I pretty much new where I was tuning at all times. This allowed me to target specific beacons and wait for them to fade up.

When first published, Mike suggested the BF966 MOSFET seemed to work well and I purchased five of them with the intention of someday building a 1AD for the NDB band. The purchase came in handy, as today, the BF966 is no longer available. Apparently the similar, and still available BF998 works well (from tests done by Steve Ratzlaff) but is now in an SMD package at just 18 cents! No doubt there are dozens of MOSFETS that will do the job and at these prices, experimenting with various devices would be a very worthwhile project.

When operating, the regen proved to be surprisingly sensitive, and by using my 10' x 20' loop, I was able to put my local pest (AP-378 kHz and 1/2 mile away) into a deep null so that its huge signal was no longer blocking the top half of the NDB band. The null allowed me to hear beacons within a few kHz of the blowtorch signal as shown below:

This coming weekend will see the 'Barn Door' CLE, mentioned in a previous blogspot here. Listeners are required to challenge themselves by listening on a receiver using a wide enough bandwidth that several kHz worth of signals can be heard at once.




The 'immersive' effect this wider bandwidth mode provides is much different than when listening with narrow filters and can make digging out IDs a lot more challenging. Throwing in some mid-summer lightning noise makes it even tougher, but if it were easy, it just wouldn't be much fun!

Many, including myself, will be using homebrew single MOSFET regenerative receivers, often called a '1AD' since they normally use just one active device. I've just finished testing my own version and have been able to hear some night time DX so hopefully the band will be quiet enough to hear some signals during the CLE.

From CLE organizer Brian Keyte, here are the details explained ... and good luck to all participants!

Hi all

It is an opportunity to bring back to life basic kinds of receiver - anything with low selectivity which allows you to hear NDBs on several frequencies simultaneously - leaving the barn door wide open!

Listening with 'back to basics' equipment often gives very satisfying and unexpected results.  It can also show us ways of improving our listening when operating more normally.

Our last Barn Door CLE was No. 209 in July two years ago.

Here comes our fifth 'Barn Door' CLE.  Between us there will be a great variety of different receiver types in use.

    Days:      Friday 27 to Monday 30 July 2018
    Times:    Start at  ## 11 a.m. on Friday 27th, your LOCAL time
                   End at   ## 3 p.m. on Monday 30th, your LOCAL time
    Frequencies:   Centred on 360 kHz (see below)
    NDBs:     NOT MORE than 100 'normal' NDBs including any UNIDs
                   (That is not intended to be a target to reach)

We are all asked to listen with NON-SELECTIVE receivers - i.e. with a WIDE
filter or NO filter.  Your 'barn door' should be open wide so you could
hear, at the same time, any NDBs 2 kHz away on both sides of your receiver
setting - E.g. NDBs on 348, 349, 350, 351 and 352 kHz with the receiver set
to 350 kHz.

## The extra daytime hours on the first and the last day might help some of
us planning to listen out of doors.

You could listen with:

1. A simple home-made receiver, such as a single transistor set with regen.
    (e.g. based on the sets used by Mike, Finbar and others).

2. OR - an Ultralight receiver, maybe one converted to cover the NDB
    frequencies with a modified aerial.

3. OR - an 'antique' receiver (e.g. Eddystone, R1155, Scott, etc.)
    Perhaps you have something you've not switched on for many years?

4. OR - a normal receiver but with NO filtering, or using a WIDE FILTER,
    (not less than about 2 kHz and no selection of an audio filter).

You choose how wide a RANGE of frequencies you will listen in, CENTRED ON
360 kHz.  You could choose 350-370 kHz or 330-390 kHz or 260-460 kHz, etc.
   (This allows each of us to choose a +/- range with enough NDBs to
   match our equipment's capability.  It will also allow our loggings to
   be compared in the Combined Results, at least around 360 kHz).

Logs should show NOT MORE THAN 100 NDBs please (if more than 100, the
harvester program will 'drop' the loggings furthest from 360 kHz).

There are several extra targets you could set yourself - maybe the wide
bandwidth, the centre frequency of 360 kHz and the 100 loggings limit do not
challenge you enough!

You could listen only in daytime and/or away from home.
Or how about NDBs on 360 +/- 10 kHz or even +/- 5 kHz?
The Twente remote receiver in Holland could be interesting to use for the
whole of your (only) CLE log.
( Go to http://websdr.ewi.utwente.nl:8901/ and read the advice there:Select AM and 'MAX IN', enter e.g. 354.7 in the frequency box and change the
filter's limits to 2 or 3 kHz from the centre frequency on both sides )

We’ll summarise everyone's equipment on the first page of the combined
results, so please describe:
The RECEIVER/AERIAL you used and the FILTER(s) selected, if any.
If homebrew, please quote:  the total number of active devices used –  e.g.
1 for a single transistor stage ( 1AD ) -  the transistor/valve types,
whether using regen.,  etc.

All the usual procedures for making logs apply:

Send your CLE log to NDB List, if possible as a plain text email and not in
an attachment.

Please show on EVERY LINE of your log:
    # The full date (or Day No.) and UTC (the day changes at 00:00 UTC).
    # kHz - the beacon's nominal published frequency, if known.
    # The Call Ident.

Show those main items FIRST on each line, before other optional details
such as Location, Distance, etc.  Please send your complete log with
CLE234 and FINAL  in the Subject line.

Whether you are a first time CLE-er or a regular, make your log interesting
to everyone by showing your own location and your equipment details.
Do feel free to share any comments you have on this unusual event.

Joachim or I will send the usual 'Any More Logs?' email at about 17:00 UTC
on Tuesday 31st so that you can check that your log has been found OK.
Make sure your log has arrived on the List at the very latest by 08:00 UTC
on Wednesday 1 August.   We hope to complete making the combined
results a day or so later.

However you choose to take part, we hope you will find your 'back to basics'
listening enjoyable and worthwhile.


P.S.   NOT FOR YOU?

Listening without narrow filters is not going to revolutionise our hobby!
But there ARE some unexpected benefits and advantages:

1. Hearing several beacons on a few adjacent frequencies at the same time
becomes easier as you get practice at recognising them by listening to their
very different audio tones. At first, when listening to a random frequency
setting, you may hear just one or two beacons. But after listening for a
little while you realise that there are three - - four, maybe more, all of
them audible without altering any of the receiver controls.
It is a skill that gives satisfaction as you improve.

2. Hearing multiple beacons like that can be useful because, with no extra
tools, you can hear NDBs over a wide frequency range much more quickly than
usual, perhaps spotting the arrival of new UNIDs or the return of occasional
beacons.  (To protect your hearing, keep your receiver gain controls fairly
low, except on very quiet frequencies).

3. With normal listening it is easy to miss any NDBs that have abnormal
carrier frequencies or non-standard offsets.  With 'Barn Door' listening
they won't escape because everything is let through.

4. When using a wide filter, you may be surprised by hearing some Broadcast
Station signals (e.g. harmonics) among the NDBs and you will be able to
identify them.
With a narrow filter, often you may not recognise an AM signal as audio
- it just sounds like nondescript 'hash' affecting a wide range of
frequencies around the central carrier.


Maybe listeners will report some other good things about their barn door
listening during the CLE - and probably some bad things too!

Do join in if you can.

   Brian
----------------------------------------------------------
From:   Brian Keyte  G3SIA          ndbcle'at'gmail.com
Location: Surrey, SE England         (CLE coordinator)
----------------------------------------------------------

Don't forget that help and chat regarding NDB DXing can be had on the ndb group list here.

For those of you following this summer's regenerative receiver building adventure, I am pleased to say that all testing has now been completed. My earlier doubts about receiver-performance have now been totally resolved.

I've also published a new page on my website which contains more pictures and details of all phases of the project. The page also has a recording of the 40m CW band, made a few evenings ago, which really best demonstrates how the receiver is working.

In the meantime, much consideration has been given to the next project work ... it will be a return to my earlier lightwave experiments. During the recent visit here by Toby (VE7CNF) and Mark (VA7MM), both expressed interest in building some lightwave equipment (in fact ... 'parts' have been ordered!) to try some direct LOS work as well as to try some QRSS clear-air scatter / cloudbounce work. It's really exciting to see some new interest in this fascinating mode as the field for experimentation in both transmitting and receiving systems is quite vast.

My first task will be to build a 4" optical tube receiver or another boxed Fresnel-lens type for portable operation, here on Mayne Island, to see if I can scatter a signal to the other side of the island and detect it while operating in the field. There are a couple of nearly 600' peaks on Mayne which should provide a good shielding effect for testing ... maybe too good. Time will tell.

courtesy: http://en-ph.topographic-map.com/

Work has begun on a new "summer project" (as well as re-shingling the woodshed and garden shed roofs) ... a 3-tube audiodyne receiver.





This one appeared in the January 1933 addition of QST (Rationalizing the Audiodyne by George Grammer) and then in subsequent Handbooks for a few years. It's the type of building I like to do, with lots of pre-planning before breaking out the tools, measuring all components carefully and refurbishing some of the 85+ year old parts.

courtesy: arrl.org

This particular receiver has lots of metalworking involved as it uses two shielded compartments to keep the detector and RF stage from seeing each other. As well, it uses a set of ganged tuning capacitors to have the RF stage track the oscillator. The coils are wound to produce a lot of ham-band bandspread on the big drum dial... hot stuff in '33.


So far, I've completed all of the shielding and drilling of critical holes ... all measured three or four times before taking the plunge. The only chassis available (Hammond or Bud) is about 1/2" smaller in width and depth, making everything just a little snugger, but still maintaining proportions.


I have no idea how it will perform but so far it's been a fun project. If it works well, even better yet ... but handily, it's given me a good excuse to avoid more important things, like the two roof projects!