Friday 27 February 2015

BCB DX - Two New States

With the recent quieting of the geomagnetic field, resulting in K values of 0's and 1's, along with a positive-going DST value, the broadcast band on Wednesday and Thursday night was much more vibrant than it has been in several weeks.

Being located on the eastern shoreline of Mayne Island, the direction towards all of the U.S.A. is over many miles of saltwater, so my main interest is in domestic / U.S.A. DX.

Wednesday evening netted two new states on the BCB ... Kansas and Indiana, for states #27 and #28 respectively, both heard on the Perseus SDR and my 10' x 20' amplified loop.

KWOD, on 1660KHz, identifying as "The Business Channel", was logged during a short top-of-the-hour fade-up at 0600z (10PM local time). Their night power is listed as 1,000 watts while their day power is 10,000 watts.

KWOD - Kansas courtesy:

KWOD Towers courtesy

The transmitter site is located in the middle of a quiet residential district of older homes ... on all four sides.

I shudder to think what RFI problems those living in the adjacent homes must suffer when they are on daytime power!

WSLM - Indiana courtesy :

WSLM, on 1220KHz, was also logged at 0600z, during a two-minute fade-up and in the middle of the local weather report.

Interestingly, the station's night-power is listed as "82 watts", which, judging by the readability of their signal, was not the case. Perhaps the engineer just 'forgot' to switch from their daylight power of 5,000 watts!

Their phased antenna array puts their main lobes, due east and west, so evidently I was catching the northern edge of their pattern.


See what you can hear their during the short recording made of  the "Country WSLM" weather report

I have yet to check last night's recordings to see if conditions have held-up for two night's running ... more later if so.

Wednesday 25 February 2015

'29 MOPA - Small Step

This morning I completed the wiring of the test-bed MOPA's Hartley oscillator circuit. I was using the 80m tank at the time, wound with 3/16" copper tubing. Oscillator keying is about what I expected ... stable but with some ripple on the note. Even with DC on the filaments, many of these open-breadboard oscillators suffer from RF-modulated notes. Sometime wrapping the power supply or keying leads in a ferrite toroid help or eliminate the slight rasp. On the other hand, some builders prefer to have a note that sounds more '29-like, as in all likelihood, not many notes sounded like pure DC back in the day.
I'm really having second thoughts about my construction method and may just jump to the next (final) construction phase rather than slog through completion of the test-bed model. I've already learned much about the layout by getting to this stage and the extra work involved in completing the test-bed model may not tell me anything new.

I'm using a VT-25 version of the somewhat pricey and hard-to-find type '10' tube. The final version will be built in a similar fashion to my Tri-Tet-Ten, on an aluminum sheet atop the breadboard. Hopefully having the groundplane and shorter leads, will lead to a cleaner note in the final version.

I'm rather dreading this next final phase as there is little room for error. The aluminum sheet must be precisely pre-drilled, as well as the breadboard, and protected at all times (especially when making soldered connections) to prevent any finger marks or scratching on the aluminum sheet. There are still several drilling details to be worked out before I can move forward.

Monday 23 February 2015

CLE191 Results
This past weekend's CLE191 activity focused on a small range from 260KHz - 269.9KHz as well as from 470KHz and above. From the looks of the Sun, you would think that conditions would have been pretty good but they were not. Except for a couple of brief propagation lifts in the early morning hours of Sunday and Monday, propagation was very poor over most parts of North America. Even though the sun looks quiet, there are two large coronal holes that have been creating geomagnetic disturbances, juggling the K index from 1 to 4 throughout the three-night activity.

With my Perseus SDR taking 2-minute spectrum captures once per hour, from dusk through dawn, the short propagation lifts become quickly evident ... the majority of my loggings were made during these short windows of propagation:

21 04:00 260 ZXS Prince George, BC, CAN
21 02:00 260 YSQ Atlin, BC, CAN
22 07:00 260 AVZ Terrell, TX, USA
21 02:00 260 AP Sedalia, CO, USA
21 13:00 261 D6 Fairmont Hot Springs Apt, BC, CAN
22 09:00 263 ZQT Thunder Bay, ON, CAN
21 09:00 263 YGK Kingston, ON, CAN
21 09:00 263 YBB Kugaaruk, NU, CAN
21 13:00 263 JDN Jordan, MT, USA 

21 08:00 263 3Z Russell Apt, MB, CAN
21 08:00 264 ZPB Sachigo Lake, ON, CAN
21 08:00 266 XD Edmonton, AB, CAN
21 02:00 266 VR Vancouver, BC, CAN
21 08:00 266 SL Turner, OR, USA
21 08:00 266 SAA Saratoga, WY, USA
21 08:00 266 ICK Annette Island, ALS
21 08:00 266 BZ Bozeman, MT, USA
21 13:00 268 ZWL Wollaston Lake, SK, CAN
21 08:00 269 ZW Teslin, YT, CAN
21 04:00 269 YK Castlegar, BC, CAN
21 08:00 269 UDE Delta Beach, MB, CAN
22 09:00 269 SWT Seward, NE, USA
22 09:00 269 PK Park Rapids, MN, USA
22 09:00 269 ISB Sibley Municipal Apt, IA, USA
21 08:00 269 CII Choteau Apt, MT, USA
23 08:00 510 OF Madison, NE, USA
21 10:00 512 HMY Lexington, OK, USA
21 10:00 515 SAK Kalispell, MT, USA
23 08:00 515 PN Ponca City, OK, USA
23 08:00 515 OS Columbus, OH, USA
21 10:00 515 CL Cresent Beach, WA, USA
22 09:00 516 YWA Petawawa, ON, CAN
23 08:00 521 TO Topeka, KS, USA
22 08:00 521 ORC Orange City, IA, USA
21 10:00 521 INE Missoula, MT, USA
23 08:00 524 HRD Hawthorne, TX, USA
21 09:00 525 ICW Nenana, ALS
21 09:00 529 SQM Big Level Isl, ALS

21 08:00 1725 WH2XDE/3 MA
21 08:00 472.4 VE7CNF BC
21 06:00 474 VE7BDQ BC
21 08:00 475.5 WG2XSV WA

In just a few years the Sun should be very very quiet for several winters, offering some superb LF listening once again.

Thursday 19 February 2015

CLE191 Addendum

WC-332KHz - White Rock, BC

From Neil (WØYSE):

 WG2XSV (experimental callsign) will be running a CW beacon on 475.475 kHz for this event.
​(​In fact it is already running as of 0001 UTC 20 Feb)​.

Power is ~1 watt ERP (+/- 1 dB) from SW Washington State.

Reports appreciated to wØyse [at] ARRL[dot] net

I'm sure Neil would be delighted to receive any heard reports from his weekend CW beacon. Remember that this CLE also covers the 630m band and CW beacons that may be operational there.

If you know of any other 630m CW beacons that will be activated, please let me know and I will post the information here.

Also, CLE reports may be mailed to either myself, the CLE Yahoo list or to Brain Keyte, CLE organizer. Brian's address is:

Reports should include your exact location (Lat/Long preferred or exact Gridsquare), your full name and e-mail address in case Brian needs to send an enquiry regarding your log.

The finer-details of CLE191 may be found in Wednesday's blog.

Lets hope conditions stay nice and quiet as they appear to be doing.

Wednesday 18 February 2015

Hunting For NDB's In CLE191

One CLE Target - 'VR'  266KHz / Vancouver Int'l Approach

How time flies. For you low-frequency buffs, another challenge awaits. From CLE coordinator Brian Keyte (G3SIA) comes the following reminder:

"Our February Co-ordinated Listening Event will soon be here.
We'll be hunting for normal beacons in two contrasting frequency ranges.
One range also gives the possibility of hearing several amateur beacons.
As always, first-time CLE logs will be extra welcome.

Days: Friday 20 February - Monday 23 February
Times: Start and end at midday, your local time
Frequencies: 260.0 - 269.9 kHz
plus: 440.0 - 1740.0 kHz

Many of us should be able to hear beacons in both ranges, though Europe
only has a handful in the '260s'. From 440 onwards, Eastern Europe and
North Africa have several beacons and some regular UNIDs and some NDBs
can be found among Europe's Medium Wave Broadcast Stations.

Many of us are within range of some of the amateur beacons on frequencies around 470 kHz and 500 kHz - we'll be listening for ANYTHING OPERATING IN BEACON MODE, preferably with normal speed Morse.
(We ask operators who sometimes use QRSS, PSK, WSPR, etc., which need
software to receive them, to PLEASE CHOOSE THE SIMPLER MODE during
the CLE so that we shall all be able to receive and report them).

Send your CLE log to the List, preferably as a plain text email
and not in an attachment, with CLE191 at the start of its title.
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 you know it)
# The Call Ident.

Other optional details, Location, Distance, etc., go LATER in the same
line (or in footnotes). Any extra details about UNIDs, especially strong
ones that may be near to you (maybe their approximate direction, etc.)
will help us to discover more about them. As always, please make your
log useful to old and new members alike by including your own location
and brief details of the equipment and aerial(s) you were using.

I will send an 'Any More Logs?' email at about 18:00 UTC on Tuesday
evening. From it you can check that your log has been found OK.
Do make sure that your log has arrived at the very latest by 09:00 UTC
on Wednesday 25 February.
I hope to finish making the combined results on that day."

These listening events serve several purposes. They:
  • determine, worldwide, which beacons are actually in service and on-the-air so the online database can be kept up-to-date
  • determine, worldwide, which beacons are out-of-service or have gone silent since the last CLE covering this range
  • will indicate the state of propagation conditions at the various participant locations
  • will give you an indication of how well your LF/MF receiving system is working
  • give participants a fun yet challenging activity to keep their listening skills honed

Final details can be found at the NDB List website, and worldwide results, for every participant, will be posted there a few days after the event. If you are a member of the ndblist Group, results will also be e-mailed and posted there.

The very active Yahoo ndblist Group is a great place to learn more about the 'Art of NDB DXing' or to meet other listeners in your region. There is a lot of good information available there and new members are always very welcome.

If you are contemplating getting started on 630m, listening for NDBs  is an excellent way to test out your receive capabilities as there are several NDBs located near this part of the spectrum.

You need not be an ndblist member to participate in the CLEs and all reports, no matter how small, are of much value to the organizers. 'First-time' logs are always VERY welcome!

Reports may be sent to the ndblist or e-mailed to either myself or CLE co- ordinator, Brian Keyte (G3SIA), whose address appears above. give the CLE a try....then let us know what NDB's can be heard from your location! Your report can then be added to the worldwide database to help keep it up-to-date.

Monday 16 February 2015

630m Crossband Summary

Saturday evening's crossband operation was a fun time. Conditions were reasonably undisturbed and some things were learned about the potential of our 'new band'. I really do hope that US amateurs can gain access to the band soon as there appears to be much interest in this part of the spectrum by hams south of the border.

Operating at the specified top-of-the-hour time slots only, proved to be a good way to go as it relieved the boredom of calling CQ for hours at a time while providing a wide variance in propagation conditions throughout the evening.

The breakdown of my log is as follows:

0305z K7EK Gary - Tacoma, WA 80m 599 / 559

0500z WA3TTS calls me following CQ ... sent several reports but N/C. He is 599 on 80m

0510z W7RH Bob - AZ 160m 579 / 579 reports no QSB and 'solid signal' 

0515z WØYSE Neil - near Vancouver, WA 160m 589/ 599 

0520z WA3TTS calls me on 80m following CQ ... sends 429 /QSB report but his 579 report sent several times not acknowledged, N/C [he later reports technical problems]

0555z AB0CW Mark - CO answers my 'early' CQ on 80m ... 599 / 559 solid QSO

0602z NO3M Eric - PA 160m, answers my CQ and we exchange reports 599 / 339

0704z NO3M calls me on 80m to report my signal now solid 559 and we have a few exchanges. Eric is really burning the midnight-oil for this one and much appreciated.

0707z W7DRA Mike, near Seattle, WA calls on 80m 599 / 569

0735z W7DRA 160m reports 579/ 579 

0740z QRT

John, VE7BDQ, operating from a small suburban backyard (80m Inverted-'L' loaded) reports working:

0203z  K7MXE WA / 80m
0259z  WØYSE WA / 160m
0517z  K7EK WA 80m
0707z  NO3M PA / 80m
0730z  W7DRA WA / 160m

One thing that was learned, and will be of interest to small backyard suburban locations, is that low 'cloudwarming' antennas will produce good strong signals both locally and on first-hop skywave stations. John's antenna system is both lower and smaller than my own and nowhere near the ocean. My antenna is probably about twice the height of John's and parallels the beach, almost suspended over the ocean and at an effective height of around 70' ... probably even more at low-tide ... yet, two stations (one in Washington) and one in Arizona, both reported John's signal slightly stronger than my own. Power-wise, I run a bit more output power as well. This bodes well for those who might be thinking that their low and short 630m antennas will not be effective radiators ... It seems that our new band is very forgiving and that not all of the RF is being used to cook earthworms after all!

My thanks go to all of those amateurs that took the time to work us, as well as those that sent SWL reports (received from WA, AZ, IL and CA) ... without your interest, there would be no event.

With two more VE7 stations now on the band (VE7CNF and VA7MM), it is great to see the interest building. It will soon be possible to call CQ and actually have another station respond, on 630m!

Hopefully, one more crossband evening can be had before the winter conditions vanish and maybe, by next season, there will be more VE stations on the other side of the Rockies to talk to!

Saturday 14 February 2015

630m Crossband Tonight!

Just a reminder about the 630m crossband activity night this evening. There have been two updates to the plan. VE7SL will start one hour later than originally planned and John, VE7BDQ, will be listening on both 160m and 80m QSX frequencies for callers.

The frequencies will be:
  • VE7SL TX 473.00KHz QSX (listening) 1808KHz (160m) and 3535KHz (80m)
  • VE7BDQ TX 474.00KHz QSX (listening) 1813KHz (160m) and 3532KHz (80m)
John will operate from 0200Z (1800 PST) - 0700Z (2300 PST) while I will start one hour later. Both stations will call several CQs at the top of each hour segment, at full eirp,  and listen for any callers on the specified calling frequencies.

The last time this was done, transcontinental contacts were completed ... hopefully conditions will continue to co-operate and propagation will be good tonight.

Thursday 12 February 2015

The Boys of Summer

This past week,  Les Rayburn (N1LF), compared his yearn for the start of spring baseball to the late spring return of summer VHF openings, with this delightfully nostalgic post to the VHF reflector.

It occurred to me this morning that being a VHF operator is a lot like being a baseball fan. It was warm and sunny here yesterday, and this morning the air has that first touch of Spring in it.

Sure, there arestill cold days ahead--but you just have that feeling that we've turned the corner on Winter. The days are getting a bit longer, and the sun doesn't set quite so early anymore.

And like baseball fans, we start to look forward to those first
rumblings out of the Spring league.

For me, that means the confident voice of August, K5HCT. Nothing heralds
the arrival of the season like those first faint signals and the
familiar refrain..."Here Comes Texas!". This is nearly always the first
call I hear in the season, and the last remaining on the band at it's end.

In my boyhood days, I loved listening to baseball on the radio at night.
Those far away places, and the crack of the bat---mixed with the static
and pops of Summer storms. It was like a magic carpet that could
transport me thousands of miles away...The rest of the year, I still
enjoyed tuning the dial during the overnight hours--maybe listening to
the Herb Jepko Nightcap show from Salt Lake, or Larry King---but radio
wasn't the same without baseball. And those months between the World
Series and Opening Day were the longest of the year.

All these years later, things haven't changed much. I still love
listening to baseball on the radio---but now while waiting for opening
day, I find myself turning another dial...listening hard in the static
to see if I can hear that faint signal on the calling frequency. A deep,
rich, confident voice calling "This K5HCT, Here Comes Texas!".

Somebody press play on that MP3 player or I-Phone---cue up Don Henley's
"Boys of Summer"...I'll hum along and wait for Spring.


Les Rayburn, N1LF
121 Mayfair Park
Maylene, AL 35114

Tuesday 10 February 2015

'29 MOPA Progress

Another few small steps were taken this past weekend in the construction of my 1929-style MOPA, previously described in earlier blogs. Now that all of the parts have been either procured or manufactured, I've been playing with developing a suitable layout.
I've always liked the longer, skinnier appearance of breadboard rigs compared to the short, deeper ones and have combined this look with my love of the early 30's style. This was a transitional period in construction methods, as fabrication slowly changed from breadboard to metal chassis construction. The period in between involved mounting a metal sheet on top of a wooden breadboard, taking on an attractive 'art-deco' appearance, also popular in this period. A good example of this type of construction is seen in George Grammer's landmark 'tritet' oscillator rig which I duplicated several years ago, in a much modified version, for 10m CW.

The new MOPA will take on a similar appearance, with an aluminum plate over a mahogany breadboard. The tentative parts layout is shown below, minus the metal plate. I used the photograph to plan the wiring and to make layout notes.

Amplifier on left - oscillator on right
Although this early 30's style is visually attractive and offers the advantage of shorter and more efficient ground connections, it is a bit of a nightmare to construct. Many of the parts must be both mounted and insulated on the groundplane, while other connections must go through and under the breadboard chassis ... but I think the overall result will be worth it.

In order to mount all of the tuning capacitors above ground, a set of hardwood spacers were turned on the lathe. The spacers have been coated with two coats of spray-on lacquer to finish them in appearance as well as to keep moisture from penetrating


One of the hardest vintage components to source are era-appropriate fixed resistors. Even when found, so many of the original ones have drifted in value and cannot really be trusted to stabilize. Accordingly, I have  manufactured all of the ones needed, using more modern brown-body resistors.

First, the color bands were sanded off and then reproduction "OHMITE" labels were made, very similar to the original style.

The labels were then glued to the resistor bodies and given an orange color-wash using highly diluted acrylic paint. It would be nice to find good originals but these should work as a suitable substitute and will certainly maintain their value for many years.

The next job will be to fasten all of the components to the test-bed, wire it up and test everything out before stripping and rebuilding the finished version ... lots of work still ahead.

My old single-tube Hartley is starting to look not so bad after all!

Sunday 8 February 2015

630m Crossband Activity Night

630m to HF Crossband
Since getting the new 630m band (472-479KHz) here in Canada, one of my favorite ways of promoting interest in the new band has been 'crossband' activity ... that is, transmitting on 630m while the other stations transmit on a predetermined HF (QSX) frequency, usually on 80 or 160m. There are many amateurs in the U.S. who are interested in getting the band as well as many Canadians that are interested in getting on the band and the crossband activity usually generates a lot of interest. Both myself and John, VE7BDQ, have enjoyed making several crossband contacts this past winter and will once again be soliciting crossbanders this coming Saturday evening.

Our plan is to operate from 0200Z through 0700Z, (1800-2300 PST Saturday). Beginning at the top of the hour, we will both be calling CQ on CW and listening for any callers on HF. CQ's will continue until there are no more callers and will begin again at the next top of hour time slot. This should allow for a wide variation in propagation and the possibility of eastern contacts as the evening progresses.

The frequencies will be:
  •  VE7SL TX 473.00KHz QSX (listening) 1808KHz (160m) and 3535KHz (80m)
  • VE7BDQ TX 474.00KHz QSX (listening) 1813KHz (160m)
It is hoped that as many stations as possible will give a listen for us and be able to call on one of the HF QSX frequencies. Both John and myself will be running at the maximum allowable eirp for the duration of the activity.

If you have not had a look for any 630m stations, hopefully you will take the opportunity this coming Saturday night ... you really do not need any special antennas for receiving on 630m. Many of the stations that I have worked on crossband have been using HF dipoles for low-noise reception.

I'll be promoting this event on several of the reflectors and groups that I regularly enjoy and I also invite you to pass the word on to others. Please watch the blog for further updates.

See you Saturday I hope!

Thursday 5 February 2015

House Number Four - Update

Regular readers will likely recall  my early January blog describing the sudden and very unwelcome appearance of a severe noise problem badly affecting my LF reception. I had spent an afternoon D/F'ing the noise source (which was being radiated via the local power lines), only to discover that the residence in question was not occupied ... and has been vacant for the past seven weeks as the noise continued.

The culprit

Yesterday I noticed that the home was once again occupied and this morning, with radio in hand, I paid visit. It seems that the part-time residents had been spending the past several weeks in Hawaii and had just returned to the house to check up on things. I explained to the owner what I believed to be the problem and, as suspected, it was a CFL light ... a particularly noisy one. Turning the light on and off quickly verified the culprit light and swapping the bulb out for a different one produced no observable noise, as was the case for one that had been left switched-on in the living room.

Whether the offending bulb was just a poorly designed one, a very early manufactured model or one that was about to fail, I do not know ... but I am amazed at the strength of the QRN (and QRM) that the bulb was able to produce at such a distance, about ten properties away!

CFL Crud on LF

The owner was very concerned that he had unknowingly caused a problem and was very apologetic, as I have found with similar situations in the past.

One of the worst was also a CFL bulb that had actually burned-out and was located in a nearby (three properties away) crawl space. When finally traced, the bulb was heavily charred and had partially melted at the base, yet was still producing an ear-shattering level of crud right into the HF spectrum.

In cases like these, it is often difficult to get an accurate D/F on the signal through normal means since the signal is being propagated via the overhead powerlines. Attempts to D/F the signal almost always point to the closest powerline and not to the signal source. Usually such a noise generator will be confined to your local power grid ... that is, the homes that are powered between the two large power distribution transformers in your local neighborhood. In my case, this limits the search to about 15 homes.

I have found that the best way to tackle this is to make a 'noise map' and to try and measure the noise intensity at a similar point for each property - ie. directly beneath the powerline as it enters the property. This will usually put you at the same vertical distance from the line and will give you a better noise sample that is directly (or not) associated with that property. After mapping this out, if the culprit property is not obvious, then you will at least have narrowed it down to a very few choices. Other types of noise, that can be detected into the VHF range, are probably best detected using normal D/F methods.

After bringing the offending bulb home, I Google-searched the product name and number and came up with a 'product recall' for this particular model.

"According to a Health Canada and Electrical Safety report, the lamp may overheat and melt the enclosure exposing live parts, posing a risk of fire and/or electric shock."

Apparently they were indeed manufactured incorrectly and it's just as well that it was found and removed before causing serious damage!

Once again  LF sounds as it should. Hopefully it can remain this way for a long time but with the proliferation on noise-making appliances and 'improvements', I have my doubts.

Tuesday 3 February 2015

CLE 'Listeners' Survey

The following message was sent to Yahoo Group's ndblist members early this morning, from Brian Keyte (G3SIA), CLE activity co-ordinator. Perhaps you are a member that doesn't get the mail or maybe a non-member that occasionally reads the group postings but missed the message. In any event, this short survey would help Brian to keep up with your ideas and activity when it comes to CLE planning. All that is needed is to 'copy and paste' the questionnaire into an email and send it to Brian's address, listed in the message.

I'm the chap who looks after our monthly Co-ordinated Listening Events (CLEs).

About 70 of our NDB List members have taken part in recent CLEs - and the other 550 members haven't. Only about 250 members have ever sent a CLE log (including all ex-members), so more than 300 current members haven't.

If you are one of the 300+, do you sometimes look at our monthly CLE results and maybe find bits of them interesting or useful?

This is NOT a sales pitch to try and make you take part, welcome though that would be! However, if several 'non-CLE' Members are finding the results helpful, I would like to know whether we might improve the way the results are presented to make them more understandable and more useful to our members generally?

If you are interested, it would help me if you could please reply DIRECT TO ME at

Please just edit the 7 questions below to show your answers.

It will only take a few minutes.

I will keep your reply confidential and I will try to acknowledge all replies individually - there may be just yours or there might be 100 of them !!

(No replies from regular CLE-ers, please - many of them commented individually about CLEs generally in a recent Survey. Any changes would not devalue the results for CLE-ers themselves, of course)

1. How often have you found any individual listener's CLE log of interest?

Once or twice

2. How often have you looked at any of the CLE combined results?

Once or twice

3. (if any) Which results were of interest?

Tables, etc. in the emails sending the results
Tables, etc. in the Excel attachments
Tables, etc. in the CLE Archives

(accessed via our CLE Page )
Things in the 'Co-ordinator's Comments' emails after the events.

4. Did you find that the results needed further explanation?

Yes, sometimes
Yes, often
Yes, always

5. If 'Yes' how could they, or anything else, be improved?

6. Have you sent your own listening log(s) to NDB List?

Once or twice

7. Finally, please confirm that you are one of the 300+

I've never sent a CLE log
I've only sent 1 or 2 CLE logs


Brian Keyte

(CLE Co-ordinator)

(I'll have your email address to reply - no need to give your name or country if you'd rather not)

Sunday 1 February 2015

Measuring The New Lenses

Yesterday I had the chance to have a closer look at the two lenses recently purchased for a new portable lightwave receiver. The initial testing procedure of the page-size fresnel (actual size is 200mm x 270mm) proved incorrect and required more space than the bench top could provide. Eventually the focal length was measured as ~ 368mm +/- for an f/d, or F number, of 1.36 ... a convenient value and much better than the 'other' common fresnel page reader focal length of ~ 600mm. This jibed nicely with the recommendations given in Clint's (KA7OEI) website optical information:

"For practical reasons, it is recommended that an optical system using Fresnel lenses be designed using lenses that have an F-number in the range of 0.5 to 1.5 - that is, around 1. Remember: The "F-number" is the focal length divided by the diameter of the lens, so for an F-number of unity or one, the diameter of the lens would be the same as its focal length."

The lens was able to bring a small LED flashlight (consisting of an array of 21 white LEDs) into surprisingly sharp focus although the shot below does not reflect that due to my camera's poor focus in the darkened room.

The glass 4.5" magnifying lens proved to have a focal point of 203mm for an F number of 1.8. This lense produced an even sharper image of the same light source and may be the best candidate for the portable receiver although the larger aperture of the fresnel might not be worth counting out at this point.

The fresnel may work well for a transmitter and will likely require a small (inexpensive) secondary focusing lens between the LED and the fresnel, in order to have the LED efficiently illuminate the fresnel. The secondary should effectively gather and focus as much of the emitted LED light to just within the boundaries of the fresnel without any wasted light energy being lost to spill-over at the edges.

It would be great to have a permanent lightwave 'beacon' that one could test various receiver lenses and combinations but at present there is very little activity here in VE7 land ... although that is changing, with the interest of another local, VE7IGH (Greg) near Vancouver and right across Georgia Strait from my location. Grant has already built a receiver and will soon start on transmitter construction ... way to go Greg!