ARRL Homebrew Challenge 3 radio update: re-use of an old radio chassis

I picked up this old Nemes Clarke receiver at a local hamfest. It is a VHF FM tube receiver.

I then salvaged the chassis of this receiver, removing all internal components and saving those for a later date for re-use in other projects.

Some of these salvaged components included a nice power supply transformer for tube gear, two chokes, and a pair of 10 uF oil capacitors. A number of tubes were pulled out including a few 12AU7's, a full-wave rectifier, and a voltage regulator. Sounds like the beginnings of another vacuum tube audio power amplifier to me....

I plan to use this rack-mount chassis for my homebrew challenge 3 radio. Chassis like these are readily available at local hamfests at very low cost, therefore i believe that it is a valid part to use. Furthermore i believe that we homebrew radio enthusiasts should recycle this legacy equipment instead of throwing it in the trash, sending it over seas to be recycled, or letting it sit on the shelf for decades without use.

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update on the MIT Prof Ed 1-week radar course: SAR image of Kresge auditorium

Student results from the final day of the MIT Professional Education 1-week radar course, where everyone learns about radar, then makes one, then uses it in a series of field tests.

Shown here is a SAR image using the student-built radar kit of the outside of Kresge auditorium. The railing around the underground garage entrance shows up really well, as does the edge of Kresge itself.

An excellent image for a radar built out of coffee cans.

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What are these lines I wonder.....?

10 metre WSPR 5th August 2011

I noticed the 10metre beacons were a bit active this morning, first I heard F5ZWE/B (10:13utc) RST 549 , followed by I0KNQ/B (10:18utc) RST 428.

Then I had to go QRT for a few hours

Later in the afternoon I set up WSPR on 10 metres to see if there was anybody about, given the beacon reception this morning.




As luck would have it, on what seemed a completely quiet band ...... the following were put in the log..

Timestamp	Call	MHz	SNR	Drift	Grid	Pwr	Reporter	RGrid	km	az
2011-08-05 15:44	MW0MJB	28.126109	-22	1	IO71lu	1	CN8LI	IM63nx	1993	185
2011-08-05 17:32	MW0MJB	28.126131	-26	0	IO71lu	1	CT1JTQ	IM57ma	1678	192
2011-08-05 16:26	MW0MJB	28.126094	-24	0	IO71lu	1	OK/AD6XP	JN89ff	1541	92
2011-08-05 18:28	MW0MJB	28.126082	-27	0	IO71lu	1	DL2ZQ	JO42vj	1013	81
2011-08-05 18:16	MW0MJB	28.126103	-13	-1	IO71lu	1	DK6UG	JN49cm	967	100
2011-08-05 18:16	MW0MJB	28.126079	-26	0	IO71lu	1	DL8BBY	JO43jb	945	76
2011-08-05 20:28	MW0MJB	28.126090	-14	0	IO71lu	1	G3THQ	IO91un	329	94

F5ZWE/B

Beacon 28.242,7 MHz

Loc : JN02tw

FOIX alt 1205 m asl

France

What are these lines I wonder.....?
I noticed on the WSPR graph this curved trace....is this caused by aeroplane scatter?

I don't know enough about what the WSPR graph represents, perhaps someone can explain what these lines are exactly...

There is a transatlantic flight path just to the North of my QTH ...I wonder if that has something to do with the  unusual WSPR trace...

73 fer now 

Mark  MW0MJB

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update on the MIT Prof Ed 1-week radar course: RTI plot of Longfellow Bridge

Student results from day 3/5 of the MIT Professional Ed. 1-week radar course.

Range time intensity plot of vehicles crossing the Longfellow bridge from Cambridge to Boston. This plot shows both the remarkable range of the coffee cantenna radar kit and this student's ability to make a small radar and use it to acquire real measurements.

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20m WSPR report de MW0MJB.

I've been rearranging the shack recently and tonight was the first night that all was back to normal.

I thought why not try out all the connections and cables with a bit of
WSPRing........

These past few weeks I 've been thinking  of trying out a cb vertical on the 20m band 

By using a cb half wave antenna I could have a fair chance of WSPR on 20m,and hopefully a quite good antenna  to pick up the beacons on 10metres.......

Still haven't put it up though....

 No rush...  HI.....  :0)

Tonight's WSPR report from IO71LU:

Timestamp	Call	MHz	SNR	Drift	Grid	Pwr	Reporter	RGrid	km	az
2011-08-04 21:28	MW0MJB	14.097006	-27	0	IO71lu	1	WB8HWF	EN80sc	5832	290
2011-08-04 20:52	W3GXT	14.097142	-24	0	FM19ol	5	MW0MJB	IO71lu	5505	50
2011-08-04 20:52	WA3DNM	14.097136	-21	1	FM29fw	5	MW0MJB	IO71lu	5390	51
2011-08-04 19:48	CN8LI	14.097030	+8	0	IM63nx	5	MW0MJB	IO71lu	1993	4
2011-08-04 19:56	MW0MJB	14.097003	+2	0	IO71lu	1	CN8LI	IM63nx	1993	185
2011-08-04 19:38	LA6TPA	14.097067	-31	0	JP54rl	0.02	MW0MJB	IO71lu	1694	222
2011-08-04 19:18	SM0IKR	14.097157	-2	-1	JO99cc	1	MW0MJB	IO71lu	1660	251
2011-08-04 19:38	OK2SAM	14.097158	-22	0	JN99du	0.5	MW0MJB	IO71lu	1646	287
2011-08-04 19:32	IV3DXW	14.097164	-4	0	JN65qq	5	MW0MJB	IO71lu	1508	304
2011-08-04 21:20	MW0MJB	14.097010	-30	0	IO71lu	1	IW4ENS	JN54kp	1420	118
2011-08-04 20:50	MW0MJB	14.097001	-23	1	IO71lu	1	LB1A	JP50mt	1398	38
2011-08-04 20:34	LB1A	14.097099	-19	0	JP50mt	5	MW0MJB	IO71lu	1398	232
2011-08-04 19:24	DH5RAE	14.097167	-3	0	JN68pv	5	MW0MJB	IO71lu	1337	291
2011-08-04 21:06	SA6BOK	14.097074	-26	-1	JO67pj	10	MW0MJB	IO71lu	1326	250
2011-08-04 20:04	MW0MJB	14.097001	-4	0	IO71lu	1	I1-12387	JN44ln	1313	123
2011-08-04 20:06	IW2OHP	14.097112	+1	0	JN45lq	1	MW0MJB	IO71lu	1231	309
2011-08-04 19:20	M6SSA	14.097033	-26	-1	IO93	5	MW0MJB	IO71lu	325	238

It's about time I tried some PSK31, it's been weeks since I had a look at the waterfall......

Something for the next report maybe.

Might catch you in my psk log...

73 fer now

Mark   MW0MJB.

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More on The Spiral Challenge

A Homebrew_PCB Yahoo Group User; DJ, suggested that I try to fix my flawed 10 mil Spirals as reported on my previous post. With the aid of a 15 power Microscope I was able to fix each of the "opens". A few were hard to find, but tracing them around-and-around with an Ohm Meter under the Microscope did the trick.

Fixing the trace breaks was a job for very sharp soldering iron and a steady hand. Building a solder bridge at this scale is an interesting process.

The Flaw Fixed with a Solder Bridge
Click Image to Enlarge

The above photo show a typical solder bridge fix. The Tee Pin is included as a pointer and for scale.

Solder Bridge

When all flaws were fixed, each of the trace resistance was measured end-to-end and then between traces:

• First Trace = 23.4 ohms
• Second Trace = 23.3 ohms
• Trace to Trace = multi-meg ohms

The Challenge suggests the resistance should be 18.0 ohms per trace.

While investigating the Double Spiral Challenge, it seemed like my traces were smaller than proposed by the Challenge. But, I did not have anything to verify my PCB Toner Transfer Method fabrication results.

Until, I thought of including a calibrated scale inside of the photos. But alas, I do not have a small calibrated scale, so I decided to use a coin, but it was far to big. Then I hit upon the idea of using an Standard SMD part. The following photo contains a Standard 0805 SMD Resistor, from it a scale can be calibrated and distance measured.

Looking at the circuit board at this Magnified scale you wonder how any electronic device could possible work, with all of its flaws.

I may need to think about this more (later, it is very late at night) and now my thinking is dull. An update will follow.

The Tee Pin, Solder Bridge and the 0805 SMD Resistor

A Side Note: While futzing with my Cell Phone Camera and the add-on Attachment Lens (which was used to take these photos), I inadvertently twisted the Lens into two parts. With only the Lens base part attached, the Lens becomes a much higher power Macro Lens.    Hum, . . I wonder why I did not know that before.

---

UPDATE

I received the following email from DJ, the owner/keeper of the Challenge, via the Homebrew_PCB Yahoo Group, it is included here for completeness.

---

Sweet!

Here's a tip: you know the track-to-track spacing is 20 mil (you did say 10/10 pattern, yes?). Given that, you can calculate the actual DPI of the photo (about 4300 dpi for the spot I was measuring). Also measure a track, and you can compute the actual track width (about 9.2 mil in some spots, 7.1 in others).

But simply measuring pixels-of-copper vs pixels-of-space should tell you how close to "perfect" you are.

Your ohms are a little high, some things that might cause that:

* pinholes cause "necks" in the copper which add resistance
* cleaning/scraping/sanding the copper might thin it somewhat
* thinner traces on average would increase it

If you just go by the ohms ratio, it says your average trace width is 18/23 * 10 = 7.8 mil, which sounds close enough.

Did you measure the high ohms between the two tracks?

Also, if you have a flatbed scanner, they're often useful for high-accuracy PCB scans.

---

--

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Tuesday evening RSGB 144MHz Activity Contest de GW0LVH

I make it well known that I’m not a contester or for that matter have any interest in that part of the hobby. 
For me a 59 and serial number is not what amateur radio is about.


Anyway I’d been contacted by a couple of friends from my old club, Macclesfield & District ARS, to try and hook up in the RSGB 144MHz Activity Contest that’s held on the first Tuesday evening of the month. 


I was intending to operate in the low power section running 5 watts from my FT-817ND.

Greg, 2WØRXX was on holiday in Anglesey, almost a totally sea path from my location at Dale Airfield and we’d arranged to have a QSO prior to the start of the contest.

    The Cloud SOTA Summit G/SP-015 Xmas 2009.

My 5 element yagi had been packed away since a rather cold & windy outing to activate The Cloud SOTA Summit G/SP-015 Xmas 2009.


The antenna had been subjected to a garden test over the weekend and all appeared fine. 

Of course all was not to be fine once it was up in good time for a QSO with Greg. 

A high SWR was a problem I was unable to fully resolve. I think it may have had something to do with coupling to the wire sheep fence directly below, because the only way I could get an acceptable SWR to transmit was to hand hold the antenna well away from it. 

Saying that the SWR wasn’t that high to compromise its ability to receive and I only heard two stations, both of which were way too weak to even resolve their call signs.

                                             144MHz AC attempt 2 August 2011:

I never heard my other colleague either, Roger  M0GMG, who was operating from the Macclesfield Forest. 

I gave up and went onto 20 metres CW, far more fun.

Initial conclusions, IO71jr is probably not a good location for VHF around the UK, although from my cliff top looking over the sea to the west I had expected to have worked several EI stations.

Perhaps it’s worth another go when I’ve fully resolved the SWR problem.

Charles GW0LVH

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update on the MIT Prof Ed 1-week radar course: DTI plot of an exercise bike

Student results from Day 2/5 of the MIT Professional Ed. radar course:

A first in the history of Radar engineering and measurement: a doppler time intensity (DIT) plot of an exercise bike!

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The Spiral Challenge

I have been making a lot of Homebrew PCB lately, using the Toner Transfer Method. Must of the boards are prototypes, which will be later be fabricated by one of the online PCB suppliers. I have been feeling very good about the Homebrew Process and have created several small boards with high resolution for very dense SMD projects. The highest resolution projects are 6 mil traces with 10 mil separations between traces or ground plane. My more typical project are created with 15 mil traces and 12 mil separations. Some of the details of these projects have been posted in my previous blogs.

The Spiral Challenge

Several years ago, when I first started Homebrewing PCB via the Toner Transfer Method, my resolutions and yield - was Horrible!

I saw the Homebrew_PCBs Yahoo Group Double Spiral Challenge web page, that provided the art work for process challenge, with several standard widths traces and spacing. The image is used to produce two concentric PCB trace spirals, where the acceptable resistance between and end-to-end specifications are given.

In my early days of trying to make PCB, I could only hope for something that actually worked, regardless of the asthetics or (then low) resolution.

Now that I can produce High Resolution Homebrew Printed Circuit Boards almost 100% of the time, I decided to take the Yahoo Group Double Spiral Challenge. I selected the (mid range) "spiral-10mil" Challenge as a starting point. It is 10 mil traces with 10 mil spacing. A quick calculation, suggests that each spiral is about 200 inches (16 feet) long.

2 inch radius / (10 mil trace + 10 mil space) / 2 spirals * 4 inch average turn length ) = 200 inches

Currently, I use a Brother 1200dpi Laser printer (I know, most Toner Transfer users suggest it can not be used). A modified GBC Laminator and Pulsar Transfer Paper.  See previous posts and my Salmoncon Take-Away-Notes.

I recently received a new stock of Double Sided PCB Material and wanted to try this new material.

My first attempt to Transfer an Toner Image, was flawed, a small hair or fuzz was trapped between the transfer paper and the PCB material. That is no real problem, I just re-scrub, reprint and to try again.

My Initial Results

On the second attempt, the Transferred Image looked promising, but the process  had it's share of problems, I must have been just too anxious for the results.

The first thing that I forgot in the process, was to tape over the back side, to avoid unnecessarily etching of the extra copper. The process took much more time and Ferric Chloride than I expected.  I thought this could be a problem.

From my previous Homebrew PCB build process, I know that the faster the etch and the smaller the copper area to be etched, creates the best results. This etch was taking to long!

The results, . . . . FAILURE !

The flaw is on the forth trace
above the ink spot

Resistance between traces implied there were NO shorts. But, end-to-end of each spiral was open. Under close Microscope inspection (and a with considerable amount of time), one spiral was found to be open in one spot, and the other was open in three spots. The one spiral is open on the forth trace, just above the ink dot on the photo.

All of the open flaws appear to be the results of etching through toner pin holes or single point under cutting. The opens did not appear to be the results of general narrowing of the traces. Each opens spot was shorter than the traces width themselves.

I will take the Challenge again, maybe even at a high resolution, but I will pay much more attentions to the details.

For now, I have a nice new, . . coaster.

--

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QRP Portable, July 2011 de MW0BBU/p.

Now that July has flown past with great speed I thought I would do a little summary of the QRP portable activities here at MW0BBU. 

As you all know I am a great fan of SOTA and  it is a great activity to get out of the shack and try out the QRP kit from up high.

Anyway, firstly the bands. 

When Mark, MW0MJB, and myself did the first QRP portable from Foel Cwmcerwyn in June, 20m had produced many QSO's, so this became a starting band for me on my outings. 

This however during July, proved to be very poor, resulting in only four qso's over the five outings. 

30m didn't fair much better with a slight rise to six qso's.

40m however was the backbone of the portable activations, 148 qso's in total, which I must admit I was very happy with. 

Bare In mind each activation was less than 2 hours.

As for countries, I managed to work 18 dxcc entities over the five outings and in these were a couple of Summit to Summit contacts which I was very pleased with. 

A small list of Countries I have listed below...

F, OK, UA, PA, DL, G, I, EA, ON, HB9, SP, S5, MM, SM, LX, OE, LA and MW.

Just to share a few facts of the places I have been to in July...

Foel Cwmcerwyn, GW/MW-011, 536m / 1759ft, 31 QSO's

Mynydd Carningli, GW/MW-033, 347m / 1138ft, 32 QSO's

Frenni Fawr, GW/MW-028, 395m / 1295ft, 29 QSO's  

Brandy Hill, GW/MW-037, 205m / 673ft, 18 QSO's

Rhos Ymryson, GW/MW-035, 327m / 1073ft, 48 QSO's

During these activations I have always used the FT817nd with an output of 5w into a 66ft Doublet. 

This combination has served me well on my outings and the only grumble really I have on the FT817 is that it really needs a good CW filter.. which I must add is now on the shopping list. 

Anyway, just to add again, its been great fun activating these summits and more fun again getting out of the roof space, sorry, Shack!!.

More are on the cards for August and just maybe some VHF SSB, I have been assured that SSB is the way to go on the hill tops, well after my recent attempts at FM I really hope so. 

Anyway that's all for now, I hope you have enjoyed reading these little postings as much as I have done doing them. 

Take care and all the best for now.

 

Steve...MW0BBU.

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MIT prof ed 1-week radar short course update: 35 cantenna radar kits

Here they are, 35 cantenna radar kits prior to distribution as part of the 1-week MIT professional education radar course. Shown on the top figure are the 70 cantennas. Second photo shows the bags of parts for each kit.

Each kit contains 6 uwave modules, solderless breadboards, a piece of plywood, 50 ft tape measurer, a handfull of analog parts, and 8 AA batteries, plus other stuff.

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