Update on the High-School Direct Conversion Receiver Project: Board #4 Completed

One of the receivers. (l to r) AF, PTO, Mixer, BP filter

The students continue to make great progress on their direct conversion receivers.  Yesterday they were enthusiastically sitting down to workbenches, building Manhattan-style circuits, working directly from schematic diagrams.  It was really impressive.  They are building receivers. 

This week we had two sessions of about two hours each. We introduced the final board:  the audio amplifier.  Many of the students began work on this amplifier; others were catching up with work on boards presented earlier. 

The AF amp is their most challenging board:  It used 14 Manhattan pads and about 26 components.  We warned the students that amplifiers often aspire to be oscillators.  We told them to pay attention to layout, and to keep their leads short.  

One of my builds, and a Manhattan board pattern

At first, the students just built the first stage on the AF amp board. They tested this, then moved on to build the other two stages.   

By the end of Friday, two groups had completed the build of the AF amplifier board.  

We think there are about 13 receivers in production.  Some are near completion, others will need more work.  

On Thursday of next week those teams that have completed all four boards will put the circuits together and will test the entire system.  They will then add all needed front and back panels and socketry. 

We really want the students to complete as many of these receivers as possible.  Exam season and the end of the school year is approaching, so we have to get this done.  We will remind students that they don't want to that person who ALMOST finished a project!  We will urge them to GET IT DONE!   They can tweak it and mod it later.  This kind of tweaking and modification is part of the homebrew experience. 

We have been presenting awards to the students who are first to complete each stage:  The winners of the PTO board competition got a copy of SolderSmoke:  Global Adventures in Wireless Electronics.   Those who won the mixer competition got a W1REX Hamfest Buddy transmitter.  Thanks Rex!  And this week we presented an award to the students who were the first to complete their bandpass filter.  You've heard of the Tony, the Emmy and the Grammy?  Well, we presented "The Torry"  (from Toroidal).  The trophy was made from a toroidal winding tool made in Alaska by KL7FLR.  I explained to the students who had made it.  Thanks Paul! 

"The Torry"

A Surprisingly Good Movie from the Late 1960s: "The Ham's Wide World" (Video)

I found this movie to be surprisingly good.  Narrated by Arthur Godfrey, it features Barry Goldwater, and a lot of other hams.  There is a homebrewer too!  Lots of  old rigs we know and love:  a Drake 2-B, a couple of Galaxy Vs, a Benton Harbor lunchbox, Heathkit SB-series rigs, many Swans, and was that an HQ-170 that I saw in there?  There are also many cool antennas, including a 15 meter quad set up by a bunch of Southern California teenagers. 

Near the end, when they visit ARRL Headquarters, we briefly see none-other-than Doug DeMaw, W1FB!  FB!  

Please take a look at this video and post comments about the rigs, antennas, and radio amateurs that you see in the film. 

A Satellite Ground Station (Receiver) Made from Junk

Very cool.  This guy (who brew up on an island in Alaska) really knows how to use aluminum tape and the junk that fills most workshops. I like his use of the security camera mount as an az-el antenna rotator. 

I foolishly discarded a Direct TV dish.  I could have been receiving GOES images by now! 

Just last week I got the same RTL-SDR.com V3 dongle that he is using.  Very FB.   It does HF direct sampling with no hardware mods and no upconverter. 

More from the builder, Gabe Emerson (KL1FI): 

https://www.youtube.com/channel/UCNLRcEn78Vc62C3GkMvBgtA

http://www.saveitforparts.com/

A Toroid Winder from the Wizard of Wasilla -- Paul KL7FLR

Paul KL7FLR has been sharing tribal knowledge with us for several years now.  He recently provided insights on how to tap threads into metal.  In 2017 he told us about his Alaskan road-kill microphone.  And in the midst of the current quarantine he built this really neat toroid winding tool.   Winding coils is often a show-stopper for would-be homebrewers;  Paul's device should help then get past this perceived impediment. Thanks Paul! 

Paul writes: 

A few weeks ago I needed a way of holding a T37-6 toroid to wind an LP filter coil. Being of the fumble fingered crowd I slapped together a quick and dirty holder using a crudely tapered ¼” wooded dowel. As fate would be, I soon needed to wind some other coils of a larger diameter and my wham bam holder wouldn’t do the job. Time to make a holder for more than just one size with the materials I had on hand.

I measured the id of the smallest toroid and the largest toroid I had and plugged them into an online taper calculator. https://www.easycalculation.com/shapes/taper-degree-calculator.php. Calculated taper was 6.65 degrees so I settled on an even 6 degrees with a length of 1 1/2”.  The final of the taper was extended to 3”.  Using my small 6” metal lathe I set the compound to 6 degrees and chucked up a 4” piece of a ¾” wooden dowel. I would have liked to have an ash, maple or other hardwood dowel but I used what I had on hand. Then I turned the 6 degree taper for 3” until the smallest end was 1/8” making the large end almost ¾”. Some sanding with 320 grit sandpaper followed by some ultra-fine 400 grit made it ready for a coat of clear sealer and a quick stain.

Moving over to the milling machine, I set the 6 degree angle with a 6 degree parallel in the vise.  Positioning the mill spindle to the center of the dowel I used a #0 center drill to mill a slot the entire length of the taper to about .015” deep as I didn’t have a 1/32 end mill.  This slot also can be accomplished with a rotary tool or a hobby knife and a steady hand.

I had a couple of 6-32 wood brass insert nuts in the hardware bins. Believe I bought these at Lowes and the Hillman part #880546 is what I used. Drilling a 3/16” diameter hole ½” deep I screwed the insert in until it was flush with the bottom of the dowel. My previous toroid holder had a wooden base but it proved to be too light and easily moved around on my bench.  I dug out a scrap hunk of ¾” steel about 2.5 inches square.  I then drilled a hole through the base using a #27 drill. Now the toroid holder can be mounted on the steel base using a 6-32 machine screw about 1 ¼” long and removed for a different size spindle when necessary. A wood base can also be used with appropriate length wood screw. Be sure to drill a pilot hole large enough in the spindle to prevent from the wood screw from splitting the spindle. A #6 wood screw long enough to pass through the base and into the spindle about ½” would be adequate.

Winding consists of passing the wire up (or down) the slot, lifting the toroid up and rotating slightly and back down on the spindle for the next winding. This has proved to be a very useful fixture when needing to wind some toroid coils.

The picture at the top shows a T-37-6, T50-2 and a T68-2 top to bottom. Will also fit a up to a T-106. Any larger toroids would require a larger spindle to be made.

Enjoyed your YouTube “Quarantined Receiver”  and all the doings from Pete.

Paul

KL7FLR

630 Meter DX from Wasilla, Alaska

Kl7L's 600m Part 5 station

Hi Bill - It's been a few years and I'm sort of glad my global wanderings have been curtailed to a point and I'm now based out of Alaska and via a couple of call signs (KL1X KL7UK etc) have ended up with KL7L. I still travel with the Oil Company but no China on the horizon.

I had a chuckle when you and Pete mentioned the new 630 and 2200m bands - and the real estate requirements - Well, I've been active with the experimental callsigns since 2003 and very glad we have finally got the bands - so a small form to fill out on the UTC web site and a 30 days wait to check you are not within 1Km radii of the co channel PLC on Trunk power lines, if no "disapprove" away we go - and I and many have! 

Just turn off all those nasty dimmers, LED lights and SMPSU wallwarts - plonk your radio on 474.2kHz USB and decode using WSPR or JT9 and I think youll be surprised on what you can hear even on a short typical 80m or topband wire or so.  There a lot of activity all around you

The station for both band is homebrew soldersmoke heaven - transverter/PA and filters/Couplers/Phase meters etc with only my ol' TS850 doing the prime driving, or a Hans  Summers U3S.

Size does matter - but my best RX for both bands is a 2ft long active probe up a pine tree, that's all - and some 300ft of RG6, and the Tx antenna is a 60ft high  Marconi or more over an inverted L with a 3 wire top cap all nested in the Birch forest - loads or radials but still very lossy in the Summer - nothing special here - Of course with the QRP per se we have to use CW or digital modes mostly but DX can be done - after all my closest active neighbor on 2200/630m is over 2000Kms away!

So, for the first time I sparked up on JT9 on 630m this early morning and first blood to QSO with VK4YB @ 5W EIRP!

 Not bad for a first qso on what is a fairly typical back yard antenna - so, there is hope and many people appear to be putting transcontinental signals out this power, so everyone is on the same playing field - just the ground and location and latitude will change things! It tends to be more flaky, lossy and geo/solar events tend to hit us hard up here compared with say Seattle.

On 2200m TX its a loop of thick wire hanging in the trees - literally 500ft circumference and a beefy coupler to deal with the 50A or so of antenna current to make the 1W ERP or so - still its getting out OK and again should be putting signals over the Pole to EU and across the Pacific as it becomes more and more dark up here.

I'm now caught up with past Soldersmoke pod casts and thanks to you and Pete for making me smile

Take care

Laurence KL7L  aka G4DMA et al
Wasilla Alaska 23rd Oct 2017

Alaskan Road-Kill Microphone

I got a kick out of Paul's message from Alaska -- on my bench I have an almost identical project, including the sink strainer (see below).  And of course the now-iconic SolderSmoke podcast mic is just an electret element inside what used to be an IKEA floor lamp. 

N2CQR Lamp Mic 

Hi Bill and Pete,

I have been following your and Pete’s adventures on Soldersmoke for a while and want to say that each episode always brings some of my past experiences to the surface.  I have been fiddling with radios and electronics for over 60 years, licensed since 1964.

I needed a mic for Bitx40 build and started thinking about this as I was working on other projects. Every day I walk a mile and a half to my mailbox. Wednesday’s and Friday’s happen to be the days of trash pickup and people put the trash bins out next to the road for pickup.  Last week I spotted a little desk lamp sitting on top of one of the trash bins with the cord cutoff so on my return from the mailbox it was still there and it followed me home.  (fig1)

Removing the shade left a flexible vertical support for a mic, (fig 2).

Your recent podcast you mentioned your D-104 microphone, that was my first mic once I had phone privileges back in ’65.  Scrounging through my treasure box I came across a 1 ¼” to 2” PVC pipe coupling that looked just like the basis for a mic. A few hours of mediation and a couple hours at the lathe and mill produced a mic with stand and a PTT switch (fig 3).

Some scrap bin aluminum and a free lamp from the trash and another hour at the lathe, (fig 4 & fig 5). And yes, it has some heft as the base has a large hunk of cast iron in it. Will admit I spent $1.24 for the sink strainer that sacrificed itself to become the grill ala D-104.

The self-satisfaction of building your own gear and accessories is one of the rewards of this hobby, can’t buy that in a store. And repurposing someone’s trash into something useful is a plus.

Keep the soldering iron hot.

73’s

Paul KL7FLR

Wasilla, Alaska

PS JoAnn’s is one of my favorite places for finding useful materials.

More WSPR DX

I was pleased to find this report (above) on my screen this weekend. Wake Island.

This morning I saw that yesterday I was picked up by one of the world's most globe-trotting hams: Laurence KL1X (by his remote-controlled station Kl7UK).

GO WSPR!

Alaska QRSS Grabber Controlled from CHINA!

Our friend Laurence leads an interesting life...

http://www.kl1x.com/

Hi Bill and greetings from the NE coast of still summery China - actually its cooling down a bit from boiling over to just cooking.

Just been home to Alaska. Whilst and between lumberjacking 20 dead trees on the property I had a few mins to throw up a K9AY and connected it via 250ft of Walmarts best RG6U into the R75 - with a little help of Ham radio delux, Citrix and Skype I have control of the radio from here in China - Mostly on 30m but really shoved it up for the winter lf/mf season but of course WSPR and visual modes have proved very popular. So until a moose walks thru, a Wolf chews threw or wife cuts thru the antennae wire it will be up.

Here in China I'm sporting the second r75 and this supplements the SDR IQ - my antennae are gradually getting blocked towards the states and Eu by every rising high rises just in front and I can actually measure the increasing losses at LF and HF as the beast rise. Still looking for your WSPR signal and keep up the good work.

Regards
Laurence G4DMA et al - KL1 X and in BY3A