Tuesday, May 26, 2020

A Man with two Watches..

Old proverb:
A man with one wristwatch knows what time it is; a man with two watches is never quite sure.
I use my scope a Tek 7704A ("Old Betsy") from the 70s and my OHR WM-2 watt meter alternately whichever one is most convenient when I am building and testing radios.
A couple of points here: I am a dilettante and not a wizard like my friend Dick, WB6JDH, who knows everything and can solve any problem you throw at him. (And, believe me, I have thrown a lot of problems at Dick!) Also, I have old-timey test gear that is wa-a-a-a-y complex -- like my 7704A -- and I don't know how to push the envelope on it but I try to learn. That's the fun part of ham radio.

But, some time last year during a spate of building some kits and other projects, I noticed that the WM-2 did not agree with the Tek scope. It got to be annoying so the OHR calibration process was revisited -- but it did not obviate the discrepancy. Some time ago, Marshall Emm, N1FN (SK), and I communicated on the WM-2 re calibration and he assured me that -- in essence -- whatever gets you through the night works just fine for calibration. Obviously, the beauty of the WM-2 was that one could build a reasonably accurate QRP watt meter and calibrate it by looping DC voltage levels through the meter circuit and at each level for the three scales, setting the meter to full scale ensured an accurate RF reading. Marshall's email assured me that using a scope to calibrate the WM-2 was preferable. And that brings me to the nut of the story: how accurate is the stuff on my bench?

The WM-2 watt meter is one of the best little watt meters going because (1) it's a kit and you can build it and (2) it's reasonably accurate and (3) it covers the 0-100 mW range. The downside is that it is a little expensive (around $150) and it is not that accurate.

My Bird wattmeter (a gift from my late father) was the purported gold standard in my younger days and I relied on that.

And I have one or two Diamond SX-200 (and other models) and find them to be surprisingly accurate. But how do I know this? Well, I checked it against "Old Betsy". In fact, I have checked them all against the Tek scope and calibrated them (when I can). I am not a metrician nor do I make any pretense at achieving a heavenly degree of accuracy, but a calibrated scope will get you "close enough for government work". There's a great web page on the subject by Adam Farson, AB4OJ, that can be found here. It begins as follows:

Adam goes into how a scope can be used to measure RF power from the peak-to-peak voltage (Vpp) of a signal displayed on an oscilloscope and his calculation of power from Vpp borders on a derivation so I will confine the formula I discovered in one of Wayne Burdick's Wilderness Radio creations -- I think it was the Sierra. Wayne says, simply:

So, when I found my Tek 7704A annoyingly out of sync with my WM-2, I bailed on the OHR calibration routine (using the test loop voltage values) and set it against what my scope told me. By using an FT-817 at 30 meters (10,100 Kc; middle of 2-30 Mc HF band) as a power source. The 5.0, 2.5, and 1.0 watt levels can be used for the 10-watt range and the 1.0 and 0.5 watt levels can serve to calibrate the 1-watt range. For the 100 mW range, I used an attenuator in series on the 0.5 watt level. See the table below for mine.

The last four were obtained by means of feeding the 0.5 watt output into an attenuator and knocking the signal down to levels that allow the WM-2 to be "spot checked" on the 100 mW range. Note that none are close to the actual scale markings so they have to be "eyeballed". (This is, in fact, true of the 10 watt and 1 watt range as well.) However, an eyeball approximation was far better than the inaccuracy the WM-2 displayed by using the voltage/test loop method. Here's the attenuator setup:

I happened to score that Telonic attenuator at a swap meet for $10 and it is immaculate as well as dead balls on. But you have to be careful with the power input as more than a watt will probably fry the unit.

Incidentally, much earlier on I discovered the dirty little secret that the Bird watt meter slugs can become notoriously inaccurate and are not to be trusted. When it was discovered that my HF 50 watt and 100 watt slugs were all over the map, I followed the procedures outlined in several videos of which WB9FOL's is typical.

I pried open my two slugs and found that the pot had wandered off value bit but could be adjusted and I did so scaling them against the scope for lower power values. It was then that I noticed that the Diamond SX-200s were surprisingly accurate at low power and I used them to scale the two bird slugs up to the 100 watt level on my IC-706MKIIg and IC-7200 rigs.

There are, of course, methods to "reduce" or divide higher levels of power so they can be measured by a scope. These are merely extensions of the attenuator in the scope and the 10:1 probe but huskier. In fact, AB4OJ includes the principles for one in his write-up:

But, by reputation and use, the SX-200 and similar models are very accurate ballpark references. (I know, I know..) The scaling is as good as the WM-2 and these will handle up to 200 watts.
..as I said, close enough for government work.

Post Script: Here is a handy Vpp to Power conversion chart for 2 Vpp intervals up to power in watts.

Monday, May 25, 2020

Tidying Up Loose Ends

Governor Hair Gell
I was wrapped up over the last couple of weeks with how to occupy myself during the house arrest that Governor Hair Gel (the stupidest Democrat in California) and the Los Angeles County Crypt Keeper - "Dr" Barbara Ferrer - has imposed on California and Los Angeles.

"Dr" Barbara "Crypt Keeper" Ferrer
Yeah, I know I don't live in that Dem shit hole that is Los Angeles (thank you, God!) and I am not in Hell -- but I can stand on my tippy toes and see it from my QTH. But enough of politics (sort of). Because the COVID-19 farce has conspired to cause virtually every aspect of our lives to be cancelled, we members of the Zuni Loop MEF group have decided to not trek to the mountains and do Field Day. Actually, Field Day will not be the get-together it always is as alternate plans are being concocted to accommodate social distancing and the like. (I just hate that term but understand it's necessity.)

Anyway, I prattle. I decided to resume kit building and reached into my stockroom to pick a thing or two out of my inventory.

Me emerging from the treasure trove with a couple of items

Long story short, I built two 30 meter kits: one of Diz's Kits and Parts 5-Watter and the remaining Midway ME-30+ I got several weeks ago. Both went smoothly at first but the road had some "bumps" and I had to iron out some tools and techniques. I will write up one of the "bumps" here and will write up the other "bump" and the 5-Watter build in a subsequent post.

Let's cover the Midway ME-30+ kit first. I won't do the full review because, let's face it, it is basically identical to the ME-80+ kit in assembly and materials except for the band differences and it went together quite well. I still love these little radios and -- years on from my original cruise through Dave Benson's kits -- I now understand the circuit and marvel how neat it really is. The VFO is rock stable and the receiver is incredibly sensitive. Both the ME-80+ and ME-30+ hear down to -130 dBm.

However, in completing the ME-30+ and being generally happy with the build, I was somewhat apprehensive because the most that could be coaxed out of it was just a smidge over a half a watt. Going back over the rig, I noted that I had populated the BPF middle cap with a 68 pF value instead of a 680 pF cap. (That is, "680" does NOT mean 680 pF, it means 68 pF.)

Live and [re]learn, I guess. That got me up to just over 1 watt. So as I was trouble shooting this, I started a letter to to the Midway Express owner, Rick Choy, about this matter:


Sorry to intrude on your Memorial Day holiday -- and this need only be addressed in your convenience -- but I have some questions re your 30m kit I just recently finished, to wit, is it performing to spec? I believe it is; just wanted to confirm. Here are the facts:

(1) Basically, there were no problems with the build/checkout but I could only manage to get just over 1 watt out of it when done.

(2) Went back through and checked ALL components and found none misplaced nor any solder bridges, bad joints, etc.

(3) I checked most of the voltages versus the schematic -- specifically the XMIT chain -- and they were 100 percent.

(4) I checked the signal levels and the appeared normal.

(5) Specifically, I checked the signal at the base of Q6 and found that to be approx 2.5 Vpp.

(6) The output at the collector with the pot wide open was 27 Vpp or 1.8 watts (27^2/400).

(7) The output at the BNC with the pot wide open was 23.5 Vpp or 1.4 watts (23.5^2/400).

(8) I note that the BPF drops the signal almost 1/2 watt.

I wanted to see if this is normal because the ME-80+ I built had an output of more than 2 watts. Of course, that was 80m and this is 30m. Also, I have no heartburn about this because I will throttle this little radio back to 990 mW so I can work QRPp. Just checking. Screen shots below.



But, after I got to thinking about this, I realized I could do a comparison of the ME-80+ and the ME-30+ and see what's what. So the letter was not sent. Basically, what came up was the ME-30+ was not losing a lot into the BPF -- at least not as much as the ME-80+ was. Here is a comparison table of the results:

So, it appears that the ME-30+ is doing the best it can despite having more drive (2.4 Vpp versus 2.0 Vpp) which probably means that the Q6 in the rig is a little weak. Here are the traces for comparison.

ME-30+ Signals
ME-80+ Signals

So the bottom line is that these kits are fun to build and operate and they are small and have a "heft" to them so that you won't hesitate to take the radio with you to a local park or mountain top, etc. (Some of the these fragile "pocket" radios feel like they will fold up in a stiff breeze.)

..so that's it for now. Next up, a man with two watches is never quite sure.

Wednesday, April 15, 2020

Midway Electronics ME-80+ Kit

The previous post mentioned Midway Electronics' ME-XX+ kits -- the reincarnation of Dave Benson's mid-1990s SW-XX+ kits -- and how I was looking forward to building them to recapture a misspent youth. Well, as of this writing, I have completed the ME-80+ (80m version) and wanted to offer up some comments and pictures for your perusal.

Firstly, let me say that I ordered the full-blown kit -- board, parts, case, and all the fixins' -- and I do not regret it at all. At first, I thought I would have to replace the 100K Ohm tuning pot with the obligatory 10-turn replacement but the case does not allow it space for it. However, the original pot is of good quality and certainly adequate.

All considred, the Midway guy has done a superb job of offering up a complete radio with some really nice touches.

In addition to the decent case and hardware and knobs, there are some thoughtful "extras" thrown in that make the kit and resultant radio a "keeper". Thoughtfully provided are the header strips and cabling to give the radio that finished look. Also, the snap-in standoffs are pretty easy to install. Although I went with my own standoffs, the ability to extract the board from the case by unfastening the cables and lifting it out makes for easy debugging and repair. I would only add that Dave's original kits did not have an on/off switch and the Midway kits don't either; it was something I always lamented. (As you can see from the pictures below, I added a a switch.)

Diving into the kit is a lot of fun. While, conceptually, it's straight forward to build and the manual is nearly identical to Dave Benson's SWL manuals, it is not part-by-part but rather block by block. (Or, if you will, quadrant by quadrant; see sample below.)

My philosophy regarding kit building is like my old adage: "I burn up more rolls of solder than I do log books." I take it slowly and enjoy it. I mean, after all, it's not like I don't have any radios to operate. At a decent, leisurely pace, it took me four days to build the kit working two hours per night.

The board is superb! In fact, it is better than Dave's boards as I recall. But I would caution you that, if you are not an experienced kit builder, you'd best inventory the parts and organize them so you gain some familiarity. There is nothing worse than stuffing a 47 Ohm resistor into the holes for a 47K Ohm resistor's holes and have to dig out the mistake during the checkout process. Also, read and understand the freaking manual first. There are some tips and caveats in there that add to the fun of getting the build right.

Once assembled, the checkout is very simple and -- quite literally -- can be accomplished with a DMM and your station rig. For example, at power-up, I heard nothing on both receive or transmit and resorted to the voltage schematic provided. I discovered no Vcc present at the two receive SA612 ICs and scattered places around the board. When I examined the traces from the 78L08 voltage regulator output to these ICs I noted that I had installed D2 (a 1N4148 diode) "upside down" and it was a roadblock to the DC rails. This little tidbit was addressed in the manual:

Correcting this (flipping the diode) cleared up 99.99% of the problems.

This next point was not really an error on my part. Dave's design uses three of the old Toko IF transformer cans -- two in the transmitter and one on the receiver. Aligning the radio is a simple matter of tweaking the cans to obtain a peak signal out (transmitter) or a peak signal in (receiver). The transmitter was no problem and I was able to peak the radio at 2.5 watts. (Despite the advisory to throttle the rig back to 1.5 watts, I felt comfortable at having it output 2 watts.)

But, when I attempted to peak the receiver, it was number than a rock. In adjusting the receiver transformer, I noticed that the slug in the can neither moved up nor down and reasoned that the threads had been stripped. The best it could hear was about -70 dB. So, since I had a couple of those Toko transformers on hand (marked "412F123"), I opted to wick out the old one and replace it. This was a tricky job but, once accomplished, the little receiver heard all the way down to an honest -130 dB!

My recommendation is that, when you inventory the parts, check out each transformer by carefully screwing the slug in and out to make sure it travels up and down. If one does not, ask Midway for a replacement. Also, please note that I do NOT lay this at Midway's feet. Their conscientiousness and customer service and kit quality is stupendous! One just slipped through!

The final step is to set the frequency by inserting in an NP0 cap into C7 for the desired range. As it turned out, mine required a 56 pF cap (that actually measured 60 pF) which gave the little radio a range of 3.499-3.537 MHz.

I can live with that! Anyway, here are some pictures:

This is a fun kit that results in a serious radio that has been proven over the years and is a great starter kit for those who have graduated from the Chinese Pixies and want to get their hands on something with a little meat on its bones.

..now on to the ME30+ kit!

Tuesday, March 31, 2020

Living in the past - Dave Benson's SW+ radios reincarnated!

Back in my early days of QRP -- mid 90s to be approximate -- I fell in love with building kits as a byproduct of this black art. My first was the marvelous OHR-100 One which convinced me that low-power contacts to Northern California (I live in SoCal) were do-able on five watts.

This was followed by one of Dave Benson's SW+ series -- an SW-30+ for 30 meters -- that was started on a Friday evening and concluded with an alignment session on a rainy Sunday evening. After strapping it to an old 4BTV vertical leaning against my patio wall (the only option available), I pumped 1.5 watts out to the ionosphere and landed WB0CFF in Minnesota. The memory of that QSO still makes my hair stand on end even though I have worked considerable DX since then.

That said and in a possible effort to re-live past triumphs, I ordered a Midway Electronics ME-30+ kit -- the "board only" option -- as a means to "fill in the gap" between my old SW-40+ and SW-20+ builds that grace the shelves. For the curious, I thought I'd pass along a few comments and impressions.

It seems that Dave Benson granted the proprietor license to exactly reproduce and distribute his popular SW+ 2-watt kits, arguably part of QRP's heritage and as significant as the NorCal 40A and similar.

The kit was received in short order but, sadly, it was the 80m kit. (80 meters is dogmeat in Southern California and in my neighborhood specifically.) However, email conversations with the owner resulted in him sending along the 30m components with an advisory to keep the 80m components. I was flummoxed with the initial speed of delivery, the follow-up correction, and the overall friendliness and attitude of Midway with respect to customer service. (To be sure, I planned to return the 80m part but read on.)

The kit(s) -- boards, parts, manuals -- are, as stated, an exact replica of Dave's original product. Moreover, the prices are very similar to the very reasonable prices that Dave used to charge: $60 (versus $55) for the board kit, $92.50 for the board kit and controls and project box (versus $95). Given that the Toko coils and 8-pin DIP NE602s are rare, I find this astounding. The quality of the PCB is extremely good and it is identical to Dave's. The manual comes spiral bound and as easily understandable as Dave's was.

I was so wrought with guilt over being told to keep the 80m parts that I requested he send me the makings for both radios to be "full" kits. That's an additional board, front and back panel components and knobs, and two cases; a very reasonable price was quoted and they are on their way. The subsequent order was delivered and the quality of the cases are quite good. The only niggling downside is they fit the board and controls and connectors exactly leaving little room to stuff additional items like a keyer chip board and frequency enunciator. But that's not Midway's problem, that's my problem.

The kits, components, cases, etc. are available in 80m, 40m, 30m, and 20m editions on Midway's website:


They are also available on eBay. Search for ME40+, ME30+, or ME20+ -- and presumably the ME80+ will be available there soon.

In summary, I am very happy this gentleman has chosen to bring back this kit. It provides us old codgers a chance to relive our past. For those "new" to QRP an opportunity, it's a opportunity to develop their understanding of radio and electronics as "Elmer 101" courses and in depth discussions abound for this radio.

When I get this kit built, I will post pictures and notes for those interested.

Usual disclaimer: no pecuniary interest, etc.

Wednesday, January 22, 2020

Zuni WFD Get-Together Venue Change!

Mike, N6MST, just saved our bacon. All the way up in Bakersfield, he spied that Mile Square Park -- where we were originally to meet - was going to be occupied the entire wekend by the Vietnamese New Year -- Tet - celebration so, consequently, we are moving the venue a little down from there.

My so-called Plan "B" has become Plan "A" and it involves our commandeering a part of the green belt in my community. There are trees and a vast open space and, with our bringing two or three portable tables and chairs, we can set up there. See the pictures below. The Green Valley Park offers these advantages:

(1) Some trees.
(2) Open spaces where verticals and poles for antennas can be erected.
(3) Abundance of free parking that is walking-close to where we would set up.
(4) No crowds to speak of.
(5) Restaurants/7Elevens close by. CostCo also close. ($1.50 dog and a coke special ant their "food court".)
(6) Close to my QTH so we can grab some stuff from my shack/bench if we need to.

Some downside: we are going to need for folks to bring chairs and another table. I have a table and two chairs but it's not conducive to operating or outgassing if everyone does not have a chair.

So, we will still coordinate on the PAPA System so give us a call there if you are lost.

Sorry for the change but this should still be tons of fun and we're still doing the pizza debrief afterwards.

To get here, head South on the 405  to the Brookhurst Street and go under the freeway and loop around so you're heading North on Brookhurst. turn right on Warner and proceed past Ward (the next light) to Los Jardines wher you take a right. we'll be listening on PAPA or 146.52 MHz to talk you in.

Monday, January 13, 2020

Get a grip..

In an attempt to scrape some rust off my CW fist, I am currently matriculating through the CW OPs CW Academy and it is a marvelous experience. Sure it's the beginner class and sure I can solid copy around 15 WPM but I am doing this for the discipline -- and getting myself into a routine of practicing my CW daily.

But more on that later. The purpose of this post is to bring CW operators attention to a discovery I made -- thanks to my wife. She found this stuff called Grip Liner Magic Cover which is billed as a non-adhesive and non-slip cupboard liner for dishes and glassware. It is by Kittrich Corp in Pomona, California and can be found in many homewares stores, super markets, and it and variants are available on Amazon. (You do your own search.)

A small square of this stuff anchors my paddles to the desktop and essentially squelches any side-to-side slipping. So far, the squares I have been using for my Bencher (below) and Kent (out on the shack) are well over six months old. So, a roll of this stuff should last a lifetime -- and more.

Wednesday, January 8, 2020

It Begins! Prepping for Zuni Loop MEF Field Day 2020!

Rust Never Sleeps!
The Zuni Loop Mountain Expeditionary Force is an ad hoc association of some of the best and brightest QRP ops who came together each year for ARRL Field Day. One of the groups consistent mainstays and organizer for the past 35 years was Cam Hartford, N6GA, who ensured that QRP and antenna and operation experimentation resulted in good contest results, an enhancement of participant knowledge, operating skills, and -- mainly -- fun!

Sadly, Cam left us last year before Field Day and we carried on as best we could. But, armed with that rebuilding experience and a determination to regain past glory, we are resolved to not let the tradition of Zuni Loop fade away. What we have going for us is this tradition and one heck of a great location. But we will peak of that later on. For now, the planning begins.

Where We Sit Now
We need more ops. So far we have a commitment from three veterans and four promising new-comers: John, n6vcw (trustee of Cam's N6GA callsign - now officially assigned to the Zuni Loop MEF), Ed, KM6TNT, Matt, KM6TOA, and Mike, N6MST. The returning regulars include Dick, WB6JDH, myself, K6WHP, and long-time Zuni veteran, Keith Clark, W6SIY. Ed has done a great job in recruiting and has secured three new hams to join us for 2020. We welcome them and others with a profound interest in QRP and pushing the envelope. If you are intrigued and proximate to Southern California, let us know. My email is good in QRZ under my call sign or click on this link and blast away!

Preparation and Related Logisics
Our first step in preparing for Field Day will be participation in the Winter Field Day on 25-26 January. We will be setting up in Orange County at Mile Square Park in Fountain Valley.

While Winter Field Day is a contest and we will set up to operate -- patterned after the Summer Field Day but with a few rule changes -- our emphasis will be a little different. Our main goals will be to get to know one another, check out some equipment and antennas, orient folks not familiar to in-the-field QRP operation, and generally observe the newly coined variant of the Zuni Loop motto:

We're deadly serious about having fun!

Although Winter Field Day goes overnight (like Field Day) for two days, we will only set up and operate for a short time, from about 0900L PST until about 1500L PST. Note that the actual contesting starts -- like FD -- at 1100L but we want to get a head start with prep and such. Also, I live adjacent to the park and will be heading over early to stake out tables and trees at an appropriate site. (Probably will be "spot #2" per the map below.) If you wish to coordinate the entry and "carpool" into the park, there is parking in the adjacent strip mall next to my QTH. I would recommend coordinating with Ed, KM6TNT, on this noting that we both can be found on the PAPA system. It is one of those sprawling, linked "closed but welcoming" repeater system whose info can be found at this link here. Suggest PAPA 03 or PAPA 04 as you penetrate Orange County.

Mile Square Park park charges $5 admission on Saturdays and does not allow re-entry (unless you pony up again), so I recommend picking up something -- sammiches, sodas, etc. -- for lunch around noon time if only to stave off hunger. We will probably have donuts and/or bagels available at first but if you you are a coffee drinker, you are on notice that I am not and your daily caffeine hit is your responsibility. 

We plan on folding our tents and heading over to a pizza joint close by where we can eat, "hydrate ourselves", and debrief. This socializing will be an invaluable opportunity to gather our thoughts and ideas in preparation for the real thing.

Prerequisites and Skills Required
Again, if it looks like you want to participate in the Zuni Loop MEF effort this is a great way to get to know the folks. If your CW is rusty or non-existent, don't worry! we do phone too and you will be surprised how -- with a little coaching -- you can pick up CW contesting by logging and using a CW reader. Also, don't let low power throw you. Up at 7,000 feet, a five watt signal carries pretty far. Several of us have done WAS (Worked All States) during a field day. (I have done it three times and once I came within four states of doing a "double WAS".) Also, foreign countries now participate in Field Day so there's a chance for DX as well.

Send me an email and I'll answer any questions you might have.

Park Environment
For reference and orientation, here's some pictures of the Mile Square Park surrounds.

K6WHP QTH, External Parking, and Mile Square Park Spots

Map of Mile Square Park