YRARC General Meeting, 7:30pm EDT Tuesday October 6th, 2020

Until further notice we are meeting on-line to comply with COVID-19 regulations and recommendations.

The meeting link and other access information will be sent to the membership email list. If you do not receive the message by the morning of Monday, October 5th, please contact our club secretary (secretary@yrarc.org) to register. The meeting is open to club members and everyone with the genuine interest in ham radio (just like our in-person meetings).

The speaker this month will be Pablo, VA3HDL, with a presentation on the tower project he completed this summer.

Look forward to seeing you on-line!

73, Chris

Notes from the Shack - March 2016

It's been a while since I wrote one of these (and I'm sure I've written those same words before). However, it is time to improve the antenna situation at the VE3NRT QTH which will prompt many investigations and conversations about all things antenna. Brad VE3HII stated once that the budget for antennas should be at least 3 times that of the transceiver, and now that I've started budgeting it may turn out to be an understatement.

Up to now there are 4 antennas in rotation at the QTH:

1. A Butternut HF6V. This is been my mainstay antenna for over 30 years (including 20 years where it sat on the ground beside the driveway at the old QTH in London while I was getting established in the Greater Toronto Area. It is now quite unreliable despite several attempts to refurbish it.
   
2. A G5RV at about 35'. Well the middle is about 35'. One end is almost as high. With the recent ice storm, the other end is at about 20'. It still works pretty well and has yielded me quite a number of new DX contacts. The biggest problem with the G5RV is the 150' of not very good coax that feeds it. On 6 metres it's absorbing at least 40% of my output power.
   
3. A 40m dipole. I used this at home on 40 and 15 (and sometimes 6) before I had the G5RV. I originally built it on vacation in Florida to run as an inverted V. Consequently it is a bit short to use as a dipole, as inch for inch, an inverted V tunes lower.
   
4. A home-made 6m loop. This antenna worked well (Venezuela was my best contact on it) even though it was hung in a tree at less than 20'. It had a tendency to fall out of the tree in a strong wind.
   

Usually at least one antenna was working at any given moment. But it's time to do something better. The first step in my study has been to look at transmission lines, and the book "Low Band DXing" by ON4UN has been one of the main references. In the chapter on transmission lines, it mentions calculating the loss in coax by measuring the SWR. Now with new coax, you can just look up the loss. Each brand usually has a chart, table, and/or formula for calculating the loss at various frequencies.

However, it might be the case that you have existing coax (whether it be in storage or actual operation) that you want to test. I happened to have a nice 50' piece of RG-213 lying around that I could experiment with, and ON4UN's book had a formula for loss based on measuring VWSR with one end of the cable unterminated. The idea is that you measure VWSR (with an SWR meter or an analyzer - I used the latter) and use the formula to derive the loss.

The formula given in the book is:
$$Loss(dB) = log_{10}\bigg[{SWR+1 \over SWR-1}\bigg]$$
Armed with this formula I measured the cable from 50 to 600 MHz. There were peaks and valleys in the reading (the book never mentioned those) so I used the peaks and came up with an answer of about .4 dB at 570MHz. I realized there must be a mistake as my piece of RG213 had not taken on magical low-loss properties.

In addition, most formulas involving decibels (except ones with ratios of decibels) have the number 10 in them someone, and my result seemed about 1/10th of what it should have been.
Sure enough, on checking some other references I found that the formula should have been expressed as:
$$Loss(dB) = 10 \times log_{10}\bigg[{SWR+1 \over SWR-1}\bigg]$$
Increasing the resolution of the analyzer and reducing the sweep to 550MHz±50MHz showed an undulating pattern of VSWR rising and falling across the range of frequencies. The gap between peaks was about 6.2MHz. An Anritsu web page recommended averaging the SWR in the peaks and valleys. Here's what a 10Mhz segment looks like on the analyzer.


Frequency is on the x-axis and VSWR on the y-axis.

In the 550±50Mhz range the maximum VSWR was 3.525 and the minimum 1.762, yielding an average VSWR of 2.643 and a calculated loss of 3.459 dB. The chart says reads about 6.8 dB so this tells me that the measurements and calculations are likely correct and that the cable is in good condition. A 2005 QEX article by AI1H recommends combining this measurement with the same method applied to a shorted, rather than unterminated, coax. I haven't tried this yet.

The label says that it is JSC Wire & Cable RG213/U part #3780 with a velocity factor of .66. Loss at 400MHz is supposed to be only 4.8dB per 100' at 400Mhz and 8.2dB per 100' at 900 MHz so either the manufacturer is a bit optimistic (say it ain't so), the cable is longer than I think it is, or something else is wrong. So it appears the numbers work well but I want to try a few more examples before declaring that I really understand it.

The above equation means that as the cable loss goes up, the VSWR at the radio end goes down. So cheap cable, especially a long run of cheap cable, will make your VSWR look good but not achieve any real value in terms of communications. Quite the opposite in fact.

A final thought is that the equation for "Return Loss", which is a term I'm starting to notice quite often, is:
$$Return loss(dB) = 20 \times log_{10}\bigg[{SWR+1 \over SWR-1}\bigg]$$
This is just double the value of the cable loss, and represents the "there and back" loss, not just the one-way loss from antenna to transceiver, or vice-versa.

Next steps: measure the cable physically and electrically.

Compendium of old links

My hobby: Reading old editions of the Splatter... However, I started this post some time ago intending to republish old links that are still interesting and that still work but couldn't find a whole lot (not that I have a complete collection of Splatters). So instead I'm publishing a lot of more recent links sent out on the Yahoo reflector. Apologies to those I neglected to credit.

• Built-it-yourself precision GPS instrument (1cm accuracy). [Patrick VE3WST 2009-12-09]
  
• Shows what stations are spotted on the air.
  
• Lists all ham contests each week
  
• A spotting network for testing your signal (cw)
  
• A ham search engine
  
• Propagation prediction software.
  
• CWGET Program for learning Morse code
  
• CWTYPE Program for learning Morse code
  
• 45 minute documentary on laying transatlantic cables
  
• Video about ham radio and the lead up to the Internet. I've found a nasty link on this web site by the way, and have complained to the owner.
  
• Hints about putting wires in trees
  
• All things 160 metres
  
• Antennas on a chip. Just the ticket for the Internet of Things [Steve VA3SRV]
  
• Repeater Database [Geoff VA3GS]
  
• Good site for those interested in DXing [Geoff VA3GS]
  
• Yet another antenna site [Geoff VA3GS]
  
• QRP [Geoff VA3GS]
  
• Analogue & Digital Radio Information & Courses [Don VE3IXJ]
  
• IEEE Article on the exploration of Pluto [Don VE3IXJ]
  

Elecraft K3 20M Receive Performance - mystery solved

I can't believe how long I managed to live with this problem. At first I thought it was something to do with my antenna. Later I thought it might be the K3, and I looked in vain at the schematics to find any components in the receive path that were unique to 20M.

The most telling sympton was the noise. The noise level was always much lower on 20M. Sometimes it didn't register on the S-meter, but it rarely if ever got as high as S3. Still, I managed to work plenty of stations including DX on it. I might have even managed to work 20M digital at Field Day with it last year, as I think the problem has been around for that long.

It all came to head recently on JT65/JT9 where almost always the signal reports I received were much less than the ones I sent. I have a vertical antenna and the reports are S/N ratio so was it some man made noise source? The low S-meter reading was evidence against that. Occasionally the report I received would be 25 db higher than the one I sent, even though I was only running 10W (medium power on this mode). Usually they were about 10-12 db higher.

Here's a look at the transceiver as it was set at the time. The astute K3 owner may immediately see the problem, if he or she hadn't already figured it out from the description.

In the middle of this was a North American QSO party RTTY. 40 and 80M aren't working on my antenna right now (another painful story will unfold, I'm sure) so I tried to use 20M and found I couldn't hear much. Around the same time, trying to work PSK I also found a lack of signals, but a guy I chatted with on 30M said the band was crowded. Hmm.

The problem turned out to be (embarrassingly) simple. If I'd written Elecraft I'm sure they would have responded with the answer right away. The K3 has a separate receive antenna. It is selected by a switch right next to the power button just above the volume control. If you look just under the first zero in the frequency display you can see the letters "RX". I must have hit the button accidentally some time ago. The K3 has per-band settings for a lot of things and this is one of them, so in fact I had no antenna connected to my rig while receiving on 20M.



There's some leakage between the main antenna and the RX antenna path. It's not quantified in the manual but I estimate it's around 30db. It just goes to show how sensitivity isn't the most important thing in a receiver. I managed to work a lot of DX with that 30db "attenuator" in the signal path, although I'm happy to report that 20m is quite a bit more interesting these days!

I hope some day I'll be able to erect a separate receive antenna for even better DX. Unfortunately the noise level now usually hovers around S7.

Good thing I was on 40m not 20 at Field Day 2015 otherwise I might have received the "Melted Coffee Pot Award" for a second time.

Notes from the Shack - Where there's a will there's a way

Some of you know that I've been having antenna troubles. A permanent solution awaits in the Summer, but until then I've been making do with my flaky 30 year old Butternut HF6V. For a vertical, it's a great antenna - when it works, which is some of the time on some of the bands. But even when it's not working, contacts are still possible.

Now that the year of W1AW is in the history books, I've been trying to fill in some of the missing bits of my log. The sunspot cycle is heading towards a trough, so I've been focused on 12m during the day while the conditions are still somewhat favourable. At night, I've mostly been working 80m as it is my weakest band in the 10 - 80 range. One night, the noise level on 80m was unusually high at S9+20 and almost as high on every other band. My noise blanker works on some types of noise but not others, and this night I was happy to see it drop to about S6 after hitting the switch.

Because the antenna was working so poorly, I decided to use JT65/JT9 as it works well with low power. With the noise blanker on the display was quite unusual.

The signals appeared as adjacent bands in the spectrogram (a.k.a. waterfall) which was clearly an artifact of the noise blanker. This was confirmed by the text display.

Just like the waterfall, each signal had shadows above and below the actual frequency. This is very similar to when Ron VE3CGR is working JT65 on the same band as me at the same time. In that case I just turn my preamp off and everything is fine. The other strategy is to make sure I'm transmitting on the same time slot as he is and it solves the problem for both of us. With the noise blanker, though, it was a case of living with it or turning the radio off.

A difference between the signal overload and the noise blanker artifacts is that the former will exhibit equally strong signals on either side of the actual frequency, e.g -24db, -18db, -12db, -18db, -24db at regular spaced intervals of a few hundred hertz. The noise blanker artifacts were equally spaced at 220hz apart but with asymmetrical signal to noise ratios, with the better signals being below the actual frequency.

The trick with a display like this is to pick the strongest signal, and even with the noise, the compromised antenna, and the artifacts from the noise blanker I was able to work several stations. That's one of the great things about the JT modes - you can make contacts no matter what the circumstances.

Links of the Summer

July and August have been slow months for the submission of interesting links so I've combined July and August. If I've missed any that are still in my inbox then I will include them next month.

73,
Chris VE3NRT

1. Canadian Amateurs Receive the Order of Canada: ARRL Article; Southgate News Article; The original RAC link, submitted by Steve, VA3SRV, was broken in their web site move. Google to the rescue!
   
2. UK APRS Balloons Circle Globe [Patrick VE3WST]
   
3. Bringing down a 380' Cell Phone Tower [Steve VE3EZ]
   
4. Info on VE3PIC repeater. Steve VE3EZ is interested in receiving signal reports for both the current and future location of this repeater. It is located in Durham but provides coverage in York.
   
5. Field Day Press Coverage [Barry VA3LLT]
   
6. ISS on Field Day [Steve VA3SRV]. As many of you know from the last meeting Brad VE3HII managed to contact several of the astronauts on Field Day, prior to his computer packing it in due to a power surge.
   
7. The Open Repeater Project. This project based on Raspberry Pi or Beaglebone single board computers is in its early stages. [Steve VA3SRV]
   

My Field Day 2014 - Digital Station

As band captain of the digital station once again, I had two important goals for 2014. The first was to beat last year's score (and targeted 500 contacts compared to 243 last year). The second and far more important goal was to lose the competition for the coffee pot award, which I won handily last year due to antenna and software problems. Fortunately this year things went better and there was more competition so I lost by a mile.

The antenna setup was much easier using the club's radial-free Cushcraft R8 instead of my 30 year-old Butternut HF6V. By Friday evening we had it up, tested and made a couple of DX contacts on 15 metres. We also strung up a home made 40m dipole which I'd built and tuned as an inverted V during my diving trip to Florida in April. True to theory, in the dipole configuration the antenna tuned a bit higher in the band but with about 2:1 VSWR on the digital subband of 40m and 3:1 on 15m it was well within the capabilities of my tuner. The club tri-bander was also available but we soon decided that it would need some repair work before it could be used again, so we set it aside for the event.

Another advantage over FD 2013 was a year's experience with my transceiver. My first contact on that transceiver was on Field Day 2013 and since that time it has logged another 5000 or so, probably about 1/2 of those in one digital mode or another.

Start-up was not without challenges, though. Digital operation requires an audio interface, rig control, PTT, etc. etc and the software didn't work quite right at the beginning causing a few minutes delay that was quickly resolved. I'd brought my docking station to provide extra USB ports and used every single one of them. The worst of the problems was that input monitor switch on the audio interface became set by accident and caused a sharp feedback sound on transmit that took a few minutes to locate, but we were shortly up and running RTTY on 15 metres.

Unfortunately Brian VE3IBW and I didn't get the QSO rate we were looking for, partly because of band conditions and partly because there was less RTTY activity than expected, so by about 6pm we were well short of the QSO rate we needed to be to hit our target. We had started on 15m but had trouble finding new RTTY stations to work so we went to 20m to work some more. After a while 20m became unproductive so I went over to the 40m CW station and talked to John VA3JI who was the operator at the time to let him know that I was going to try 40m and to let me know if he was getting any QRM. Fortunately there was no QRM even though we were operating at the maximum power for our class and the next 12 hours or so was entirely on 40 and the QSO rate started to pick up.

As night fell the tent filled up with mosquitoes and other annoying insects so Publius VE3XS commandeered the bug zapper from the (now closed) kitchen which made short work of them, and surprisingly didn't cause any QRM. On my list for next year is to bring my own zapper.

By 3AM however, the doldrums set in once again so in desperation I took a break to configure FLDIGI (software for digital modes) with N1MM. Having access to the Internet via my cell phone really helped get it up and running. Once configured, we went to PSK and spent most of the remaining time in that mode. There were many more PSK operators and we really started to make hay, even though the sunshine was still hours away. By the time Brian returned at 6:30 AM I was able to turn the station over to him with just 25 contacts to go to beat the previous years' high water mark.

The other change we made this year was to use a home-made dipole and an additional antenna. On 40m it seemed to work better than the Cushcraft so we turned the R8 over the GOTA station and ran the dipole for most of the remainder of the contest.

I went home to get a few hours of sleep and when I got back to the site at around 1PM I found that Brian had had an outstanding morning on PSK and we were closing in on 300 contacts. By the end we'd reached 309 QSOs using two modes on 3 bands, a new high water mark to beat in Field Day 2015. Next year we are thinking about using a second receiver for spotting unworked stations and maybe setting up for 80 metres as well. The multi-band capability of the digital station really helped rack up the points. In the picture below, you'll see the Coffee Pot Award being presented to someone other than me.



With the great weather, great food (Thanks Peter!), great organization (Thanks Steve!) and great company (Thanks everyone!) it was all in all an excellent weekend.

Notes from the Shack, July 2014

Under the Whip

Pardon the title! A while back I discovered that my 30 year old mobile mag mount, made by Larsen, only matched on 2 metres. On 450 it was more than 4:1 VSWR across the entire band. On close inspection it should not have been a surprise as the housing for the coil that separates the upper and lower halves of the antenna had broken open exposing the interior which had become a congealed mass of rusty metal. It was a wonder it matched OK on 2 metres.

More recently, the club acquired a couple more mag mount dual band antennas from a local donor, and I decided to test them as well. Initially I did this using a filing cabinet as a ground plane but when neither worked on either band I tried them on top of my Toyota to see if they'd fare any better. They didn't.

Eventually I found that one of the donated antennas worked fine matching less than 1.5:1 across both bands if I mounted it on my Larsen base. It works well even on the shack filing cabinet.

What have I learned? To trust but verify. Seemingly good antennas can go bad and need to be watched.

Postscript

I'm now the happy owner of a vehicle with a permanent antenna mount on the roof. I expect that most of the time it will sport a 1/4 wave whip about 19" long because that's all the clearance I have into the garage. Long trips may give me the chance to run with something a little larger. I'm happy to have a rig in the car again!

I wrote this back in March but neglected to publish it. Better late than never.