Feature Articles
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- Written by: Maintenance Guy
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When I was a young lad, messing around on the 11m CB bands and theoretically pushing the boundaries of my theoretical CB licence theoretically quite a lot, there were certain radios and certain bits of kit which marked some of the operators out as being pretty cool. I spent probably too much money on some of the shiny things that were offered to me by some of my friends who were amateurs, and some of whom were 'rig doctors' as we used to call them. One of them was a very well-known and respected electrical engineer, and I remember the first time I dropped my radio off to him for a re-tune and one or two 'enhancements'.
His property was absolutely chock-full of radio exotica - every room, including the kitchen, was stacked with the radios that we all coveted at the time, and more test gear than you could shake a stick at. Huge power supplies, linears, oscilloscopes, signal generators and various meters, analysers and other lab gear.
The one thing though, that just seemed way more impressive and desirable than anything else were the big digital frequency counters. They were DIGITAL, even though they were of course totally analogue apart from the bright, colourful seven-segment LED displays.
I really wanted one, but they were just too expensive for the likes of me to purchase.
Now that I'm old and can no longer remember what I had for lunch, I still want one. I bought one of those super-cheap Chinese frequency counters off eBay for about a tenner. It looked interesting, but was about as useful as a chocolate teapot. Several weeks later I found a job lot of radio bits and bobs from an SK shack sale. It was cheap, and included in the bundle was a much better-looking portable frequency counter, so I pulled the trigger.
It's been an interesting gadget to get to know. Certainly not a professional piece of equipment, but useful and yet another opportunity to learn about amateur radio and RF technology in general.
So it turns out that I don't have enough hands to key a radio to generate a test signal, press the buttons on the frequency counter, and photograph it all happening - so I fired up my beloved WSJT-X and transmitted a 'Tune' signal on 20m. That allowed me just enough hands to hang out of the upstairs window and wave the counter in the direction of my wire antenna. The counter has a run/stop scan function so you can freeze the current screen image. That way I could then get a reasonable photo with both feet on the ground.
Above, you can see the result of my first test. Initially it was a little bit nerve-racking, because the manual warns repeatedly about not overwhelming the input of the meter with significant amounts of RF at close range, so I started off cautiously, and then generally upped the ante until I got some sensible output.
I was quite impressed. The display was large enough to be perfectly readable even with these aged peepers, and the frequency reading was reasonably accurate. I of course checked the figures I was seeing with another reference receiver, and yes - pretty good results. Signal strength indication is also noteworthy, though not that useful as both the distances involved, slight variations in orientation/polarisation as well as the proximity of other real-world objects made it less than reproducible shall we say.
The meter covers a vast frequency range from 2MHz all the way up to 2800MHz so after larking about on the HF bands, I thought I'd test it out on UHF - including the fact that it will also supposedly read the CTCSS tones used to open analogue repeaters.
Lo and behold, it grabbed the following from GB3HY
I was again more than satisfied with the accuracy and ease of use. I obtained this reading by throwing some RF around my shack using a homemade indoor 2m/70cms dipole at approximately 2W output. The meter had no problem with ascertaining both primary and sub-frequencies correctly.
After a bit more testing and playing with all the settings and ranges, I returned to HF and performed a check on 40m FT8.
Of course, that will give me 7.074MHz or thereabouts...
Turns out that it's also a useful tool for checking your unwanted harmonic outputs!
That was 50W full duty cycle at around ten feet from the antenna, and with the range (mistakenly) set to 27MHz - 2.8GHz, it was never going to read 7MHz. I was childishly excited to see the 7th harmonic registering on the counter though.
As far as I remember, the actual transmit frequency was around 7.073500MHz, so I'm not really sure why the counter reads what it does, or why it didn't pick up the 5th harmonic for example, but it does also have an f2 reading of 50.4809MHz.
I guess there is more experimenting and testing to be done. I might even consider reading the manual.
It only took me 40 years to get to this point. Not so cool after all, though I try to appease my ego by imagining that I must be a tad wiser and have slightly better dress sense.
Berni M0XYF
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Alex never fails to impress with the quality of his home project builds.
This line following robot is as tidy as you like, and of course it works flawlessly as you can see in the attached video (around 55MB download).
All images nicely annotated by Alex, who I'd once again like to thank for sending in his project documentation.
If anyone else has anything to send in, be it electronic projects, antenna builds, repair or restoration work, then please do.
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Alex Henderson M0TOT has been hard at it in the construction department once again. I love receiving details of his projects, they're all really interesting and/or useful.
This time he's come up with a neat gadget to detect a mains failure and let you know all about it!
Alex tells me:
Here is something for the club’s web site. I have some spare P.C.Bs. if anybody is interested in making one of these small units.
Well done Alex, and I appreciate you sending in your project documentation to share.
If you'd like one of the PCBs mentioned, you can contact me via groups.io and I'll hook you up with one.
73s
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- Written by: Ken Gibson
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The need for change
My 20m Delta Loop had been in place since April 2019 when the lunchtime net moved from 15 to 20m and had the point fixed about 37 feet up in one of the large Oak trees at the top of my garden.
Since then the Oak trees have grown and new branches and a multitude of leaves and twigs covered up the antenna changing its impedance when wet and pulling the wires out of place.
After some thought I decided to dismantle the triangular Delta Loop and install a single 20m square Quad Loop further away from the Oak trees putting the antenna in the clear yet still facing towards the east coast of the States.
Recycling and replacing
I already had one aluminium mast which supported one end of my 80m Doublet so I strung a new (blue) polyprop rope from this and utilised the original halyard and pulley which had supported the point of the Delta Loop for the other end. This gave me a horizontal rope at 37 feet on which to hang my new antenna.
I then made up a square loop from 2.5 mm stranded plastic covered copper wire (blue) with 17 foot 9 inch sides fitting thimbles at three corners with one bottom corner connected to the 450Ω feedline via a commercial junction piece. The above lengths are the result of my calculations to construct an antenna which would resonate at 14.345Mhz. I pegged out the loop on the lawn with tent pegs to form an accurate square and cut 73 feet of wire from the roll to make up the 20m loop which actually measures 71 feet around.
I then fitted two 20 foot lengths of cord to the thimbles on the bottom two corners to prevent the square Quad loop from moving about and hoisted it all into the air.
Testing
The result is that I now have a vertically polarised square Quad Loop (with no front to back ratio) with the top wire at 37 feet and the bottom about 19 feet off the ground. This faces Bob, N4XAT and David, WB1EAD and puts an S9+30db signal into Barry, SA7GDB (his report to me yesterday). David WB1EAD was still able to read my SSB signal when I turned the output of my FTDX 3000 down to 5 watts output. Bob was also able to work me on CW from his home using his MFJ magnetic Loop even when I reduced power so that satisfied me that the new loop is working well.
Because I choose to feed this loop with 450Ω line rather than coax I am also able to match (but not resonate) the loop and feedline for a 1:1 match on 21, 18, and 7 Mhz giving 4 HF bands from a single length of wire, and you could do this too.
I fitted a commercial 1KW 1:1 Current Balun at the shack end of the 188 feet of 450Ω line I need to reach the loop and the balun connects to my manual ATU via 6 feet of mini 8.
Why 450Ω Ladder Line?
I don’t worry about needing 188 feet of feedline since 450Ω line has a loss of only 0.15db per 100 feet at these frequencies. Compare that with the coax feeder you are using. You could make up one of these square loops and feed it with coax but in this case you’d need to fit an electrical quarter wave matching stub made from 75Ω coax between the loop and your 50Ω coax but then you’d only have a single frequency loop since that set up would not match on other bands.
There you are, something to think about. The wire and ropes used don’t have to be blue but as I’ve said many times before, It’s all about antennas!
73, Ken G3WYN.
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I built this unit for my Yaesu FT-871 transceiver. There may not be much interest by other club members, but if anyone wants some more information, I have the schematics and the layout of the PCBs. The unit will supply 3A and 20V maximum.
Regards
Alex M0TOT
