July 30-31, 2024. This was the club’s first attempt to host a DIY build of a 2m Yagi antenna. The popular 3 element tape measure beam was successfully built using NT1K’s online drawings. To keep costs low, we used cheapo Harbor Freight 1″ tape measures, 1/2″ PVC plastic pipe, and cable ties.
http://nt1k.com/wp-content/uploads/2012/11/3L-Tape-Measure-Yagi-Assy.pdf
Our guinea pigs were 3 student interns: Faheem KJ5HLH, Sarah KC1VCT, and Sean (awaiting his license).
For this activity, we moved a folding table from the adjacent Scuba Shack to the W5RRR shack to take advantage of better AC and cleaner air- the Scuba Shack reeked for musty and musky air possibly due to the defective drainage issue from the air handler AND co-sharing the room with Gilruth janitorial cleaning stations and tools.
Jeff AB4ME, Kelvin K5KGH, and I (W5OC), each brought tools and helping hands for the construction and test.
Overall, the construction was quite easy and we used 2 days (Tuesday and Wednesday) to get it all done.
With exception of the somewhat awkward and tricky soldering together of a copper hairpin matching link to both the tape measure feed point attached also to a coax braid/center conductor feedline. Because of the heat needed to overcome the thermal heat sink of the tape measure, we deployed the good old Weller solder GUN, no longer seen too much anymore. In most cases it took 3 persons to help position the wires, coax, tape measure, soldering gun, solder to properly position and perform the soldered connection.
Using a trusty MFJ 259 SWR meter, all the antennas were measured around 2:1 SWR or better.
A few lessons learned for our first foray into Yagi building:
- Flux worked great when soldering onto the tape measure exposed metal.
- Need a fan to disperse the soldering fumes.
- Sheared off ends of the tape measure were super sharp. We used tape and heat shrink, but next time we need to dull the ends by cutting a curve pattern.
- With exception of the driven element, tie wraps and Velcro worked great to secure the reflector and driven elements. Otherwise, it’s about $10 extra to buy and use hose clamps.
- Folding and tucking the tape measure ends into the open PVC joints worked great to a compact the antenna for transport
Testing. So this was an unexpected disappointment.
We tried to demonstrate the peaks and nulls of using their newly made directive beam by rotating their Yagi while monitoring a distant transmission. In all cases, the nulls and peaks were NOT very in distinct. We tried a using a beacon and keyed down HT at 500′ away- no remarkable effect. We also tried to key up the repeater with similar little results. Lastly, we tried an inline Fox attenuator which injected a variable 4 MHz heterodyne signal and tuned to the mixed signal with not too much observable improvement in the Front to Back nor Front to Side gain differences.
Likely these work much better for quite distant and weak signals with lesser performance nearby – unless one has various attenuator provisions.
It was fun nonetheless and with the remaining time, we got Sarah KC1VGT on the Flex radio to make her 1st QSO (20m SSB). Jeff gave a quick demo of the Satellite Station.
Many thanks to Faheem KJ5HLH who ultimately encouraged us to try out this Yagi DIY build.
