Just Another Lowly Ugly Sorta DIY Dipole
Look, it didn’t stop me from buying one, but I resent the IC-705 for not having an internal antenna tuner. The KX2 has one. The Xiegu has one. Heck, the 7300 has one. Its not like its some weird foreign concept to Icom. Three compatible “small” external tuners are – or will be – available: the MAT-705Plus ($229, 10 ounces), the ICOM AH-705 ($349, 15.8 ounces), and the Elecraft T1-ATU ($239, 5 ounces). The LDG-Z100Plus (20 ounces) will work as well, but its so heavy for a qrp accessory. (For a qro companion for my 891 on the other hand, the Z100Plus is perfect.) Of course, we all want the T1-ATU which is backordered. In fact, we all probably really want a KX2…which is also backordered. But, that 705 does have the super sweet unrivaled waterfall…not to mention the sophisticated Peovi cage with “KM1NDY” engraved in it. Let’s be real here: the bling allured me. It is the newest slick Ferrari of portable rigs.
I have made exactly one contact via a vhf repeater on the IC-705. Other than that, it has been nothing but a (beautiful) shortwave radio since I got it several weeks ago. And that is because I do not have a resonant antenna. And quite frankly, that is frustrating…as if qrp alone is not frustrating enough!
AA1F wanted to play radio today. He suggested a POTA of Plummer’s Landing in Northbridge MA, part of K-2419 Blackstone River and Canal Heritage State Park.
I was itching to transmit with the 705 and scrounged together some odds and ends for the construction of Frankenstein’s dipole.
I had an SO-239 panel mount connector with wires already soldered into the center conductor and chassis. I had used it as test equipment for this project. I also had an LDG 1:1 choke unun and a few dozen feet of stranded copper 14ga generic electrical wire. A handful of cable ties, a short coax jumper, and two wire nuts later, and I would soon be transmitting on a resonant 20M dipole. A picnic table at Plummer’s Landing was recruited to be my workbench.
Two wire radiators of equaI lengths were cut more than twice as long as the 8 foot picnic table. The goal was 16.36 feet total length after trimming for each leg of the 20M half-wavelength dipole. Attention now turned to the center piece of the antenna, I used cable ties through its screw holes to secure the SO-239 panel mount to the unun. This would also provide some strain relief to the soldered wire ends. Another cable tie would function as the unun’s hanger. Wire nuts adjoined each leg of the dipole to the panel mount wires. The coax jumper connected the unun to the chassis mount.
A 25 foot length of RG8X was connected to the unun and the antenna centerpiece was then hoisted by paracord about 15 feet up into a tree. The legs were extended away from one another into an inverted-v configuration. The ends were secured approximately five feet off of the ground so that they could be easily manipulated for trimming. The minimum vSWR started off a 1.36 at 12.94MHz. After trimming approximately 2 feet of wire from each leg, I settled on a minimum vSWR of 1.37 at 14.14MHz.
The final vSWR sweep across the 20M band was quite pleasing. I was able to transmit with the 705’s full power (10W) with no rollback. Unfortunately, I was not able to make any contacts to definitively prove the antenna was working. I operated for less than 20 minutes due to time restrictions.
Just a couple of more notes. The cable ties make useful end insulators by looping the wire, securing with one cable tie, wrapping the wire back onto itself and securing with another cable tie. And finally adding a third cable tie as a loop for hanging.
Finally, the IC-705 was operating on its own BP-272 battery pack which was subsequently being charged by a 15ah Bioenno lifepo battery. The current draw on the external Bioenno battery on receive hovered around 0.3A, while the current draw on transmit was around 0.8A. This is less than what Icom published for maximum current draw for both receive and transmit (0.5A and <3A respectively). I am not sure how the charging of the internal battery pack with an external battery works when determining current draw on this radio.
So, at the end of the day, I do not think that the IC-705 would be the best choice of radio for a new ham. When running 100 watts on a portable radio station, there is a lot of forgiveness for sloppy operating built in. You will make contacts even on 80M with a EFHW antenna cut for 20M, and an vSWR of 8:1. Just ask AA1F! (Who made over 30 contacts compared to my zero, thus successfully activating this POTA). But precision counts in qrp, and I am starting to get into a phase where the difficult qsos may taste really really sweet.
de KM1NDY
(“and did you think this fool could never win?”)