THIS is the classic – but unfortunately, it has been out of production for more than 25 years. Ahh… the bye-gone days, when high quality items were not terribly expensive, but built to last..!! The Collins TD-1 was functionally identical to the HyGain 18TD.
I used to have HyGain 18TD – a great, portable antenna which contained two stainless-steel measuring tapes which could be extended into a dipole configuration. Unfortunately, nobody makes that antenna any more (MFJ/HyGain – are you listening..??!!) – because I think they’d sell a bunch of these to ARES organizations around the world if they did. Why in the world I either sold or lost that Hy-Gain antenna is beyond me..!!
..
There have been many valiant efforts to duplicate (read : CHEAPEN) the design – some using yo-yo’s or the equivalent of Coleman Camping Clothes-lines. but they’re all quite fragile or in some cases quite large. So I was thinking – how could we make a sturdy, yet light-weight antenna that didn’t require extensive fabrication – that could be duplicated by almost anybody for less than $120..??
..
Here’s my idea – and y’all are welcome to take it, steal it, improve on it, then share the results with all of us so that we can all benefit. Basically, it starts with two FLY-Fishing Reels – stainless steel in construction so as to be impervious to the weather, a fishing rod like a Black Widow which extends to 10-feet and a 1:1 balun which acts as our feed-point and coupling device.
..
I used (relatively) inexpensive Fly Reels (Hobbs Creek HC-III Reels from Bass Pro Shops for $39.99 each) which are silky smooth and made of alloy, so they’re only about 5 oz each.What’s nice about these reels, compared to super-cheap versions, is that they have replaceable reels, so you could have a set of reels that had #26 wire and another set that has #18 for longer lengths. Of course, two reels are required – one for the left and the other for the right side of the dipole. Thus far, we have $80 in the two reels.
..
Next, we need the center support for the antenna – but also it would be good to have a 1:1 balun, so I decided to find a balun that would accept a PL-259 from the coax, then terminate in BINDING-POSTS for easy attachment of the antenna wire. I just happened to have an LDG Electronics 1:1 current balun handy (never used it before) so I put it to use in this project. Of course, that means that this particular antenna will need to be a symmetrical dipole – equal length on each side of the center.
..
I’ll also make a version of the antenna as an Off Center Fed Dipole (OCFD), so I’ll need to use a 4:1 balun – again, I just happened to have an LDG balun that could be put to good use. An LDG 4:1 voltage balun is ideal for this project and should provide an excellent match for the OCFD. Both these baluns are only rated at 200wCW, so be careful – but as long as you’re not QRO with an amplifier, all should be fine. Below are pictures of both baluns. Current cost is about $30 each for either of the baluns. Also be careful since neither of these baluns are weather-tight, so don’t use them during inclement weather lest you short them out. Total cost now is about $110.
..
Okay, so we have the reels for winding the wire, as well as the baluns – so now we should decide on the wire type and size. I will be using two sizes of wire – #26 copper clad steel wire with a black insulation which is virtually invisible and a #18 copper clad steel wire without insulation. The #26 is invisible from a distance greater than about 10 feet – so it’s ideal for “sensitive” locations (remember, these are temporary, since the balun is not waterproof).
..
Wire size (diameter), in part determines VSWR bandwidth – the larger the diameter of wire (or tube) the greater the bandwidth – therefore the #18 wire will have substantially greater bandwidth than the #26 which I expect to be quite sharp when being swept with an antenna analyzer. I’ll provide comparative VSWR plots from the AIM/UHF Antenna Analyzer when I get some time. It will be interesting to see the difference caused but the wire gauge. I expect that an antenna tuner will be recommended (if not required) in order to get excellent matches – especially in a field deployment scenario. My normal source for high-quality antenna wire is The Wire Man in South Carolina – always at the local (and Dayton) hamfests, but also close-by via UPS. His #26 wire is called #534 and is currently $0.16 per foot when purchasing more than 100 feet. The #18 is much less expensive and is listed as #501 at $0.06 per foot when purchasing more than 100 feet. Call it $10 for the wire (overkill) and you have the system for less than $120.
..
Primary use of these antennas will be with QRP radios – in particular the Elecraft KX1 and the K2. In the case of the KX1, I’ll be experimenting with high-speed, computer generated CW at 50+ wpm. This would seem to be ideal for ARES work when conditions are horrible since 5w of CW will “punch-thru” abysmal propagation conditions unlike SSB. Of course, the premise is that the receiving station will also be using computer CW decoding. If it works (and it should), it will be faster than 45.5wpm RTTY and have more “punch” than any other digital or voice mode. When SSB is needed, I’ll either use the Elecraft K2 or one of the K3′s.
..
I mounted each of the reels on opposite sides of the LDG balun using velcro to attach the reels to the baluns, since they’re quite light (even with the wire spooled and ready to go), but you could also SuperGlue or Epoxy the reels to the baluns for a more permanent attachment.The wire will come out of each reel and be tied to one of the respective binding posts – after all the measurements are made. In the case of the #26 wire, I anticipate stripping the insulation at the appropriate points for each amateur band – making it easy to field deploy without having to measure the length of the wire. When using the #18 wire, I’ll crimp a conductive ferrule on the wire at each of the band lengths to signify 6m, 10m, 12m, 15m, 17m, 20m, 30m, 40m, 60m and 80m. In the case of the OCFD, only 1 marking is needed for each side of the dipole, so a single ferrule on each side should suffice.
..
The tension on the reels can be adjusted with a knob on the back of the reels – I normally make a very loose when deploying the wire, then tighten it afterward to avoid the spool from running free – even though the wire will already have been secured to the respective binding post. Retrieval of the wire is very simple since the gear radio of the winder is quite high (and it’s absolutely silent in operation).
..
Finally – add a couple of Cable Ties to be able to hang the contraption by the balun (binding-posts facing UP) and we’re ready to deploy.
..
So here is the finished product.. First, the Straight Dipole (Symmetrical using a 1:1 balun)
Then the unit intended for all-band operation using an OCFD configuration, which requires a 4:1 balun:
..
In a future article, we’ll actually deploy this contraption and show you the SWR curves, as well as the VSWR bandwidth difference using different gauge of wire. Should be interesting.
). All standard accessories included, except that I don’t have the manual (just download it online). Asking $475. Guaranteed working and to full manufacturer’s spec. Already converted to PowerPole connectors. All standard accessories included. Pictures below.
