2m Station Development

Well, it's been busy up here at Copper Mountain recently.  New carpets, general throwing out of old stuff, and trying to get enough exercise in increasingly wet and windy conditions!

With a bit of calm weather the past two days, I assembled the new, Serbian-made Antennas-Amplifiers, 8-element 144MHz Yagi, bought via UK distributor, Waters and Stanton for £128.

Assembled and awaiting a suitable mounting pole.  Boom is 2.91m long.

The antenna is well though-out and made of good materials, with a very strong, perhaps slightly too big cross-section boom.  It's a moderately heavy antenna, and needs a good pole for mounting.

Living in sea spray for most of the winter, it's important that any boom joiners and fixings are stainless steel - which I was pleased to see they all are.  Only the boom-to-mast clamp is plain steel, but it is powder coated.  A good coating of grease once assembled will protect this, but it would have been much better were it also stainless.

Clear labelling makes assembly easy and confusion-free.  Screws are secured further with thread-locking paste. Stauff-type clamps may have been a better selection.

The element clamps, which are nylon or similar plastic, are screwed with self-tappers into pre-drilled holes on the boom.  Each position is clearly labelled both for position and correct handedness.  One element clamp position did have the holes drilled slightly, inconsequentially off-centre.  The printed instructions are very clear, written in proper English, and full of technical analysis.

The driven element has a pre-connected coax balun, sealed with glue-gun type sealant.  It's a serious question as to how long that will last when exposed to the weather and sun, but it can be coated or taped for protection.

The coax is preconnected at the other end to an N-type socket, which is accommodated on a plastic offstand.  The coax-to-socket connection is also sealed with glue-gun sealant, but is at least protected from light within its box.

Sealing the N-socket offstand box.  Coax balun is pre-installed with the antenna.

The N-socket holder is not quite properly thought through, because the coax from the balun runs slightly downwards into the offstand, meaning that any rain that falls onto it will run into the inside of the socket holder box, eventually filling it with water.

I've addressed this by wrapping self-amalgamating tape, which solves the potential water ingress problem easily.  I would have preferred to have a better design, and I will have to later drill a small vent hole for water vapour and/or any rain that does get in to evaporate or drain away (probably easier just to remove one of the four N-socket holding screws, actually!)

I've now had a chance to mount the antenna on a short pole for testing.  In fact, this 4m-high testing point will be its permanent height, because HFTA terrain modelling shows the maximum low-angle gain is achieved at this height above ground (the antenna is already on a ridge, 100m above sea level).

The matching is pretty much as expected.  Because the property is now quite full of antennas, they inevitably have slight effects on one another.  Even so, the overall matching curve is flat at no more than 1.04:1 across the whole 2m band, even with other antennas around the site:

 

 

 

One thing to look out for with 2m antennas is PL259-to-N-type adapters.  Often, as I do, we have existing coax runs with PL259 plugs at the end, which we try to reuse for speed and convenience by connecting via these adapters.  But they invariably introduce significant impedance mismatches.  Removing the adapter I was using, and replacing the PL259 plug with an N-type plug saw the SWR drop from around 1.35:1 to 1.03:1 at its best point. 

Mechanically, I'll give it 8.5/10, only because the boom could have been at least 15% smaller in cross section, and the slight annoyances highlighted.  But it's likely much better built than many of the alternatives, and is reasonably priced.  The only alternative I would consider are the Innovantennas LFA and similar antennas.  Sadly, the company was a little slow to respond to enquiries through the New Year period, so I had to move on.