ARCHIVE: Australian Ham Radio Discussion Forum ( AHRDF )

Clearly, I didn't think this through.

Late yesterday afternoon, probably subconsciously prompted by an email from Nick Hacko's DXing.com.au mail list, I decided to cut a wire dipole for 6m and have a play.

I have never used 6m before.

I worked out the starting lengths of the wire and cobbled together a "suck it and see" dipole out of bibs and bobs that were laying around. So far so good.

This morning after cooking breakfast on the BBQ I wandered to the shed and grabbed a ladder, picked a handy eucalypt tree and hoisted up the antenna.

Again, so far so good.

I ran some coax to the bench and started to hook it up.

Then I realised why I haven't done 6m before. I don't have an antenna analyser or VSWR meter that does 50MHz.

 

I guess I need to order a NanoVNA or something, meanwhile I will investigate how to use the internal SWR meter in the FT-857D.

Like I said, I didn't think this through... 

You can't think things through

If you do that, then things all work out perfectly and you lose all the fun of working out why things don't work and what you did wrong

Yes, it does seem the best way  

Although I must be a genius at cutting wire.

According to the internal SWR meter it is perfectly flat right across the 6m band!  So why do I feel sceptical?

When we get back from holidays, I can see a NanoVNA in my future...

Ahhh.. Perfectly flat across the band...    Maybe that 'coax' is one of those new-fangled attenuators that is manufactured to look like coax cable ??? 

In reality the coax might not be far off being a total attenuator in it's characteristics at 50MHz so full power in, none reflected, because it is all swallowed in the cable !!

Doug,

I have a sneaking suspicion that you may be onto something...

Hello Colin,
if in doubt abut it working, have a listen to 50.456 (BV on Mt Kitchener) or 50.450 (Mt Lofty area) for the two 'local' beacons. if wanted I can easily put up some data on 50.313 FT8. VK9DX only appears here spasmodically as Es at this time of year can be quite fickle

Cheers Peter.

I retrieved the dipole from the tree on Sunday.

It is currently on a workbench waiting for the waterproofing silicon to set.

I will put it back up and have a listen for the beacons, as you suggest.

I must say working on wires (or elements I suppose) that are in the region of 1.42m long is far easier! Who needs two tress when two branches will do!

Well, I have finally got back to this.

A couple of weeks of illness, then a couple of weeks in YJ land got in the way. (After over 30 years of visits to YJ I appear to have come home with one of the tropical bugs - waiting on tests for malaria, dengue and ross river. However the sun is out and I have a brand new NanoVNA in my hot little hand, so dengue or not the ladders came out.

Now, you see, this is why I don't like making antennas (kidding). As I am waiting for some SMA to PL259/SO239 adapters for the VNA, I decided to forge ahead with a combination of adapters and leads. After an hour or so of up and down ladders, trim this,change that I still had weird numbers from the VNA, 4 ohm impedance, then 150 ohm, etc.

Time to start again. I'll recalibrate the VNA and go step by step. As I started to disconnect VSWR suddenly dropped to 1.13:1. Hmmm. I started moving and flexing cables and adapters and up it went again. It was one of the test cables, which is now two halves of a test cable...

Why does this always happen? I chase my tail for ages only to find it's not the DUT but the test set up. Just lucky I guess

After lunch I might just have a listen around 50MHz to see what I can hear!