More bits of wet string…

…well actually aluminium. I finally cut down an old ‘fm’ radio dipole to 2m and quietly ran yet another run of WF103 into the loft. So the Trio TR-9130 I got a few weeks ago finally has an aerial. SWR is not bad at 1.2 or so on the VNA. It’s mounted horizontally as I got the transceiver in the hope of one day finding some 2m SSB… well it’s been 3 hours, nothing yet! Impatient!

Anyway it worked fine for the local RSGB News this morning, and to hear someone asking if 145.5 was in use but with no callsign…

This also means I finally have a use for the KW520 SWR/power meter. However, it would not register any power on the 20W setting on the 140-525MHz range but did on the 1.8-200MHz range (both of course cover 2m). I took the lid off, discovered it would be rather difficult to get at the switches to check them so put it back together. Of course it now works fine. Perhaps the initial swearing at it actually worked.

The Trio causes some QRM on the speakers of one of our PCs – actually in the room below the dipole. But as I cured our mains-bourne QRM in general I feel I’m still winning.

More on the loft dipole

I added a 20m dipole to the loft fan dipole today, and fixed the leg of the 6m wire that pulled out of its crimp eyelet. I have yet to cut the coax and insert a coupler so I can use the VNA, so I installed it and hoped. The VNA gave it a SWR of just over 3 and the FT450D tuner is happy at that. But the band is absolutely dead!


Do radio amateurs develop a desire to go ferrite hunting? I’ve often wondered this. Many years ago when I used to go to radio rallies – this is when there were some close to here – there were always people wandering round examining various torrid and such. I never questioned this but always witnessed it. And I seem to have joined them! I now have four T130-2’s, one of which will be a 9:1 un-un and a box of assorted toroids on order to see if I can shut the hash up from a couple of wall warts. This is since I got my license, so it must be catching.

First loft dipole

Having acquired a FT405D from my good mate Steve over at Mullard Magic I experimented last night with a loft dipole – my aim is to make up a fan dipole for 40 thru 6 metres (for 40m it will be a zig zag). So, having measured the coax distance from the proposed centre point to the radio I made up a choke round a bit of 7″ PVC and hung it from a wire dipole centre supported by string.

Ok so far. As 6m is the shortest wire I decided to make that one up and see how it looked on the VNA.

So, two bits of PVC coated wire with crimp connectors for the dipole centre went up in a more-or-less inverted-vee stapled to the rafters. The SWR was 3-ish, not bad for a first go. Then the cable went loose but the SWR dropped – one end pulled out of its crimp! Huh. Eventually, after a bit of a fiddle I got to 2-and-a-bit SWR, fine for now. Coax pushed thru the hole in the ceiling to the little bedroom and into the radio, after merrily knocking everything over. Coax into radio, and the internal tuner is happy. But absolutely no signals! Hmmm. Well, it transmits, I can pick it up on the IC-R2. But no idea if it transmits more than 6 foot…

I tried the local repeater, no joy. Mind you, I’ve never even heard signals from that so maybe it’s just too much to ask.

Of course having made one continual length (17 metres of Westflex WF103 in all) of coax I cannot now use the VNA in the loft! So I need to cut it and add a couple of plugs so adjustments can be made up there… probably a good time to wrap the choke in tape too as I can imagine it trying to unwind itself given the chance.

Experiments with a bit of wet string

I had time the other day, surprisingly, to have a fiddle with the HF active aerial in the loft. This is a Datong AD170 that I’ve had for decades now. It feeds into a Yaseu FRG7000 and also a Watson SDR dongle.

There is a heck of a lot of noise here and the aerial is far from ideal, being mounted on a purlin in an inverted-vee formation with the ends held on the floor joists, mains and data wiring and the house alarm wiring nearby. So, noise.

But it seemed to fair reasonably well on 40 metres even so. I caught one conversation on the SDR and checked I could receive it on the FRG7000 too which sounded better, probably because the PC has dinky speakers attached. But more to the point I used the Hack Green webSDR and found the same signal. Other signals via Hack Green did not appear here, but fair enough, they won’t be using the same bit of wet string and are a way from here. But it was a useful experiment that both my bit of wet string and their setup received the same amateur signal, and neither could hear the other end of the conversation.

Next step, move the AD170 to the apex inside the roof and see if that sorts the noise out. More later.



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