G4NSJ – 4 metres 70mHz



4 metres, the friendly band.

I’m now active on the 4 metre 70mHz amateur band, monitoring 70.450mHz. It’s been twelve years since I was last on the band so I’m really looking forward to it. I have an Anytone FM radio, thanks to my old mate, Nick, a local radio amateur. My aerial is  Sirio CX 4-68 vertical fed with RG8X coax. My QTH is Worthing, on the Sussex coast. Give me a call!

Worthing West Sussex 4 metre net.

There are now five of us in the Worthing and surrounding area regularly lurking or chatting on four metres. We’ve decided on 7pm every Friday for our regular net on 70.325mHz. Please call in, if you can hear us. Also, we try to monitor the FM calling frequency 70.450mHz as often as we can so give us a call.

Update – 9th October 2019.

The aerial has arrived. As you can see from the photos, I’m sealing the joints where the ingress of water might cause problems. The aerial is extremely well constructed but, as with even the most expensive aerials, it’s best to seal the joints as a safeguard.  I’ve used Araldite around the base of the rubber skirt surrounding the S0239 socket. Once the PL259 plug in screwed in, I’ll cover the whole thing with self-amalgamating tape. I’ve used silicone sealer where the base of the aerial meets the mounting bracket. I’ve used self-amalgamating tape where the aluminium rod meets the brass section but I’ve left the drainage hole open, see photo. Sealing this joint will keep water away from the joint and help prevent electrolysis occurring.

Sirio CX 4-68 aerial

My Sirio CX 4-68 70mHz aerial.

Here’s a very good article on the Sirio CX 4-68 aerial by Frits, PA0FRI.


Anytone AT5189 FM

I’m using an Anytone AT5189 FM radio for 4 metres.

Update – 10th October 2019.

I’m not obsessed with SWR but, 1.5:1 was too high for my liking. After repeated adjustment of the telescoping top section of the aerial, and some bad language, I’ve finally achieved an SWR of 1.2:1 in the centre of the band. It was raining so I got wet in the process. But it was worth the effort.

The base of the aerial is only 8 feet above the ground but it’s working well. At some stage, when the weather improves, I’ll get the aerial higher up.

Update – 12th October 2019.

Worked some real  DX today… all the way to Mark in Pagham. That’s 16 miles as the RF flies! The base of the aerial is now at 12 feet above ground, which has improved things greatly. Height  is very important at these frequencies. Raising the aerial by a mere 4 feet has brought received signals up out of the

Update – 22nd October 2019.

I’ve now added the coax RF choke, 4 turns about 4 inches diameter, which should stop the coax radiating. The  SWR is 1:1.1 so I’m happy with that. The base of the aerial is still only 12 feet above the ground. I’m planning on increasing the height soon.

Coaxial RF choke