Hi All,

As the regular users of GB3JB will have noticed, we have recently been suffering from interference from users of GB3PC, who put a strong signal into the ‘JB’ site and are splattering across the ‘JB’ input frequency, presumably as a result of not have a narrow deviation capability on their equipment.

Because GB3PC has the same ctcss tone as GB3JB, this has resulted in our repeater opening up at various times, and retransmitting the splatter along with the invitation to transmit tone, for, in some cases, significant period of time.

We can obviously do nothing with regard to the stations splattering across the ‘JB’ input, other than to perhaps ask all operators to switch to narrow deviation setting, if their equipment has that option.

Therefore, following on from communications with our zone manager on the ETCC, in an attempt to reduce the potential for interference, and to stop ‘JB’ opening up, as described above, we have decided to change the ctcss tone that is required to access ‘JB’, from it’s current 71.9 hz, to 88.5 hz. Obviously the tone transmitted by the repeater will also change to this new frequency.

The change will take effect on the 1st May.

In addition to emailing this information to all on the blanket email update list, we will be adding it to the web site. The ETCC will also be changing the data on the “ukrepeater.net” web site. However, it would be appreciated if you could mention this to all those that you work via ‘JB’ and simplex, in the intervening period, as there are more users of ‘JB’ than we have on the email list.

It would also be appreciated, if those associated with radio clubs etc., within the ‘JB’ coverage area, could bring this information to the attention of their members.

73’s
Jan, G8CYV – GB3JB Team

To cut a long and boring story short, I decided the best option (for now) was a rotary dipole for 80m – and it needed to be discrete if it was to avoid complaints.

And withstand ‘very’ high winds on a regular basis.

The ingredients:

3 sections of 5 foot swaged alloy pole
1 tee-piece from Sandpiper
2 80m mobile whips bought on ebay
black silk spray-paint
lots of cable as the ’shack’ is now upstairs.

All in all quite a decent result – barely visible from all but one angle, until you get right up close – given the much higher contrast of the stairwell it would be a very unreasonable person indeed to whine about that aerial

The balun is simply about 18-20 feet or so of the coax close wound on a slice of cola-bottle and secured with gaffa-tape, then tied to the mast with cable-ties.

How well does it work?

On 80 it’s got a bandwidth of about 40khz without using the atu, and can still reach the USA at a readable strength despite being only 16 feet wide. The high-angle radiation that was missing from it’s predecessor makes inter-G contacts much easier.

It loads up quite happily for both 40 and 20 – I haven’t tried it anyplace else yet – and performs a lot better than I expected it to given the loading-coils.

I’m happy to call this experiment a success.

Sources:

Tee-piece from http://www.sandpiperaerials.co.uk/ (£5 plus postage)

80m whips from eBay seller chalesantennaman (about £11 each)

Sectional mast from http://www.haydon.info/
(I bought some rejects – 3 20 foot sets of 2″ mast for £49 plus carriage)