Monday, 27 January 2014

Blogs

Here are a couple of amateur radio blogs from around here.
Norman 2E0FAS
Lawrie M3UHQ
Dave 2D0YLX

Sunday, 26 January 2014

Fire Up 99

The Fire Up 99 is a replacement top section for the Antron 99 CB antenna. I was using one on mine. The normal top section is a straight length of wire inside fibreglass but the Fire Up has a coil at the top, to lengthen the wire whilst keeping the resonant frequency at 27MHz.
The A99 is a half wave normally, so to work with the existing matching circuit, the length would have to be extended to around a full wavelength. Whether it makes any difference to 27MHz performance is debatable, I've not seen a decent review of one where anybody has measured a difference before and after adding it. When I put mine up, I was replacing a broken A99 and had no known signals to compare it with.
The A99 is just a half wavelength wire inside a tube, and without adding to the length, can't see there being a way of improving it on 27MHz without doing something like changing the matching circuit (there are losses in there, which would have an even bigger effect at lower frequencies - see this article).
At lower frequencies the top loading might help reduce these losses, so it could be an improvement for those wanting to use it on other bands like 14 and 18MHz.

I tried the Fire Up 99 on the car using a magmount which is far to small to drive anywhere with it. Not that it would be any use as an antenna on its own, as you can see from the SWR plots.
It seems to be a 3/4 wavelength at 34MHz and a 5/4 wavelength at 55MHz. Compared to a mobile CB antenna received signals are much worse at 28MHz.



Saturday, 25 January 2014

GB5LBC

Today I made my first HF voice contact for over a year (and the first voice QSO of 2014). 99% of the time the HF radio gets used to transmit and receive WSPR, with a little bit of other data modes. For that, the 5 watts from my Flex1500 is good enough (hardly anybody uses over 5 watts on WSPR), on SSB it's not that good compared to the usual 100 watts most people run.
But I had my microphone plugged in for a change (it's the one off my FT-817, the wiring is the same) and called GB5LBC (Roa Island lifeboat station) on 7.180 MHz, who was only 7.3Km away from me. That worked OK and it was the furthest this Flex1500 has ever got on SSB since I bought it.



Baofeng

Some Baofeng BF888S UHF handhelds I've been programming.

TV signal

TV signal from the antenna on the chimney, from Winter Hill.

Broken A99

This is the base of the middle section. The wire inside had not snapped.

10m Vertical

Last Sunday I took the Antron 99 down from the house after it had snapped in December. I didn't have anything very good to replace it with quickly so I put a 28MHz mobile antenna on a bracket in its place. It doesn't really work as there aren't any radials (the metal pole its on might help a bit) and the SWR is around 3:1 on everything above 18MHz.
I did a few checks on performance by transmitting from the car on 28MHz and remotely viewing the Flex1500's signal readings on my phone using TeamViewer. I'd taken some readings last year on the Antron 99 and the new antenna worked out as around 9dB worse over a 1km path. That was without any tuner in line at home, it probably wouldn't have made much difference to the signal anyway.
I'm using it on 20,17,15,12 and 10m bands with a tuner and on receive for all other bands. At lower frequencies I think it it works better on receive than the wire as it is further away from the phone wire.
I've been using the 160m band quite a bit in the last few months (using WSPR), as I found my wire antenna will tune up on there since I extended it in the summer. The noise level at home is such that I still transmit better than I receive, even on a wire which is far too short. I wonder if the phone wiring re-radiates the signal.