WADARC WEEKLY BULLETIN – Nov 25 2016
Happy Birthday to our ever lovely Hon. Treasurer!
THE PAST WEEK
Saturday. The net-via-repeater is now a regular feature of the weekly round..7.00 pm. 430.975 up 7600, GB3WO
Sunday. 80 m net was, as ever, sparsely populated but made up for that in intellectual quality of discussion 😉
Wednesday. Construction contest was in the best amateur tradition; thoughtful and informed projects with a patina of cheerful irreverence. One could laugh with the humorous items or engage in enlightening discussion with a constructor. While tea was being served there was even a practical test of an antenna entry using a Field strength meter entry.
Of course such tests will be all the more practicable when we set up an antenna test range at THE NEW PREMISES which the committee have been arranging for the past 14 months ……?
. A week ago it was light-heartedly suggested here that the Dec. 21 meeting would be an excellent time for our Chairman to bring us all our Christmas presents. On Wed. this week, without batting an eye-lid, he stood up to tell us that the meeting for Dec. 21st had been cancelled.! Now that is POWER.
Rallies this weekend
Nah!. That’s it for 2016′ – think of all the bargains you missed by staying in bed..
|THIS WEEKEND ON THE RADIO
Forthcoming Club Meetings
Note: doors open at 7.15 for chat and for fighting over the freebies.
WEST MALAYSIA, 9M2. A group of operators will be QRV as 9M4LI from Lalang Island, IOTA AS-072, from November 25 to 27. Activity will be on the HF bands. QSL via operators’ instructions.
EAST MALAYSIA, 9M6. Saty, JE1JKL will be QRV as 9M6NA from Labuan Island, IOTA OC-133, in the CQ World Wide DX CW contest as a Single Op/Single Band entry on 20 meters. QSL to home call.
The prediction for this weekend, remains uncertain as the Earth succumbs again to the last of the, weaker than expected, plasma stream from a large recurrent coronal hole on the sun. NOAA has this weekend’s solar flux index predicted around 80 and the K-index at three or four, but geomagnetic conditions may improve slightly as we move into next week.
It is hard to say exactly how conditions will be for this weekend’s CW leg of the CQ Worldwide contest. If we continue to be hit with solar plasma maximum usable frequencies may be impacted adversely. However, as contesters tend to use larger than average antennas and power levels you should find the bands open to DX, at least up to 21MHz. Short occasional openings on 10 metres may also be possible, especially to the southern hemisphere, southern Europe and equatorial Africa. But we certainly won’t see the kind of conditions we have enjoyed during the last two or three CQ.
VHF and up propagation
The Moon is at apogee today so path losses are at their highest. Moon declination is still negative so with the Sun close to the Moon on Tuesday it is a lousy week for EME.
We had a Leonid fireball meteor last week. While spectacular, a single rock doesn’t help meteor scatter conditions, so just hang in there for the major Geminids shower in a few weeks’ time.
Mysterious Coax. Why do we use 50 Ohm coax for amateur radio but 72 ohm for TV reception? Why not 40 ohm or 100 ohm. Who decided on 50 ohms ?Coaxial cable was first developed in the 1930’s for high powered radio transmitters there were no plastics so early designs involved air spacing. We’ll skip the maths here, but it can be shown that for air spacing, the optimum impedance for low losses is 77 ohms but for high power handling is 30 .. ( lower voltages). Perhaps 50 ohms was settled on as a “happy medium” because it pre-dated the invention in 1939 of a material that changed everything. PTFE Trade name Teflon.The dielectric constant for Air is 1, for foam PTFE it’s 1.43 and for solid PTFE it’s 2.2. This makes quite a difference to the sums. Our lowest loss coax impedance becomes 64 ohms with foam and 52 with solid PTFE, So,entirely fortuitously, 50 ohm turned out to be a good choice. There now, and all the time you thought it was something to do with dipoles !
Overheard on 20m
ZEEGEW DE EGGS, ZEEGEW DE EGGS izza ItalyWAN DELTA PAPA XRAY. ZEEGEW DE EGGS OUTSIDA EUROPE ONLY.
I1DPX this is G4ABC over,
No, Negatiff Outsida Europe onnly, you are nota outsida Europe..
G3GV? (breaking in ) Ah! but any day now Marco.., we will be! .(Turns on Radio 4 with theme music of The Archers before releasing PTT)
Keep warm kids,
Bryan – G3GVB