VK1DA's Blog

Toys Down Under

andrew — Sun, 13 May 2012 21:01:52 +0000

Toys Down Under offers kits for helicopters and other items useful for experimenters, such as Arduino and Picaxe products and kits.

APRS tx, mini Fox tx, Receivers, GPS receivers

andrew — Tue, 17 Apr 2012 10:57:38 +0000

I came across the Byonics website today.

While I cannot understand why anyone would want to advertise the location of their car via a continuous beacon on a 2m fm radio, especially when the car is unattended in a car park, the devices offered by Byonics look interesting and may have other uses for the enterprising electronics or amateur radio experimenter.

The APO3 automatic power-off device is one example. If your battery voltage drops below a predetermined level, it turns off the power to the radio.

QRP Hours contest – after the event

andrew — Sat, 14 Apr 2012 13:21:50 +0000

As planned I operated in this relaxed event tonight, for a couple of hours.

I decided to use my IC703, partly because it has a CW filter and I know how useful that is even in a quiet cw contest. (I should get one for my FT817). The other advantage the IC703 has over the FT817 is that it has a speech compressor which improves the average power output on SSB. But as a test and a self imposed handicap I decided to cut the IC703 power level down from its nominal 10 watts to 2 watts for this event.

First an hour on CW, where I made 11 contacts. As you can tell this is not a hard paced, highly pressured event.

Then an hour on SSB where I made 17 contacts, a few more than I did last year. I recognised some of the callsigns from last year and also made contacts with friends such as Mike VK2IG, Murray VK1MDP, Waldis VK1WJ and Peter Vk3YE.

I don’t think running 2 watts instead of 5 or 10 made any difference to the number of contacts made. While 10 watts is 5 times higher, which translates to 7 decibels, 80m generally provides good propagation and there is more than enough “head room” in the available signal levels for QRP signals to be easily readable. 80m can be a noisy band on SSB especially late at night. There was some electrical storm noise but it wasn’t too bad. Another time those 7db might have been quite important.

A few interstate stations gave me good signal strength reports so the old 80m dipole at 6 metres above ground was doing its usual job.

The low dipole isn’t any use for dx though. I have heard some US and JA signals on the CW end of the band but even the strong ones rarely even return a QRZ? to my call. Have to get a decent vertical going on that band to work dx.

QRP Hours Contest 14 April 2012

andrew — Thu, 12 Apr 2012 20:43:48 +0000

Reminder that the QRP Hours contest is on 14 April 2012. Rules are in AR for April 2012.

Here is a link to the rules on the QRP club site.
http://www.vkqrpclub.org/qrp_hours_contest_2012.php

Summary:
1000 UTC to 1059: CW section 3500-3530 khz

1100 to 1200 UTC: SSB 3550-3590

QRP stations can work any station whether QRP or not.

Exchange is signal report plus serial number starting at 001. No repeat contacts.

QRP = output power no more than 10 watts.

Participation of higher power stations is appreciated as it warms up a contest to have more in it giving contacts.

One Word Reviews

andrew — Sat, 31 Mar 2012 03:16:11 +0000

One Word Reviews allows gamers to add reviews of games for various types of computer, Xbox360, PS3, Wii, PC and others. The site uses a novel approach to buyer feedback, allowing them just one word to summarise their view of … Continue reading →

RD Contest – State Scoring formula

andrew — Tue, 13 Mar 2012 20:00:19 +0000

Is the RD contest state score formula correct, and is it fair?

There has been a lot of concern about the RD contest state score formula, and conjecture about how it can be improved.

I have written this to clarify my thoughts and to show others what my analysis of the scoring formula reveals.

A fundamental principle is that the scoring formula has to work in the simplest of all situations, ie. when all states have equal performance. We know the number of licencees is different so we cannot simply add up their logs and award the contest to the state with the biggest score. That would give the result to the largest state and that’s not fair to the smaller ones.

To analyse the situation we have to start with some assumptions.

Assume all operators across all states had the same average points per log
Assume all states had the same participation ratio, ie. logs submitted divided by licencees

Should we expect that to result in equal scores? Seems reasonable doesn’t it?

Let’s assume each log contains 10 points (this can be an average, if you wish) and that the participation rate in each state is 10%.

Table 1. Examples of varying state sizes and scores

State	Licencees	Logs	Participation rate (PR)	Pointsper log	Score(total points*PR)
A	3000	300	10%	10	3000*10%=300
B	1000	100	10%	10	1000*10%=100
C	200	20	10%	10	200*10%=20

We find that the smaller states cannot win if all operators score the same average points per log as the larger state. Their population is a fraction of the bigger state and they need a correspondingly higher average points per log than the larger state does.

This simple example shows that the current scoring formula does not allow for different sized states.

In most RD contests, the two larger states have had low participation rates and several mid sized states have had better rates. To examine how those scoring rates affect the outcomes, we can insert those factors into the model and see how that affects the state scores.

We can go further and examine what a smaller state needs to do in order to score higher than a larger one.

Table 2. Further examples showing how state score is affected by participation rate (PR)

State	Licencees	Logs	Participation rate (PR)	Points per log	Score(total points * PR)
A	3000	150	5%	10	3000*5%=75
B	1000	200	10%	10	1000*100/1000=100
C	200	20	10%	50	1000*10%=100

Firstly, to explain States A and B of this example, the participation rate of state A has dropped to half its level in the first table. But note that its computed state score has cut to a quarter of its original value. It was 300 when its participation rate was 10% but with half the particpation the final score is 75, which is one quarter of the original value. We can observe that the state score changes in proportion to the square of the participation rate. Hold that thought.

This change in State A’s participation has had a dramatic effect on its final score, allowing state B to score better than state A, with the same average log value as state B.

Secondly, for the much smaller state C, I have illustrated how it can achieve the same score as one that is 5 times bigger. Its logs contain five times as many points per log as the mid level state. Here we can observe that the state score is proportional to the average points per log for each state, provided the participation rate remains constant.

Why is the state score not proportional to the Participation Rate?

As we know the formula for state score is:

State score = PR * (total of all logs)

However the total of all logs already reflects the participation rate, as if the PR were higher or lower, the log total would be correspondingly higher or lower. Indeed if the number of logs was halved, the total score would halve. Putting that another way:

Total of submitted logs = Total of all possible logs from state * PR

Rewriting the state score formula, we see that the state score formula can be rewritten as:

State score = (total of all possible logs from the state) * PR^2 (ie. PR squared)

From this it is apparent that the state score is proportional to PR squared.

This is why the state score is affected so dramatically by the participation rate PR.

How can the state score formula be improved?

Clearly the formula currently does not compensate for the different sizes of each state.

Teams of differing sizes can be compared only by normalising results to the average effort of each team member. In the case of the states competing for the RD trophy, this translates to the average number of points earned by each state licencee.

ie. Average score per licencee = (Total points on logs) divided by (total licencees in that state).

With that formula, going back to table 1 above, the average score per licencee in each state is 1.0. The average score per licencee in the other states is also 1.0. A tie.

And since they both produced the same average effort per licencee, a tie is exactly correct. This measure works well for the case where all states perform equally. How does it work if some states perform differently?

Let’s recalculate table 2, where states had different participation rates and different points per log.

Table 3. Sample results with Average Score per licencee

State	Licencees	Logs	Participation rate (PR)	Points per log	Average Score per licencee
A	3000	150	5%	10	0.5
B	1000	200	20%	10	2.0
C	1000	220	22%	10	2.2
D	200	20	10%	50	5.0

Outcomes:

The anomalous results shown in Table 2 have gone.
State A: large state, low participation, logs submitted are average value, overall rating 0.5.
State B: medium size state with higher participation than state A, and a much higher score – 2.0.
State C: like state B but with 10% more logs. Note that the score is 10% higher.
State D: the exaggerated example of a small state with very high average logs, scores best of all at 5.0.

As can be seen the results are linear, with increased scores resulting in a proportional increase in State score.

Where to from here?

The state score formula should be changed to the following:

State score = (total points from logs submitted) divided by (number of licencees in the state) [see note below]

I would like to see this analysis considered by contest managers and other decision makers within the WIA. I believe that the state scoring formula was fundamentally flawed because it was based on incorrect mathematics.

It is recommended that this part of the contest rules be corrected at a suitable time, to reflect the results of this analysis. It may be too late for the rules to be changed for 2012, but perhaps this anomaly can be corrected for subsequent years.

This change would make it more feasible for the contest to be won by different states. I believe the run of wins for VK6 has occurred due to good promotion of the contest in VK6 combined with a severe penalty for the larger states imposed by the erroneous formula discussed here. I feel sure that with a more appropriate formula, competition would be enlivened and the contest would be a healthier and better supported event.

Note: number of licencees is adjusted to remove licencees that cannot participate in contests such as repeaters and beacons. This is already catered for by current rules, but I did not wish to complicate the description above.

Reference: Current rules for the RD Contest, rule 14.1 defines the state score calculation. http://www.wia.org.au/members/contests/rdcontest/documents/RDcontest2012Rules.pdf

Summer VHF/UHF field day January 2012

andrew — Wed, 01 Feb 2012 10:54:27 +0000

For this event I invited a former work colleague and new licencee, Adan VK1FJAW to participate and learn something about field operations. Adan operated the 6 metre station during the event and while it was fairly quiet for most of the weekend, he was rewarded with a short sporadic E opening to southern VK4 during the final hour of the event.

Apart from that his role was to carry heavy stuff, help with fuel refills, put up antennas and generally be a keen student, which he did very well!

Operating from Mt Ginini was rewarding as usual. On the bands, 2m produced a good contact score though conditions were poor in Victoria, reducing activity and stations worked somewhat. Most of the usual Melbourne area home and portable stations were worked on 2m and 70cm, some stations in the Sydney area, north and southwards of Sydney and a few in the Port Macquarie area were also worked.

Conditions for the higher bands were not good. Apart from local contacts on 1296, the only exotic contact was with Dale VK1DSH on 10 GHz, made possible by his trek through the bush to a more favourable ridgetop from which he heard us much better and we could also hear him. Some odd frequency offsets were taking place but I think my handheld fm liaison rig was creating havoc in my own 2m IF rig. We liaised via the Mt Ginini repeater – for some reason I could get into it quite well, at a distance of about 30 metres. We had to use a combination of voice and morse to get numbers exchanged to our satisfaction. Persistence paid off.

View on Flickr'/>

The field day station before assembly