VHF Field Day January 2009

As we had scheduled a house move one week prior to the January 17th VHF Field Day, I had to set aside the equipment needed for the field day so it wouldn’t get packed up and be lost for months, which can happen when you move house.
The antennas were no problem as I had to move them on the roof racks of the car. The cables were a possible problem, as were the connectors, camping gear, tent/poles, generator, power cables and distribution boards, power cables for radios, the radios themselves.

The one thing I could not put on hold was myself and I had worked very hard for 5 days straight packing and carrying boxes of household goods. The last move took ages and I had several weekends to sort through 3 garages and dispose of unwanted stuff. This time was a bit better, there was only one garage.

The upshot was that with some encouragement from Dale VK1DSH I did find the energy to pack the car early on Saturday morning and head up to Mt Ginini, a 70 km, 90 minute trip from the new QTH. It took a bit longer as I called in at the bakery and the supermarket for some essential supplies on the way.

We got the station set up by about 3pm and logged our first contacts on all bands. Right away there seemed to be antenna problems on 52 and 432 MHz. Both antennas came down, connectors checked. The 52 MHz vertical had been extended to make it work on 50 MHz on a previous field day. Removing a short length of tubing added for 50 MHz operation returned it to normal operation on 52 which was sufficient for local contacts.

On the 432 antenna, lowering that meant going off 144 as well so we had to get it done quickly. I inserted the Bird 43 meter inline with the 432 MHz feedline and first tried a dummy load on the antenna side of the meter. Perfect, very low reflected power, transmit power fine. Same with the dummy load at the antenna end of the feedline. But with the antenna, quite poor swr at about 2.6 measured at the transmitter end. Later I ran some simulations using the predicted loss in the feedline (CNT400, 10 metres) indicated that the actual SWR at the antenna was somewhat higher. This indicated the driven element of the antenna was not properly connected to the feedpoint connector. however it was sealed in epoxy and nothing I could do up the mountain to fix it. Note that I had previously used this antenna with poorer quality feedline RG/9. The increased losses of that feedline masked the antenna problem.

On other bands all appeared to be working fine, though I never made a complete contact on 1296 with Adrian 2FZ in Sydney, nor with Dave 2JDS near Bathurst. However I made a number of contacts at similar and greater distances into the vk3 area so it remains a mystery.

With Dale 1DSH operating the 6m rig and the IC910 running on 144, 432 and 1296 it was a noisy tent at times. The radios were all together on one table. The other radio on the same table was the FT290 which was the driver for the 13cm transverter.

Dale brought his 10 GHz equipment and made a contact back to Ted VK1BL on Mt Ainslie in Canberra on the Sunday morning. No other 10GHz stations were active within range. Unfortunately the power amplifier in Dale’s transverter suffered a failure so power output was limited to around 1 milliwatt.

Packing up only took 90 minutes, half what it had taken in November. A great pleasure to be on the road heading home at that time. On the way I heard Norm 7AC on 50.170 and had a 10 minute chat with him from the car. Just for a bit of extra radio for the weekend! But I forgot to get a Ross Hull contest number from him. 11 points lost from the RH log!

After scoring the log it appears we did fairly well on 2m and 432 despite the antenna problems. The log has been sent in on time so we will see what the increased activity level does to our position in the results.

Photo gallery for Summer 2009 VHF field day.

VHF/UHF Field day log pages and checklists

These two files may be of use to other entrants in the VHF/UHF contests.

The first is an empty log page which you can simply print on your own printer.  These are for handwritten logs.

The second is a spreadsheet template for the Australian VHF/UHF field days.  The first worksheet is the summary sheet and worksheets for each band follow.  There are only a couple of formulas and they are in the scoring table.

The template, if opened in either Excel or OpenOffice will create a new spreadsheet.  When you save it will be to a spreadsheet file.  The template will be unchanged so it can be reused.

Logging for field events – paper logs and spreadsheets

I use spreadsheets to record my field day log.  I don’t need to use a computer in the field – I work with computers all day and the last thing I want on a field day is yet another day of working a computer.  A paper log is quite good enough, and avoids odd things happening due to incorrect program logic, or wrong callsign recording.

In the John Moyle Memorial field day rules you need to record the grid locators of stations worked on vhf/uhf. Then you need a column for distance, then you need to work out the points earned by that contact.

I use Tiny Locator, a nice little application from ON6MU, to calculate distances from grid squares.  There are spreadsheet add-ins available for Excel, but I decided to just use an external tool and copy/paste its results into my spreadsheet. By doing the calculations only once for each callsign, the process is cut down to the minimum effort required.

I copy all the callsigns worked, with their locator codes as recorded during the contest, into a new worksheet called Grids.  Then I sort by callsign and remove the duplicates.  Then I do all the distance calculations with the help of Tiny Logger and record the distance for each station worked.

Back in the log page itself I then insert formulas into the Grid locator, distance and points earned cells of each row.

The grid locator can either be the original locator recorded during the contest, or the data copied from the Grids worksheet for that callsign.  Similarly for the distance and points data.

The formula to copy the grid locator for any callsign in the Grids sheet is =VLOOKUP($E2;$GRIDS.$A$1:$C$28;2) for OpenOffice sheet users, or =VLOOKUP($E2,$GRIDS!$A$1:$C$28,2) for Excel.

Similarly you can get the distance using the next column of the Grids sheet.

The points are calculated using a similar technique.  The score table is set up in another sheet, in the following format.

0 2
49.9 5
99.9 10
149.9 20
299.9 30
9999 50

The formula to look up the points for a distance is: =VLOOKUP(K2;$Scoretable.$A$1:$B$6;2) for Openoffice.org Spreadsheets.
Here $K2 is the cell containing the distance for the contact made. Scoretable is the sheet containing the table above in cells A1 to B6. Column 2 in the scoretable is the column containing the points to be scored. VLOOKUP returns the row containing the distance that is equal to the specified search value.  If that exact value cannot be found in column 1 of the table, it matches against the first row found that is greater than the value sought.  Thus a distance of 80 is greater than 49.9 but less than 99.9, so the row chosen is the one with a distance of 99.9, allocating 5 points to the contact.

You could continue to refine the formulas and the fine details, such as dealing with decimal points of distance correctly.  eg. what is the score for a distance of 99.999 km?  The simple table and formulas used would give the wrong result and strictly speaking the scoring table specified in the rules does not state the score for distances between 49 and 50 km, etc.  However as a way of saving typing and avoiding keying errors in distances, this approach works well enough.  Rounding the distances appropriately is also something to consider.

Summary

Using a combination of plain spreadsheets and formulas, you can ensure the grid locator, distance and point score for each contact is consistently recorded in your log sheet.

New antennas for 1296 MHz

I received the two 18 element yagis for 1296 Mhz and they appear to be strongly made. We will see whether they are any better than the previous antenna.  I have borrowed a splitter for them and will use that for the Summer field day in mid January, unless I can make my own before then.

I found a website offering data on stacking distances for yagis.  For a boom length of 1.5m on this frequency the stacking distance recommended is 2.4 wavelengths, which works out at 55cm (23cm wavelength).  The feedlines on the yagis are about 25 cm long but that’s not long enough to reach the power divider, so additional connectors and cable will be needed, eating into the stacking gain.

Next step for 23cm is to configure the power amplifier so it can be operated remotely from the tent.  I read some comments on the UK microwave reflector about power levels from IC910H not being up to the 10w level expected.  Time to get out the power meter and check mine out.

2.4 GHz transverter success

The 2.4 GHz transverter has been completed and I used it in the vhf/uhf field day on the weekend of 15/16 November.

Construction began on Sunday 9 November with the first components soldered onto the sequencer board, finishing on Friday 14th November when I finally measured the transmitter output power.

The next day I was on Mt Ginini, with a 24 db gridpack dish (obtained from The RF Shop) attached to the transverter, receiving a big signal from Ted VK1BL at Mt Coree.  I replied to his call and asked how he was hearing me.  He replied immediately! This was my first contact on 2.4 GHz, made all the sweeter by the knowledge that the transverter was home made.

Together with some other “firsts” on this field day, it made for a very good weekend.

I have written up the details of the design and construction and submitted it as an article for AR magazine.  The article was published in July 2009 and can be found in the AR archives here.

The 13cm transverter under test
The 13cm transverter under test

Preparing for spring VHF/UHF field day, November 15/16

This week’s project is to prepare for next weekend’s VHF/UHF field day.

I plan to operate from a mountain southwest of Canberra, with equipment for 50, 144, 432, 1296, 2403 and 10368 MHz.  The first four bands are bands I have used before but the last two are new for my station.  The 2403 equipment will be a simple transverter driven by a FT290R radio on 144.  The antenna for that band will be a grid type dish.

The 10368 MHz equipment has been borrowed from another local amateur.  It is a transverter driven by an Icom IC202 on 144, the antenna is a dish.  It all mounts on a tripod which readily allows azimuth and elevation adjustements.

On all bands the main mode used will be voice, using upper sideband.  For some contacts with more distant stations, morse (CW) will be used as it is much easier to hear weak morse signals than weak voices.

Amateur Radio, Computing and other activities of Andrew VK1DA/VK2UH